Unit 4 Biogeochemical Cycles, Food Webs, and Population Dynamics Review

Vocabulary flashcards covering key processes and definitions across biogeochemical cycles (water, carbon, nitrogen), food webs, and population dynamics based on the checkpoint review guide.

Sublimation

The process in the water cycle where ice and snow transition directly into water vapor in the atmosphere without becoming liquid water first.

Desublimation

The process where atmospheric water vapor changes directly into solid ice or snow without passing through the liquid water phase.

Evapotranspiration

The movement of water into the atmosphere resulting from the combination of evaporation from surface sources and transpiration from plant life.

Infiltration

The process by which surface precipitation passes down through topsoil and subsurface rock layers.

Phytoplankton

Microscopic marine organisms at the ocean surface that convert carbon through photosynthesis and support the marine food web.

Soil Organic Carbon

Carbon held within the soil reservoir, resulting from the decomposition of dead plants, animals, and organic matter.

Diffusion (Carbon Cycle)

The physical process facilitating the continuous exchange of carbon dioxide gas between the atmosphere and the ocean surface.

Atmospheric Nitrogen ($N_2$)

The inert, non-reactive gaseous form of nitrogen ($N_2$) in the atmosphere that cannot be directly assimilated by most living organisms.

Nitrogen-Fixing Bacteria

Specialized microorganisms residing in soil and root nodules that convert inert atmospheric nitrogen ($N_2$) into reactive, bioavailable forms like ammonia ($NH_3$) and nitrites ($NO_3^-$).

Nitrification

The biological process in which soil bacteria convert ammonia ($NH_3$) into nitrites ($NO_2^-$) and nitrates ($NO_3^-$).

Ammonification

The pathway in which decomposers (bacteria and fungi) break down organic waste from urine and dead animal or plant matter into ammonia ($NH_3$).

Denitrification

The microbial conversion step in the nitrogen cycle that transforms soil nitrites and nitrates back into atmospheric nitrogen gas ($N_2$).

Food Web

A complex ecosystem model composed of interconnected food chains depicting all direct energy transfer pathways between living organisms.

Energy Pyramid

A quantitative model illustrating the relative amount of energy available and stored across each trophic level from highest to lowest.

Population Density

A dynamic measure of organism concentration per unit area, expressed by the formula $\text{Population Density} = \frac{\text{Total Population} + (\text{Births} - \text{Deaths})}{\text{Area}}$.