IB Biology SL — Unit 4 Ecology

Species

Groups of organisms that can potentially interbreed to produce fertile offspring.

Autotrophs

Organisms that synthesize their own organic molecules from inorganic molecules, typically through photosynthesis.

Heterotrophs

Organisms that obtain organic molecules from other organisms through different feeding mechanisms and food sources.

Consumers

Heterotrophs that feed on living organisms by ingestion, including herbivores, carnivores, omnivores, and scavengers.

Detritivores

Heterotrophs that obtain nutrients from detritus by internal digestion, such as earthworms, woodlice, and dung beetles.

Saprotrophs

Heterotrophs that obtain organic nutrients from dead organisms by external digestion, secreting digestive enzymes into non-living organic matter.

Ecosystem

A community of organisms interacting with each other and their abiotic environment.

Sustainability

The potential of ecosystems to be maintained over long periods of time through energy availability, nutrient cycling, and waste recycling.

Decomposers

Organisms that break down dead consumers' cells with digestive enzymes, returning nutrients to the soil.

P Value

A value used to determine if the results of a statistical test are statistically significant.

Significance Level

A value is considered significant if there is less than a 5% probability (p < 0.05) that the results are attributable to chance.

Chi-Square Distribution

A statistical distribution used to test the independence of two variables.

Null Hypothesis

The assumption that there is no significant difference or association between variables.

Ecological Niche

The functional position and role of an organism within its environment, including habitat, activity patterns, resources obtained, and interactions with other species.

Fundamental Niche

The entire set of conditions under which an organism can survive and reproduce.

Realized Niche

The range of environmental conditions an organism actually lives in.

Positive Association

A relationship where the presence or abundance of one variable increases the likelihood of the presence or abundance of another variable.

Negative Association

A relationship where the presence or abundance of one variable decreases the likelihood of the presence or abundance of another variable.

Energy Flow

The movement of energy through an ecosystem from sunlight to producers, consumers, and decomposers.

Biomass

The total mass of a group of organisms consisting of the carbon compounds contained in the cells and tissues, which diminishes along food chains due to energy loss.

Pyramids of Energy

Diagrams representing the flow of energy through different trophic levels in an ecosystem.

Trophic Levels

The hierarchical levels in an ecosystem where organisms occupy based on their feeding positions.

Food Chain

A linear representation of the flow of energy from one organism to another in an ecosystem.

Food Web

A more complex representation of interconnected food chains in an ecosystem.

Autotrophs

Organisms that can produce their own food through processes like photosynthesis.

Heterotrophs

Organisms that cannot produce their own food and rely on consuming other organisms for energy.

Carbon Cycle

The biogeochemical cycle through which carbon is exchanged between the Earth's spheres.

Peat

Waterlogged soil containing partially decomposed organic matter, often used as a fossil fuel.

Fossil Fuels

Non-renewable energy sources like oil, coal, and gas formed from the decay of organic matter over millions of years.

Combustion

The process where organic compounds rich in hydrocarbons are heated in the presence of oxygen, producing energy, carbon dioxide, and water as by-products.

Biofuels

Fuels derived directly from living matter, offering advantages over fossil fuels but competing for finite land resources with food production and carbon storage.

Methane

A greenhouse gas produced by methanogens in anaerobic conditions like wetlands, marine sediments, and the digestive tracts of ruminant animals.

Limestone

Inorganic material primarily made of calcium carbonate, formed by the accumulation of shells from marine organisms, important in bio-sequestration but can release carbon dioxide when mined.

Greenhouse Gases

Gases like water vapor, carbon dioxide, methane, and nitrogen oxides that absorb and emit long-wave radiation, trapping heat in the atmosphere and influencing global temperatures and climate patterns.

Greenhouse Gases

Gases that trap heat in the Earth's atmosphere, leading to the greenhouse effect and contributing to climate change.