EVOLUTION: What are the mechanisms that promote the great variety of species on earth and that determine which species will survive in one environment but not another? SPECIES INTERACTIONS: We will look at the interactions within and between species that affect their success and shape biological communities. BIOLOGICAL COMMUNITIES: No species is an island. It always lives with other species in a biological community in a particular environment.
Density-dependent, meaning as population size increases, the effect intensifies. With a larger population, there is an increased risk that disease or parasites will spread, or that predators will be attracted to the area.
Density-independent limits to population are often nonbiological, capricious acts of nature. A population is affected no matter what its size.
Species respond to limits differently: r- and K-selected species 3-
1. Explain how tolerance limits to environmental factors determine distribution of a highly specialized species such as the saguaro cactus.
2. Productivity, diversity, complexity, resilience, and structure are exhibited to some extent by all communities and ecosystems. Describe how these characteristics apply to the ecosystem in which you live.
3. Define selective pressure and describe one example that has
affected species where you live.
4. Define keystone species and explain their importance in community structure and function.
5. The most intense interactions often occur between individuals
of the same species. What concept discussed in this chapter