Waec Expo 2024 Biology Answer

[5/23, 9:11 AM] Solution: 2024 WAEC BIOLOGY ANSWERS

NUMBER TWO

(2a)
(i) Mouth: The mouth’s role is in the mechanical breakdown of food through chewing and the beginning of chemical digestion through the action of enzymes like amylase in saliva.
(ii) Skin: The skin’s role is in regulating body temperature by sweating to cool down the body when it’s overheated, as in this case.
(iii) Tongue: The tongue helps with the manipulation of food during chewing and swallowing.
(iv) Kidney: The kidney’s role is in filtering waste products from the blood and regulating fluid balance, which may be affected by the meal’s salt content.
(v) Stomach: The stomach’s role is in further mechanical and chemical digestion of food, particularly through the action of gastric juices containing enzymes like pepsin.
(vi) Small intestine: The small intestine’s role is in the absorption of nutrients from digested food.
(vii) Large intestine: The large intestine’s role is in the absorption of water and electrolytes from undigested food and the formation of feces.
(viii) Liver: The liver’s role includes producing bile, which aids in the digestion and absorption of fats.

(2b)
(i) the mouth
(ii) stomach
(iii) small intestine

(2c)
(i) amylase (in saliva and pancreatic juices)
(ii) pepsin (in gastric juices
(iii) lipase (in pancreatic juices).

(2d)
(i) glucose (from the breakdown of cassava starch by amylase)
(ii) fatty acids (from the breakdown of fats in groundnut soup by lipase).

(2e)
(i) Excess salt in the meal might lead to dehydration or exacerbate conditions like high blood pressure.
(ii) Three advantages the individual would derive from the meal could include energy from carbohydrates in cassava, protein from groundnuts, and various vitamins and minerals from both components of the meal.
[5/23, 9:15 AM] Solution: Section A

Question 1

(a) State one function each of the following parts of the nephron:

(i) Glomerulus:
The glomerulus filters blood, allowing water and small solutes to pass into Bowman’s capsule while retaining blood cells and large molecules like proteins.

(ii) Bowman’s capsule:
Bowman’s capsule collects the filtrate from the glomerulus and channels it into the proximal convoluted tubule.

(iii) Proximal convoluted tubule:
The proximal convoluted tubule reabsorbs nutrients, water, and electrolytes from the filtrate back into the bloodstream, ensuring essential substances are retained.

(iv) Distal convoluted tubule:
The distal convoluted tubule adjusts the final composition of urine by reabsorbing sodium and water and secreting potassium and hydrogen ions.

(b) Complete the table below:OrganismStructure for excretionForm in which waste is excreted by organism Flatworm Flame cells Liquid Earthworm Nephridia Liquid Cockroach Malpighian tubules Solid |

| Human | Kidneys | Liquid
|
| Plant | Stomatal pore | Gas |
[5/23, 9:16 AM] Solution: Question 1c

(c) List five excretory products of plants:

1. Oxygen (O₂)
2. Carbon dioxide (CO₂)
3. Water (H₂O)
4. Resins
5. Tannins

Question 2

(a) State one role each played by the following organs involved in the activity above:

(i) Mouth:
The mouth is involved in the mechanical breakdown of food through chewing and the chemical breakdown of starches by saliva.

(ii) Skin:
The skin regulates body temperature through sweating, which can occur more profusely after consuming a hot meal.

(iii) Tongue:
The tongue helps in manipulating and mixing food with saliva during chewing and aids in swallowing.

(iv) Kidney:
The kidney filters blood to remove waste products and helps maintain fluid and electrolyte balance, especially when no water is consumed after a salty meal.

(v) Stomach:
The stomach mixes and churns the food with digestive juices, initiating the digestion of proteins.

(vi) Small intestine:
The small intestine is the primary site for digestion and absorption of nutrients from the food.

(vii) Large intestine:
The large intestine absorbs water and salts from the remaining indigestible food matter and compacts it into feces.

