CHAPTER 7 Focus Points

• Non-native organisms: Organisms that are moved outside their natural geographic range by people can cause ecological problems.

• Biogeography: Biogeographers study the geographic patterns of life to learn about Earth’s physical systems and Earth’s natural and human history.

• Biodiversity patterns: The tropics are the most biodiverse region on Earth. Large islands are more biodiverse than small islands. Biodiversity changes seasonally as animals migrate.

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• Patterns resulting from evolution: Biogeographic patterns of convergence and divergence result from the process of evolution.

• Niches: Species with narrow ecological niches usually have restricted geographic ranges. Species with broad niches are usually geographically widespread.

• Limiting factors: Geographic ranges of species are determined by physical and biological limiting factors.

• Keystone species: Keystone species play crucial roles in the functioning of ecosystems.

• Competition: The degree of competition among organisms depends on the similarity of their niches.

• Dispersal: Dispersal allows organisms to reduce limiting factors such as competition, to obtain more resources, and to respond to environmental change.

• Range expansion: Geographic ranges expand when organisms successfully disperse outside the boundaries of their current range.

• Dispersal modes: Organisms may disperse under their own power (called active dispersal) or with the help of wind, water, or other organisms (called passive dispersal).

• Ecological disturbance: Ecological disturbance is caused by both biotic and abiotic factors.

• Fire suppression: In North America, fires have been intentionally suppressed by people, resulting in an accumulation of fuel and subsequent catastrophic fires.

• Reducing fuel buildup: Prescribed burns and mechanical thinning reduce fuel buildup in forests caused by fire suppression.

• Ecological succession: After a disturbance event, life returns to an area through ecological succession.

• Approaches to organizing the biosphere: The biosphere can be organized on the basis of flows of energy and matter, genetic similarities, and the spatial dimensions of ecological units of life.

• The trophic hierarchy: The trophic hierarchy is based on energy flow. Higher trophic levels have less available energy and biomass.

• The taxonomic hierarchy: The taxonomic hierarchy places organisms in nested groups according to their shared genetic relationships.

• The spatial hierarchy: Ecological units of life range from the individual to the entire biosphere.

• Coconut dispersal: The coconut seed is well adapted to disperse by floating on seawater as well as for dispersal by people.

• Artificial selection: The coconut palm illustrates the influences that people and their domesticated organisms have on one another.