re a report on it.
Aim: To prove that our body shows high sensation in different parts.
Apparatus : Cock feather.
Procedure: Take a cock feather. Touch smoothly at different parts of our body with the cock feather.
Observation : It is observed that some of the body parts like palms of hands and soles of feet there is less sensation than the other body parts because the skin is thick. Some other parts where the skin is thin, the sensation is more.
Report: The nerve endings are situated in the skin. These nerve endings are responsible for the sensation of the body.
What procedure you follow to understand the effect of plant growth hormones (in agar medium) in the terminal portion of the tip of stem (coleoptile)?
Aim: To show the growth of Avena coleoptile involves a chemical substance.
Apparatus: Oat seedlings (Avena sativa), coleoptile, a slice of agar, a sharp blade. Procedure:
- Take some oat seedlings.
- Their coleoptile tips are cut off.
- Place the tips on a slice of agar and leave them for about an hour.
- Cut the agar into small blocks and place a block on one side each stump of the decapitated plants.
- The plants were kept in the dark during the entire experiment.
- Observe the plants after one hour.
- Within one hour a distinct bending away from the side on which the agar block was placed is observed.
- Agar block that had not been contact with coleoptile doesn’t show any bending.
Conclusion : The coleoptile tip exerted its effect by means of a chemical stimulus such as an electrical impulse. This chemical stimuls came to be known as auxin.
Collect information on the actions controlled by spinal cord by using reference books from your school library.
- Spinal cord is a long and cylindrical structure. It passes through vertibral column extending all along the dorsal surface of trunk.
- Vertebrae of the vertebral column protects the spinal cord.
- The spinal cord has two major functions, a) carrying information b) coordinating reflexes.
- It receives sensory information through the afferent nerves from the sensory receptors throughout the body and send them to the brain.
- It also carries information from the brain through efferent fibres to the muscles and glands.
- It coordinates reflexes without the involvement of the brain.
Thus the spinal cord has both communicative and integrative functions.
- Excepting the sensory and motor functions spinal cord controls some other important function also. These are called as reflex actions.
- The spinal cord does not take any assistance from the brain. Reflex actions are automatic, unlearned, involuntary and in born responses.
- Therefore these actions are suddenly in nature and have a purpose of protecting the individuals or his / her organs from sudden danger.
Read the following sentences and compare with endocrine glands.
Pheromones are chemical substances secreted by organisms. These act as chemical signals secreted by exocrine glands. Pheromones are used as signals by the members of same species. Honey bee secretes pheromones that attract other bees to the location of food.
|Pheromones||Secretions of Endocrine glands (or) Hormones|
|1. Pheromones are chemical substances secreted by organisms.||1. Hormones are chemical substances secreted by endocrine glands.|
|2. These act as chemical signals.||2. These are the chemical messengers.|
|3. Pheromones are used as signals by the members of same species.||3. Hormones change or control the metabolic activities in the organisms.|
|4. Honey bee secretes pheromones that attract other bees to the location of food.||4. Hormones help for growth, and stimulated organs’ function.|
Collect the information about cranial nerves, spinal nerves from internet or from your school library.
Spinal cord :
- Spinal cord is a long and cylindrical structure passing through the vertebral column.
- The vertebrae (back bones) of the vertebral column protect the spinal cord from injuries.
- From the sides of spinal cord, 31 pairs of nerves take their origin one from each side and supply branches to various parts of the body.
- Basic function of spin