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United StatesEnvironmental Science

Unit 2: The Living World: Biodiversity

7 dot points across 7 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does natural selection produce adaptations, and how do environmental changes drive new ones?

Topic 2.6 Adaptations: explain how natural selection produces adaptations and how environmental change shifts which traits are favored over time.
A focused answer to APES Topic 2.6, covering adaptations, natural selection, the role of genetic variation, structural, physiological and behavioral adaptations, specialists and generalists, and how environmental change drives evolution, with a worked selection question.
9 min answer →

How do communities rebuild after disturbance, and what roles do pioneer and keystone species play?

Topic 2.7 Ecological Succession: distinguish primary and secondary succession, describe how communities change over time, and explain the roles of pioneer, keystone and indicator species.
A focused answer to APES Topic 2.7, covering primary and secondary succession, pioneer species, the path to a climax community, keystone and indicator species, and the effects of succession on biomass and biodiversity, with a worked succession-sequencing question.
9 min answer →

What range of conditions can an organism survive, and how does this set the limits of where it can live?

Topic 2.4 Ecological Tolerance: describe the range of tolerance of organisms and explain how tolerance limits determine the distribution and survival of species.
A focused answer to APES Topic 2.4, covering the range of tolerance, optimum range, zones of stress, limits of tolerance, the law of tolerance and how tolerance varies between species and life stages, with a worked tolerance-curve question.
9 min answer →

What benefits do humans gain from ecosystems, and how does biodiversity loss threaten them?

Topic 2.2 Ecosystem Services: describe the four categories of ecosystem services and explain how the disruption of ecosystems affects the services they provide.
A focused answer to APES Topic 2.2, covering provisioning, regulating, cultural and supporting ecosystem services, examples of each, their economic value, and how disruption reduces them, with a worked valuation question.
9 min answer →

What are the levels of biodiversity, and why does greater diversity make ecosystems more resilient?

Topic 2.1 Introduction to Biodiversity: describe the three levels of biodiversity and explain how genetic and species diversity contribute to ecosystem resilience.
A focused answer to APES Topic 2.1, covering genetic, species and habitat diversity, species richness and evenness, the value of genetic diversity, bottlenecks and resilience, with a worked diversity-comparison question.
9 min answer →

Why do larger islands closer to the mainland support more species, and what does this teach us about habitat fragments?

Topic 2.3 Island Biogeography: explain how island size and distance from the mainland determine species richness, and apply the theory to habitat fragments.
A focused answer to APES Topic 2.3, covering the theory of island biogeography, the effects of island size and distance, immigration and extinction rates, endemism, and its application to habitat fragmentation, with a worked island-comparison question.
9 min answer →

How do natural disturbances of different scales and timescales shape ecosystems?

Topic 2.5 Natural Disruptions to Ecosystems: describe natural disruptions to ecosystems and explain their short-term and long-term effects on populations and biodiversity.
A focused answer to APES Topic 2.5, covering periodic, episodic and random natural disruptions, fire, drought, storms, volcanism, plate tectonics and climate change, their short- and long-term effects, and ecosystem recovery, with a worked disturbance-analysis question.
9 min answer →