🌍 Ecology

Ecology

The study of how organisms interact with each other and with their physical environment.

Ecosystem

A community of living organisms interacting with the non-living parts of their environment.

Biotic and Abiotic Factors

Biotic factors are living components; abiotic factors are non-living such as light, water and temperature.

Habitat and Niche

A habitat is where an organism lives; a niche is its role and resource use within the ecosystem.

Food Chain

A linear sequence showing who eats whom, beginning with a producer.

Food Web

An interlinked network of food chains showing feeding relationships in a community.

Producers

Autotrophs such as plants and algae that make organic compounds from light or chemical energy.

Consumers

Heterotrophs that obtain energy by eating other organisms: primary, secondary and tertiary consumers.

Decomposers

Bacteria and fungi that break down dead matter and recycle nutrients to the soil.

Trophic Levels

The feeding position of an organism in a food chain, from producers upward.

Energy Pyramid

Shows that only about ten percent of energy passes from one trophic level to the next.

Water Cycle

The continuous movement of water through evaporation, condensation, precipitation and runoff.

Carbon Cycle

Carbon moves between atmosphere, organisms, oceans and rocks via photosynthesis, respiration and combustion.

Nitrogen Cycle

Bacteria convert nitrogen through fixation, nitrification, assimilation and denitrification so organisms can use it.

Biomes

Large regions with characteristic climate and communities, such as tundra, rainforest and desert.

Symbiosis

Close, long-term interaction between species, including mutualism, commensalism and parasitism.

Population

All the individuals of one species living in the same area at the same time.

Intermediate topics (18)

Population Density

The number of individuals per unit area or volume, estimated with quadrats or mark-recapture.

Exponential Growth

Population growth at a constant per capita rate, producing a J-shaped curve in unlimited conditions.

Logistic Growth

Growth that slows as a population nears carrying capacity, forming an S-shaped curve.

Carrying Capacity

The maximum population size an environment can sustain indefinitely.

Limiting Factors

Resources or conditions that restrict population growth, either density-dependent or density-independent.

r and K Strategies

r-strategists reproduce quickly with many offspring; K-strategists have few offspring and invest heavily in each.

Survivorship Curves

Graphs of the proportion of a cohort surviving by age, classified as type I, II or III.

Age Structure

The distribution of ages in a population, which predicts future growth.

Predation

One organism hunts and consumes another, shaping prey populations and driving adaptations.

Competition

Interaction in which organisms vie for the same limited resource, intraspecific or interspecific.

Competitive Exclusion

Two species competing for exactly the same niche cannot coexist indefinitely.

Mutualism

An interaction benefiting both species, like bees and flowering plants or mycorrhizal fungi and roots.

Keystone Species

A species with a disproportionately large effect on its ecosystem relative to its abundance, like sea otters.

Ecological Succession

The gradual, directional change in a community over time, primary on bare rock and secondary after disturbance.

Primary Productivity

The rate at which producers convert energy into organic matter, gross minus respiration equals net.

Biomagnification

Persistent toxins like DDT become more concentrated at each higher trophic level.

Species Diversity

Combines the number of species (richness) and their relative abundances (evenness) in a community.

Eutrophication

Nutrient enrichment of water bodies causing algal blooms, oxygen depletion and fish kills.

Advanced topics (19)

Island Biogeography

Predicts species richness on islands from island size and distance to the mainland.

Metapopulations

A set of spatially separated populations linked by dispersal, with local extinction and recolonisation.

Lotka-Volterra Models

Differential equations describing oscillating predator and prey populations.

Intermediate Disturbance Hypothesis

Predicts diversity is highest at moderate levels of disturbance.

Trophic Cascade

Top predator effects ripple down through lower trophic levels, as in wolves reintroduced to Yellowstone.

Ecosystem Services

Benefits humans receive from ecosystems, such as pollination, water purification and climate regulation.

Biogeochemical Modelling

Mathematical models track fluxes of carbon, nitrogen and phosphorus through ecosystem pools.

Niche Partitioning

Coexisting species divide resources by space, time or diet to reduce competition.

Allee Effect

At low density, individual fitness declines, so small populations may fail to recover.

Ecological Stoichiometry

Studies the balance of elements like carbon, nitrogen and phosphorus in organisms and their food.

Landscape Ecology

Examines how spatial patterns of habitat patches and corridors affect ecological processes.

Climate Change Ecology

Warming shifts species ranges, phenology and interactions, creating mismatches in ecosystems.

Alternative Stable States

Ecosystems may flip abruptly between two persistent states, such as clear and turbid lakes.

Macroecology

Studies large-scale patterns of abundance, range and diversity, such as the latitudinal diversity gradient.

Microbial Ecology

Studies the roles of microbes in nutrient cycles and the structure of communities.

Food Web Stability

Connectance, interaction strength and omnivory affect how food webs respond to perturbations.

Plant-Pollinator Networks

Mutualistic webs typically nested, with specialists interacting with subsets of generalists' partners.

Ecological Footprint

A measure of human demand on ecosystems compared with the planet's regenerative capacity.

Species Distribution Modelling

Statistical models relate occurrence records to environmental variables to predict where species can live.