BIOLOGY SOLUTIONS
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BIOLOGY OBJ
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11-20: DDCEABDAEC
21-30: EBBBEADBDD
31-40: EDACCCBCEA
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51-60: DDABBDDDBE
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INSTRUCTION: ANSWER THREE(3) QUESTIONS ONLY
(1ai)
The cell theory States that:
(i) All living organisms are composed of one or more cells.
(ii) The cell is the basic structural and functional unit of life. It is the smallest unit that can carry out all the processes necessary for life.
(iii) All cells arise from pre-existing cells through cell division.
(1aii)
(i) Robert Hooke (1635-1703): An English scientist who, in 1665, used a crude microscope to examine cork cells and coined the term “cells” to describe the small compartments he observed, likening them to the cells of a monastery.
(ii) Matthias Schleiden (1804-1881): A German botanist who, in 1838, concluded that all plant tissues are composed of cells, suggesting that cells are the fundamental units of plant structure.
(1bi)
(i) Brightly colored petals: Entomophilous flowers often have vibrant and attractive colors to attract insects.
(ii) Nectar: They produce nectar as a reward to attract insects, which serves as a food source for them.
(iii) Fragrance: Many entomophilous flowers emit pleasant fragrances that help attract insects from a distance.
(iv) Landing platforms: These flowers have a flat or sturdy landing platform to provide a stable surface for insects to land on.
(v) Pollen: Entomophilous flowers produce sticky or spiky pollen grains that can easily adhere to an insect’s body for effective transfer between flowers.
(1bii)
– Ginger: Rhizome (an underground stem)
– Banana: Rhizome (also an underground stem called a corm)
– Sweet potato: Storage root (tuberous root)
(1c)
(i) Mouth: The digestion of bread begins in the mouth. As you chew the bread, the mechanical process of mastication breaks it down into smaller pieces, increasing its surface area. Saliva is released, containing enzymes (such as amylase) that start breaking down the carbohydrates in the bread into simpler sugars.
(ii) Esophagus: After chewing, the softened and partially digested bread is formed into a mass called a bolus. The bolus is then swallowed and travels down the esophagus through peristaltic movements. The esophagus is a muscular tube that connects the mouth to the stomach.
(iii) Stomach: In the stomach, the bread and other food are mixed with gastric juices containing hydrochloric acid and enzymes, such as pepsin. These acidic and enzymatic secretions further break down the bread into a semi-liquid mixture called chyme.
(iv) Small intestine: The chyme is then gradually released into the small intestine. The pancreas releases digestive enzymes (such as amylase, lipase, and proteases) into the small intestine, where they act on the partially digested bread and other nutrients. The bread’s carbohydrates are broken down into simple sugars, proteins into amino acids, and fats into fatty acids and glycerol.
(v) Absorption: The small intestine is lined with millions of tiny finger-like structures called villi and microvilli, which greatly increase the surface area for nutrient absorption. The digested products, including the broken-down bread components, are absorbed through the intestinal walls and transported into the bloodstream.
(vi) Large intestine: Any remaining undigested parts of the bread, along with other indigestible food particles, move into the large intestine. Here, water and electrolytes are absorbed, and the remaining waste is formed into feces.
(vii) Anus: Finally, the feces are stored in the rectum until they are eliminated from the body through the anus during the process of defecation.
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(2ai)
Amoeba —> Hydra —> Tilapia —> Toad —> Snake
(2aii)
(i) Pappus: The pappus acts as a parachute-like structure, allowing the fruit to be carried away by the wind over long distances.
(ii) Lightweight and Small Size: The fruit of Tridax procumbens is relatively small and lightweight, which enhances its ability to be carried by even gentle air currents.
(iii) Single Seed: The fruit typically contains a single seed, which ensures that it remains aerodynamically efficient during wind dispersal.
(2b)
=Aim=
To demonstrate that the shoot of a plant exhibits positive phototropism, i.e., it grows towards a source of light.
=Apparatus=
(i) Potted plant with a young shoot (e.g., a sunflower seedling)
(ii) Light source (e.g., a lamp with a bright bulb)
(iii) Ruler or measuring tape
Black cloth or cardboard
(iv) Timer or clock
=Method/Procedure=
(i) Place the potted plant in a dark room for at least 24 hours before the experiment to ensure that the shoot is not influenced by any previous light exposure.
(ii) Set up the light source at a fixed height above the plant.
(iii) Use the ruler or measuring tape to measure and record the initial height of the shoot.
(iv) Cover one side of the plant with the black cloth or cardboard, blocking the light from that direction.
