6. Tissues | Class 9 Science |notes

Chapter 6: TISSUES

• In unicellular organisms, a single cell performs all basic functions. E.g., in Amoeba, a single cell carries out movement, food intake, gas exchange and excretion.
• But in multicellular organisms, cells are specialised to carry out specific functions (division of labour).
• Each specialized function is performed by a different group of cells, which increases efficiency.
• A group of cells that are similar in structure and/or work together for a particular function is called a tissue. E.g., blood, phloem and muscle.

ARE PLANTS & ANIMALS MADE OF SAME TYPES OF TISSUES?

• Plants and animals differ in structure and function.
• Plants are stationary, with more supportive tissue (often made of dead cells) to stay upright.
• Animals move and have mostly living tissues, consuming more energy.
• Pattern of growth: Plant growth is limited to certain regions. Based on the dividing capacity, plant tissues are 2 types: growing or meristematic & permanent.

Cell growth in animals is more uniform. So, there is no

dividing and nondividing regions in animals.

• The structural organisation of organs and organ systems is more specialised and localised in complex animals compared to plants. This reflects the different lifestyles and feeding methods in plants and animals.
• These differences are also due to sedentary existence of plants and active locomotion of animals, leading to variations in organ system design.

PLANTS TISSUES

MERISTEMATIC (DIVIDING) TISSUE

• It is the tissue responsible for growth and cell division.

Plant growth occurs only in specific regions, such as the tips of roots and shoots, because meristematic tissue is located at these points. This can be proved by following experiment: