NCERT Solutions Class 9 Science Chapter 12 Patterns in Life Diversity and Classification

F R E E S T U D Y M AT E R I A L F O R E V E R Y S T U D E N T

CLASS 9 · SCIENCE

NCERT Solutions

Chapter 12: Patterns in Life:
Diversity and Classification

NCERT Textbook — Exploration

BOOK PAGES SECTIONS QUESTIONS MEDIUM

228 – 251 25 76 English

Solutions, notes, sample papers & more at 89 pages

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

CLASS 9 · SCIENCE · EXPLORATION

NCERT Solutions — Chapter 12: Patterns in Life:
Diversity and Classification
Life on the Earth runs into millions of species, so the only way to study it is to organise it. This chapter shows
how scientists moved from Aristotle's habitat groups to Whittaker's five kingdom system — using cell type,
cell structure, level of organisation, mode of nutrition and ecological role — then sorts the plant kingdom
from Thallophyta to Angiosperm and the animal kingdom from Porifera to the vertebrates, and closes with
the binomial system of naming and the reasons biodiversity is now under threat.

TEXTBOOK BOOK PAGES

Exploration (Class 9) 228 – 251

SECTIONS QUESTIONS

25 76

MEDIUM

English

Think It Over — Page 228
Chapter opener

THINK IT OVER

Q1 What do you understand by biodiversity?

Biodiversity is the immense variety of living organisms found on the Earth — from
microscopic organisms invisible to the naked eye to giant trees, from glowing jellyfish to soaring
eagles, living in countless forms and habitats.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Why it matters: biodiversity is not a list of names, it is the machinery that keeps the
planet running. The chapter gives four jobs that different groups of organisms do,
and each one is a link the rest of life depends on.

Microscopic algae in the oceans release most of the oxygen we breathe — they
photosynthesise on a scale that no forest matches.
Fungi and bacteria decompose fallen leaves and convert waste into manure,
returning minerals to the soil and making it fertile.
Birds, bees and bats pollinate flowers, so seed and fruit are set.
Plants capture sunlight and prepare the food that supports nearly all life on the
planet.

Remove any one link and the others weaken. That is why the chapter says these
interconnections sustain ecosystems and make the Earth suitable for living
organisms.

Note: biodiversity is measured at more than one level — the variety of species, the
variety within a species (the different varieties of rice a farmer keeps), and the variety
of habitats and ecosystems (mangrove, desert, coral reef). India is counted among
the world's richest countries on all three.

Q2 How does the grouping of organisms help us understand diversity?

Grouping turns an unmanageable list into a searchable structure — and because organisms
are grouped by shared features, the structure itself carries information about how they are
related.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Why it works: the chapter's own image is a library. Imagine thousands of books
scattered on the floor and you want On the Origin of Species. Without subjects,
authors and sections you would have to look at every book. Millions of organisms
are the same problem. Sorting them by shared characters does three things at once:

It compresses information. Once you know an animal is an arthropod, you
already know it has a segmented body, jointed appendages and an exoskeleton
— you do not have to learn those facts separately for every insect, crab and
spider.
It predicts. If a newly found organism has a cell wall of chitin and absorbs
nutrients, you can place it in Fungi and expect the rest of the fungal features.
It shows relationship. Similar features suggest descent from a common
ancestor, so the groups are not arbitrary boxes — they trace the actual history of
life.

Try this: group ten animals from your area by habitat, then regroup the same ten by
what they eat. The lists change. Which grouping told you more about how the
animals are built? That comparison is exactly what Activity 12.1 asks you to do.

Q3 On what basis, are plants and animals classified?

Both are classified on features that are shared because of common ancestry — scientists
start from broad, easily visible characters and then move to finer ones. The chapter lists seven
kinds of evidence.

CRITERION WHAT IS COMPARED

External features Shape, size, body organisation

Mode of nutrition Autotrophic or heterotrophic

Internal structures Skeletal patterns, presence or absence of organs, types of tissues

Cell structure Unicellular or multicellular; eukaryote or prokaryote; cell wall present or absent

Ecological role Producer, consumer or decomposer

Reproduction Asexual and/or sexual methods

Genetic similarity Similarities in inherited features, studied in detail using DNA

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Within the two kingdoms the book then applies one decisive character each:

Plantae is divided into five classes on how far the plant body has separatedefrom
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Animalia is divided first on the notochord — non-chordates (invertebrates) have none,

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chordates have one at least once in life — and then on level of organisation, symmetry, body

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cavity, segmentation and skeleton.
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Tip: a good classifying character is one that is hard to change and shared by descent.
Habitat is a poor character — a whale, a fish and a prawn all live in water but are
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Because a farmer's problems — pests, disease, poor soil, drought, pollination — are all
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How it works in practice:
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eating beetle are both Arthropoda, but correct identification down to genus

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decides whether you protect it or control it.

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Choosing the right crop variety. Farmers have for centuries conserved diverse

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varieties with useful characteristics — drought tolerance, pest resistance, the
ability to grow in nutrient-poor soils. Knowing which variety carries which
character is a classification problem, and it is why diversity reduces the risk of
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crop failure and strengthens food security.

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Using useful microbes. Rhizobium (Monera) fixes nitrogen

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Protecting pollinators. Birds, bees and bats pollinate flowers. Fruit and seed set
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depend on them, so knowing which species pollinate a crop tells a farmer what
not to spray and when.
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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Did you know? The same logic runs the other way too. Mushroom cultivation is now
a growing livelihood, but only communities with reliable knowledge of which wild
mushrooms are edible and which are poisonous can safely harvest them from the
forest — a folk taxonomy doing exactly the job scientific classification does.

Activity 12.1 — Pages 230 – 231

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Let us compare and classify — 12.3 How to Classify Organisms?

ACTIVITY 12.1

Q1 Fig. 12.2 shows the diversity of animals in an ecosystem. Observe the image
carefully. Can you guess how the organisms are grouped in the image?

DAY — the lit half NIGHT — the dark half
Canopy and open air Canopy and open air

Eagle Butterfly Dragonfly Fruit bat Owl

Trunks and branches Trunks and branches

Peacock Langur Lion-tailed macaque Python Slender loris

Forest floor Forest floor

Leopard Spotted deer (chital) Tiger
Porcupine Civet

Fireflies
Sloth bear Squirrel

Stream and its banks Stream and its banks

Small perching birds Hare Frog Crocodile

Fig. 12.2, page 230 — redrawn sketch of the textbook painting “Day and night view of an
ecosystem”. The same stretch of forest is shown twice: the lit half on the left, the same
place at night on the right, with the big trunk down the middle. Animals are drawn in
the layer of the forest in which the painting places them.

The picture is split down the middle by time of day, not by kind of animal. The left half is
the same forest in daylight and the right half is the same forest at night, so the artist has
grouped the animals by when they are active — day-active (diurnal) on the lit side, night-active
(nocturnal) on the dark side.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

How you can tell: look for animals that are obviously built for one or the other.

On the lit side — peacock, eagle in flight, spotted deer, leopard, tiger, sloth bear,
langur, lion-tailed macaque, butterfly, dragonfly, small perching birds, a hare at
the water's edge. All hunt or feed by sight in daylight.
On the dark side — bats, an owl on a branch, a python coiled on a bough, a slow
loris with huge eyes, a porcupine, a civet, a crocodile in the water, fireflies. Large
eyes, keen hearing and glowing signals are night equipment.

The habitat also groups them vertically — canopy, tree trunk, forest floor, water —
but the day/night split is the one the caption names: Day and night view of an
ecosystem.

Check it yourself: the same forest is shown twice, so any animal you can find on
both halves is active during the day and the night. That is what part (iii) of the next
question is after.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q2 Which animals can you identify in the given picture?

DAY — the lit half NIGHT — the dark half
Canopy and open air Canopy and open air

Eagle Butterfly Dragonfly Fruit bat Owl

Trunks and branches Trunks and branches

Peacock Langur Lion-tailed macaque Python Slender loris

Forest floor Forest floor

Leopard Spotted deer (chital) Tiger
Porcupine Civet

Fireflies
Sloth bear Squirrel

Stream and its banks Stream and its banks

Small perching birds Hare Frog Crocodile

Fig. 12.2, page 230 — redrawn sketch of the textbook painting “Day and night view of an
ecosystem”. The same stretch of forest is shown twice: the lit half on the left, the same
place at night on the right, with the big trunk down the middle. Animals are drawn in
the layer of the forest in which the painting places them.

Reading Fig. 12.2 at full size, the animals shown are:

GROUP ANIMALS IN FIG. 12.2

Mammals Tiger, leopard, sloth bear, spotted deer (chital), langur, lion-tailed macaque, slow loris,
porcupine, civet, bats, hare

Birds Peacock, eagle, owl, small perching birds

Reptiles Python (on a branch), crocodile in the stream

Amphibian Frog near the water's edge

Insects and other Butterflies, dragonfly, fireflies
arthropods

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

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Note: your own list may differ slightly — a picture is read, not measured. What

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matters is that you record what you actually see, exactly as a field biologist records a
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survey. Add anything you can identify that is not in the table above.
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Where are they seen?
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Each animal is drawn in the layer of the forest it actually uses, and that layer is itself a clue to

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FEATURE THAT FITS THE PLACE

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Flying high in Eagle, bats Wings; hollow bones in the bird, wing
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Flying near the Butterflies, dragonfly, fireflies, small Small light bodies; the firefly makes its own

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ground birds light

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Langur, lion-tailed macaque, slow loris, Gripping hands and feet, claws, a long
branches owl, python, perching birds balancing tail

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Crocodile, frog Streamlined body and webbed feet; moist

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Why record this: "where does it live" is the criterion Aristotle used in the 4th century
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and an eagle both fly, yet

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q4 Which animals in the picture seem active: (i) during the day? (ii) during the night?
(iii) both during the day and the night?

DAY — the lit half NIGHT — the dark half
Canopy and open air Canopy and open air

Eagle Butterfly Dragonfly Fruit bat Owl

Trunks and branches Trunks and branches

Peacock Langur Lion-tailed macaque Python Slender loris

Forest floor Forest floor

Leopard Spotted deer (chital) Tiger
Porcupine Civet

Fireflies
Sloth bear Squirrel

Stream and its banks Stream and its banks

Small perching birds Hare Frog Crocodile

Fig. 12.2, page 230 — redrawn sketch of the textbook painting “Day and night view of an
ecosystem”. The same stretch of forest is shown twice: the lit half on the left, the same
place at night on the right, with the big trunk down the middle. Animals are drawn in
the layer of the forest in which the painting places them.

WHEN ACTIVE ANIMALS IN FIG. 12.2

(i) During the day Peacock, eagle, spotted deer, langur, lion-tailed macaque, butterfly, dragonfly, small
(diurnal) perching birds, sloth bear

(ii) During the night Owl, bats, slow loris, porcupine, civet, fireflies, python
(nocturnal)

(iii) Both day and night Tiger, leopard, frog, crocodile — these appear on both halves of the picture and are
active whenever prey is available

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Why it happens: being night-active is not a habit, it is a set of structures. The owl
has very large forward-facing eyes and asymmetrically placed ear openings, so it can
locate a mouse by sound alone. Bats use echolocation. The slow loris has enormous
eyes for low light. The firefly makes its own light to signal, which is only useful in the
dark. Splitting the day this way also reduces competition — a night hunter and a day
hunter can live in the same forest and rarely meet over the same prey.

Check it yourself: if you are unsure about an animal, write "unsure" in Table 12.1
rather than guessing. An honest blank is better data than an invented entry.

Q5 Record your observations in Table 12.1.
Table 12.1: Observation table for recording the data

ORGANISM WHERE DO YOU SEE IT? WHEN DOES IT ANY
(DRAW OR (FLYING HIGH IN AIR/FLYING APPEAR TO BE VISIBLE
WRITE NEAR THE ACTIVE? FEATURE(S)
NAME) GROUND/TREE/WATER/FOREST (DAY/NIGHT/UNSURE)
FLOOR)

Owl Tree Night Feathers

Fill Table 12.1 with one row per organism. Here is a completed sample using animals from Fig.
12.2 (the book's own owl row is kept as the first line).

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

ORGANISM WHERE DO YOU WHEN DOES IT APPEAR ANY VISIBLE FEATURE(S)
SEE IT? TO BE ACTIVE?

Owl Tree Night Feathers

Eagle Flying high in air Day Broad wings, hooked beak, sharp
talons

Tiger Forest floor Day and night Striped fur, padded paws, long
canines

Spotted deer Forest floor, near Day Hooves, antlers, spotted coat
water

Bat Flying high in air Night Wing membrane between fingers,
large ears

Python Tree branch Night Long limbless body, dry scales

Crocodile Water Day and night Armoured skin, long snout, eyes on
top of the head

Porcupine Forest floor Night Long sharp quills

Butterfly Flying near the Day Two pairs of scaly wings, jointed
ground legs, coiled proboscis

Firefly Flying near the Night Glowing abdomen, jointed legs
ground

Tip: write the visible feature as a structure ("wing membrane", "quills", "hooves"), not
as a behaviour ("flies", "runs"). Structures are what classification is built on;
behaviour follows from them.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q6 Now, try grouping the same organisms in more than one way. Each time change the
criterion you are using for grouping (Table 12.2).
Table 12.2: Grouping the organisms

THE GROUPING WHICH ORGANISMS FIT WHAT FEATURE OR PATTERN
CRITERION IN THIS GROUP? HELPED YOU DECIDE?

Carnivore Eagle, tiger, leopard Eating habits

Here are four different criteria applied to the same ten animals. Notice how the membership of
the groups changes every time.

THE GROUPING WHICH ORGANISMS FIT IN WHAT FEATURE OR PATTERN
CRITERION THIS GROUP? HELPED YOU DECIDE?

Carnivore Eagle, tiger, leopard Eating habits

Herbivore Spotted deer, hare, langur, butterfly Eating habits — grinding teeth, or a
proboscis for nectar

Can fly Eagle, owl, bat, butterfly, dragonfly, Presence of wings — but of three
firefly completely different kinds

Body covered with Eagle, owl, peacock Body covering
feathers

Body covered with hair / Tiger, leopard, deer, bat, langur, Body covering; all also feed young on
fur porcupine, civet, hare milk

Jointed legs and an Butterfly, dragonfly, firefly Internal and external structure
exoskeleton (Arthropoda)

Nocturnal Owl, bat, porcupine, civet, slow Time of activity
loris, firefly

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Why it happens — and why it matters: the same organism lands in different

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groups depending on the criterion you choose. A bat is in "can fly" with the eagle,
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but in "has

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aproblem that pushes the chapter forward: scientists must choose criteria that are
fundamental — cell type, level of organisation, presence of a notochord — rather
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than criteria that are merely convenient, such as habitat or the ability to fly.
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Pause and Ponder — Page 231
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12.3.1 Some criteria to classify living organisms
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PAUSE AND PONDER

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Yes — that is the standard interpretation, provided the shared feature is a deep structural

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features in organisms suggest that they have evolved from common ancestors.

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rather than that the same complicated structure was invented twice by chance. The
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— that is a strong signal of shared

But be careful — resemblance can mislead. A shark, a dolphin and a squid are all
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streamlined, but a shark is a fish, a dolphin is a mammal and a squid is a mollusc.
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Their body shape is a shared response to water, not a shared ancestor. The wing of an

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Activity 12.2 — Page 232
Let us read a case study — 12.4 The Need for Classification

ACTIVITY 12.2

Q1 How are species distributed within a forest? Which plants and animals are closely
linked?

Species are not spread evenly through a forest — each one sits where its particular
requirements are met, so the forest is a mosaic of small, specific zones rather than one
uniform block of trees.

What the Pakke data show: the four hornbill species are found in different parts of
the same forest, and the case study names the two variables that decide where —
tree size and fruit availability. These large birds nest only in large, old trees with
suitable cavities, and each species feeds on particular fruits. Wherever a big enough
tree and the right fruiting trees occur together, that hornbill occurs; elsewhere it
does not.

Closely linked plants and animals in the Pakke example:

Large old trees ↔ hornbills. The tree supplies the nest cavity; without a cavity of the right
size the bird cannot breed at all.
Fruiting trees ↔ hornbills. The tree supplies food; the hornbill swallows the fruit and later
drops the seed far from the parent tree, so the bird disperses the seed. The link runs both
ways — this is why hornbills are called the "farmers of the forest".
Tiger ↔ deer ↔ grasses and shrubs. The reserve's food chain rests on the plants at its base.

Tip: a link that runs both ways — each partner needed by the other — is the
strongest kind. Break it at one end and both ends fail, which is what question (iii)
below asks you to work out.

Q2 How does classifying the four hornbill species help us understand biodiversity?

Because until the four are separated, the whole pattern is invisible. If a scientist records
only "hornbill", Pakke has one bird found everywhere. Once the four species are told apart, the
same forest turns out to hold four different birds, each in its own part of the wood, using

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

different trees and different fruits.

What classification buys here:

It converts a name into a count. "Nearly 300 bird species in Pakke, out of about
1,300 in the whole of India" is a measurement of richness — and it is only
possible because every one of those birds has been distinguished and named.
It lets you ask precise questions. The case study lists them: how are species
distributed within a forest, which plants and animals are closely linked. You
cannot ask either question of an unsorted heap.
It shows how the species share the forest. Four related birds coexisting means
they are not competing head-on; each has found a slightly different set of trees
and fruits. That division of resources is one of the mechanisms that lets a forest
hold so many species at once.
It makes conservation specific. "Protect hornbills" is a slogan; "protect large old
cavity trees of these species in this valley, because the Rufous-necked Hornbill
nests only there" is an action.

Q3 How can scientists keep track of so many species?

By using a system instead of memory — the same three tools the rest of this chapter builds.

1. A hierarchy. Every species is filed under Kingdom → Phylum → Class → Order → Family →
Genus → Species. Like a postal address, this narrows a search from millions to a handful in
seven steps. All four Pakke hornbills sit in the family Bucerotidae, so anything true of the
family is already known for all four.
2. A unique two-part name. Binomial nomenclature gives every species one Latin name used
worldwide, so a scientist in Arunachal Pradesh and one in France mean the same bird — no
confusion between bagh, puli, tiger and tigre.
3. Identification keys and records. Field guides, museum specimens, photographs, call
recordings and now DNA barcodes let a new individual be matched against what is already
known. Anything that does not match is a candidate new species.

Did you know? The Purple Frog of Kerala, Nasikabatrachus sahyadrensis, was
described only in 2003 — it spends most of the year underground and comes out
only in the monsoon to breed. Its existence had been missed for exactly as long as
nobody had looked in the right place at the right time.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q4 The four hornbills look similar in some ways. What features can help scientists
distinguish them from one another?

