Class 7 Science Movement and Locomotion in Living Organisms
Q: What is tropism ?
A: Tropism is the directional growth response of a plant or plant part to an external stimulus, such as light (phototropism), gravity (geotropism), water (hydrotropism), or touch (thigmotropism).
Q: Plant roots move towards the earth. Give reasons.
A: The roots of the plant grow towards the earth due to gravity. Roots grow in the direction of gravity, which helps the plant to germinate firmly in the soil and effectively absorb water and nutrients.
Q: Write about the movement of the leaves of Touch-me-not.
A: The leaves of the touch-me-not plant show sesamogenesis. When touched, the leaves close rapidly and open again after a while. This movement is a defensive response that may deter predators or protect the plant from physical damage.
Q: Briefly explain the movement of different kinds of microorganisms.
A: The following is  the movement of different types of microorganisms:
- Amoeba: Moves by using temporary projections of a cell membrane and cytoplasm to form pseudopodia.
- Euglena: It has a streamlike structure called a flagellum, and it helps Euglena to swim.
- Paramoecium: It has structures called cilia on its entire body surface, which help it swim.
Q: Write down the uses of muscles in the locomotion of animals.
A: Muscles play an important role in animal movement and are used to:
- Earthworm : Due to the contraction and discharge of the muscles, a wave motion is created for drawing lines in the ground.
- Fly and Mosquito: Muscles attached to the wings help in flying.
- Snake: Up and down muscle contraction and relaxation helps in crawling.
- Birds: Strong wing muscles allow flight, and leg muscles are used for hopping or perching.
- Humans and Mammals: Muscles attached to bones help in walking, running and handling various types of locomotion.
Q: What is the process by which roots grow towards the earth?
A: Geotropism.
Q: How does the stem of a plant respond to light?
A: The stem grows towards light, a process known as phototropism.
Q: What is the movement of roots towards water called?
A: Hydrotropism.
