| A | B |
|---|
| Population density | number of individuals per unit of area or volume |
| Population distribution | the general pattern in which the population members are dispersed through its habitat; ex: clumped, uniformly, randomly |
| Population growth formula | G=rN |
| Population size | number of individuals making up its gene pool; dependent on births, immigration, deaths, emigration |
| Predator | an animal that kills and feeds upon another animal |
| Prey | an animal that is hunted and killed for food by a predator |
| Primary consumers | plant eaters (herbivores) that occupy the second trophic level of a food chain; feed on other producers |
| Primary producers | autotrophs; organisms that make their own food |
| Primary succession | starts from barren ground; ex: new islands or de-glaciated areas |
| Producer | plants and other organisms that make their own food |
| Resource partitioning | the resources are divided, permitting species with similar requirements to use the same resources in different areas, ways and/or times |
| Secondary consumers | Carnivorous animals that occupy the third trophic level; eat primary consumers |
| Secondary succession | starts from disturbed areas; ex: abandoned farm land or storm ravaged land (vegetation removed, but soil not destroyed) |
| r-selected organisms | put most of their energy into rapid growth and reproduction; ex: weeds, rabbits |
| k-selected organisms | put most of their energy into growth; ex: redwoods, humans |
| Tertiary consumers | Larger carnivores of the fourth trophic level that kill and eat the smaller secondary consumers |
| Trophic level | an organisms' position in a food chain, according to energy transfers |
| First trophic level | contains autotrophs which build energy-containing molecules |
| Second trophic levels | contains primary consumers which eat primary producers including herbivores, decomposers and detritivores |
| Third trophic level | contains secondary consumers, primary carnivores which eat herbivores; ex: mice, spiders, many birds |
| Fourth trophic level | contains tertiary consumers, secondary carnivores that eat the primary consumers; ex: weasel, owl, wolves |
| Water cycle | a model that describes how water moves from the surface of Earth to the atmosphere and back to the surface again |
| Weather | the condition of the atmosphere at any given time |