All four are large fruit-eating birds with the same body plan, so they must be separated on fine,
repeatable characters rather than on general appearance.

The casque and the bill. The horn-like casque on top of the bill differs in size, shape and
colour between species — this is the single most useful character in hornbills, and it is why
the group is named after it.
Plumage colour and pattern. The rufous (reddish) neck of the Rufous-necked Hornbill; the
black-and-white body of the Oriental Pied Hornbill; the yellow bill and neck of the Great
Hornbill; the pouch and bar pattern of the Wreathed Hornbill.
Body size. The Great Hornbill is much the largest of the four; the Oriental Pied is the
smallest.
Call. Each species has its own loud call, which is often how it is detected before it is seen.
Ecological characters. Which fruits it eats, which tree species and cavity size it nests in,
which part of the forest it occupies — as the case study says, these differ between the
species.
Genetic similarity. Comparing DNA settles the relationships when appearance is
ambiguous.

Why appearance alone is not enough: in many birds the male and female look
different, and a young bird looks different again. A character that changes with sex,
age or season is a bad character. Casque shape, call and DNA stay constant, so they
are the ones a taxonomist relies on.

Q5 What would happen if the large, old trees disappeared from the forest?

The hornbills would stop breeding, and their loss would then work its way outwards
through the forest. The case study is explicit: these large birds nest only in large, old trees with
suitable cavities.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

The chain of consequences, step by step:

1. No cavity → no nest. A hornbill cannot dig its own hole; it must find one. A big
cavity takes many decades to form. Remove the old trees and the birds have
nowhere to lay.
2. No nest → no chicks. The adult birds may survive for years, so the forest still
looks as though it has hornbills — but the population stops replacing itself.
3. No hornbills → no seed dispersal. Hornbills swallow fruits whole and drop the
seeds far from the parent tree. Without them, the seeds of many large-fruited
forest trees fall directly under the parent, where they are crowded and heavily
eaten.
4. No dispersal → fewer new trees. Over decades the tree species that depended
on hornbills decline — including, eventually, the very kinds of tree that would
have become the next generation of nest trees.
5. Other cavity users suffer too. Owls, parakeets, squirrels, bats and many insects
share these cavities. Losing old trees removes housing for all of them at once.

Notice the shape of it: the damage is delayed and self-reinforcing. Nothing dies on
the day the tree is cut, which is precisely what makes this kind of loss easy to miss
and hard to reverse.

Tip: a species like the hornbill, whose removal changes the whole forest, and a
resource like the old cavity tree, on which many species depend, are why
conservation protects habitat structure and not only individual animals.

Activity 12.3 — Page 234

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Let us study — 12.6 Five Kingdom Classification
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ACTIVITY 12.3

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Study
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Q1

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Classification of Living Organisms

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Cell type

Prokaryotes
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Primitive nucleus
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(Unbounded membrane)
Membrane-bound nucleus Eukaryotes

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Monera Level of organisation

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(Bacteria, Archaea,

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Cyanobacteria)

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Unicellular Multicellular

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(Amoeba, Paramecium,

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Protista
Chlamydomonas, Euglena)

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(May or may not

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have a cell wall)
Cell structure

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With cell wall Without cell wall

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Chitin Mode of nutrition Cellulose Heterotrophic
Ecological role Consumers
(Depend on others for food)
Heterotrophic Autotrophic
Decomposers Producers

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Animalia

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(Depend on others for food) (Process of photosynthesis)

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Ant, Snake, Frog,

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Bird, Cat, Human
Fungi Plantae

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Mushroom, Yeast, Aspergillus Mosses, Grasses, Ferns,

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Pines, Roses

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Fig. 12.5, page 234 — Five kingdom classification (the concept map redrawn; the book
a prints a photograph beside each kingdom, replaced here by the example names).

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Fig. 12.5 is a decision tree. You start at the top with any living organism and answer one

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question at each fork; after at most four questions you are standing in one of the five kingdoms.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Any living organism

1. Cell type?

Prokaryote — Eukaryote —
primitive nucleus nucleus membrane-bound

2. Level of organisation?

MONERA
Unicellular Multicellular
Bacteria, Archaea,
Cyanobacteria 3. Cell wall?

PROTISTA

Amoeba, Paramecium, Cell wall No cell wall
Chlamydomonas, Euglena
4. Nutrition?

FUNGI PLANTAE ANIMALIA
chitin wall; heterotrophic
cellulose wall; autotrophic
heterotrophic
decomposers producers consumers

Fig. 12.5 redrawn as a decision tree: four questions place any organism in one of the five kingdoms.

Read the map carefully — two details are easy to miss. Protista may or may not
have a cell wall (when present it is of cellulose), which is why the map settles Protista
on level of organisation and not on the wall. And Fungi and Plantae are separated
only at the last fork, by what the wall is made of and how the organism feeds —
chitin plus absorption for Fungi, cellulose plus photosynthesis for Plantae.

Q2 List the criteria which form the basis of five kingdom classification.

Reading Fig. 12.5 from the top down, the concept map turns on five criteria:

1. Cell type — prokaryote (primitive nucleus, no bounding membrane) or eukaryote
(membrane-bound nucleus).
2. Level of organisation — unicellular or multicellular.
3. Cell structure — cell wall present or absent, and if present, made of chitin or cellulose.
4. Mode of nutrition — autotrophic (makes its own food by photosynthesis) or heterotrophic
(depends on others for food).
5. Ecological role — producer, consumer or decomposer.

Page 20 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Why these five and not others: each one is a property of the cell or of the
organism's basic way of living, so it cannot be switched on and off by circumstances.
Contrast this with habitat or the ability to fly, which Activity 12.1 showed will put a
bat with an eagle. A bacterium cannot acquire a nucleus and a plant cannot start
eating other organisms — these are the deepest divisions available.

Q3 Compare the criteria you have listed after studying the concept map and the
criteria given below: Cell type — prokaryote or eukaryote; Cell structure — presence
or absence of a cell wall; Level of organisation — unicellular or multicellular; Mode
of nutrition — autotrophic or heterotrophic

Classification of Living Organisms

Cell type

Primitive nucleus
Prokaryotes (Unbounded membrane)
Membrane-bound nucleus Eukaryotes

Monera Level of organisation

(Bacteria, Archaea,
Cyanobacteria)
Unicellular Multicellular

(Amoeba, Paramecium,
Protista
Chlamydomonas, Euglena)
(May or may not
have a cell wall)
Cell structure

With cell wall Without cell wall

Mode of nutrition

Chitin Mode of nutrition Cellulose Heterotrophic
Ecological role Consumers
(Depend on others for food)
Heterotrophic Autotrophic
Decomposers Producers
Animalia
(Depend on others for food) (Process of photosynthesis)
Ant, Snake, Frog,
Bird, Cat, Human
Fungi Plantae

Mushroom, Yeast, Aspergillus Mosses, Grasses, Ferns,
Pines, Roses

Fig. 12.5, page 234 — Five kingdom classification (the concept map redrawn; the book
prints a photograph beside each kingdom, replaced here by the example names).

All four listed criteria appear in the concept map, in exactly the order the map uses them.
The only item on my list that is not in the four given is ecological role (producer / consumer /
decomposer), which Fig. 12.5 prints alongside mode of nutrition at the last fork.

Page 21 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

CRITERION WHERE IT ACTS IN FIG. WHAT IT SEPARATES
GIVEN 12.5

Cell type First fork, at the very top Monera (prokaryote) from all four other kingdoms
(eukaryote)

Level of organisation Second fork, on the Protista (unicellular) from Fungi, Plantae, Animalia
eukaryote branch (multicellular)

Cell structure Third fork Fungi and Plantae (cell wall) from Animalia (no cell
wall)

Mode of nutrition Fourth fork Fungi (heterotrophic, chitin wall) from Plantae
(autotrophic, cellulose wall)

Why the order is not interchangeable: the criteria are applied from the most
fundamental to the least. Having or not having a nucleus is the single biggest
difference between cells, so it splits first. Nutrition is applied last because it
separates the finest pair — and even then it must be used together with the wall
material, since a mushroom and a moss are both multicellular eukaryotes with cell
walls, and only chitin-plus-absorption versus cellulose-plus-photosynthesis tells
them apart.

Check it yourself: run yeast through the map. Eukaryote → unicellular → so it
should land in Protista. But its cell wall is made of chitin, so the book places it in
Fungi. That single exception is a good reminder that a decision tree is a summary,
not a law.

Activity 12.4 — Page 235
Let us explore — 12.6.1 Kingdom Monera

ACTIVITY 12.4

Q1 In the school laboratory, observe the available permanent slides of bacteria and
cyanobacteria under the microscope.

Place the slide on the stage, focus first on low power (10×) to find the material, then switch to
high power (45×) and finally to the oil-immersion objective (100×) if your microscope has one —
bacteria are only a few micrometres across and stay a blur at low power.

Page 22 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

What you should see:

Bacteria — extremely small, stained dots, rods or spirals. Nothing inside them is resolvable:
no nucleus, no chloroplast, no visible organelles. Often they lie in chains or clusters.
Cyanobacteria — noticeably larger, blue-green, usually as unbranched filaments of cells
joined end to end (for example Nostoc, Oscillatoria). The colour is spread through the whole
cell, not packed into chloroplasts.

