A tissue is a group of similar cells performing similar functions. Class 9

A tissue is a group of similar cells performing similar functions. Class 9

Question 1.

During the discussion in class, Rohan gives a statement that, “A tissue is a group of similar cells performing similar functions”. But Rajiv counter argues that, “this is true in case of simple tissues but little different in case of complex tissues”. Provide your explanation in view of the discussion in class. Class 9

Answer:

Both Rohan and Rajiv are partially correct. Rohan's statement is true for simple permanent tissues like parenchyma, collenchyma and sclerenchyma - in these, all cells are of the same type and perform the same function (e.g., all parenchyma cells store food).

Rajiv's counter-argument is correct for complex permanent tissues. Xylem is a complex tissue made of four different types of cells - tracheids, vessels, xylem parenchyma and xylem fibres. Each type of cell in xylem has a different structure and performs a different function (e.g., tracheids and vessels conduct water; xylem parenchyma stores food; xylem fibres provide support). Similarly, phloem has sieve tubes, companion cells, phloem parenchyma and phloem fibres with different structures and roles. However, all these different cells work together as a team to achieve the overall function of the complex tissue (water transport in xylem, food transport in phloem).

So a better definition would be: A tissue is a group of cells (similar or different in structure) that are organised and work together to perform one or more specific functions for the organism.