(viii) Liver:
The liver produces bile, which helps in the digestion and absorption of fats, and processes nutrients absorbed from the small intestine.

(b) Name three of the organs listed in 2(a) that contain enzymes needed to break down the food:

1. Mouth (saliva contains amylase)
2. Stomach (gastric juices contain pepsin)
3. Small intestine (intestinal juices and enzymes from the pancreas such as trypsin, amylase, and lipase)
   [5/23, 9:18 AM] Solution: 1a. one function for each part of the nephron:

I. Glomerulus: It filters blood to form a filtrate containing water, ions, glucose, and small molecules, while retaining larger molecules like proteins and blood cells.

II. Bowman’s capsule: It collects the filtrate produced by the glomerulus and funnels it into the proximal convoluted tubule.

III. Proximal convoluted tubule: It reabsorbs the majority of the filtrate’s water, ions, and nutrients back into the blood.

IV. Distal convoluted tubule: It fine-tunes the reabsorption of ions and water, contributing to the regulation of blood pH, potassium, and sodium levels.

[5/23, 9:24 AM] Solution: *Biology*

**Section A**

**Question 2**

(c) Explain briefly how genes are involved in the process of evolution:

Genes are involved in evolution through the processes of mutation, natural selection, and genetic drift. Mutations introduce new genetic variations, which may provide some individuals with advantageous traits. Natural selection acts on these variations, favoring individuals that are better adapted to their environment, thereby increasing their chances of survival and reproduction. Over time, these advantageous traits become more common in the population, leading to evolutionary changes. Genetic drift, a random process, can also affect gene frequencies in a population, especially in small populations, contributing to evolution.

**Section B**

**Question 5**

(a)

(i) What is competition?

Competition is the interaction between organisms or species that vie for the same resources in an ecosystem, such as food, water, light, space, or mates. It occurs when the demand for these resources exceeds their availability, leading to a struggle for survival and reproduction.

(ii) List two types of competition:

1. Intraspecific competition: Competition between individuals of the same species.
2. Interspecific competition: Competition between individuals of different species.

(iii) List four factors that organisms compete for in a habitat:

1. Food
2. Water
3. Shelter/space
4. Mates

(iv) Explain briefly the relationship between competition and succession:

Competition and succession are interconnected processes in ecosystems. During succession, different species colonize and establish in a habitat over time. Early successional species, often fast-growing and tolerant of harsh conditions, initially dominate. As succession progresses, competition among species for resources like light, nutrients, and space intensifies. This competition can lead to the displacement of some species and the establishment of others, driving the successional changes that eventually lead to a stable climax community.

(b)

(i) What is structural adaptation?

Structural adaptation refers to physical features or characteristics of an organism’s body that enhance its ability to survive and reproduce in its environment. These adaptations can include body shape, coloration, specialized organs, or anatomical structures that improve the organism’s chances of obtaining food, avoiding predators, or reproducing.

(ii) State four types of structural adaptations in animals:

1. Camouflage: An animal’s coloration or pattern that allows it to blend in with its surroundings to avoid predators (e.g., a chameleon’s color-changing skin).
2. Mimicry: When an animal evolves to resemble another species for protection or other advantages (e.g., a viceroy butterfly mimicking a monarch butterfly).
3. Specialized limbs: Adaptations of limbs for specific functions (e.g., webbed feet in ducks for swimming, wings in birds for flying).
4. Body armor: Physical structures like shells, spines, or scales that provide protection (e.g., a turtle’s shell, a porcupine’s quills).
[5/23, 9:24 AM] Solution: 3.

I. **Four likely changes that would be observed in the meat**:
1. **Color change**: The meat may turn from red or pink to brown, grey, or greenish due to oxidation and microbial growth.
2. **Odor**: The meat will likely develop a strong, unpleasant smell due to bacterial decomposition and production of gases like ammonia and hydrogen sulfide.
3. **Texture**: The meat may become slimy or sticky as bacteria and fungi produce extracellular substances.
4. **Presence of mold**: Visible growth of mold or fungal colonies may appear on the surface of the meat.