Tip: use the fine adjustment only on high power, and reduce the light with the
diaphragm — unstained prokaryotes are nearly transparent and are much easier to
see in dim, contrasty light than in bright light.

Q2 Compare them with Fig. 12.6.

Fig. 12.6, page 235 — Members of the Kingdom Monera, redrawn. Four shapes are
printed, unlabelled: a grape-like cluster of round cells (cocci), comma-shaped cells
(vibrio), rod-shaped cells (bacilli) and spiral cells (spirilla).

Fig. 12.6 shows the members of Kingdom Monera. Match what is on your slide to the figure
point by point.

Page 23 of 89

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

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FEATURE BACTERIA CYANOBACTERIA (BLUE-GREEN

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ALGAE)

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Cell type Prokaryote — no membrane- Prokaryote — no membrane-bound nucleus

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bound nucleus

Level of organisation Unicellular Unicellular, often in filaments or colonies

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Size seen under the Very small dots, rods, spirals Distinctly larger; chains of cells

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microscope

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Colour Only what the stain gives Naturally blue-green

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Nutrition Mostly heterotrophic; some Autotrophic (photosynthesis) — and also act

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autotrophic as decomposers

a g
a s em
a gl Why both are in the same kingdom despite looking different: the kingdom is
decided at the first fork of Fig. 12.5 — cell type. Neither has a true nucleus, so both

om have a true nucleus and therefore goes a s
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are Monera, whatever their colour, shape or way of feeding. Compare this with an
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amoeba, which is also a single cell but

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to Protista.

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What do you observe?
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Q3

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Both are single-celled prokaryotes — no true nucleus and no membrane-bound organelles

a se
com l
— which is why both are grouped under Monera. Beyond that, the two differ in size, colour
. a g
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and how they feed.

ase
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What follows from being a prokaryote: with no internal compartments, everything
a bacterial cell does happens in one space. Its DNA lies free in the cytoplasm. This
co m
makes the cell small and simple, and also makes it fast — a bacterium can divide in
m .
m as e
l
twenty minutes, which is why bacteria colonise new conditions so quickly.
.co a g
a s emWhere these organisms live and what they do — from the chapter:
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Bacteria are found everywhere — soil, water, air, hot springs and other extreme

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environments where most organisms cannot survive, and even inside human bodies.

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They live in the gut of ruminants and are responsible for the production of biogas from the

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dung of these animals.
Some are harmful pathogens and cause diseases, but many are useful — Lactobacillus and
Rhizobium.

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m .
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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Cyanobacteria are autotrophs and decomposers; besides nutrient cycling, some bacteria
break down pollutants such as oil, pesticides and sewage.

Did you know? Cyanobacteria were among the first organisms to produce oxygen
by photosynthesis. About 2.5 billion years ago that oxygen accumulated in the
atmosphere and made the Earth suitable for other forms of life. Their fossils are
found in structures called stromatolites, and stromatolites have been found in
Rajasthan and Madhya Pradesh — some of the earliest evidence of life on the Earth.

Activity 12.5 — Pages 235 – 236
Let us make — 12.6.2 Kingdom Protista

ACTIVITY 12.5

Q1 To make a hay infusion, follow the steps given below — 1. Collect a small sample of
grass after the lawn has been mowed, or collect straw or fodder. 2. Take a small
glass bottle and fill one fourth of it with the grass, straw or fodder. 3. Fill the bottle
with stagnant water or pond water and mix it with the collected plant material. 4.
Cover the bottle with a muslin cloth and tie it using a thread. 5. Keep the bottle
aside undisturbed for a week. 6. Slightly open the mouth of the bottle by removing
the muslin cloth, just enough to insert a dropper inside it and carefully take a drop
of water. 7. Put the drop of water on a clean slide and observe it under a
microscope.

Follow the seven steps exactly. What matters is why each step is there — the activity is a small,
deliberate experiment, not just a jar of dirty water.

Page 25 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

STEP WHAT IT IS FOR

Grass, straw or Supplies dead organic matter — the food that bacteria will multiply on first
fodder

Stagnant or pond Supplies the starting protists; clean tap water would give you almost nothing
water

Muslin cloth, tied Lets air (oxygen) in but keeps insects and dust out

Undisturbed for a Time for the population to build up. Bacteria bloom on the decaying grass, then protists
week that eat bacteria multiply on them

One drop on a clean A thin film — thick water will not focus, and the organisms swim out of the plane of view
slide

Caution — follow the book's safety rule. The hay infusion may smell bad. Wear a
lab coat, mask and hand gloves, and discard the hay infusion after autoclaving.
Autoclaving kills everything in it before it goes down the drain.

Tip: take the drop from near the surface and from the edge of the floating scum, not
from the clear middle — that is where the protists concentrate. Lower a coverslip at
an angle to avoid air bubbles.

Page 26 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q2 Do you notice moving organisms in the drop of water under the microscope? Can
you identify them by comparing them with Fig. 12.7?

Amoeba Paramecium Euglena

Fig. 12.7, page 235 — Microscopic illustration of common protists, redrawn: Amoeba
(pseudopodia, no fixed shape), Paramecium (slipper-shaped, cilia all round, oral groove)
and Euglena (spindle-shaped, one long flagellum, red eyespot, chloroplasts).

Yes — the drop is full of movement, and that movement is itself the first identification
clue. Fig. 12.7 shows three of the commonest protists you will meet: Amoeba, Paramecium and
Euglena. Each moves in a completely different way.

ORGANISM HOW IT LOOKS HOW IT MOVES HOW IT FEEDS

Amoeba No fixed shape; a granular Flows slowly by pushing Heterotrophic — engulfs
blob with a visible nucleus out pseudopodia (false food particles
feet)

Paramecium Slipper-shaped, fixed Fast, spiralling, driven by Heterotrophic — sweeps
outline, covered all over beating cilia bacteria into an oral groove
with fine hairs

Euglena Spindle-shaped, green, Whips forward using a Autotrophic in light;
with a red eyespot single long flagellum heterotrophic in the dark

Page 27 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Why they are all in the same kingdom: every one of them is a single eukaryotic cell
— one cell with a true nucleus, living in water or a moist place. They differ wildly in
shape, in movement and even in how they feed, and that is exactly why Protista is
such a mixed kingdom: it is defined by cell type and level of organisation, not by
lifestyle.

Note: Euglena is the awkward one — green and photosynthetic like a plant, but
swimming and able to eat like an animal. It is precisely such organisms that broke
the old two kingdom system and forced Haeckel to add Protista in 1866.

Pause and Ponder — Page 236
12.6.2 Kingdom Protista

PAUSE AND PONDER

Q2 How can a single-celled organism carry out all its life processes when billions of
cells are required to perform similar functions in multicellular organisms like us?

Because a single cell is small enough that it does not need organs at all — it can do
everything by diffusion across its own surface, and by using organelles inside it as
miniature organs. Our billions of cells are not needed to do the jobs; they are needed because
we are large.

Page 28 of 89

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a g l
Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

co m
m.
The mechanism — surface area to volume ratio. Every cell exchanges oxygen,

m l a se
food and waste across its surface, but it uses those substances throughout its
o g area, so the
.c a body gets bigger, volume grows much faster than surface
a
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volume. As

l a se becomes too small to supply the inside.
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surface

For a sphere of radius r:
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em
. c ag
s
2 3
a
surface area = 4πr volume = (4/3)πr

Surface area / volume = 3 / rag
l
So if r is doubled, surface area per unit volume is halved.
co m
em.
m l as
.co
An amoeba is a few hundredths of a millimetre across, so its surface-to-volume ratio
a g
a s em
is enormous. Oxygen diffusing in at the surface reaches every part of it in a fraction

a gl of a second. A human is about 1.7 m tall — diffusion alone would take years to carry
oxygen from skin to heart, so we must have lungs, blood, a heart and vessels.
m a s
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What does the work inside one cell:

g l a
LIFE PROCESS
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IN A PROTIST (ONE CELL) IN US (ORGAN SYSTEMS)

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Taking in food Pseudopodia engulf it, or cilia sweep it into
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Mouth, stomach, intestine

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an oral groove

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Digestion Food vacuole with enzymes Digestive glands and gut

agl Gas exchange Straight across the cell membrane Lungs and blood

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Contractile vacuole pumps it out
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Removing excess Kidneys

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water

Movement agl
Pseudopodia, cilia or flagellum Muscles and skeleton

Energy release Mitochondria
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Mitochondria — in every one of our

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cells too

m l as
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m The point to take away: multicellularity is not an upgrade in what a cell can do — it
l a se
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divide the labour among specialised cells, tissues and organs. That is the same story
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the animal kingdom tells later in this chapter, from sponges (cellular level) up to

e m
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organ systems.

a g l

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.co


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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Bridging Science and Society — Page 237
Lichens as bioindicators — 12.6.4 Kingdom Plantae

BRIDGING SCIENCE AND SOCIETY

Q1 Have you ever seen white-green patches on the tree trunk, damp walls or stones?
What do you think about these patches? Visit a village and talk to an elderly person
about these patches.

Those patches are lichens — and both the village elder and the researcher read them the
same way: as a sign of clean air.

What a lichen actually is: not one organism but two, living in a symbiotic (mutual)
association — one partner is an autotrophic alga, the other a heterotrophic
fungus. The fungus provides protection and holds water; the alga photosynthesises
and provides food. Neither could occupy a bare rock or a dry tree trunk alone.

