Life Science Grade 12 | Essential Revision 7
Various options are given for questions below. Choose the best answer
Question: The part in the amniotic egg that provides nutrients to the developing embryo:
A, Yolk
B, Chorion
C, Amnion
D, Shell
Answer is: A
The yolk sac contains the food reserve (yolk) which is the primary source of nutrition for the embryo in an amniotic egg.
Question: Which gland is responsible for the secretion of prolactin?
A, Thyroid gland
B, Adrenal gland
C, Ovary
D, Pituitary gland
Answer is: D
Prolactin is produced and secreted by the anterior pituitary gland to stimulate milk production in females.
Question: After an accident, a person can still walk, but has poor control and coordination of the skeletal muscles. Which parts of the central nervous system are probably damaged?
(Based on the diagram: K = Cerebrum, L = Medulla Oblongata, M = Cerebellum)
A, K, L and M
B, K and L
C, K and M
D, L and M
Answer is: C
The cerebrum (K) initiates voluntary movements like walking, while the cerebellum (M) coordinates those movements and maintains balance.
Question: The cranial and spinal nerves are part of the ______ nervous system.
A, central
B, peripheral
C, sympathetic
D, parasympathetic
Answer is: B
The peripheral nervous system consists of all the nerves outside the brain and spinal cord, including cranial and spinal nerves.
Question: Which combination of characteristics occurs due to the secretion of testosterone?
(1) Growth of facial hair
(ii) Deepening of the voice
(iii) Onset of menstruation
(iv) Oily skin
A, (1), (ii) and (iii) only
B, (ii) and (iii) only
C, (1), (ii) and (iv) only
D, (1), (ii), (iii) and (iv)
Answer is: C
Testosterone is the male hormone responsible for secondary sexual characteristics like facial hair, voice deepening, and increased oil in the skin.
Question: A man is fertile if his semen contains a minimum of 20 million sperm per cm3 and at least 75% of the sperm cells are active.
A man is considered fertile when his semen contains at least twenty million sperm cells per cubic centimetre, and when a minimum of seventy-five percent of those sperm cells are active and capable of movement.
The table below shows the results of a sperm analysis of four semen
samples. Identify the sample that was obtained from an infertile
Answer is: A
Sample A has 30% inactive sperm, meaning only 70% are active. This is below the required 75% activity threshold for fertility.
Question: Which One of the following is a cause of short-sightedness?
A, The eyeball is too short.
B, The lens is unable to become less convex.
C, The lens is opaque.
D, The surface of the eye is uneven.
Answer is: B
Short-sightedness occurs when the lens is too rounded (convex) and cannot flatten enough to focus light from distant objects correctly onto the retina.
Question: A person has a disorder where she is unable to secrete ADH. It is most likely that:
A, the renal tubules will become more permeable to water.
B, the blood will have a higher volume of water.
C, large volumes of urine will be produced.
D, more water is reabsorbed by the renal tubules.
Answer is: C
Antidiuretic Hormone (ADH) increases water reabsorption in the kidneys. Without it, less water is reabsorbed, resulting in large volumes of dilute urine.
Question:Which combination of strategies applies to eagles?
(1) Internal fertilisation
(ii) External fertilisation
(iii) Precocial development
(iv) Parental care
(v) Ovipary
A, (1), (ii) and (iii) only
B, (1), (iv) and (v) only
C, (ii) and (iii) only
D, (ii), (iii) and (iv) only
Answer is: B
Eagles use internal fertilization, lay eggs (ovipary), and provide Medulla oblongata
Question: The flow diagram below represents a part of the homeostasis of compound X
Which of the following combinations is correct?
Answer is: C
When carbon dioxide levels increase, receptors in the carotid artery are stimulated and send impulses to the medulla oblongata to increase the breathing rate.