NABTEB 2024 BIOLOGY (ESSAY & OBJ) ANSWERS

PART I
(1i)
To demonstrate osmosis using a non-living membrane, an experiment using a dialysis tubing as the membrane is set up. Fill the tubing with a concentrated solution of sugar or salt and immerse it in a beaker of water. Over time, water molecules would pass through the dialysis tubing membrane from the beaker into the concentrated solution, showing the movement of solvent molecules from an area of high concentration to an area of low concentration.

(1ii)
(i) Osmosis helps in maintaining proper water balance in cells, ensuring they function efficiently.
(ii) It aids in the transportation of nutrients and molecules across cell membranes.
(iii) Osmosis plays a crucial role in regulating the internal environment of organisms by controlling the movement of water and solutes.

(1iii)
(Draw the diagram)

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*PART II*

(2a)
(i) Positive phototropism is the growth or movement of an organism towards a source of light. An example of positive phototropism is the way plants grow towards sunlight to maximize their energy intake for photosynthesis.

(ii) Negative geotropism is the growth or movement of an organism in the opposite direction of gravity. An example of negative geotropism can be seen in roots that grow away from the force of gravity, such as the roots of a plant growing sideways along the surface of a rock.

(2b)
The chemical equation for aerobic respiration is:
C₆H₁₂O₆ (glucose) + 6O₂ (oxygen) —> 6CO₂ (carbon dioxide) + 6H₂O (water) + ATP (energy)

(2c)
(i) Surface Area: Respiratory structures have a large surface area for efficient gas exchange. Example: Alveoli in the lungs provide a large surface area for the exchange of oxygen and carbon dioxide.

(ii) Moisture: Respiratory structures are moist to help in the exchange of gases. Example: The mucous lining in the respiratory tract keeps the surface moist for efficient gas exchange.

(iii) Thin Membrane: The respiratory structures have thin membranes to facilitate rapid diffusion of gases. Example: The respiratory membrane in the alveoli is very thin to allow for quick exchange of oxygen and carbon dioxide.
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(3a)
(i) Decomposition: Microorganisms break down organic matter in the soil, such as dead plants and animals, into simpler substances, releasing nutrients like nitrogen, phosphorus, and potassium back into the soil.

(ii) Nitrogen fixation: Certain bacteria can convert atmospheric nitrogen into a form that plants can use, helping to increase soil fertility by providing plants with essential nutrients.

(iii) Enhancing soil structure: Some microorganisms produce substances that help bind soil particles together, improving soil structure and preventing erosion.

(iv) Disease suppression: Beneficial microorganisms can help suppress the growth of harmful pathogens in the soil, protecting plant roots and enhancing plant growth.

(v) Recycling nutrients: Microorganisms play a crucial role in recycling nutrients in the soil, ensuring that essential elements are available for plant uptake and growth.

(3b)
(i) Afforestation helps in combating climate change by absorbing carbon dioxide from the atmosphere and releasing oxygen through the process of photosynthesis.

(ii) Increased forest cover due to afforestation helps in preventing soil erosion, maintaining soil fertility, and promoting water conservation.

(iii) Afforestation provides habitats for a diverse range of plant and animal species, thus fostering biodiversity conservation.

(iv) Wildlife conservation is crucial for maintaining ecological balance and preserving the delicate interconnections between various species within an ecosystem.

(v) Protecting wildlife helps in safeguarding genetic diversity and ensuring the survival of endangered species, which play key roles in ecosystem functioning.

(3c)
(i) Water erosion
(ii) Wind erosion
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PART III

(4ai)
A joint is a point where two or more bones come together in the body, allowing movement and providing structural support.

(4aii)
Muscles are the primary tissues responsible for movement in the body. They contract and relax to generate force, enabling the body to move limbs, breathe, pump blood, and perform various other functions. Muscles work in pairs or groups, with one muscle contracting while the other relaxes to create movement in a specific direction.

(4b)
(i) Hinge Joint: Elbow, Knee
(ii) Pivot Joint: Neck, Wrist

(4c)
(i) Tendon: Tendons are connective tissues that attach muscles to bones, enabling movement and transmitting the force generated by muscles to the bones they are connected to.

(ii) Ligament: Ligaments are fibrous connective tissues that connect bones to other bones, providing stability to joints and preventing excessive movement, thus supporting the joints.

(iii) Synovial fluid: Synovial fluid is a lubricant present in joint cavities, reducing friction between the articulating surfaces of bones during movement and providing nourishment to the cartilage.

(iv) Ball and socket joint: Ball and socket joints allow for a wide range of motion in multiple directions, enabling movements like rotation and circumduction. An example is the shoulder joint.
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(5ai)
(i) Hydrostatic skeleton
(ii) Exoskeleton
(iii) Endoskeleton

(5aii)
(i) Hydrostatic skeleton – Earthworm
(ii) Exoskeleton – Crab
(iii) Endoskeleton – Human

(5b)
(i) The skeleton provides structural support for the body, allowing us to stand upright and maintain our shape.
(ii) The skeleton protects vital organs such as the brain, heart, and lungs from injury.
(iii) The bones and joints of the skeleton work together with muscles to allow movement.
(iv) The skeleton stores important minerals which are essential for bone strength and various bodily functions.

(5c)
(Draw the diagram)

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*PART IV*

(6a)
(i) Genetics: Genetics is the branch of biology that involves the study of genes, heredity, and variation in living organisms.

(ii) Alleles: Alleles are different forms of a gene that occupy the same position on homologous chromosomes and can result in different traits or characteristics in an organism.

(6bi)
(Draw the diagram)

(6bii)
The genotypic ratio of the cross between a heterozygous tall plant (Tt) and a homozygous short plant (tt) is 2Tt : 2tt Or 1Tt : 1tt

(6c)
BIOTIC FACTORS:
(i) Plants
(ii) Animals
(iii) Fungi