Why they work as pollution meters: a lichen has no roots and no waxy cuticle. It
takes everything it needs — water and minerals — straight out of the air across its
whole surface. Whatever the air carries goes in with it, including sulphur dioxide and
other pollutants, which the lichen cannot exclude or excrete. So it accumulates what
the air contains. Lichens change their colour with air pollutants, and researchers
use that colour to work out the concentration of pollutants in the air. This makes
them natural bioindicators for the measurement of air quality.

What the elder is likely to tell you (this is the part of the activity you must actually do — the
notes below are what such conversations usually contain):

The patches mean the air here is clean; where there is smoke or a factory, they disappear.
Some kinds, commonly called patthar ke phool, are collected as forest produce and used as
a spice.
Some are used as medicines.
Since ancient times some have been used to make dyes giving maroon, violet or burgundy
colour to woollen and silk fabrics.

Caution — and the reason classification matters: some lichens are poisonous.
Identifying them properly is not an academic exercise; it decides whether a collected
lichen goes into food or into a dye pot. That is precisely why the box ends by
insisting they be classified and identified correctly for safe and proper utilisation.

Page 30 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Sample answer for your notebook: "I spoke to Shri Ram Singh of our village. He
showed me grey-green crusts on the neem trunk near the well and said they grow
only where the air is good; he remembers them vanishing from the trees along the
road after the brick kiln started. His family collects a leafy kind called patthar ke
phool from the hill for use in masala. He warned that not every patch on a rock is the
same thing and that only some can be eaten."

Activity 12.6 — Page 238
Let us explore — Bryophyta, 12.6.4 Kingdom Plantae

ACTIVITY 12.6

Q1 Observe some bryophytes with the help of a hand lens. Collect them in a watch
glass.

Look for bryophytes as green mats on damp shaded surfaces — the walls of old buildings,
damp rocks, the base of trees, or the soil surface after the monsoon. Lift a small piece with a
blunt knife, keeping it damp, and put it in a watch glass.
What the hand lens shows:

The whole plant is tiny — usually only 1 to 3 cm tall.
There are thin, hair-like threads at the base that hold it to the surface. These are rhizoids —
root-like, but not true roots.
Above them, in a moss, is a slender stem-like axis with very small leaf-like structures spirally
arranged around it. In Marchantia (a liverwort) there is no such axis at all — the body is a flat
green ribbon lying on the soil.
You may see fine stalks rising from the mat with a capsule at the tip — the spore-producing
part.

Caution: collect only a small piece and leave the mat intact. A moss mat may take a
whole season to regrow.

Page 31 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q2 Put a drop of water on it and observe it under a dissecting microscope. A dissecting
microscope enables us to view magnified images of live specimens.

The drop of water does two things: it keeps the specimen alive, and it makes the very thin leaf-
like structures transparent so light passes through them.
What you should see under the dissecting microscope:

The "leaf" is usually one cell thick, so you can see the individual cells and the green
chloroplasts inside them without any staining or sectioning.
There is no midrib and no network of veins.
The rhizoids are simple threads, not branched absorbing roots.
The whole plant may spring back and unfold as it takes up water — a dry moss revives in
minutes.

Tip: a dissecting microscope gives a low magnification but an upright, three-
dimensional image of a whole living specimen. That is why it is the right instrument
here — a compound microscope would need the plant to be cut into a thin section
and would kill it.

Q3 How do they differ from the leaves that you usually observe in plants in your
surroundings?

A bryophyte "leaf" is not a true leaf at all. It is a flat, usually one-cell-thick green flap with no
veins, no midrib, no stalk and no waxy cuticle. An ordinary leaf from a neem or mango tree is
many cells thick, has a midrib with a branching network of veins, a petiole, and a waxy cuticle
with stomata.

Page 32 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

FEATURE BRYOPHYTE (MOSS) LEAF OF A FLOWERING PLANT

Thickness Usually one cell thick Many cell layers — epidermis, mesophyll,
epidermis

Veins Absent — no xylem or phloem Midrib and a branching vein network carrying
xylem and phloem

Cuticle Absent or extremely thin Waxy cuticle with stomata

Attachment Attached directly to the stem-like Attached by a petiole
axis

Water supply Absorbed directly over the whole Delivered by xylem from the roots
surface

Size of the whole A few centimetres Can be tens of metres
plant

Why it happens: every one of these differences comes from the same fact —
bryophytes have no vascular tissue. With no xylem to lift water and no phloem to
distribute food, every cell must get its water directly from the surroundings, so the
body has to stay thin and low and permanently damp. Being one cell thick is what
makes that possible. A cuticle would block the very absorption the plant depends on,
so it is not there either. And with no xylem there is nothing stiff to hold a tall body up
— which is the real reason mosses never grow into trees.

Then why do they survive at all? Bryophytes still require water for reproduction,
because the male reproductive cells must swim to reach the female cells. That is why
they are called the 'amphibians' of the plant kingdom — they live on land but cannot
yet leave water behind.

In-text Questions — Page 238

Page 33 of 89

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Pteridophyta — 12.6.4 Kingdom Plantae
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Q1
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Look at Fig. 12.11a. What changes do you observe in the plant structure as
m a g
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compared to thallophytes and bryophytes?

a g

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g l as
a
Young frond, still
coiled up (crozier)

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True leaves — a frond

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made of many leaflets

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a
True stem (rhizome)

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Soil

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True roots

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a
Fig. 12.11a, page 238 — redrawn sketch of the textbook photograph of a fern. Unlike a
thallophyte or a bryophyte, the fern has true roots, a true stem and true leaves; the
young fronds are still coiled up.

co m
m .
o m l a se
.c a g
m
se fern in Fig. 12.11a has, for the first time in the plant kingdom, true roots, a true stem

g l a
a The

m
and true leaves. Thallophytes had none of these — only a thallus, an undifferentiated body.

a se
com l
Bryophytes had rhizoids and merely stem-like and leaf-like structures. The fern has the real
. a g
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organs.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

THALLOPHYTA BRYOPHYTA PTERIDOPHYTA

Body Thallus — Slight differentiation of True roots, stems and
undifferentiated parts leaves

Anchorage None / holdfast Rhizoids True roots that absorb

Vascular tissue Absent Absent Xylem and phloem present

Height possible Very small, water- A few centimetres Up to metres — tree ferns
supported exist

Water needed for Yes Yes Yes — still
reproduction

Seeds No No No

Why the change is so large: a plant with true roots can pull water from soil that is
deeper than its own body, and a plant with a stiff stem can hold its leaves above its
neighbours. Neither is possible without a pipe system to move the water up. So the
visible change in shape — a taller, upright, divided plant — is really the outward sign
of a hidden change: the arrival of vascular tissue.

Q2 How do you think that the transport of water and food takes place in all parts of
these plants?

Through specialised transport tissue running from root to leaf tip — xylem carrying water
upward and phloem carrying food. This is the "one possible explanation" the chapter offers,
and it is the correct one.

Why some such tissue is needed at all: in a moss, every cell is within a fraction of a
millimetre of the outside, so water reaches it by diffusion. A fern frond may stand 30
cm or more above the soil. Diffusion over that distance is hopelessly slow — the
same surface-area-to-volume problem that forces animals to grow blood vessels. A
plant that grows tall must therefore build pipes.

What the two tissues do:

Xylem — hollow, dead, thick-walled tubes joined end to end. It carries water and dissolved
minerals from the roots upwards, and its lignified walls also stiffen the stem, which is what
allows the plant to stand up.

Page 35 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Phloem — living tubes that carry food made in the leaves to every other part, including
downwards to the roots, which cannot photosynthesise.

Connect it back: the fern's problem is exactly the problem the animal kingdom
keeps meeting later in this chapter. A sponge lets water flow through pores to reach
every cell; a bigger animal must build a circulatory system instead. Transport tissue
is the plant's version of the same solution.

Q3 How can you test this explanation?

Cut a thin cross section of a fern stem and look at it under a microscope. If the explanation
is right, the cut surface must show the pipes; if the fern had no transport tissue, the section
would be uniform.
Method:

1. Take a fresh fern stem (rhizome or frond stalk) and cut a very thin transverse slice with a
sharp blade — thin enough for light to pass through.
2. Mount it in a drop of water on a slide, add a coverslip, and examine under the low and then
high power of a compound microscope. A permanent slide of a fern stem cross section from
the school laboratory works equally well.
3. Look for groups of thick-walled tubes arranged in bundles.

What you find: Fig. 12.11b shows the result — the cross section carries vascular tissues,
xylem and phloem, which transport water and food respectively throughout the plant. The
prediction is confirmed.

Why this counts as a test: the explanation made a specific, checkable claim about a
structure that had not yet been observed. Looking at the section could have refuted
it — a uniform mass of similar cells would have shown the explanation was wrong.
That is what makes it a test rather than a demonstration. Making a prediction, then
looking, is the whole method the chapter uses again in Activity 12.7.

Activity 12.7 — Page 238

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Let us compare — Pteridophyta, 12.6.4 Kingdom Plantae

ACTIVITY 12.7

Q1 Recall the cross section of the sunflower stem you have studied in Chapter 3 (Fig.
3.7).

Epidermal hair

Epidermis
Collenchyma

Ground tissue
Cuticle
Parenchyma

Sclerenchyma

Sunflower (Helianthus annuus)
Phloem

Lateral meristem

Xylem

Ground tissue

T.S. of the stem

Fig. 3.7, page 32 of Chapter 3 — Internal structure of a sunflower stem, redrawn. A
wedge of the cross section magnified, and the whole T.S. below it with the vascular
bundles in a ring around a large pith.

