A Level H1 Biology Ecology Quiz

Answer Key - A-Level Biology H1 Quiz: Ecology

1. Ecological Niche [2]

   • The specific role of a species within an ecosystem, including its use of resources and its interactions with other organisms. (1)
   • Includes both the physical environment (abiotic) and biological interactions (biotic). (1)

2. Population vs Community [2]

   • Population: A group of organisms of the same species living in the same area at the same time. (1)
   • Community: All the populations of different species living and interacting in the same area. (1)

3. Abiotic vs Biotic [2]

   • Abiotic: Non-living chemical and physical parts of the environment (e.g., temperature, pH, sunlight). (1)
   • Biotic: Living components of an ecosystem (e.g., predation, competition, symbiosis). (1)

4. Carrying Capacity [2]

   • The maximum population size of a species that a particular environment can sustain indefinitely. (1)
   • Limited by available resources such as food, water, and space. (1)

5. Role of Decomposers [2]

   • Break down dead organic matter and waste products. (1)
   • Recycle essential nutrients (e.g., N, P, K) back into the soil/water for uptake by producers. (1)

6. Interspecific vs Intraspecific Competition [3]

   • Intraspecific: Competition between individuals of the same species; usually more intense due to identical niche requirements. (1.5)
   • Interspecific: Competition between individuals of different species for a shared resource. (1.5)

7. Predator-Prey Fluctuations [3]

   • Populations typically oscillate in cycles. (1)
   • An increase in prey leads to an increase in predators. (1)
   • High predator density then causes a crash in prey population, subsequently leading to a predator decline. (1)

8. Parasitism vs Mutualism [4]

   • Parasitism: One organism benefits (parasite) while the other is harmed (host). Example: Tapeworm in human gut. (2)
   • Mutualism: Both organisms benefit from the interaction. Example: Mycorrhizae (fungi and plant roots). (2)

9. Primary Succession [4]

   • Starts on bare rock/substrate with no soil. (1)
   • Pioneer species (e.g., lichens) colonize and break down rock. (1)
   • Organic matter accumulates as pioneers die, forming thin soil. (1)
   • More complex plants colonize, leading to a climax community. (1)

10. Competitive Exclusion [3]

    • Two species competing for the same limiting resource cannot coexist if their niches are identical. (1)
    • One will outcompete the other, leading to the extinction or migration of the weaker species. (1)
    • Alternatively, they may undergo niche partitioning to reduce competition. (1)

11. Invasive Species Impact [4]

    • Lack of natural predators in the new environment allows rapid population growth. (1)
    • Outcompete native species for resources (food/space). (1)
    • May prey upon native species that have no evolved defenses. (1)
    • Leads to a decrease in overall biodiversity and potential collapse of local food webs. (1)

12. Pioneer Species [3]

    • Characteristics: Hardy, fast-growing, wind-dispersed seeds/spores, tolerant of extreme conditions. (2)
    • Importance: They initiate soil formation by breaking down substrate and adding organic matter. (1)

13. Energy Loss [3]

    • Energy is lost as heat during metabolic processes (respiration). (1)
    • Not all parts of an organism are consumed or digestible (e.g., bones, cellulose). (1)
    • Energy is used for movement, growth, and reproduction. (1)

14. Inverted Pyramid of Numbers [3]

    • A single large producer (e.g., one oak tree) can support thousands of primary consumers (e.g., aphids). (2)
    • The biomass of the producer is high, even though the individual count is low. (1)

15. Eutrophication [4]

    • Nutrient runoff (nitrates/phosphates) enters water body, causing algal bloom. (1)
    • Algae block sunlight, killing submerged plants. (1)
    • Bacteria decompose dead algae and plants via aerobic respiration. (1)
    • This depletes dissolved oxygen, leading to the death of fish/aquatic animals. (1)

16. Nitrogen-fixing Bacteria [3]

    • Convert atmospheric nitrogen ($\text{N}_2$) into ammonia ($\text{NH}_3$) or nitrates. (2)
    • This makes nitrogen available for uptake by plants to synthesize proteins/nucleic acids. (1)

17. Carbon Cycle [3]

    • Photosynthesis removes $\text{CO}_2$ from the atmosphere to create organic glucose. (1)
    • Cellular respiration releases $\text{CO}_2$ back into the atmosphere as a byproduct of glucose breakdown. (1)
    • This creates a continuous cycle of carbon exchange between biotic and abiotic components. (1)

18. Biomagnification [4]

    • Accumulation of persistent, non-biodegradable toxins in tissues. (1)
    • Toxins are passed up the food chain; since biomass decreases at higher levels, the concentration of toxin increases. (2)
    • Top predators consume the most contaminated prey, leading to toxic levels that affect reproduction/survival. (1)

19. Grazing vs Detritus Food Web [3]

    • Grazing: Starts with living green plants; energy flow is more direct but often less efficient due to indigestible plant matter. (1.5)
    • Detritus: Starts with dead organic matter; highly efficient at recycling nutrients and energy from waste. (1.5)

20. Deforestation and Carbon Cycle [5]

    • Removal of trees reduces the amount of $\text{CO}_2$ absorbed via photosynthesis (carbon sink loss). (2)
    • Burning trees releases stored carbon immediately as $\text{CO}_2$. (1)
    • Decomposition of remaining organic matter further releases $\text{CO}_2$. (1)
    • Increased atmospheric $\text{CO}_2$ enhances the greenhouse effect, trapping heat and causing global warming. (1)