II. **Biological process that led to the changes observed in the meat**:
   The biological process responsible for these changes is **decomposition** or **putrefaction**, which is primarily driven by bacterial and fungal activity.

III. **Four methods of preserving the meat and one principle involved in each preservation method**:

1. **Refrigeration/Freezing**:
   – **Principle**: Lowering the temperature to slow down the growth and reproduction of microorganisms and enzymatic activity.

2. **Drying/Dehydration**:
   – **Principle**: Removing moisture from the meat to inhibit the growth of microorganisms, which require water to survive.

3. **Salting/Curing**:
   – **Principle**: Adding salt to the meat to create an environment with high osmotic pressure, which dehydrates microbial cells and inhibits their growth.

4. **Smoking**:
   – **Principle**: Exposing the meat to smoke, which contains antimicrobial compounds and reduces moisture content, thus preserving the meat.

[5/23, 9:19 AM] Solution: (1a)
(i) Glomerulus:
The glomerulus filters blood to form a filtrate, which includes water, ions, and small molecules like glucose and amino acids, while retaining larger molecules such as proteins and cells.

(ii) Bowman’s Capsule:
The Bowman’s capsule collects the filtrate produced by the glomerulus and funnels it into the proximal convoluted tubule.

(iii) Proximal convoluted tubule:
The proximal convoluted tubule reabsorbs essential substances such as glucose, amino acids, and ions (e.g., sodium and chloride) from the filtrate back into the blood.

(iv) Distal convoluted tubule:
The distal convoluted tubule fine-tunes the reabsorption of ions and water, and it secretes additional waste products into the filtrate, helping to regulate electrolyte balance and pH.

(1b)
TABULATE

=ORGANISM=
(i) Flatworms
(ii) Earthworm
(iii) Cockroach
(iv) Human
(v) Plant

=STRUCTURE FOR EXCRETION=
(i) Flame cells
(ii) Nephridia
(iii) Malpighian tubules
(iv) Kidneys
(v) Stomatal pore

=FORM IN WHICH WASTE IS EXCRETED BY ORGANISM=
(i) Ammonia
(ii) Urea
(iii) Uric acid
(iv) Liquid (urine)
(v) Oxygen, carbon dioxide, and water vapor

(1c)
(i) Oxygen
(ii) Carbon dioxide
(iii) Water vapor
(iv) Resins
(v) Gums
[5/23, 9:19 AM] Solution: *2024 WAEC BIOLOGY ANSWERS*

*NUMBER ONE*

(1a)


(1ai)
(PICK ONE)
(I)Filtration of blood to form urine.
(I) Regulation of blood pressure by controlling filtration rate.
(III) Removal of waste products from the blood.

(1aii)

(PICK ONE)

(I) Collects the filtrate from the glomerulus.
(II) Prevents large molecules such as proteins from entering the tubule.
(III) Initiates the process of urine formation.

(1aiii)

(PICK ONE)

(I) Reabsorption of glucose, amino acids, and water from the filtrate.
(II) Secretion of hydrogen ions and organic acids into the filtrate.
(III) Regulation of pH balance by reabsorbing bicarbonate ions.

(1aiv)

(PICK ONE)

(I) Regulation of potassium and sodium ions through reabsorption and secretion.
(II) pH regulation by secreting hydrogen ions and absorbing bicarbonate ions.
(III) Reabsorption of water and calcium ions under hormonal control.

(1b)
COMING SOON

(1c)

(PICK FIVE)

(i) Oxygen
(ii) Carbon dioxide
(iii) Water vapor
(iv) Organic acids (e.g., citric acid)
(v) Ethylene
(vi) Resins
(vii) Latex

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