GATE 2026 Question Paper Ecology and Evolution (EY)

FOR GATE EXAM PREPARATION

GATE 2026
Question Paper ·
Ecology Evolution (EY)
EXAM YEAR TYPE SUBJECT

GATE 2026 Question Paper Ecology Evolution (EY)

Notes · Sample Papers · Previous Year Papers · Mock Tests

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General Aptitude (GA)
Q.1 – Q.5 Carry ONE mark Each

Q.1 Expedite, Hasten, Hurry, __________

Fill the blank by choosing a word with a meaning similar to that of the words
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given above.

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(A) a Accelerate

(B) Retard

(C) Provide

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(D) Disable

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Q.2 A black square PQRS has been cut into two parts. One part of it is shown in
Panel I. Which one of the shapes in Panel II is the other part?

(A) (i)

(B) (ii)

(C) (iii)

(D) (iv)

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Q.3 A day can only be cloudy or sunny. The probability of a day being cloudy is 0.5,
independent of the condition on other days. What is the probability that in any
given four days, there will be three cloudy days and one sunny day?

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(A) 1/4

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(B) a 3/4

(C) 2/3

(D) 3/8

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Q. 4 The values of Stock A and Stock B on a particular day are Rs. 50 and Rs. 80,
respectively. An investor invests Rs. 100 in Stock A and Rs. 80 in Stock B. He
sells all the stocks the next day when the value of Stock A is Rs. 55 and Stock B
is Rs. 70. The profit made by the investor is Rs. ________

(A) 0

(B) 5

(C) 10

(D) 20

Q.5 ‘When it is raining, peacocks dance.’

Based only on this sentence, which one of the following options is necessarily
true?

(A) Peacocks dance only when it is raining.

(B) When peacocks dance, it is raining.

(C) When peacocks are not dancing, it is not raining.

(D) When it is not raining, peacocks do not dance.

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Q.6 – Q.10 Carry TWO marks Each

Q.6 Water : P :: Food : Q

Choose the P and Q combination from the options below to form a meaningful
analogy.
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(A)
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P =aThirst; Q = Hunger
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(B) P = Drink; Q = Hunger

(C) P = Thirst; Q = Satiated

(D) P = Wet; Q = Critic

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Q.7 Two tiles are missing in Panel I. Which one of the options in Panel II is the
appropriate choice for the missing tiles?

(A) (i)

(B) (ii)

(C) (iii)

(D) (iv)

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Q.8 Figures (i) and (ii) represent intercity highway systems. The black dots represent
cities and the line segments between them represent intercity highways.
A salesperson needs to make a trip. She needs to start from a city, visit each of the
remaining cities exactly once, and finally return to the same city from which she
started.

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Which one of the following options is then true?
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(A)
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Such a trip is possible for (i), but not for (ii).

(B) Such a trip is possible for (ii), but not for (i).

(C) Such a trip is possible for both (i) and (ii).

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(D) Such a trip is possible neither for (i) nor for (ii).
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Q. 9 The figure in Panel I below is a grid of cells with four rows and four columns.
The numbers on the top and on the left represent the number of cells that are to
be shaded in that column and row, respectively. Which one of the options shown
in Panel II below represents the grid shaded correctly?

(A) (i)

(B) (ii)

(C) (iii)

(D) (iv)

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Q.10 An unbiased six-faced dice whose faces are marked with numbers 1, 2, 3, 4, 5,

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and 6 is rolled twice in succession and the number on the top face is recorded
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each time. The probability that the sum of the two recorded numbers is a prime
number is ________
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(A) 3
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(B) 13
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Q.11 – Q.35 Carry ONE mark Each

Q.11 Two sister species, A and B, are distributed along a continuous elevational
gradient in the Himalayas. Species A is distributed from the foothills to 1800
metres above sea level and species B is distributed from 1800 to 3500 metres
above sea level. Which one of the following modes of speciation best explains
their distribution?

(A) Sympatric speciation

(B) Allopatric speciation

(C) Parapatric speciation

(D) Peripatric speciation

Q.12 Which one of the following is an invasive plant species in India?

