Ecosystems and biodiversity flashcards

Ecosystems are communities of living organisms interacting with their nonliving environment through flows of energy and cycles of matter. Students must understand how energy moves through trophic levels via food webs, why only about 10% of energy transfers between levels, and how biogeochemical cycles (carbon, nitrogen, phosphorus, water) sustain life. Biodiversity refers to the variety of life at genetic, species, and ecosystem levels, and it supports ecosystem stability and resilience. Key concepts include primary and secondary succession, keystone species, ecosystem services, and the factors that threaten biodiversity such as habitat loss, invasive species, pollution, overexploitation, and climate change. Understanding how human activities disrupt ecosystem function and reduce biodiversity is central to this topic.

1. Card 1

   What is an ecosystem?

   An ecosystem is all the living organisms in an area plus the nonliving physical environment, interacting together as a functional unit.

2. Card 2

   What does the 10% rule describe in ecology?

   The 10% rule states that only about 10% of energy stored at one trophic level is transferred to the next; the rest is lost mainly as heat through metabolism.

3. Card 3

   What is the difference between a food chain and a food web?

   A food chain shows a single path of energy flow, while a food web shows all the interconnected feeding relationships in an ecosystem, which is more realistic.

4. Card 4

   What is a keystone species?

   A keystone species has a disproportionately large effect on ecosystem structure relative to its abundance; removing it causes dramatic changes in community composition.

5. Card 5

   What is the difference between primary and secondary succession?

   Primary succession begins on bare substrate with no soil; secondary succession occurs where a community was disturbed but soil and some organisms remain.

6. Card 6

   What are the three levels of biodiversity?

   Biodiversity exists at the genetic level (variation within species), the species level (variety of species), and the ecosystem level (variety of habitat types).

7. Card 7

   What is net primary productivity (NPP)?

   Net primary productivity is the energy stored by producers after subtracting their own respiration; it represents energy available to consumers in an ecosystem.

8. Card 8

   What role do decomposers play in an ecosystem?

   Decomposers break down dead organic matter, releasing nutrients back into the soil and water, making them available for producers to use again.

9. Card 9

   How does nitrogen enter the biological nitrogen cycle?

   Nitrogen fixation converts atmospheric N2 into ammonia (NH3), carried out by certain bacteria in soil and root nodules, making nitrogen available to plants.

10. Card 10

    What are ecosystem services?

    Ecosystem services are the benefits humans receive from ecosystems, including clean water, pollination, climate regulation, soil formation, and cultural value.

11. Card 11

    What is an invasive species and why is it harmful?

    An invasive species is a non-native organism that spreads rapidly in a new habitat, often outcompeting native species and reducing local biodiversity.

12. Card 12

    What is a pioneer species?

    A pioneer species is the first organism to colonize a disturbed or barren area, beginning succession by modifying the environment so other species can establish.

• Many students confuse the 10% rule by thinking 10% of energy is lost at each trophic level, when in fact 10% is transferred and roughly 90% is lost, mostly as heat.
• Students often treat food chains as accurate models of energy flow, overlooking that real ecosystems operate as complex food webs where most organisms feed at multiple trophic levels.
• A common error is assuming that high species richness alone equals high biodiversity, when true biodiversity also includes genetic diversity within species and the variety of ecosystem types present.

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