Question

I. How do plants and animals continue to grow all their lives?
II. Do all cells in a plant divide all the time?
III. Do you think all cells continue to divide in all plants and
animals?
IV. Can you tell the name and the location of tissues having cells
that divide all their life in higher plants?
V. Do animals have similar meristematic tissues?

Answer 1

Part 1: Growth in plants and animals.
The multicellular organisms like plants and animals grow by cell division. All the cells, usually involved in non-reproductive functions, multiply by mitosis. These daughter cells can themselves grow and divide, giving rise to a new population of cells. Besides, protoplasm accumulation and cell elongation also occur.

Part 2: Cell division in plants.
Growth in plants is largely restricted to specialised regions of active cell division called meristems. Differentiated cells usually lose their ability to undergo cell division until they are signalled to do so

Part 3: Cell division in animals.
In animals, cell division is exhibited by specific cells. Certain matured cells like heart cells and neurons lose their ability of continuous cell division.


Part 1: Cell division in plants.
All the cells don't divide all the time in plants. Cells present in meristematic tissues have the ability to divide. The structurally and functionally specialised cells lose their ability to divide. Such cells aggregate together to attain a common function, and are termed as permanent tissues. They regain their ability of cell division when signalled to do so.


Part 1: Cell division in plants.
No, all the cells do not divide all the time throughout their lives in plants. Growth by cell division occurs continuously throughout their life span in some specialised region known as meristems. This ensures the growth of plants throughout life. Some meristematic cells after differentiation get specialised in certain functions. The aggregation of such specialised cells to attain a common function are termed as permanent tissues. Differentiation cells usually lose their ability to undergo cell division until they are signalled to do so.

Part 2: Cell division in animals.
No, all the cells do not divide all the time throughout their lives in animals. Hormonal influence regulates growth to a certain extent. Besides, most of the matured and differentiated cells like heart cells, neurons lose their ability of division. However, epidermal cells continue to divide. Hair and nails show continuous growth indicating cell division taking place there.


Part 1:Meristematic tissue.
Meristematic tissue is the tissue having cells that have the ability to divide all their life in higher plants

Part 2: Type of meristems.
There are three broad types of meristem tissue based on their location in plants:-
Apical meristem- Tissue present at tips of root and shoot responsible for apical growth of the plant.
Intercalary meristem- Tissue present between mature tissue and at the nodes in monocots.
Secondary or lateral meristem- Present in lateral position of plants and help in secondary growth.