(A) Lantana camara

(B) Myristica malabarica

(C) Terminalia tomentosa

(D) Santalum album

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Q.13 Phytoecdysone is a defensive secondary chemical that __________.

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(A) mimics a neurotransmitter and can cause paralysis or even death in caterpillars

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(B) mimics insect hormones and interferes with insect metamorphosis

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belongs to a category of tannins and reduces the digestibility of plant tissues

(D) belongs to a category of lignins and deters herbivores

Q.14
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The physiologist Ivan Pavlov conducted an experiment on dogs, in which a bell

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was sounded every time food was provided. In this experiment, dogs eventually

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showed the salivary reflex (a response to food) when the bell was sounded, even if
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food was not provided. This is an example of ________.
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(A) conditioning

(B) imprinting

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(C) instinct

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Q.15 Ecologists have studied the distributions of birds on archipelagos. Some studies
found an interesting ‘checkerboard’ pattern within island groups. Sister species
were never present on the same island, even when the islands were very close to
each other. Which one of the following processes best explains this checkerboard
pattern?

(A) Mutualism

(B) Competition

(C) Predation

(D) Commensalism

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Q.16 Which one of the following phylogenetic trees illustrates the relationship between
Archaea, Bacteria and Eukarya?

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(B) Q

(C) R

(D) S

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Q.17 The Biological Species Concept was proposed by _________.

(A) Ernst Mayr

(B) Ronald Fisher

(C) Sewall Wright

(D) J. B. S. Haldane

Q.18 In a diploid population of N individuals, the probability of fixation of a new neutral
mutation (assuming no other mutation occurs) is _________.

(A) 1/N

(B) 2/N

(C) 1/(2N)

(D) 1/(4N)

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Q.19 Species that co-occur in space and time tend to be similar to each other in traits
such as tolerance to heat or to drought. This is most likely because of _________.

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(A) limiting similarity
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(B) divergent evolution

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(C) aenvironmental filtering

(D) competitive exclusion

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Q.20 Which one of the following statements is true for most ants and bees?

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(A) Males are diploid and develop from fertilised eggs

(B) Males are haploid and develop from fertilised eggs

(C) Females are diploid and develop from fertilised eggs

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(D) Females are diploid and develop from unfertilised eggs
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Q.21 Which one of the following concepts describes a co-evolutionary arms race
between a pathogen and its host?

(A) Red Queen hypothesis

(B) Green Beard model

(C) Sympatric speciation

(D) Reinforcement

Q.22 A flask containing nutrient-rich media is seeded with 100 isogenic bacteria.
Assuming that no bacteria die in the flask, after approximately how many
generations will the population reach a size of 105?

(A) 10

(B) 1000

(C) 100000

(D) 1

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Q.23 The field of allometry assesses how species traits scale with each other. Given the
relationship between metabolic rate and body mass, which one of the following
statements is true?

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Elephants expend more energy per gram per hour than mice do
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(C) Elephants expend less total energy per day than mice do

(D) Humans and elephants expend similar amounts of total energy per day

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Q.24 According to life history theory, when parents
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and care to their offspring, the number and size of the offspring are expected to be

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___________.
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(A) negatively correlated

(B) positively and linearly correlated
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(C) uncorrelated

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(D) positively and exponentially correlated

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Q.25 Which one of the following elements cycles the LEAST (mass per year) through
the atmosphere?

(A) Carbon

(B) Nitrogen

(C) Phosphorus

(D) Sulphur

Q.26 The colour and markings of the eggs of the common cuckoo (Cuculus canorus) are
similar to those of the eggs of the great reed warbler (Acrocephalus arundinaceus).
Which one or more of the following options explain(s) this similarity?

(A) The two species are closely related and belong to the same genus

(B) The two species compete for the same insect larvae to feed their chicks

(C) The common cuckoo is a brood parasite of the great reed warbler

(D) The great reed warbler is a predator of the common cuckoo

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Q.27 Which one or more of the following is/are NOT essential for evolution by natural
selection to take place in a population?