(v) Turn on the light source and expose the uncovered side of the plant to the light for a specified period (e.g., 6 hours).
(vi) Make sure to keep the plant and light source undisturbed during the experiment.
(vii) After the specified time, measure and record the final height of the shoot.
=Observation=
The shoot of the plant will show noticeable bending or growth towards the side exposed to the light source.
=Conclusion=
The experiment demonstrates that the shoot of the plant exhibits positive phototropism, as it grew towards the source of light. This response is essential for plants to optimize their light exposure for photosynthesis and growth.
(2c)
TABULATE
=AEROBIC RESPIRATION=
(i) Oxygen acts as the final electron acceptor, leading to the production of water as a byproduct
(ii) More efficient – Produces a large amount of ATP per glucose molecule
(iii) Carbon dioxide and water are the end products
(iv) Yields more energy (ATP) per glucose molecule
(v) Takes place in the presence of oxygen, primarily in the mitochondria
=ANAEROBIC RESPIRATION=
(i) An inorganic molecule (e.g., nitrate or sulfate) or an organic molecule (e.g., pyruvate) acts as the final electron acceptor, leading to the production of compounds like alcohol or lactic acid
(ii) Less efficient – Produces a small amount of ATP per glucose molecule
(iii) Various end products depending on the type of anaerobic respiration (e.g., ethanol and carbon dioxide in alcoholic fermentation, lactic acid in lactic acid fermentation)
(iv) Yields less energy (ATP) per glucose molecule
(v) Takes place in the absence of oxygen, in the cytoplasm (fermentation) or specialized organelles (e.g., hydrogenosomes) in some microorganisms
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(3ai)
(i) Ponds
(ii) Streams
(3aii)
TABULATE
=COMPLETE METAMORPHOSI=
(i) Larval stage looks completely different from the adult stage.
(ii) Pupal stage: a non-feeding and usually immobile stage for transformation.
=INCOMPLETE METAMORPHOSI=
(i) Nymphs resemble adult forms but are smaller and lack full reproductive capabilities.
(ii) No pupal stage; nymphs gradually develop into adults through a series of molts.
(3b)
=Aim=
To demonstrate that chlorophyll is essential for photosynthesis to occur.
=Apparatus=
(i) Two healthy green plants of the same species.
(ii) Two small boxes or containers (e.g., shoeboxes) with lids.
(iii) Black construction paper.
(iv) Aluminum foil.
(v) Light source (e.g., a lamp).
(vi) Water.
=Method/Procedure=
(i) Take the two green plants and place them in separate boxes or containers. Label them as “Plant A” and “Plant B.”
(ii) Cover the entire top surface of the lid for “Plant A” with black construction paper to block out light completely. This will serve as the control group.
(iii) Cover the entire top surface of the lid for “Plant B” with aluminum foil to block out light but allow air to pass through. This will serve as the experimental group.
(iv) Place both boxes in an area where they can receive the same amount of warmth and ensure that they have access to the same amount of water.
(v) Provide a light source near the boxes and keep it on for a set duration each day.
(3ci)
(i) Overuse of chemical fertilizers, which can change the soil pH and kill beneficial microorganisms.
(ii) Overuse of pesticides and herbicides, which can also kill beneficial microorganisms and lead to soil degradation.
(iii) Deforestation, which can lead to soil erosion and nutrient loss.
(iv) Overgrazing, which can lead to soil compaction and nutrient depletion.
(3cii)
(i) Hearing loss, which can be temporary or permanent depending on the intensity and duration of the noise exposure.
(ii) Sleep disturbance, which can lead to fatigue, irritability, and decreased performance in daily activities.
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(4ai)
(i) Crop diversity: planting different crops in the same field to prevent soil-borne diseases and pests.
(ii) Soil management: using cover crops, green manure, and compost to improve soil fertility and structure.
(iii) Timing and sequence: rotating crops at the right time and sequence to maximize yields and minimize soil depletion.
(4aii)
(i) Thick and fleshy leaves/stems: store water and reduce surface area for water loss.
(ii) Hairy or waxy surfaces: reduce water loss by reflecting sunlight and trapping moisture.
(iii) Deep roots: reach groundwater and maximize water uptake.
(iv) CAM photosynthesis: a type of photosynthesis that reduces water loss by opening stomata at night and closing them during the day.
(v) Succulence: storing water in swollen stems or leaves.
(4bi)
(i) Feathers: Birds have feathers, which are unique to them among extant animal groups. Feathers are also found in certain non-avian dinosaurs like Velociraptors and Archaeopteryx, indicating a possible shared ancestry.
