Human Biology: Ecology and the Nature of Ecosystems

Vocabulary flashcards covering the nature of ecosystems, energy flow, food webs, and global biogeochemical cycles based on Chapter 24 of the lecture notes.

Biosphere

The portion of the Earth that contains living organisms.

Ecosystem

A specific area of the biosphere where organisms interact with each other and with the physical and chemical environment.

Biomes

Types of terrestrial ecosystems defined by climate conditions, such as the tropical rain forest, savanna, temperate grasslands, deserts, the taiga, and the tundra.

Estuaries

Diverse aquatic ecosystems where fresh and saltwater mix.

Abiotic components

The nonliving components of an ecosystem, including nutrients in the soil, water, and the weather.

Biotic components

The living components of an ecosystem, categorized by how they obtain their energy as autotrophs or heterotrophs.

Autotrophs

Also called producers, these organisms use inorganic nutrients and an outside source of energy to produce organic nutrients.

Heterotrophs

Also called consumers, these organisms must consume food to obtain energy.

Herbivores

Heterotrophs that feed directly on producers, such as deer, rabbits, caterpillars, and protists in aquatic ecosystems.

Carnivores

Heterotrophs that feed on other animals, such as snakes and hawks.

Omnivores

Heterotrophs that feed on both plants and animals, such as humans.

Detritus feeders

Organisms like earthworms, beetles, termites, and ants that feed on decomposing particles of organic matter.

Decomposers

Organisms such as bacteria and fungi that release inorganic substances which can then be taken up by plants.

Niche

The specific role of an organism in an ecosystem, such as being a producer or a carnivore.

Energy flow

A phenomenon in ecosystems that begins when producers absorb solar or chemical energy.

Nutrient cycling

The process where producers take in inorganic chemicals from the environment to make organic nutrients used by themselves and others.

Food web

A diagram describing trophic, or feeding, relationships within an ecosystem.

Grazing food web

A food web that begins with producers like an oak tree and grass.

Detrital food web

A food web that begins with wastes and dead organisms.

Food chains

Diagrams that show a single path of energy flow, such as $oak\text{ }leaves \rightarrow caterpillars \rightarrow mice \rightarrow hawks$.

Trophic level

A level composed of all the organisms that feed at a particular link in a food chain.

Ecological pyramid

A diagram representing the flow of energy with large losses occurring between successive trophic levels, following the general 10% rule.

Biomass

The number of organisms multiplied by the weight of organic matter contained in one organism.

Biogeochemical cycles

Pathways including gaseous and sedimentary cycles by which chemicals circulate through ecosystems.

Reservoir

A source of chemicals normally unavailable to producers, such as nutrients in fossil fuels, minerals in rocks, or sediment in oceans.

Exchange pool

A source from which organisms can directly take chemicals, such as the atmosphere, soil, or water.

Transpiration

The process of water evaporation from plants.

Runoff

Precipitation that does not enter the ground but flows directly into streams, lakes, wetlands, or the ocean.

Aquifers

Rock layers that contain water and release it to wells and springs.

Groundwater mining

Withdrawals from aquifers that exceed the possibility of recharge, leading to dropping groundwater levels.

Greenhouse gases

Gases like $N_2O$ and $CH_4$ that allow solar radiation to penetrate the atmosphere but block the escape of heat back into space.

Global warming

The rise in Earth’s temperature contributed to by greenhouse gases, which may lead to a rise of $2.0$ to $8.1$ degrees F by 2100.

Nitrogen fixation

The conversion of $N_2$ gas into ammonium ($NH_4^+$), a form of nitrogen that plants can use.

Nitrification

The production of nitrates ($NO_3^-$) during the nitrogen cycle, either from $N_2$ in the atmosphere or from $NH_4^+$ in the soil.

Denitrification

The conversion of nitrate back to $N_2$ gas by bacteria living in anaerobic mud.

Eutrophication

The overgrowth of algae and aquatic plants, often caused by fertilizer runoff, which can lead to oxygen depletion and fish kills.

Acid deposition

Commonly known as acid rain, it occurs when nitrogen oxides ($NO_x$) and sulfur dioxide ($SO_2$) from burning fossil fuels combine with water vapor.

Phytochemical smog

A condition where nitrogen oxides and hydrocarbons react in the presence of sunlight.

Thermal inversion

A weather pattern where pollutants are trapped near the Earth beneath a layer of warm, stagnant air.

Phosphorus cycle

A sedimentary cycle where phosphorus moves from rocks to the soil and into the biotic community without entering the atmosphere.