Ecology

3. A behavior in which an animal defends a bounded physical space against encroachment by other individuals, usually of its own species.
6. The total mass of organic matter comprising a group of organisms in a particular habitat.
7. An herbivore; an organism that eats plants or other autotrophs.
10. An area containing several different ecosystems linked by exchanges of energy, materials, and organisms.
11. A species that is not necessarily abundant in a community yet exerts strong control on community structure by the nature of its ecological role or niche.
13. Referring to any characteristic that varies according to an increase in population density.
14. The pathway along which food energy is transferred from trophic level to trophic level, beginning with producers.
16. Dead organic matter.
17. The amount of added nutrient, usually nitrogen or phosphorus, that can be absorbed by plants without damaging ecosystem integrity.
18. The integrated study of ecology, evolutionary biology, physiology, molecular biology, and genetics to sustain biological diversity at all levels.
20. A function performed by an ecosystem that directly or indirectly benefits humans.

1. A group of individuals of the same age in a population.
2. A parasite that feeds on the external surface of a host.
4. Reproduction in which adults produce offspring over many years; also known as iteroparity.
5. A permanently frozen soil layer.
8. A species that has a positive effect on the survival and reproduction of other species in a community and that influences community structure.
9. An element that must be added for production to increase in a particular area.
12. The warming of Earth due to the atmospheric accumulation of carbon dioxide and certain other gases, which absorb reflected infrared radiation and reradiate some of it back toward Earth.
15. The part of the ocean’s benthic zone between 2,000 and 6,000 m deep.
19. The entire portion of Earth inhabited by life; the sum of all the planet’s ecosystems.
21. The area where a freshwater stream or river merges with the ocean.