(ii) Hollow Bones: Birds and some theropod dinosaurs (e.g., Tyrannosaurus rex) have hollow bones, which are advantageous for reducing weight, making them more aerodynamic for flight.
(iii) Eggshell Structure: The eggshells of birds and certain theropod dinosaurs are similar, indicating a common evolutionary origin for their reproductive strategies.
(4bii)
(i) Producing bile, which helps in digestion and absorption of fats.
(ii) Detoxifying harmful substances such as alcohol and drugs.
(iii) Storing vitamins and minerals such as iron and vitamin A.
(iv) Regulating blood sugar levels by storing or releasing glucose.
(v) Producing blood clotting factors.
(4c)
(i);Sustainable Logging Practices: Implementing sustainable logging practices, such as selective cutting and reforestation, helps maintain the health and diversity of forest ecosystems while allowing for a continuous supply of timber.
(ii) Protected Areas and Reserves: Establishing protected areas, national parks, and wildlife reserves helps conserve biodiversity and protects sensitive forest ecosystems from human activities.
(iii) Reforestation and Afforestation: Reforestation involves planting trees in areas that were previously deforested, while afforestation involves planting trees in areas that were not previously forested. These practices help increase forest cover and restore degraded landscapes.
(iv) Conservation Education and Awareness: Educating communities and the general public about the importance of forests and their conservation can lead to increased support for sustainable practices and reduced demand for products that contribute to deforestation.
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(5a)
(5bi)
(i) Protection: The calyx, which consists of sepals, plays a vital role in protecting the developing flower bud. The sepals act as a protective covering around the flower bud, shielding it from potential damage, desiccation (drying out), and certain herbivores or pests.
(ii) Support: The calyx provides structural support to the flower. As the flower bud develops and grows, the sepals provide a supportive base, ensuring the proper positioning and arrangement of the floral parts within the flower bud.
(5bii)
(i) Insulin: Produced in the pancreas, insulin regulates glucose metabolism and helps lower blood glucose levels by promoting the uptake of glucose by cells.
(ii) Growth hormone (GH): Secreted by the pituitary gland, GH stimulates growth and cell reproduction, playing a crucial role in the growth and development of tissues and bones.
(iii) Testosterone: Primarily produced in the testes (in males) and in smaller amounts in females, testosterone is a sex hormone responsible for the development of male reproductive tissues and secondary sexual characteristics.
(iv) Estrogen: Mainly produced in the ovaries (in females) and in smaller amounts in males, estrogen plays a key role in the development and maintenance of female reproductive structures and secondary sexual characteristics.
(v) Thyroid hormones (T3 and T4): Produced by the thyroid gland, these hormones regulate metabolism and influence various physiological processes, including energy production and body temperature.
(5ci)
(i) Understanding Genetic Disorders: The principles of heredity have allowed researchers and medical professionals to understand how genetic disorders are inherited. By studying patterns of inheritance, they can identify the specific genes responsible for certain disorders and assess the likelihood of passing them on to offspring. This knowledge has been crucial in genetic counseling and family planning to reduce the risk of passing on genetic conditions.
(ii) Development of Gene Therapies: Heredity principles have paved the way for the development of gene therapies. Gene therapy involves introducing functional genes into cells to correct genetic defects that cause diseases. By understanding how genes are inherited and expressed, scientists can target specific gene mutations and potentially treat or even cure certain genetic disorders.
(5cii)
(i) Broad, Flat Shape: Most leaves have a broad and flat shape, which maximizes their surface area exposed to sunlight. The increased surface area allows leaves to capture more sunlight, which is crucial for photosynthesis. Additionally, the flat shape helps to reduce shading of lower leaves, ensuring efficient light absorption throughout the plant.
(ii) Thin and Transparent Epidermis: The epidermis is the outermost layer of the leaf. It is usually thin and transparent, allowing light to penetrate easily into the underlying mesophyll cells where photosynthesis occurs. The transparency of the epidermis ensures that light reaches chloroplasts within the leaf cells, where chlorophyll molecules absorb light energy.
(iii) Presence of Chloroplasts in Mesophyll Cells: Chloroplasts are specialized organelles responsible for photosynthesis. Leaves have a high concentration of chloroplasts, especially in the mesophyll cells, which are the middle layer of the leaf. The mesophyll cells are well adapted to facilitate gas exchange (CO₂ uptake and O₂ release) and the diffusion of light to reach chloroplasts efficiently.
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