▶️ Answer/Explanation
The graph represents a population growth curve. At point $Y$, there is a noticeable decrease in the number of water fleas before the population stabilizes at a lower level. Options (A), (B), and (C) are all factors that would typically cause a population to increase or remain high by improving survival conditions or reproductive output. However, the introduction of a predator, as suggested in option (D), increases the death rate and reduces the overall population size. This shift leads to a new, lower carrying capacity for the water fleas within the pond ecosystem.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
An ecosystem is defined as a biological system consisting of all the living organisms (biotic factors) in a particular area interacting with their physical, non-living environment (abiotic factors). In this question, the text identifies diverse species like corals and sharks, which represent the biotic component. Crucially, it also mentions temperature, salt, and oxygen levels, which are abiotic factors. While a “community” only refers to the interacting living species, the inclusion of the physical water conditions makes “ecosystem” the most complete and accurate description. A population would only involve one species, and a food web focuses strictly on feeding relationships.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
The size of a population increases when the birth rate and immigration exceed the death rate and emigration. Option (B) provides more resources, which reduces competition and allows for higher survival and reproductive success. In contrast, disease (A), pollution (C), and predation (D) are all limiting factors that increase the mortality rate, leading to a decrease in population size. Since food is a primary requirement for growth and energy, its abundance directly supports a larger carrying capacity in the ecosystem.
✅ Answer: (B)
✅ Answer: (B)