The sunflower is a dicot angiosperm — the most advanced plant group in this chapter. Its stem
cross section, from Chapter 3, is arranged as follows:

An outer epidermis with a cuticle.
A zone of cortex below it.
The vascular bundles arranged in a ring, evenly spaced, each bundle with xylem towards
the inside and phloem towards the outside.
Between the xylem and phloem of each bundle, a strip of cambium — a layer of dividing
cells.
A large central pith.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Tip: the two things worth fixing in your mind are the ring arrangement and the
presence of cambium. Both are about to become the point of the comparison.

Page 38 of 89

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

co m
m.
Compare the cross section of the stem of a fern, a pteridophytic plant (Fig. 12.11)
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Q2

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with a cross section of sunflower stem you studied in Chapter 3 (Fig. 3.7).

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micrograph. The xylem sits inethe
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wedge of the cross section magnified, and the whole T.S. below it with the vascular
bundles in a ring around a large pith.

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m .
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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

FEATURE FERN STEM (PTERIDOPHYTA, SUNFLOWER STEM
FIG. 12.11B) (ANGIOSPERM, FIG. 3.7)

Xylem and phloem Present Present

Arrangement of Scattered bundles / a central core, Bundles in a regular ring around a central
vascular tissue not in a neat ring pith

Cambium Absent Present, between xylem and phloem

Growth in thickness Very limited — no new vascular Possible — the cambium keeps making
tissue can be added new xylem and phloem

Vessels in the xylem Mostly tracheids only Vessels present — wider, faster water
conduction

Pith Small or not clearly marked off Large and well defined

pith

Fern — scattered Sunflower — bundles
bundles, no cambium in a ring, with cambium
The same tissue, differently organised: a fern's bundles are scattered and fixed in number; a
sunflower's lie in a ring and can add more through cambium.

Page 40 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q3 What difference do you observe in the vascular tissue of the fern stem and of the
stem of higher plants? Write your observations. Share and discuss them in class.

Both have xylem and phloem — the difference is in how the tissue is organised and
whether it can go on being made.
Observations to write down:

1. The fern's vascular tissue is simpler and less organised: bundles scattered through the
ground tissue rather than a regular ring around a pith.
2. The fern's xylem consists mainly of tracheids, which are narrow; higher plants also have
wide vessels, so water moves faster and in greater volume.
3. The fern has no cambium. The higher plant has cambium between the xylem and phloem of
every bundle.

Why the cambium is the important difference: without cambium, a fern is born
with all the vascular tissue it will ever have. As the plant grows, the same fixed set of
pipes has to supply an ever-larger body — so the fern quickly hits a ceiling on how
tall and thick it can get. With cambium, a sunflower or a tree keeps adding new
xylem inward and new phloem outward every season. The pipe system grows with
the plant. That is why the largest living things on land are seed plants and not ferns,
and it is the anatomical reason wood exists at all.

Talking point for the class: the fern has solved transport but not growth in girth,
and it has not solved reproduction on land either — it still needs water for
fertilisation and makes no seeds. Each plant group in this chapter solves the
previous group's problem and leaves one of its own.

Pause and Ponder — Page 238

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Gymnosperms — 12.6.4 Kingdom Plantae

PAUSE AND PONDER

Q3 Which plant features reduce their dependence on water but still require moist
conditions?

The features that reduce dependence on water are the ones that solve transport and support;
the features that keep the plant tied to moisture are the ones connected with reproduction.
Pteridophytes are the group where these two pull in opposite directions.

FEATURE WHAT IT FREES THE PLANT WHAT IT DOES NOT SOLVE
FROM

True roots Reaching water deeper than the —
plant body; anchorage

Xylem and Carrying water and food to a tall —
phloem body, and stiffening the stem

A cuticle on the Losing water to dry air —
leaf

Motile male — The sperm must swim to the egg, so a film of water
gametes is essential for fertilisation

No seed — The spore has no stored food or protective coat, so it
can germinate only where it is already damp

Why the split exists: vegetative life and reproduction are two separate problems. A
fern's roots and vascular tissue let it grow well away from open water and stand a
metre high. But at the moment of fertilisation the male cell has to travel to the
female cell under its own power, and it can only swim. Solve transport and you can
live on land; you cannot breed on dry land until you solve fertilisation as well. That is
exactly what gymnosperms do next — and it is why the chapter titles them
"Reproduction without water".

Bryophytes fit the same pattern one step lower. They have rhizoids and a slightly
differentiated body, so they left the water; but with no vascular tissue and swimming
sperm, they need moisture both to live and to breed. Hence the name —
'amphibians' of the plant kingdom.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q4 Why do taller plants need specialised transport tissues?

Because diffusion is far too slow over long distances, and because a tall body needs
something rigid to hold it up. Transport tissue answers both needs at once.

The distance problem. Diffusion works well over fractions of a millimetre and
hopelessly badly over metres — the time taken rises with the square of the distance.
In a moss a few centimetres tall, water absorbed at the surface reaches every cell. In
a fern, a pine or a gulmohar tree, the leaves may be metres above the soil and the
roots metres below the nearest leaf. Neither end can supply the other by diffusion.

Roots absorb water — but cannot photosynthesise.

Leaves make food — but cannot reach the soil.

Xylem: water + minerals, roots → leaves.

Phloem: food, leaves → every other part, including roots.

Without both, one end of a tall plant starves and the other dries.

The support problem. Xylem is more than a pipe. Its cells have thick walls stiffened
with lignin and they die at maturity, leaving hollow, rigid tubes. Bundled together
these behave like scaffolding — the same tissue that carries the water also holds the
plant upright. A small plant can be held up by the turgor pressure of its cells alone; a
tall one cannot. This is why no non-vascular plant is tall, and why wood (which is
mostly old xylem) is what lets trees exist.

Why height is worth the cost: light. A taller plant intercepts sunlight before its
neighbours do. Every structure in this section — roots, xylem, lignin, cambium — is
part of the price plants pay to get their leaves above the competition.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

co m
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How do seeds and fruits affect, where and how plants can survive?
e
Q5

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a
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a gl free a plant from needing water to reproduce; fruits free its offspring from having
Seeds
to grow where the parent stands. Together these two structures explain why angiosperms are

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the most diverse plant group on the Earth.

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What the seed does
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ag inside a tough coat, so the new plant can survive drying,
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cold and time — it can wait, dormant, until conditions are right.

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s e m already moist
coat nor food store, which is why a fern spore can only germinate somewhere

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and sheltered.
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Inegymnosperms
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lets plants breed in dry regions.

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What the fruit does

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It encloses and protects the seeds while they mature.
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seed that germinates under its parent competes with the parent for light, water and

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minerals; a dispersed seed does not.

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How this shows in where plants live:
a g
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ag Gymnosperms — pines and cycads — are well adapted to cold and dry regions.
Their needle-like or scale-like leaves reduce water loss, and their seeds sit
se m
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exposed on cones. Fertilisation without water is what allows them there at all.
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s move the seeds. These features allow
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Activity 12.8 — Page 239
a

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Let us discuss — Angiosperms, 12.6.4 Kingdom Plantae

ACTIVITY 12.8

Q1 Collect different leaves from your surroundings, and observe their shape and
venation. Group them as monocots or dicots. Discuss how their structures help
them adapt in different conditions to survive.

Sort the leaves by venation — that single character separates monocots from dicots
reliably.

FEATURE MONOCOT LEAF DICOT LEAF

Venation Parallel — veins run side by side from Reticulate — a midrib with a branching
base to tip network

Shape Long, narrow, strap- or blade-like Broad, often with a distinct blade and
petiole

Examples you can Grass, maize, wheat, sugarcane, Neem, mango, peepal, hibiscus, tulsi, rose,
collect banana, canna, onion gram, sunflower

How the structures help them survive — points for your discussion

Parallel veins and narrow blades (monocots) bend rather than tear in wind, and shed
water quickly. Grasses grow from the base of the leaf, so the blade regrows after being
grazed or cut — one reason grasses dominate grasslands where animals feed heavily.
Broad reticulate leaves (dicots) present a large area to sunlight, so they trap more light —
an advantage in a shaded forest understorey. The branching vein network also means a torn
leaf still supplies the rest of the blade, because water can travel round the break.
Thick, waxy or reduced leaves — as in many plants of dry places — cut water loss; the
extreme case is the needle-like leaf of a pine.
Large, soft, thin leaves — as in a banana or a rainforest plant — go with plenty of water
and little wind; a banana leaf splits along its parallel veins in wind, which relieves the strain
instead of uprooting the plant.

Sample answer for the notebook: "I collected 12 leaves. Grass, maize, banana and
canna had parallel veins and long narrow blades — monocots. Neem, mango,
hibiscus, peepal, tulsi, rose, gram and sunflower had a midrib with a branching
network — dicots. The neem and mango leaves were leathery and shiny, which
reduces water loss in our dry summer, while the tulsi leaf was thin and soft and the
plant wilts quickly if not watered."

Page 45 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Activity 12.9 — Pages 239 – 240
Let us study — Table 12.3, Classes of Kingdom Plantae

ACTIVITY 12.9

Q1 Carefully study the salient features of each plant group.

Read the five groups in order and watch for the one problem each solves. Set out that way,
Table 12.3 stops being a list and becomes a sequence.

