Ecology flashcards

Ecology is the study of interactions between organisms and their environment. Students must understand the levels of ecological organisation, from individual organisms through populations, communities, ecosystems and the biosphere. Key concepts include how energy flows through trophic levels via food chains and webs, and why energy is lost at each level, limiting the length of food chains. Nutrient cycles, particularly the carbon and nitrogen cycles, show how matter is recycled. Students must also grasp how population size is regulated by biotic and abiotic factors, the concept of carrying capacity, and how species interact through predation, competition, mutualism and parasitism. Understanding how human activity affects ecosystems, including habitat destruction, introduced species and climate change, is essential. Sampling techniques such as quadrats and transects are used to estimate population size and distribution.

1. Card 1

   What is the difference between a community and an ecosystem?

   A community is all the organisms of different species in an area. An ecosystem includes the community plus all the abiotic factors of that environment.

2. Card 2

   Why is energy lost between trophic levels in a food chain?

   Energy is lost through respiration, heat, movement, and undigested material in faeces. Typically only about 10% of energy is transferred to the next trophic level.

3. Card 3

   What is carrying capacity?

   Carrying capacity is the maximum population size that an environment can sustainably support, limited by available resources such as food, water and space.

4. Card 4

   Describe the role of decomposers in an ecosystem.

   Decomposers such as bacteria and fungi break down dead organic matter, releasing nutrients back into the soil and making them available for producers again, completing nutrient cycles.

5. Card 5

   What is the difference between interspecific and intraspecific competition?

   Intraspecific competition occurs between individuals of the same species. Interspecific competition occurs between individuals of different species competing for the same resources.

6. Card 6

   How do quadrats help ecologists estimate population size?

   A quadrat is a defined sample area. By counting organisms in multiple randomly placed quadrats, ecologists can estimate the population size or density across a larger area.

7. Card 7

   What is a trophic level?

   A trophic level is a feeding position in a food chain. Producers occupy the first, primary consumers the second, and so on, with energy decreasing at each successive level.

8. Card 8

   Explain how nitrogen is returned to the atmosphere in the nitrogen cycle.

   Denitrifying bacteria in the soil convert nitrates back into nitrogen gas through denitrification, completing the nitrogen cycle and returning N2 to the atmosphere.

9. Card 9

   What is meant by a niche?

   A niche describes the full role of a species in its ecosystem, including what it eats, where it lives, and how it interacts with other species. No two species can occupy the same niche.

10. Card 10

    What is the difference between primary and secondary succession?

    Primary succession begins on bare, lifeless substrate with no soil. Secondary succession occurs where a community has been disturbed but soil and some organisms remain.

11. Card 11

    How does the mark-release-recapture method estimate population size?

    Animals are caught, marked and released. A second sample is taken and the Lincoln index formula is used: population = (first catch x second catch) divided by number of recaptured marked individuals.

12. Card 12

    What is the difference between mutualism and parasitism?

    In mutualism both species benefit from the interaction. In parasitism one species, the parasite, benefits while the other, the host, is harmed but usually not immediately killed.

• Students often confuse food chains with food webs, forgetting that a food web more accurately represents feeding relationships because most organisms feed on or are eaten by more than one species.
• A common error is assuming that all the energy at one trophic level is passed on to the next, when in reality roughly 90% is lost, meaning only about 10% is available to the next level.
• Students frequently mix up the terms population and community, using them interchangeably, when a population refers only to individuals of one species whereas a community includes all species in an area.

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