One mark questions
1. What is irritability?
A: The property of responding to changes in the environment is called irritability.
2. What are reflex actions?
A: Reflex actions are fast, immediate, automatic and involuntary responses of the body and occur without our thinking. They save
us from painful or dangerous stimuli.
3. What is epiglottis?
A: The cartilaginous flap which acts as a lid over the glottis preventing the food from entering the larynx is called the epiglottis.
4. How is trachea prevented from collapsing?
A: The walls of trachea are supported by several ‘C’ shaped cartilaginous rings which prevent the trachea from collapsing and
closing.
5. Why is spleen called the graveyard of R.B.C?
A: Spleen is called the graveyard of RBC because old red blood cells are destroyed in spleen.
Two marks questions
1. What are gyri and sulci? What is advantage of these structures?
A: Gyri: The several ridges or elevations in the cerebral cortex are gyri.
Sulci: The grooves in the cerebral cortex are sulci. They increase the surface area of the cortex so that it can accommodate more number of neurons.
2. Give an account of Tetany.
A: If the parathormone secretes in large quantities, the muscles become very active and remain the contracted state. This condition
is called Tetany.
3. What is a reaction centre?
A: In chloroplasts, the chlorophyll and other accessory pigment molecules are situated in the thylakoid membranes. These are organized to form the reaction centres called photosystem-I and photosystem-II.
4. What is an electron acceptor? Give some examples.
A: The acceptors which accept electrons are called electron acceptors.
e.g.: NAD, NADP, Cytochromes, ferredoxins.
5. What is systole and diastole?
A: Systole: The contraction phase of heart. This pumps blood into arteries.
Diastole: The relaxation phase of heart. This brings the blood vessels, chambers return to their normalcy.
Four marks questions
Four marks questions
Q. Plant growth substances act together and against each other. Give suitable examples in support of the statement.
A: Growth regulating substances act in a different manner. In many cases they act together and produce same action and sometimes they act opposite to each other.
Examples of their combined actions are given below:
1. Interaction of auxins and cytokinins together controls the differentiation of roots and shoots in tissue culture experiments.
2. Dormancy of buds and seeds is broken by gibberellins and cytokinins.
3. ABA and gibberellins regulate bud dormancy and seed germination.
4. Root growth is influenced by the levels of auxin and ethylene.
5. Cytokinins are synthesized usually in the roots and they move to
shoots through xylem and act along with auxins for promoting bud growth.
The following are the examples for the growth regulating substances which act against each other:
1. Dormancy induced by ABA in buds, tubers and many seeds can be broken by using gibberellins and cytokinins.
2. ABA and ethylene induce senescence and abscission of leaves and flowers.
3. These two processes can be delayed by the action of auxins and cytokinins.
Q. Write the differences between Red blood cells and White Blood Cells (RBC and WBC) or Erythrocytes and Leucocytes.
Redblood corpuscles
1. The cells are red in colour because of the presence of a red pigment called haemoglobin.
2. Cells are circular or biconcave in shape.
3.They are more numerous in the blood.There are about 4.5 to 5.5 ×
109cells per ml of blood.
4. They are produced in the bone marrow of long bones.
5. Life span is about 120 days.
6. They carry oxygen and carbondioxide to different tissues.
7. They cannot kill the foreign germs.
8. Only one type of cells is present.
9. Old cells are destroyed in spleen and liver
Whitebloodcorpuscles
1. They are colourless.
2. They do not have any fixed shape.
3. They are less numerous than RBC.
4. There are about 5 to 9 × 106
5. They are produced in the lymph nodes, spleen and thymus.
Life period is only 12 to 13 days.
6. They cannot carry oxygen and carbon dioxide to different tissues.
7. They can kill the foreign germs, which cause diseases.
8. Different types of cells like Eosinophils, Neutrophils and Basophils. Lymphocyte s and monocytes are present.
9. Old cells are destroyed in the blood, liver and lymph.