GROUP SALIENT FEATURES PROBLEM IT SOLVES

Thallophyta Body is a thallus; direct exchange of gases, nutrients and None yet — it is simply well
water with the surroundings; mostly aquatic. Example: suited to water
Spirogyra

Bryophyta Rhizoids, stem-like and leaf-like structures; no vascular Living on land — but only
tissue; water needed for reproduction. Examples: where it stays damp
Marchantia, moss

Pteridophyta True roots, stems and leaves; xylem and phloem; no Transport and support — so
seeds; water needed for reproduction. Example: fern the plant can grow tall

Gymnosperm Needle-like or scale-like leaves; seeds not enclosed in Reproduction without water,
fruits, exposed on cones; no water needed for and survival in cold and dry
fertilisation. Examples: pine, cycad places

Angiosperm Well-developed roots, stems and leaves; sexual Efficient pollination and seed
reproduction through flowers; seeds enclosed within dispersal — hence the widest
fruits; seeds dispersed by insects, birds, animals, wind or range of habitats
water. Example: gulmohar

The one line to remember: from algae to angiosperms the plant groups show a
sequence of structural changes that meet the challenges of life on land. Early plants
relied on water for support and reproduction; gradually plants evolved transport
tissues, then seeds, then flowers.

Page 46 of 89

Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q2 Analyse the salient features, and write the advantages for survival of the group and
the exceptions or challenges faced in the given columns.

Here is Table 12.3 completed. The book's own entries are kept and the blank lines are filled in.

PLANT ADVANTAGES OF THE GROUP FOR EXCEPTIONS / CHALLENGES
GROUP SURVIVAL

Thallophyta Simple plant body facilitates survival and its They cannot live on land. With no roots,
dispersal in water. The whole surface absorbs no cuticle and no vascular tissue they
water, minerals and gases directly, so no dry out at once out of water, and cannot
transport tissue is needed. Many are the grow tall or support themselves.
base of aquatic food chains and release
oxygen.

Bryophyta They are plant amphibians. Their body is They always need moisture. No vascular
adapted to live on moist land. Rhizoids anchor tissue, so they stay small and low; male
them to rock and soil, so they can colonise gametes must swim, so reproduction
bare surfaces where nothing else grows, and stops in dry weather.
they hold moisture like a sponge, which
helps soil form.

Pteridophyta They live on land. They transport food and Reproduction does not take place
water to all parts of the plant. True roots reach without water. They produce no seeds,
water deep in the soil and xylem stiffens the so the spore has no food store or
stem, so they can grow tall and hold their protective coat and can germinate only
leaves above competitors. in a damp, sheltered place.

Gymnosperm Leaves are adapted for dry conditions. They do Seeds are not covered in the form of
not require water for reproduction. They form fruits. Without a fruit there is little help
seeds for continuity of life. Needle-like leaves with dispersal, and the exposed seed is
and a thick cuticle survive cold, wind and easily eaten; pollination depends on
drought, so they dominate high mountains wind, so a great deal of pollen is wasted.
and cold regions.

Angiosperm They produce flowers, fruits and seeds. They Reproduction is dependent on
have a well-developed system for reproduction. pollination by different agents. They
They produce seeds for continuity of life. Their have complex processes through a well-
seeds are covered. Flowers attract developed tissue system. If the
pollinators, so far less pollen is wasted; pollinator disappears, seed set fails — so
fruits carry the seed away from the parent, the plant's survival is tied to another
so the offspring do not compete with it. species' survival.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

The pattern across the whole table: every advantage brings a new dependence.
Vascular tissue lets a fern grow tall, but a tall plant must now maintain a pipe
system. A seed frees the gymnosperm from water, but the naked seed is vulnerable.
A flower makes the angiosperm's reproduction efficient, but ties it to insects, birds
or bats. There is no group without a challenge — which is exactly why so many
groups still exist side by side today instead of the "best" one replacing the rest.

In-text Questions — Page 241
Porifera and Cnidaria — 12.6.5 Kingdom Animalia

Q1 Sponges remain fixed in one place and are found in aquatic environments. Do you
think they would be able to survive on land? Why or why not?

No. A sponge cannot survive on land, because every one of its life processes depends on
water flowing through its body.

Why — the mechanism: a sponge is multicellular but lacks tissues and organs. It
has no mouth, no gut, no gills, no heart, no muscles and no nervous system.
Instead, numerous pores allow water to flow continuously through it, and that
current does all four jobs at once:

it brings food particles directly to individual cells;
it brings oxygen directly to individual cells;
it carries the waste away;
it also carries the sponge's reproductive cells out and in.

Take the water away and all four stop at once. There is no organ that could take over,
because there are no organs. A land animal needs lungs or tracheae to breathe, a
gut to digest, and a waterproof covering to stop drying — a sponge has none of
these, and its body is porous, so it would dry out in minutes.

Did you know? Research studies show that one kilogram of sponge can filter up to
24,000 litres of sea water per day. That single number tells you how completely the
animal depends on the current: it is not living in water so much as living on the water
passing through it.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

co m
m.
However, cnidarians possess a single opening that functions for both food intake
e
Q2

have?.co
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and waste removal. Can you hypothesise what limitations this body structure might
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A single opening means feeding and waste removal cannot happen at the same time, and
. co ag
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digestion cannot be divided into stages. Three limitations follow.

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1. Feeding must stop while waste is expelled. The same door is used both ways, so the
animal cannot eat continuously. A gut with a mouth at one end and an anus at the other lets

m
food move in one direction and keeps the two flows separate.
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2. No specialisation along the gut. In a one-opening body cavity, all of digestion happens in a

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Why it still works for a cnidarian: a hydra or jellyfish has a thin body only two cell
em agl
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layers thick, so every cell of the inner layer touches the digestive cavity directly and
can absorb food from it —ano
once the animal gets larger and thicker. That is exactly what the next steps in the

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chapter do about it: nematodes have two openings, a mouth and an anus, which is
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the first true one-way gut in this sequence.

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In-text Questions — Page 242
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Annelida and Arthropoda — 12.6.5 Kingdom Animalia

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Their bodies are cylindrical and are divided into segments. What advantages
a c
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segmentation might offer to an organism? Observing how an earthworm moves

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may help you form a hypothesis.

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Segmentation allows greater flexibility and more precise control of movement — because
each segment can be operated separately instead of the whole body having to act as one block.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Watch an earthworm and you can see the mechanism. A wave of shortening-and-
thickening passes down the body from front to back. At any instant some segments
are long and thin (gripping the burrow ahead), others short and fat (anchoring). If
the whole body had to contract together it could only shorten in one lump and
would go nowhere. Because the body is divided, each segment has its own circular
and longitudinal muscles and its own fluid-filled compartment of the body cavity
(Fig. 12.15) to push against — so a wave can travel along the animal and drive it
forward. The nerve cord runs the length of the body with a branch to each segment,
which is what makes the timing precise.

The advantages, listed:

Flexible, wave-like movement — essential for burrowing through soil.
Precise local control, because muscles and nerves are repeated segment by segment.
A safety margin — damage to one segment does not disable the whole animal.
Room to specialise. Repeated units can later take on different jobs — which is exactly what
arthropods do, where different segments become head, thorax and abdomen with legs,
wings, antennae and mouthparts.

Note: annelids also show organ system level of organisation and possess a body
cavity. The cavity matters as much as the segments: it separates the gut from the
body wall, so the animal can move without squeezing its own intestine, and the fluid
in it acts as a skeleton for the muscles to work against.

Q2 A defining structural feature of arthropods is the development of a hard external
skeleton (rigid external covering). What advantages can the outer covering
provide?

The exoskeleton provides protection, reduces water loss and supports powerful muscles —
and together these let arthropods survive in dry and exposed environments where soft-
bodied animals cannot.

1. Protection. A rigid case shields the soft organs from predators and from physical damage.
2. Reduced water loss. The covering is waterproofed with wax. This is the decisive advantage
on land — an earthworm must stay in moist soil because it loses water through its skin; a
beetle can walk across hot dry ground.
3. Support for powerful muscles. Muscles are attached to the inside of the case and pull on it
as a lever. A rigid anchor lets a small animal generate large forces — this is why insects jump
many times their own length and why a crab's claw can crush a shell.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

4. Jointed appendages. The name says it — arthro means jointed and poda means
appendages. Hinges between rigid plates give precise, strong, controlled movement of legs,
wings and mouthparts.

The cost: a rigid case cannot grow. An arthropod must periodically moult — shed
the old exoskeleton and harden a new one — and while the new covering is still soft
the animal is defenceless. The exoskeleton is also heavy relative to its strength,
which is one reason there are no insects the size of a dog.

Pause and Ponder — Page 242
Arthropoda — 12.6.5 Kingdom Animalia

PAUSE AND PONDER

Q6 An earthworm (annelida) and a beetle (arthropoda), both have segmented bodies
but the beetle has a hard external skeleton. How does the beetle's external
skeleton help it survive?

The exoskeleton is what lets the beetle live out in the open, dry world that the earthworm
cannot enter. Both animals are segmented, so segmentation is not the difference — the rigid,
waxy external covering is.

