IB MYP Integrated Sciences e-Assessment : Variation, natural selection, and adaptation Exam Style Practice Questions - New Syllabus
Question a (2 marks)
Charles Darwin and Alfred Wallace developed the theory of natural selection, which describes how evolution occurs. Organize the phrases in the correct sequence to describe the process of natural selection.
- Limited resources amongst individuals
- Large population of individuals showing variation
- Individuals with best traits more likely to survive and reproduce
- Best traits passed on to the next generation
▶️Answer/Explanation
Correct Sequence:
1. Large population of individuals showing variation
2. Limited resources amongst individuals
3. Individuals with best traits more likely to survive and reproduce
4. Best traits passed on to the next generation
Explanation:
Natural selection begins with a large population exhibiting genetic variation. Due to limited resources, individuals with traits that make them better suited to the environment are more likely to survive and reproduce. Over time, these advantageous traits become more common in the population as they are passed on to the next generation.
Question b (2 marks)
Match the following terms with their correct definitions:
- Parasite
- Predator
- Producer
- Prey
Definitions:
- An organism that lives in or on another organism and benefits at the host’s expense
- An animal that eats plants only and not other animals
- An animal that kills and eats other animals
- An organism that converts inorganic substances into organic ones
- An animal that is eaten by other animals
▶️Answer/Explanation
Correct Matching:
1. Parasite: An organism that lives in or on another organism and benefits at the host’s expense.
2. Predator: An animal that kills and eats other animals.
3. Producer: An organism that converts inorganic substances into organic ones.
4. Prey: An animal that is eaten by other animals.
Explanation:
– A parasite depends on a host for survival, often harming the host.
– A predator hunts and consumes other animals.
– A producer (usually a plant) converts sunlight and inorganic substances into organic matter through photosynthesis.
– Prey are animals that are hunted and eaten by predators.
Question c (4 marks)
Camels have several adaptations that allow them to live in sandy deserts. Choose four adaptations from the list below and state why each adaptation helps the camel survive in the sandy ecosystem.
- Hump containing fat
- Long eyelashes
- Tough lips
- Light-colored fur
- Tough pads on knees
- Long legs
- Large flat feet
▶️Answer/Explanation
Adaptation 1: Hump containing fat
– Why it helps: The hump stores fat, which can be metabolized into water and energy when food and water are scarce. This allows camels to survive long periods without food or water in the desert.
Adaptation 2: Long eyelashes
– Why it helps: Long eyelashes protect the camel’s eyes from sand and dust, which are common in desert environments. This helps prevent eye irritation and damage.
Adaptation 3: Tough lips
– Why it helps: Tough lips allow camels to eat thorny desert plants without injuring their mouths. This ensures they can access food sources that other animals might avoid.
Adaptation 4: Large flat feet
– Why it helps: Large flat feet help camels walk on soft sand without sinking. This adaptation allows them to move efficiently across the desert terrain.
Question d (Page 7) (3 marks)
The discovery of fire allowed early humans to cook food. Cooking makes food easier to digest and absorb into the bloodstream. Humans evolved a narrow waist and shortened digestive tract because they were able to cook food.
Cows have adapted to their available food source in a different way. Cows evolved a process called rumination to digest plant fibres.
Compare and contrast the features shown in the animation of the cow’s digestive system with the human digestive system.
▶️Answer/Explanation
Comparison:
– Both humans and cows have digestive systems that break down food into nutrients that can be absorbed into the bloodstream.
– Both systems involve the use of enzymes to aid in digestion.
Contrast:
– Cows: Cows have a four-chambered stomach (rumen, reticulum, omasum, abomasum) to digest plant fibres through rumination. The rumen contains microbes that break down cellulose, which humans cannot digest.
– Humans: Humans have a single-chambered stomach and a shorter digestive tract. Humans rely on cooking food to make it easier to digest, whereas cows rely on microbial fermentation in their stomachs.
Conclusion:
Cows have evolved a specialized digestive system to process plant fibres, while humans have evolved to rely on cooking to make food more digestible.
Question e (3 marks)
A cow has one stomach that is made up of four chambers. The first three chambers are full of microbes that digest plant material. The last chamber is called the abomasum, which contains acids and enzymes as in a human stomach.
When the cow goes out to feed, it eats grass as quickly as possible and swallows it almost unchanged. Food that goes into the first chamber of the stomach, the rumen, is difficult to digest. The microbes cannot enter the plant fibre to start the chemical process of digestion. The cow has evolved the process of rumination to break down plant fibres.
Explain the process of rumination in cows and how it helps them digest plant material.
▶️Answer/Explanation
Process of Rumination:
1. Ingestion: The cow eats grass quickly and swallows it almost unchanged. The food enters the rumen, the first chamber of the stomach.
2. Fermentation: In the rumen, microbes break down the plant fibres through fermentation. The microbes secrete enzymes that start the chemical digestion of cellulose.
3. Regurgitation: The partially digested food (cud) is brought back up to the cow’s mouth, where it is chewed again to mix it with more enzymes.
4. Re-swallowing: The food is re-swallowed and passes through the reticulum and omasum, where further digestion and absorption of nutrients occur.
5. Final Digestion: The food finally reaches the abomasum, where acids and enzymes complete the digestion process.
How it Helps:
Rumination allows cows to efficiently break down tough plant fibres, which are difficult to digest. The microbes in the rumen play a crucial role in breaking down cellulose, a component of plant cell walls that cows cannot digest on their own. This process enables cows to extract nutrients from plant material that would otherwise be indigestible.