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Across 3. A group of organisms of one species that interbreed and live in the same place at the same time. 5. Plants that colonise disturbed sites or raw mineral soils and make them easier for succeeding plants species to grow in. 10. A form of competition between members of the same species. 11. Countries or nations with an average income that is relatively lower than in highly industrialized countries, and are in the process of change toward economic growth. They are comparatively lower than the developed countries in terms of health care, literacy, and per capita income. 12. A measure of the capacity to reproduce offspring 14. The plateau of the growth curve after log growth in a culture, during which cell number remains constant. New cells are produced at the same rate as older cells die. 18. The ecological role and space that an organism fills in an ecosystem. 19. Migration to a country of which you are not a native in order to settle there 21. The birthrate, which is the ratio of total live births to total population in a particular area over a specified period of time; expressed as childbirths per 1000 people (or population) per year 22. An ecological succession that occurs following an opening of uninhabited, barren habitat or that occurs on an environment that is devoid of vegetation and usually lacking topsoil.

Down 1. The number of a species that an environment can sustain, considering the limiting factors at play. 2. Any species which is in danger of extinction throughout all or a significant portion of its range. 4. An S-shaped curve which depicts the growth of a population in an area of fixed limits. 6. An ecosystem in which populations of all organisms are in balance with each other and with existing abiotic factors. 7. An enumeration of a population, originally for taxation and military purposes, now with many other purposes; basic facts about all persons-age, sex, occupation, nature of residence, etc.- are recorded. 8. A density ...... factor whose effects on the size or growth of population vary with the population density. 9. A form of symbiotic relationship between two organisms of unlike species in which one of them acts as predator that captures and feeds on the other organism that serves as the prey 13. A symbiotic relationship between individuals of different species in which both individuals benefit from the association. 15. A group of interdependent organisms living and interacting with each other in the same habitat 16. The ecological succession that occurs on preexisting soil after the initial population has been disrupted or destroyed due to a disturbance that reduced the population of the initial inhabitants. 17. A square or rectangular plot of land used to mark off at random a physical area to isolate a sample and determine the percentage of vegetation and animals occurring within the marked area. 20. The science concerned with the interactions of living organisms with each other and with their environment.