NCERT Book Class 9 Science Chapter 6 Tissues

C hapter 6
TISSUES
From the last chapter, we recall that all living There are noticeable differences between
organisms are made of cells. In unicellular the two. Plants are stationary or fixed – they
organisms, a single cell performs all basic don’t move. Since they have to be upright, they
functions. For example, in Amoeba, a single have a large quantity of supportive tissue. The
cell carries out movement, intake of food, supportive tissue generally has dead cells.
gaseous exchange and excretion. But in multi- Animals on the other hand move around
cellular organisms there are millions of cells. in search of food, mates and shelter. They
Most of these cells are specialised to carry out
consume more energy as compared to plants.
specific functions. Each specialised function
Most of the tissues they contain are living.
is taken up by a different group of cells. Since
Another difference between animals and
these cells carry out only a particular function,
they do it very efficiently. In human beings, plants is in the pattern of growth. The growth
muscle cells contract and relax to cause in plants is limited to certain regions, while this
movement, nerve cells carry messages, blood is not so in animals. There are some tissues in
flows to transport oxygen, food, hormones and plants that divide throughout their life. These
waste material and so on. In plants, vascular tissues are localised in certain regions. Based
tissues conduct food and water from one part on the dividing capacity of the tissues, various
of the plant to other parts. So, multi-cellular plant tissues can be classified as growing or
organisms show division of labour. Cells meristematic tissue and permanent tissue. Cell
specialising in one function are often grouped growth in animals is more uniform. So, there
together in the body. This means that a is no such demarcation of dividing and non-
particular function is carried out by a cluster dividing regions in animals.
of cells at a definite place in the body. This
The structural organisation of organs and
cluster of cells, called a tissue, is arranged and
organ systems is far more specialised and
designed so as to give the highest possible
localised in complex animals than even in very
efficiency of function. Blood, phloem and
muscle are all examples of tissues. complex plants. This fundamental difference
A group of cells that are similar in structure reflects the different modes of life pursued by
and/or work together to achieve a particular these two major groups of organisms,
function forms a tissue. particularly in their different feeding methods.
Also, they are differently adapted for a
6.1 Are Plants and Animals Made sedentary existence on one hand (plants) and
active locomotion on the other (animals),
of Same Types of Tissues? contributing to this difference in organ system
Let us compare their structure and functions. design.
Do plants and animals have the same It is with reference to these complex animal
structure? Do they both perform similar and plant bodies that we will now talk about
functions? the concept of tissues in some detail.