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There must be variation in the trait
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(B) The trait must be linked with differential reproductive success

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(C) aThe trait must be either fully or partially heritable

(D) The population must comprise of sexually reproducing organisms

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Q.28 In a null hypothesis significance test, the significance level α was set to 0.01. For

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which one or more of the following p values would the null hypothesis be rejected?
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(A) p = 0.004

(B) p = 0.02

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(C) p = 0.10

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p = 0.009
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Q.29 Which one or more of the following benefits can explain the evolution of dispersal
of animals from their natal area?

(A) Reduced competition with kin

(B) Increased predation risk outside natal areas

(C) Inbreeding avoidance

(D) Outbreeding avoidance

Q.30 Which one or more of the following is/are signalling mechanism(s) that birds are
known to use to beg their parent for food?

(A) Playing dead

(B) Vocalisations

(C) Fluttering of wings

(D) Mouth gape and colouration

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Q.31 Which one or more of the following diseases is/are zoonotic?

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(A) Nipah virus infection

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Cholera

(D) Kyasanur Forest Disease

Q.32
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vulnerable to extinction?

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(A) Inbreeding depression

(B) Demographic stochasticity

(C) Intraguild predation

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(D) Continuous population growth
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Q.33 In a population of birds, the proportion of blue individuals is 0.4 and the proportion
of males is 0.3. Assuming that colour and sex are independent of each other, the
probability that a randomly sampled individual from this population is a blue male
is ______

(Round off to two decimal places)

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Q.34 Assume that the human haploid genome is 3 × 109 base pairs long. The mutation
rate, when DNA is copied, is 5 × 10−11 per base pair per replication. Based on these
numbers, the expected number of mutations that take place per replication of the
human haploid genome is _______

(Round off to two decimal places)

Q.35 The coefficient of relatedness r is the probability that a gene in one individual is
identical by descent with a gene in another individual. In a large, diploid, sexually
reproducing population with outbreeding, the value of r for two offspring with the
same mother but different fathers is __________

(Round off to two decimal places)

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Q.36 – Q.65 Carry TWO marks Each

Q.36 Living in groups confers benefits but also imposes costs. The figure below depicts
how per capita benefits (solid line) and costs (dashed line), both measured in the
same units, vary as a function of group size. Given these patterns in benefits and
costs, which one of the group sizes P, Q, R, S best represents the optimal group
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(A) P

(B) Q

(C) R

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Q.37 The table below provides the abundances of species 1 to 10 for communities
P, Q, and R, with a total of 100 individuals in each community. The Simpson’s
diversity index D for each of these communities can be calculated using the
formula: D = 1 − Σ𝑖 𝑝𝑖2 , where 𝑝𝑖 is the proportion of individuals in the
community that belong to the ith species.

Species Community P Community Q Community R
1 69 45 70
2 18 43 21
3 5 4 4
4 4 4 3
5 1 1 0
6 1 1 0
7 0 0 1
8 1 1 0
9 0 0 1
10 1 1 0

Which one of the following statements is true about the comparison of Simpson’s
index between these communities?

(A) P is more similar to Q than either of them is to R

(B) P is more similar to R than either of them is to Q

(C) Q is more similar to R than either of them is to P

(D) P, Q, and R are equally similar to each other

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Q.38 Many species of reef fish change sex once during the course of their lives. In these
fish, big body size increases competitive ability. When high male-male competition
results in high variance in fitness among males, which one of the following
scenarios is most likely?

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(A) Fish start their reproductive life as females and become males at larger sizes

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(B)
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(C) Female-female competition leads to male sterility

(D) Male-male competition does not influence the sequence of sex change in an
individual

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Q.39 When comparing life-history traitsaacross animal species, which one of the
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following relationships is LEAST

(A) Development time is positively correlated with age at first reproduction

(B) Development time is negatively correlated with lifespan
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(D)

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Q.40 Two isolated populations M and N have population sizes of 100 and 1000
individuals, respectively. The starting allele frequencies p and q are 0.5 in both
populations. Assuming no selection, which one of the following is expected after
100 generations?

