Key Terms

Mastering the core terms is the key for succeeding in the Ecology section! Ecology may seem overwhelming at first, but don't worry—you've got this. Learning these definitions will give you a solid foundation for any ecology question that comes up.

Remember: Ecology is a guaranteed long question, so it's worth putting in the effort to master this section!

Tip: Print out this list and add any additional challenging terms you come across to keep everything in one place. Revise this list frequently to keep these terms fresh in your mind

Biosphere	Part of the planet that contains living organisms.
Ecosystem	Group of clearly distinguished organisms that interact with each other and their environment
Ecology	The study of the interaction between living things and between living things and their environment.
Habitat	Place where a plant or animal lives
Population	All the members of the same species living in an area
Community	All different populations in an area
Niche	Functional role an organism plays in an ecosystem or habitat
Environment	All external factors that influence an organism
Competition	When 2 or more organisms struggle for a resource that is in short supply.
Contest Competition	Active physical struggle between different organisms. Produce one winner and one loser.
Scramble competition	A struggle for a limited resource and the resource is shared by all.
Predation	The catching, killing and eating of another organism for food
Parasitism	Feeding of a living host
Climatic factors	Concern weather over a long period of time
Edaphic factors	Factors relating to soil
Humus	Decaying organic matter
Food chain	Sequence of organisms where each organism is eaten by the next one in the chain. Energy is lost at each stage.
Trophic level	Feeding stage in the food chain
Detritus	Begin with dead/decomposing material
Grazing food chain	Starts with a producer
Food web	Series of interconnected food chains
Pyramid of numbers	Shows the number of organisms at each trophic level
Apex predators	No natural predators eg killer whale
Nutrient recycling	The way in which elements or minerals are absorbed by organisms, released into the atmosphere when organisms decompose and are absorbed by other organisms.
Global warming	As the level of C02 in the atmosphere increases, the planet heats up.
Symbiosis	Two organisms from different species that live in close association, where at least one of them benefits.
Species	A group of similar organisms capable of interbreeding and producing fertile offspring.
Interspecific competition	Competition between members of a different species
Intraspecific competition	Competition between members of the same species
Parasite	A living organism that takes its food from another living organism, called a host, and usually causes harm.
Mutualism	Form of symbiosis where both organisms benefit. Eg bacteria in the small intestine of human
Pollution	Any undesirable change in or harmful addition to the environment. Results from unwanted materials called pollutants
Conservation	The wise management of our existing natural resources in order to allow as many species as possible to survive.
Qualitative survey	Records if a species is present or absent.
Quantitative survey	Gives the number of species in an area.
Key	Used to identify flora (plants) and fauna (animals) in an area.
Nitrogen fixation	Conversion of atmospheric nitrogen (N2) into usable form
Producers	Organisms that make their own food using simple molecules (autotrophs).
Consumers	Organisms that cannot make their own food and use food made by others (heterotrophs).
Herbivores	Organisms that eat plants
Omnivores	Organisms that eat both plants and animals
Carnivores	Organisms that eat animals
Decomposers	Organisms that live and feed on dead organisms
Adaptation	A feature that helps an organism to survive and reproduce.

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Key Terms

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