Ecology

• species: a group of identical organisms capable of interbreeding to produce fertile, living offspring
• population: all the individuals of one species that live together in an area at any given time
• community: all the populations of different species that live together in an area at any given time
• ecosystem: community plus its physical environment (abiotic factors)
• habitat: place where an animal or plant lives
• interspecific competition: the competition between individuals of different species
• intraspecific competition: the competition between individuals from the same species
• limits of tolerance: the upper and lower limits to the range of particular factors within which an organism can survive
• adaptive feature: any heritable trait that helps an organism survive and reproduce in its environment
• physiological adaptation: an internal body process that helps an organism survive in its environment
• Behavioural adaptation: something an animal does usually in response to some type of external stimulus to survive
• structural adaptation: physical features of an organism that help it survive in its environment
• optimum range: a set point of ideal conditions, with a range that they can tolerate
• biotic factor: living things that affect the population of an organism, such as predators and parasites
• abiotic factors: non-living environmental factors affecting populations, such as temperature and water availability
• ecological niche: the range of conditions within which a species can survive and reproduce
• fundamental niche: the range of conditions in which an organism can survive and reproduce
• realised niche: the range of conditions in which a species can live and survive with external factors taken into account
• Liebig's Law of the Minimum: the functioning of an organism is limited by the essential environmental factor that is present in the least favourable amount
• Gause's Law of Competitive Exclusion: two species that compete for the same resources cannot stably coexist
• Autroph: organisms which have the capability to produce their own food from organic molecules
• Heterotroph: Organism that derive energy from other living organisms
• Saprotroph: Lives in or on nonliving organic matter, secreting digestive enzymes into it and absorbing digestive products 
• Decomposers: Organisms that derive energy from nonliving organic matter
• Food Chain: A chain which shows how energy is transferred between interacting organisms
• Food Web: Shows how food chains are linked together into more complex feeding relationships
• Trophic levels: Relationship between organisms within the same species (position within the food chain)
• Symbiosis: A close and prolonged association between two different organisms
• Mutualism: Relationship where both members benefit
• Parasitism: When one organism lives in or on another organism
• Coexistence: Working together to ensure mutual survival
• Grazing: Feeding on tissue of soft plants
• Commensalism: one organism benefits and the other is not harmed.
• Social hierarchy: Order of importance in a population
• Browsing: Feeding on the tissue of woody plants
• Niche Exclusion: Once species forces another out of a habitat
• Territory: Area which organisms utilise and defend
• Host species: Species which provides food or shelter
• Predation: Hunting another animal species for food
• Scavenger: Species that feed on predators left-over food