(A) p is expected to be higher than q in population M but not in population N

(B) p is expected to be lower than q in population M but not in population N

(C) 2pq in population M is expected to be higher than 2pq in population N

(D) 2pq in population M is expected to be lower than 2pq in population N

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Q.41 Two bacterial variants are growing together in the same flask. At any relative
frequency of the two variants, the population growth rate of the rarer variant is
higher. The above is an example of ________.

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(A) sexual selection
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(C) negative frequency-dependent selection

(D) positive frequency-dependent selection

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Q.42 The graph below shows a plot of annual rainfall on the X axis and number of plant
species on the Y axis. Based on the pattern in the graph, which one of the following
statistical methods would be most appropriate to model the relationship between
annual rainfall and the number of plant species?

(A) Kruskal-Wallis test

(B) Student’s t-test

(C) Linear regression

(D) Chi-squared test

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Q.43 The phylogeny of six species of birds is illustrated below, where the horizontal
branch lengths correspond to genetic distance. These six species are distributed in
three islands X, Y, and Z. Island X harbours species 1, 4, 6; Island Y harbours
species 1, 2, 4; and Island Z harbours species 3, 4, 5. Which one of the following
is true about the phylogenetic diversity of these islands?

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(A) X>Y>Z
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(B) X<Y<Z

(C) X > Y and Z > Y

(D) X < Y and Z < Y
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Q.44 Terrestrial biomes such as tundra, taiga, temperate forests, and tropical forests are
distributed in different parts of the world. Which one of the following options best
represents the environmental factors that determine the distribution of these
biomes?

(A) Temperature and elevation

(B) Rainfall and wind

(C) Temperature and rainfall

(D) Fire and elevation

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Q.45 In a population, the frequency of an allele changes with time as given in the table:

Year (x) 0 10 20 30 40

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Allele 0.1 0.2 0.3 0.4 0.5
frequency (y)
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Which one

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(A) y = 0.01x + 0.1

(B) x = y + 0.1

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(C) x = 0.1 + 0.01y

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Q.46 Despite their striking morphological similarity to each other, Old World and New
World vultures are not phylogenetically related. Old World vultures are most
closely related to eagles, while New World vultures are most closely related to
storks. The morphological similarity between Old World and New World vultures
is an example of ____________.

(A) adaptive radiation

(B) cladogenesis

(C) divergent evolution

(D) convergent evolution

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Q.47 The distributions of beak size in a bird population at two different times are shown
below. In going from time t = 0 to t = t1, the variance of the distribution in beak size
in the population has _________.

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(A) increased

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(B) decreased
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(C) reduced to zero

(D) stayed the same

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Q.48 Percent sequence divergences between two sister species were calculated for an
exon (E), intron (I), and the flanking neutral (N) region of a gene under purifying
selection. Which one of the following options best describes the expected
divergence in E, I, and N between the sister species?

(A) E>I>N

(B) E>I=N

(C) E<I=N

(D) E=I>N

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Q.49 Islands typically have higher species extinction rates and are more isolated than the
mainland. In the figures below (P, Q, R, S), the solid line denotes the relationship
between species richness and increasing area within a mainland; the dashed line
denotes the relationship between species richness and islands of different sizes.

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Which one of the figures above represents the most likely relationships?
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(A) P

(B) Q

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(C) R

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(D) S

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Q.50 A bacterium can be approximated as a cylinder with a hemisphere at each end, as
shown in the figure. The cylinder has a height of 1 µm and diameter of 1 µm.
Assuming that the density of the bacterium is equal to that of water, what is the
approximate mass of this bacterium?

Given: density of water = 103 kg/m3; 1 µm = 10-6 m

Volume of a cylinder = 𝜋𝑟 2 ℎ, where r is the radius and h is the height of the
cylinder
4
Volume of a sphere = 𝜋𝑟 3, where r is the radius of the sphere
3

(A) 10–12 kg

(B) 10–18 g

(C) 10–15 kg

(D) 10–15 g

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Q.51 Students M and N sampled body lengths of two populations of a fish species using
the same study design. A summary of their data (mean ± standard error) is shown
below.

