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BIOLOGY OBJ
01-10: DEBEBDCDAE
11-20: CCAABBBDBE
21-30: BAACEECEAC
31-40: BBDEABDEBD
41-50: DEAEEABDBE
51-60: CEBACDDCEC
COMPLETED
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INSTRUCTION: ANSWER THREE(3) QUESTIONS ONLY
(1a)
(i) Calyx (sepals)
(ii) Corolla (petals)
(iii) Androecium (stamens)
(iv) Gynoecium (carpels/pistil)
(1bi)
(i) Mouth: Mechanical digestion begins by chewing, but no significant chemical digestion of protein occurs here.
(ii) Stomach: Hydrochloric acid (HCl) denatures protein molecules, unfolding their structure, making them accessible to enzymes. The enzyme pepsin, activated by HCl, breaks peptide bonds, converting proteins into shorter polypeptides.
(iii) Small Intestine: Pancreatic enzymes like trypsin, chymotrypsin, and carboxypeptidase further break down polypeptides into smaller peptides and amino acids. These enzymes are secreted as inactive precursors and activated in the intestine.
(iv) Absorption: Amino acids are absorbed through the microvilli lining the small intestine into the bloodstream for use in body cells.
(1bii)
(i) Parenchyma
(ii) Collenchyma
(iii) Sclerenchyma
(1ci)
[TABULATE PLEASE]
=MITOSIS=
(i) Involves one cell division
(ii) Produces two identical daughter cells
=MEIOSIS=
(i) Involves two successive cell divisions
(ii) Produces four genetically different cells
(1cii)
(i) They are biological catalysts that speed up the rate of chemical reactions.
(ii) They are specific in their action.
(iii) They are affected by temperature and pH.
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(2a)
(2bi)
=AIR POLLUTANTS=
(i) Carbon monoxide (CO)
(ii) Sulphur dioxide (SO₂)
=WATER POLLUTANTS=
(i) Oil spillage
(ii) Sewage
(2bii)
(i) Marginal placentation
(ii) Axile placentation
(iii) Parietal placentation
(iv) Basal placentation
(2c)
(i) Barrier methods (condoms, diaphragms)
(ii) Hormonal methods (birth control pills, patches, injections)
(iii) Intrauterine devices (IUDs)
(iv) Surgical methods (vasectomy or tubal ligation)
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(3a)
=Opening of Stomata=
Light triggers proton pumps in guard cells to actively export H⁺ ions, creating an electrochemical gradient that causes potassium ions (K⁺) to enter the cells. The influx of K⁺ and other solutes lowers the water potential inside the guard cells, causing water to enter by osmosis and increasing turgor pressure. As the guard cells become turgid, their unevenly thickened walls cause them to bend outward, opening the stomatal pore.
=Closing of Stomata=
When water is scarce, the hormone abscisic acid (ABA) signals guard cells to release ions like K⁺, Cl⁻, and malate, increasing the water potential inside the cells. Water then leaves the guard cells by osmosis, reducing their turgor pressure and causing them to become flaccid. This loss of turgidity causes the guard cells to return to their original shape, closing the stomatal pore to reduce water loss.
(3bi)
(i) Temperature
(ii) Light intensity
(iii) Soil pH
(3bii)
(i) Kidneys
(ii) Lungs
(iii) Skin
(3cii)
(i) Knee-jerk reflex
(ii) Blinking of eyes
(iii) Withdrawal of hand from hot object
(iv) Sneezing
(3cii)
(i) Chromosomes carry genes, the units of heredity, arranged linearly along their length.
(ii) During cell division, chromosomes replicate and ensure accurate transmission of genetic information to daughter cells.
(iii) Chromosomes undergo segregation and independent assortment during meiosis, leading to genetic variation.
(iv) The DNA in chromosomes contains the genetic code that determines inherited traits, making chromosomes essential for heredity.
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(4ai)
(4aii)
Hypermetropia is an eye defect in which distant objects are seen clearly but near objects appear blurred. It occurs when light rays from nearby objects are focused behind the retina, often due to a shortened eyeball or a flat lens.
(4bi)
(i) Brightly colored petals to attract insects
(ii) Presence of nectar to reward pollinators
(iii) Strong scent or fragrance to lure insects
(iv) Sticky or spiky pollen grains that adhere to insect bodies
(4bii)
(i) Destruction of habitats and displacement of animals and plants
(ii) Waterlogging of soil leading to reduced oxygen availability for roots
(iii) Spread of waterborne diseases among humans and animals
(iv) Loss of crops and damage to agricultural land
(4c)
(i) Auxins
(ii) Gibberellins
(iii) Cytokinins
(iv) Ethylene
(v) Abscisic acid
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(5a)
(5bi)
(i) Ribosome: Site of protein synthesis.
(ii) Lysosome: Contains digestive enzymes to break down waste and cellular debris.
(5bii)
In a food chain, energy transfer from one trophic level to the next is inefficient, with only about 10% of the energy passed on. The remaining energy is lost as heat, used in metabolism, movement, respiration, or lost in undigested materials. This causes a progressive decrease in energy up the food chain.
(5biii)
(i) Presence of a semipermeable membrane.
(ii) A concentration gradient of water across the membrane.
(5c)
(i) Contour ploughing
(ii) Terracing
(iii) Crop rotation
(iv) Afforestation (planting trees)
(v) Mulching
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