Notes
Levels of biodiversity
- Genetic diversity: variety of genes within a population. More genetic diversity helps a population survive disease or change.
- Species diversity: includes richness (number of species) and evenness (how evenly individuals are spread among species).
- Habitat diversity: variety of habitats in an area.
- A bottleneck (a sudden drop in population) reduces genetic diversity.
Ecosystem services
Nature provides provisioning services (food, timber, medicine), regulating services (climate regulation, pollination, water filtration), supporting services (nutrient cycling, soil formation) and cultural services (recreation, spiritual value). Losing biodiversity can harm these services and cost money.
Island biogeography
- Larger islands support more species (more habitats and resources).
- Islands closer to the mainland get more colonizers.
- Habitat fragments act like islands; that's why habitat corridors help.
Ecological tolerance and disruptions
- Each species has a range of tolerance for conditions like temperature or salinity. Outside it, organisms are stressed or die.
- Disruptions can be natural (fires, hurricanes, volcanoes) or human-caused, and they can be periodic, episodic or random.
- Adaptations come from natural selection; species that can't adapt or move may go extinct.
Ecological succession
- Primary succession starts on bare rock (after a lava flow or glacier). Pioneer species like lichens and mosses break down rock and make soil.
- Secondary succession happens where soil remains (after a fire or abandoned farmland) and is faster.
- Over time, the community moves toward a mature climax community, with biodiversity usually increasing.
Practice
Richness counts species; evenness compares their abundances.
Larger size and closeness to a source both increase species number.
Pollination regulates and supports food production; it's classified as a regulating service.
Less variation means fewer individuals might have traits to survive a change.
There's no soil yet; lichens are pioneer species.
The soil is still there, so it's secondary succession.
28 °C is outside its range of tolerance.
Corridors connect fragmented habitats.
Free response
Write your answer first, then open the scoring guide.
Free-response question
A forest is cut into several small, separated patches by new roads.
(a) Explain how this fragmentation could reduce biodiversity.
Show the answer and scoring guide
Small, isolated patches support fewer species and smaller populations, which are more likely to die out, and animals can't move between patches to find mates or food.
Check off the points you earned:
(b) Describe one negative effect of reduced genetic diversity in an isolated population.
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Inbreeding can increase harmful traits, and the population is less able to adapt to disease or climate change.
Check off the points you earned:
(c) Propose a solution that would reduce the impact of the roads on wildlife.
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Build wildlife overpasses or underpasses (corridors) so animals can cross between patches safely.
Check off the points you earned: