IB ESS SL Topic 2.1 Key Terms

species

group of organisms (living things) that share common traits, and can interbreed (within themselves) and produce fertile offspring

population

group of organisms of the same species living in the same area at the same time, where they can interbreed

community

group of 2 or more populations consisting of the same species living in the same area at the same time

habitat

environment in which a specific species normally lives

ecosystem

made up of organisms, their physical environment, and those organisms’ interactions between the living and non-living things in their environment

niche

set of abiotic and biotic conditions and resources that an organism or population depends on

biotic factors

living parts of an ecosystem, including all organisms, their interactions, and waste that could directly/indirectly affect another organism

Examples: producers, consumers, decomposers

abiotic factors

non-living parts of an ecosystem that influence organisms and the ecosystem itself

Examples: Temperature, sunlight, pH, water

ecological niche

role of a species in an ecosystem that is unique to the specific species

fundamental niche

all conditions of resources that species need to survive and reproduce

realized niche

the actual conditions and resources in which a species exists due to biotic factors

predator

consumer that preys on other animals

prey

animals a predator eats

carnivores

consumers that eat other animals

herbivores

consumers that eat plants

parasites

things that live on or in living hosts in order to obtain food from it

saprotrophs

organisms that eat dead/decaying organisms

scavengers

usually carnivores that mostly eat decaying biomass/flesh

detritivores

organisms that eat dead organic matter and then break it down by using enzymes

Example: earthworms

decomposers

organisms that secrete enzymes in order to break down dead organic matter but do not actually “eat” it

Example: bacteria

limiting factors

things that slow down the growth of a population as it comes close to its carrying capacity

carrying capacity

maximum number of species in a given area

density-dependent limiting factors

causes population growth rate to typically decline as the population density increases

Examples: Biotic factors such as disease, predation, competition

density-independent limiting factors

changes size of a population regardless of the population density

Examples: Abiotic factors such as forest fires, earthquakes, floods, and pollution

biosphere

ecological system that includes parts of life on earth, such as ecosystems, communities, populations, and individual organisms

intraspecific competition

between members of the same species, where species become more territorial

interspecific competition

between members of different species, where one species outcompetes the other or both species balance out

predation

a predator kills and eats prey, where both of these organisms are animals

herbivory

an animal (herbivore) eats a green plant

parasitism

a species (parasite) lives on/in another species (the host) and parasites feed off of the host (high parasite densities lead to host death)

Examples: vampire bats, fleas

mutualism

relationship between two species where both benefit

Example: lichens, where the fungus gets sugar from photosynthetic algae and the algae gets minerals and waters that are absorbed by the fungus

saprotrophism

where an organism feeds on dead organic material, where nutrients are recycled

Examples: scavengers, decomposers, detritivores

disease

pathogens (organisms) that cause harm to its animal/plant host, and higher species densities lead to easier spread of disease

Examples: rabies, viruses

j-curve

Exponential/geometric growth that has no limiting factors alongside a boom-bust pattern with heavy exponential growth then a collapse/dieback

Examples: microbes, fish, invertebrates, small mammals

s-curve

Exponential growth unaffected by limiting factors until the carrying capacity is approached, where the population remains constant - this happens due to environmental resistance