EARTHWORM (ANNELIDA) BEETLE (ARTHROPODA)

Body Segmented, soft, cylindrical Segmented, with segments specialised into
head, thorax, abdomen

Skeleton None — a fluid-filled body cavity acts as a Hard exoskeleton
hydrostatic skeleton

Water loss High — skin must stay moist; it also Low — waxy covering seals the body
breathes through the skin

Where it can Only in moist soil; dies in the open sun Dry and exposed environments, including
live deserts

Appendages None — moves by muscle waves and Jointed legs and wings
bristles

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

The three things it does, and why each matters:

Protection. The beetle's hardened forewings and body plates are armour against
predators and against being crushed among stones and bark.
It reduces water loss. This is the crucial one. The earthworm's skin must stay
wet because it exchanges gases through it, so the worm is confined to damp soil
and comes out only at night or after rain. The beetle's waxy covering stops
evaporation, and it breathes instead through small openings that it can close.
That is why beetles are found in the driest places on the Earth.
It supports powerful muscles. Muscles pull on the inside of the rigid case, so
the beetle gets strong, precise leverage — for walking, digging, gripping and
flying. The earthworm can only push against fluid.

Tip for the exam: the question asks how it helps the beetle survive. Answer with the
three functions and then name the consequence — arthropods are the most
numerous and widespread animal group precisely because the exoskeleton solved
drying out, the biggest single obstacle to life on land.

Bridging Science and Society — Page 244
Forests as barriers against disasters

BRIDGING SCIENCE AND SOCIETY

Q1 How do forests with rich and highly diverse flora and fauna work as a barrier and
reduce the impact of disasters?

A biodiverse forest acts as three barriers at once — physical, biological and chemical. The
chapter gives one worked example of each.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

TYPE OF EXAMPLE FROM THE CHAPTER MECHANISM
BARRIER

Physical The 1999 super cyclone in Orissa: Dense mangrove roots and trunks break the force of
villages with more mangroves wind and storm surge, and hold the sediment so the
experienced less destruction shoreline is not stripped away

Biological Monkey Fever (Kyasanur Forest Many of the animals a tick feeds on are hosts in
Disease, KFD) in the Western which the virus cannot replicate. The more such
Ghats: rich biodiversity correlates species there are, the more tick bites are "wasted" on
with lower tick-borne disease risk dead-end hosts, so fewer infected ticks reach people

Chemical Forest soils and plant roots; Diverse microorganisms absorb, transform or break
mangrove soils down pollutants, improving water quality; mangrove
soils trap sediments and heavy metals, preventing
pollution from spreading into oceans and rivers

Why diversity and not just tree cover: in each case the protection comes from
having many different kinds of organism doing overlapping jobs. A single-species
plantation gives some wind break, but it has one root architecture, one set of soil
microbes and one set of animal hosts. If a pest or a disease or a salt surge takes out
that one species, the whole barrier fails at once. A diverse forest keeps working
because when one species fails, others are still doing the job. That property has a
name worth knowing: ecological redundancy, and it is what makes a diverse
system stable.

Connect it forward: this is also the reason section 12.10 treats biodiversity loss as
urgent. Losing species does not only reduce the number of names on a list — it thins
out the barrier, and the damage shows up only when the next cyclone or outbreak
arrives.

In-text Questions — Page 244

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Tiger Pea

Kingdom · Animalia Kingdom · Plantae

Phylum · Chordata Phylum · Magnoliophyta

Sub-phylum · Vertebrata Class · Magnoliopsida

Class · Mammalia Order · Fabales

Order · Carnivora Family · Fabaceae

Family · Felidae Genus · Pisum

Genus · Panthera Species · P. sativum

Species · P. tigris

Fig. 12.17 read as nested boxes: each level sits entirely inside the one above, and every step down
means fewer members but more features shared.

The inference, in the chapter's own image: this arrangement works like an
address. A house address narrows from country to state to district to street to house
number — each step is inside the last, and by the end exactly one place is named. In
the same way, Animalia → Chordata → Vertebrata → Mammalia → Carnivora →
Felidae → Panthera → P. tigris narrows from millions of animals to one species. This
lets scientists identify, compare and study organisms accurately, and understand
how they are related.

Second inference — the two pyramids have the same shape. A tiger and a pea
plant are as different as two organisms can be, yet both are filed through exactly
seven levels. The scheme is universal: it is the same ladder applied to all of life, which
is what makes comparison between distant groups possible at all.

Pause and Ponder — Page 247

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

12.9 Fossils as Evidence / 12.10 Biodiversity Under Threat

PAUSE AND PONDER

Q7 Does the term ‘biodiversity’ relate only to the variety of organisms, or does it
encompass other elements?

It encompasses much more than a list of organisms. Biodiversity is measured at three levels,
and the chapter uses all three even though it names the first most often.

1. Species diversity — the number and variety of different species. This is the obvious level:
nearly 300 bird species in Pakke, about 1,300 in India.
2. Genetic diversity, within a species — the variation among individuals of the same kind. The
chapter opens with it: for centuries farmers conserved diverse crop varieties with useful
characteristics such as drought tolerance, pest resistance and the ability to grow in nutrient-
poor soils, because diversity reduces the risk of crop failure and strengthens food security.
All those varieties are one species; the diversity is in their genes.
3. Ecosystem and habitat diversity — the variety of the places themselves. India's natural
landscape ranges from mountains in the north to desert in the west, rainforests in the North
East, plateaus in the south and long coastlines. Each region has distinct soil types and
climatic conditions, and these diverse habitats together support a wide variety of species.

Why the extra levels matter: a forest with the same number of species but no
genetic variation within them is fragile — one new disease can wipe out an entire
uniform crop, as has happened repeatedly in agriculture. And a country could in
principle keep every species alive in zoos and still have lost its biodiversity, because
the interactions — hornbill with fruiting tree, Rhizobium with pulse root, fungus
with alga in a lichen — exist only in a functioning habitat. Biodiversity includes those
relationships.

Note: the phumdis of Loktak Lake in Manipur are a good example of habitat
diversity being irreplaceable. The Sangai deer is endemic to that one floating
grassland; protecting the deer without protecting the phumdis would be
meaningless.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q8 If you find a new organism in a pond, what features will you observe to classify it
and why?

Work down Fig. 12.5 in order — from the most fundamental character to the finest — so that
each observation cuts the possibilities roughly in half.

ORDER WHAT I OBSERVE WHY — WHAT IT DECIDES

1 Cell type: is there a membrane-bound nucleus? No nucleus → Monera, and the enquiry
(needs high magnification or a stain) ends there. Nucleus present → go on

2 Level of organisation: one cell or many? Unicellular eukaryote → Protista.
Multicellular → go on

3 Cell wall: present or absent? If present, chitin or No wall → Animalia. Chitin → Fungi.
cellulose? Cellulose → Plantae

4 Mode of nutrition: is it green and making its Confirms the split between Fungi
own food, or absorbing, or ingesting? (absorption) and Plantae (photosynthesis)

5 Body organisation and symmetry; if it is an Places it within Animalia — non-chordate
animal, is there a notochord or a backbone? or chordate, and then the phylum

6 Movement, and how it feeds (pseudopodia, Narrows the group further and often names
cilia, flagella; tentacles; mouth and anus) the organism

7 Reproduction and, finally, DNA comparison Confirms the placement and shows the
closest relatives

Why this order and not another: the point of a key is that each question must be
answerable and must eliminate as much as possible. Cell type divides all of life into
two; colour or size would divide almost nothing. Starting with a fundamental
character also protects you from the trap of Activity 12.1 — that a superficial
resemblance (both swim, both are green) can put unrelated organisms together.

Practical note: in a pond sample the commonest finds are protists — Amoeba,
Paramecium and Euglena (Fig. 12.7). If your organism moves by pseudopodia, cilia
or a flagellum and is a single cell with a true nucleus, that is almost certainly where it
belongs.

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Class 9 Science Chapter 12 Patterns in Life: Diversity and Classification AglaSem · NCERT Solutions

Q9 Why do genetic studies provide deep information about living beings?

Because DNA is the instruction set itself, not one of its outward results. Every visible
character — shape, colour, mode of nutrition — is a product of the DNA, so comparing DNA
compares organisms at the level where inheritance actually happens.

Four reasons genetic evidence goes deeper than appearance:

It is the direct record of ancestry. Every living cell contains genetic material
(DNA) which carries the instructions for its growth and function, and it is copied
from parent to offspring. Organisms with similar DNA are considered to have a
common ancestry. Similar appearance may or may not mean common ancestry;
similar DNA is much harder to fake.
It sees through misleading resemblance. A dolphin looks like a fish and a bat's
wing looks like a bird's, but DNA places the dolphin and the bat firmly with the
mammals. Equally, DNA reveals hidden differences between organisms that look
identical.
It works where structure gives nothing to compare. Two bacteria may look
like identical rods under a microscope. There is almost no external character to
use. DNA gives thousands of characters instead of two.
It is quantitative. You can measure how much two sequences differ, so
relationships can be ranked, not just asserted.

What this actually changed: comparing organisms at the DNA level is exactly what
led Carl Woese, in 1977, to propose the three domain system — Bacteria, Archaea
and Eukarya. It showed that some organisms lumped together as "bacteria" were as
different from each other as either was from us, and that microscopic life forms
are far more diverse than previously believed. No amount of looking down a
microscope would have revealed that.

Q10 How can changes in climate affect the biodiversity?

Climate sets the conditions each species is adapted to. When those conditions shift faster
than species can adapt or move, populations shrink and species are lost — and because
species depend on one another, the loss spreads.

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Bridging Science and Society — Page 248
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Phumdis of Loktak Lake and the Sangai deer

BRIDGING SCIENCE AND SOCIETY
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