1) Why is control and coordination system necessary in organisms? Answer
All organisms have mechanisms to control their functions. However, in higher organisms the system required is more complex as the individual is a complex multicellular organism with the parts separated by greater distance. 2)
What is homeostasis? Answer
Homeostasis comes from two words- ‘homeo’ meaning same and ‘stasis’ meaning steady state within the body 3 )
Give examples of some of the movements shown by plants Answer
Movements as in animals is absent in plants except in cases of sperm cells of ferns and mosses swimming towards the egg. In plants, movement is association with the growth of the plants. For example, the shoot system moves towards sunlight and the root system towards earth. 4 )
What are growth regulators? Answer
Growth regulators are the chemicals that either promote or inhibit growth of the plants, their development and their responses to the environment. They are also called the phytohormones. 5)
What are the stages of growth in plants? Answer
Growth in plants has three stages: Cell division, Cell enlargement, Cell differentiation. 6 )
Name the different phytohormones. Answer
The different phytohormones are auxins, gibberellins, cytokinins, ethylene and abscissic acid 7)
What are auxins? Answer
Auxins are phytohormones that are concerned with shoot and root elongation, maintaining dormancy and apical dominance 8)
Give four major functions of auxins. Answer
Four major functions of auxins are:
- Elongation of stem and root: In high concentrations it causes stem elongation ad in low concentration, it causes root elongation.
- Apical dominance: As long as the apical buds produce auxins, the lateral buds are not allowed to grow.
- Prevention of abscission: As long as the leaves and fruits produce auxin, they remain attached to the plant. If they stop producing auxins, they fall.
- Parthenocarpy: Auxins induce the ovaries to produce fruits without fertilization and this is called Parthenocarpy. It results in seedless fruits. For example, papaya, orange, etc
What are gibberellins and where are they synthesized? Answer
Gibberellins are plants hormones that are mainly responsible for cell elongation. They are synthesized in embryos, young leaves, root tips, buds and seeds. 10)
What is the most important commercial application of gibberellins? Answer
GA-3 (gibberellic acid), a gibberellin that has been studied the most, causes the barley seeds to produce the starch- digesting enzymes like maltase, amylase. This process is called malting. It is used in the brewing industry. 11)
What are cytokinins? Give an example. Answer
They are phytohormones that induce cell division even in mature tissues. They were named ‘cytokinins’ as the cell division is also called cytokinesis. For example: zeatin, a cytokinin present in maize grains. 12 )
Give one use of cytokinins in tissue culture. Answer
Cytokinins are used in tissue culture to induce cell division in mature tissues. 13 )
Name the phytohormone that causes ripening of fruits. Give one more function of this phytohormone. Answer
The growth regulator that causes ripening is ethylene. It also promotes flowering. 14 )
Name a growth inhibitor. Give two o its functions. Answer
Abscisic acid is a growth inhibitor. Its functions are:
- It causes bud and seed dormancy
- It results in abscission of leaves and fruits
What are the control and coordination mechanisms developed in animals? Answer
The two control and coordination mechanisms developed in animals are: Nervous system, Endocrine system 16 )
How does the conduction of messages take place in?
(i) Nervous system
(ii) Endocrine system Answer
The conduction in nervous system takes place with the help of electrical impulses travelling along the nerves
The conduction in endocrine system takes place by the hormones being circulated in blood.
What are the functions carried out by the nervous system in human beings? Answer
The functions carried out by the nervous system in human beings are:
It perceives the changes around us through our senses
It controls and coordinates all the activities of the muscles in response to the changes outside.
It also maintains the internal environment of the body by coordinating the functions of the various internal organs and the involuntary muscles
It stores the previous experiences as memory that helps to think and analyses our reactions
It conducts messages between different parts of the body.
What are the units of nervous system? Answer
The units of nervous system are specialized cells called the neurons. 19 )
What is an impulse? Answer
An impulse is an electrical disturbance.