Energy & Feeding Relationships, Nutrient Cycles, and Populations

Vocabulary flashcards covering energy transfer, ecological pyramids, nutrient cycles, and population growth curves from CIE IGCSE Biology.

Food Chain

A sequence showing the transfer of energy from one organism to the next, starting with a producer.

Producer

An organism, such as grass, that makes its own food using energy from sunlight in photosynthesis.

Primary Consumer

An organism that eats the producer to obtain energy.

Secondary Consumer

An organism that eats the primary consumer to obtain energy.

Food Web

A network of interconnected food chains showing the interdependence of organisms within an ecosystem.

Pyramid of Numbers

A diagram showing how many organisms are present at each trophic level of a food chain.

Biomass

A measure of the dry mass of an organism once the water has been removed from its tissues.

Pyramid of Biomass

A diagram showing how much living matter is present at each trophic level of a food chain.

Pyramid of Energy

A visual representation showing the stored energy at each trophic level and highlighting energy lost between levels.

Combustion

The process of burning fossil fuels where carbon combines with oxygen and releases carbon dioxide into the atmosphere.

Nitrogen-fixing Bacteria

Bacteria that convert nitrogen gas ($N_2$) into ammonium compounds, living free in the soil or within plant root nodules.

Nitrifying Bacteria

Soil bacteria that convert ammonium compounds into nitrites and then into nitrates that plants can absorb.

Denitrifying Bacteria

Anaerobic soil bacteria that take nitrates out of the soil and convert them back into nitrogen gas ($N_2$).

Population

A group of organisms of one species, living in the same area at the same time.

Community

All of the populations of different species in an ecosystem.

Ecosystem

A unit containing the community of organisms and their environment, interacting together.

Sigmoid Growth Curve

An S-shaped curve showing the four phases of population growth over time in an enclosed environment.

Lag Phase

The initial phase of population growth where organisms adapt to their environment before reproducing.

Log Phase

Also known as the exponential phase, the period where food supply is abundant, birth rate is rapid, and death rate is low.

Stationary Phase

The phase where population levels out because birth rate equals death rate due to a limiting environmental factor.

Death Phase

The final population phase where population decreases because death rate exceeds birth rate due to food shortage or toxic waste buildup.