Body length (cm)
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Student N 10.0 ± 0.6 5.1 ± 0.3

Given that the data are normally distributed, when comparing the means of the
populations using a t-test, which student will find a lower p-value?

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(A) Student M
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(B) Student N a
(C) Insufficient information to comment

(D) p-values will be zero in both cases

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Q.52 Forest patches are embedded within a landscape dominated by crop fields. The crop
fields around fragmented forest patches are thought to affect the abundance of
different butterfly species to different extents. The graph below shows the pattern of
butterfly abundance (means, and error bars representing 95% confidence intervals)
of three species, M, N, and O between the forest patches and the crop fields.

Which one of the following options best describes the impact of fragmentation on
the three different butterfly species?

(A) M – strongly positive; N – weakly negative; O – strongly negative

(B) M – strongly negative; N – weakly positive; O – strongly positive

(C) M – strongly negative; N – weakly positive; O – strongly negative

(D) M – strongly negative; N – weakly negative; O – strongly positive

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Q.53 Many species in mountain ranges are shifting their ranges to higher, cooler
elevations in response to warming temperatures because of climate change. The
graph below shows how the midpoint of elevational range in the year 2025 is
related to the midpoint of the elevational range in the year 2000 for species in
temperate (open circle) and tropical (solid circle) mountain ranges. Each point

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represents a species, and the dashed line is the 1:1 or the identity line (with

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intercept = 0 and slope = 1).
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Which one of the following statements is consistent with the above graph?

(A) Tropical species are more sensitive than temperate species to temperature change

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(B) Temperate species are more sensitive than tropical species to temperature change

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(C) Both tropical and temperate species are equally sensitive to temperature change

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temperate species to temperature change

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Q.54 Two species of butterflies are equally toxic to their main potential predator. Their
morphological similarity helps to reduce predation rates on both species. This
phenomenon is known as _________.

(A) Batesian mimicry

(B) Müllerian mimicry

(C) parasitism

(D) sensory overload

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Q.55 The phylogeny below shows the relationship between six species based on whole
genome data. The sequence of a part of a particular gene from each species is
provided at the tips of the tree. Based on the principle of parsimony, which one of
the following is the expected sequence for the ancestor X?

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(A) ATGG

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(B) AACG

(C) AGCG

(D) AATG

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Q.56 Consider a predator encountering two prey types P1 and P2. Assume the energy
value of P1 is greater than that of P2. Assume also that the search time to find each
prey type is inversely proportional to its abundance in the habitat. The prey-choice
model in optimal foraging theory evaluates whether the predator should specialise
on P1 or generalise to feed on both P1 and P2. This model predicts specialising on P1
when:

𝐸1 𝐸2
>
𝑆1 + ℎ1 ℎ2

where 𝐸1 is the energy value of P1; ℎ1 is handling time for P1; 𝐸2 is the energy value
of P2; ℎ2 is handling time for P2; 𝑆1 is the search time for P1.

According to the condition given above, which one or more of the following
options does the decision to specialise on P1 depend on?

(A) Handling time of P1

(B) Handling time of P2

(C) Abundance of P1

(D) Abundance of P2

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Q.57 In some insect species, males are much larger than females. Which one or more
of the following evolutionary hypotheses can explain such male-biased size
dimorphism?

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(A)
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Body size provides a competitive advantage to females, but not to males
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(B)
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(C) Clutch size is positively correlated with body size in females

(D) The mating success of males and females is not related to body size

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Q.58 A researcher is interested in understanding whether multi-species sociality (in
which species form cohesive groups with other species) plays a role in helping
species cope with habitat disturbance. She estimates the survival rates of social
species and solitary species in undisturbed and disturbed habitats, and these are
plotted in the graph below. Circles represent mean survival rates and error bars
represent 95% confidence intervals.

Based on the means and confidence intervals presented in the graph (α = 0.05),
which one or more of the following can be reasonably concluded?

