BIOLOGY [2 Mark Question Answer]

The two main functions of leaves are –
1. Photosynthesis:
Green leaves contain chlorophyll which, in the presence of sunlight, manufacture food using carbon dioxide and water.
2. Transpiration:
The surface of leaves has minute pores which help in the loss of water by evaporation. It has a cooling effect making roots absorb more water due to suction.

Modification of leaves in Venus flytrap (an insectivorous plant) The leaves of Venus flytrap have long pointed hair. It is divided into two parts having midrib in between like a hinge. When an insect visits the leaf, it closes its two parts and traps the insect. The insect is then digested by secreting digestive juices.

Simple Leaf

1. The Lamina is undivided and is a single piece.
2. Example: mango, banana, banyan, etc.

Compound Leaf

1. The leaf blade or lamina is divided into smaller units called leaflets.
2. Example: Rose, Neem, and Palm Trees

A tendril is a specialized stem, leave, or petrol with a threadlike shop. They are sensitive to touch. As they touch any object, they coil around it and support the plant to climb up.
Example: Sweet pea (upper leaflets are modified into tendrils

It helps to maintain the concentration of the sap inside the plant body: The roots continue to absorb water from the soil. If excess water does not evaporate through transpiration, the sap will become dilute, preventing further absorption of water and minerals from the soil.
Cooling effect: In transpiration, water gets evaporated from the plant. The heat required for evaporation of water is obtained from the plant itself and thus, the plant cools itself when it is hot outside.

1. Bryophyllum is a plant whose leaves produce adventitious buds in their margin.
2. The adventitious buds grow into new plants when they fall off from the parent plant.

Tranpiration: This is the process by which there is a loss of water in the form of vapour by evaporation from the surface of leaves. It has a cooling effect, it causes the suction force to make roots absorb more water with mineral ions.

The seeds dispersed by wind have fluff or tufts of hair or wings to be easily dispersed by wind.
Seeds of some plants are so light that they get easily carried away by the slightest wind to long distances.

The different agents of seed dispersal are
1. Wind: e.g. Cotton plant disperses its pollens into the air.
2. Insects: e.g. Lavender plant attracts bees to transmit their pollen from one flower to the next.
3. Water: e.g. Coconut fruit floats and gets carried away by water.
4. Animals: e.g. Hibiscus plant is pollinated by hummingbirds.

Seeds are produced in large quantities because not all of them grow into plants.
So to ensure that at least a few of them end in a favourable place for growth, plants produce more seeds than will ever become adult plants. If they don’t overproduce, the specie would die out.

Two important functions of the stem are
1. The stem bears all the aerial parts like leaves, flowers, and fruits.
2. It conducts water and minerals upwards i.e. from roots to the leaves and transports food from leaves to all parts of the plant.

Simple Leaf

1. The Lamina is undivided and is a single piece.
2. Example: mango, banana, banyan, etc.

Compound Leaf

1. The leaf blade or lamina is divided into smaller units called leaflets.
2. Example: Rose, Neem, and Palm Trees

Terminal bud:
1. The buds that grow at the tips of the stems or its branches are called terminal or apical buds.
2. They lead to an increase in the length of the stem.
Axillary bud:
1. These buds are present in the axil of a leaf i.e.-between a leaf and a stem.
2. They give rise to new branches.
3. Simple leaf and compound leaf