Biology
Give scientific reasons for the following statements:
(i) Colour blindness is more common in men than in women.
(ii) Injury to medulla oblongata leads to death.
(iii) When an ovum gets fertilized, menstrual cycle stops temporarily in a woman.
(iv) Mature erythrocytes in humans lack nucleus and mitochondria.
(v) Blood flows in arteries in spurts and is under pressure.
Answer
(i) Colour blindness is more common in men than in women because the genes responsible for the color blindness are located on the X chromosome. Males have only one X chromosome whereas females have two X chromosomes. In males, only one defective X chromosome is enough to cause colour blindness. In females, two defective X chromosomes are required to cause colour blindness. This type of inheritance pattern is called X-linked inheritance and it primarily affects males.
(ii) It regulates involuntary movements such as breathing, respiration, circulation, the function of blood vessels etc. Thus, injury to medulla oblongata leads to death.
(iii) When ovum gets fertilized, the corpus luteum continues to release progesterone and so keeps the uterus in a state suitable for implantation. The endometrium gets thickened, and vascularized to house the embryo. The fertilised egg implants itself in the endometrial lining of the uterus and gets fixed in it. This causes the menstrual cycle to stop temporarily.
(iv) The presence of nucleus would occupy space and reduce the oxygen carrying capacity. The nucleus is also not required as a mature RBC does not divide. Mitochondria is absent so that oxygen is not utilised by the RBC and all the oxygen is transported to target areas.
(v) As the ventricles of the heart contracts, they push the blood into the small lumen of the arteries with a great force, thus making the blood in the arteries flow in spurts and under pressure.
Related Questions
The given diagram shows a stage during mitotic division in an animal cell:
(i) Identify the stage. Give a reason to support your answer.
(ii) Draw a neat labelled diagram of the cell as it would appear in the next stage. Name the stage.
(iii) In what two ways is mitotic division in an animal cell different from the mitotic division in a plant cell?
(iv) Name the type of cell division that occurs during:
A. Growth of a shoot
B. Formation of pollen grainsGive the Biological / technical term for the following:
(i) Complete stoppage of menstrual cycle in females.
(ii) Pigment providing colour to urine.
(iii) The vein which drains the blood from the intestine to the liver.
(iv) The canal through which the testes descend into the scrotum just before the birth of a male baby.
(v) The process causing an undesirable change in the environment.
(vi) The removal of nitrogenous wastes from the body.
(vii) The repeating components of each DNA strand lengthwise.
(viii) An alteration in the genetic material that can be inherited.
(ix) The process of uptake of mineral ions against the concentration gradient using energy from the cell.
(x) Blood vessels carrying blood to the left atrium.
The diagram given below is that of a developing human foetus. Study the diagram and then answer the questions that follow:
(i) Label the parts numbered 1 to 3 in the diagram.
(ii) Mention any two functions of the part labelled 2 in the diagram.
(iii) Explain the significance of the part numbered 3 in the diagram.
(iv) Define the term 'Gestation'. What is the normal gestational period of the developing human embryo?
(v) Mention the sex chromosomes in a male and female embryo.
The following diagram demonstrates a physiological process taking place in green plants. The whole set up was placed in bright sunlight for several hours. Study the diagram and answer the questions that follow:
(i) What aspect of the physiological process is being examined?
(ii) Explain the physiological process mentioned in (i) above.
(iii) Label the parts numbered 1 and 2 in the diagram.
(iv) Write a well-balanced chemical equation for the physiological process explained in (ii) above.
(v) What would happen to the rate of bubbling of the gas if a pinch of sodium bicarbonate is added to the water in the beaker? Explain your answer.