(A) There is no evidence that the survival rates of social species are different between
undisturbed and disturbed habitats

(B) Solitary species have lower survival in disturbed habitats

(C) There is no evidence that the survival rates of social and solitary species are
different from each other in undisturbed habitats

(D) There is no evidence that the survival rates of social and solitary species are
different in disturbed habitats

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Q.59 A research group studied the timing of Arctic ground squirrel emergence from
hibernation. They collected data over a 25-year period and found that female and
male ground squirrels differed in how variable their emergence times were. Across
years, no matter what the above-ground temperatures were, male ground squirrels
emerged in the same week in April. Females usually emerged during the same week

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as the males if it coincided with snowmelt; but in colder years, they re-entered

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hibernation and emerged later after snowmelt. Which one or more of the following
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statements is/are possible proximate cause(s) for this phenological pattern?

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(A)
aMales build up testosterone before emergence, which inhibits them from
re-entering hibernation

(B) Early emergence helps males increase their reproductive success by gaining
early access to females

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(C) Hibernating females respond to both hormonal levels and environmental cues

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(D)
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Female fecundity is negatively affected by colder temperatures

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Q.60 A native species of butterfly at one site in North America used to feed on plant
species P. In the 1960s, an exotic plant species Q was introduced at this site. The
butterfly switched to feeding on Q, so much so that it was no longer found feeding
on P. When the plant species Q was removed from the site in the 1990s, the
butterfly species went locally extinct. Later, a population of the same butterfly
species from elsewhere, that still fed on plant P, came and occupied the same site.
Which one or more of the processes listed below has/have occurred here?

(A) Re-colonisation

(B) Local extinction

(C) Inbreeding depression

(D) Changing trophic levels

Q.61 Species 1 and 2 belong to the same genus and co-occur at the same site. Which one
or more of the following strategies would facilitate their coexistence at the site?

(A) Species 1 has high frequency calls, Species 2 has low frequency calls

(B) Species 1 and 2 specialise on the same limited resource

(C) Species 1 nests near the ground, Species 2 nests in the canopy

(D) Species 1 and 2 breed at different times of the year

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Q.62 A researcher carried out an experiment to study how daylength and temperature
influence diapause in a moth species. He placed larvae in one of four treatment
conditions for 2 weeks, with 30 larvae in each condition. The treatments involved
two temperatures (18 °C or 27 °C) and two lighting conditions (12h:12h Light:Dark
(LD) or complete darkness (DD)). At the end of the experiment, he counted the

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number of larvae that had entered diapause and those that had not. The data are

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shown below.
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Larvae in Larvae NOT in
e Condition
s Treatment 1 l a
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diapause diapause
l a
ag 27 °C, 12:12 LD 2 28

Treatment 2
7 23
18 °C, 12:12 LD
Treatment 3
12 18
27 °C, DD
Treatment 4
29 1
18 °C, DD
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. can he reasonably make from these
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Which one or more of the following conclusions
findings?
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(A) Diapause is independent of abiotic conditions

(B) Only temperature influences diapause

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(C) Only daylength influences diapause
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Q.63 Population growth of a species can be modelled as

𝑑𝑁(𝑡) 𝑁(𝑡)
= 𝑟𝑁(𝑡)(1 − )
𝑑𝑡 𝐾
where 𝑁(𝑡) is the population size at time 𝑡; 𝑟 is the growth rate; and 𝐾 is the
carrying capacity of the environment.
𝑑𝑁(𝑡)
For 𝐾 = 9000, is maximized at 𝑁 = _____
𝑑𝑡

(Answer in integer)

Q.64 The genome of a diploid species has 10 genes. In a population of this species, if
each gene has two unique alleles, then the number of possible unique genotypes in
this population is ______

(Answer in integer)

Q.65 Bob is studying the effect of coral and sponge species on reef ecosystems using
experiments in artificial square tanks. In each tank, he places 3 species of corals and
2 species of sponges. If there are 6 species of corals and 5 species of sponges to
choose from, the minimum number of tanks required to test all combinations of
3 coral and 2 sponge species is _______

(Answer in integer)

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