Bio 171 Lecture 10: Ecosystem Ecology II: Decomposition & Nitrogen Cycling

Assimilation

The process by which organisms absorb nutrients and incorporate them into their tissues.

• Example: Plants absorb nitrogen from the soil and use it to build protein

Biogeochemical Cycle

The movement of nutrients and elements (like carbon, nitrogen, and water) through living and non-living parts of an ecosystem.

• Example: The carbon cycle involves carbon moving between the atmosphere, plants, animals, and oceans.

Biosynthesis

The production of complex molecules within living organisms.

• Example: Plants use biosynthesis to produce glucose during photosynthesis.

Bioavailable

The form of a nutrient that organisms can absorb and use.

• Example: Nitrate (NO₃⁻) is a bioavailable form of nitrogen for plants.

Chitin

A tough, protective carbohydrate found in the cell walls of fungi and the exoskeletons of insects.

• Example: Crabs and shrimp have chitin in their shells.

Dead Zones (in Oceans)

Areas in oceans or lakes with low oxygen levels, often caused by pollution and eutrophication.

• Example: The Gulf of Mexico has a dead zone caused by fertilizer runoff.

Decomposers

• Organisms that break down dead material and recycle nutrients back into the environment.

  • Example: Fungi and bacteria decompose fallen leaves in forests.

Decomposition

The breakdown of dead organisms and waste into simpler substances.

• Example: A fallen tree slowly decomposes, releasing nutrients into the soil.

Denitrification

The process where bacteria convert nitrates (NO₃⁻) into nitrogen gas (N₂), returning it to the atmosphere.

• Example: Denitrifying bacteria in wetlands help regulate nitrogen levels.

Detritus

Dead organic material, such as fallen leaves, dead animals, and feces.

• Example: Decaying plant matter on the forest floor is detritus.

Ecosystem Services

The benefits humans get from ecosystems, like clean water, pollination, and oxygen production.

• Example: Bees pollinate crops, which supports food production.

Essential Nutrient

A nutrient that organisms need to survive but cannot produce themselves.

• Example: Humans need vitamin C from food because our bodies cannot produce it.

Eutrophication

Excess nutrients in water, causing algae growth and oxygen depletion.

• Example: Fertilizer runoff causes eutrophication in lakes, leading to fish die-offs.

Flux

The movement of nutrients or elements between different reservoirs in an ecosystem.

• Example: The exchange of carbon between the atmosphere and oceans is a flux in the carbon cycle

Fungi

A group of decomposing organisms that include mushrooms, molds, and yeasts.

• Example: Mushrooms growing on a fallen log help decompose it.

Hyphae

The thread-like structures that make up the body of fungi and help them absorb nutrients.

• Example: A mushroom's underground network of hyphae breaks down dead leaves

Inorganic

A substance that does not contain carbon-hydrogen (C-H) bonds.

• Example: Water (H₂O) and minerals like iron (Fe) are inorganic.

Limiting Nutrient

A nutrient that is in short supply and restricts growth in an ecosystem.

• Example: Phosphorus is a limiting nutrient in many freshwater lakes.

Macronutrient

A nutrient required in large amounts by organisms for growth and survival.

• Example: Nitrogen, phosphorus, and potassium are macronutrients for plants.

Mycelium

The underground network of hyphae in fungi that helps with nutrient absorption.

• Example: The mycelium of a mushroom extends underground, breaking down dead wood.

Mycorhizal Fungi

Fungi that form beneficial relationships with plant roots, helping them absorb water and nutrients.

• Example: Trees grow better with mycorrhizal fungi, which extend their root systems.

Nitrogen Fixation

The process where certain bacteria convert nitrogen gas (N₂) into a form plants can use (like ammonia, NH₃).

• Example: Legume plants have nitrogen-fixing bacteria in their root nodules.

Organic

A substance containing carbon-hydrogen (C-H) bonds, often from living things.

• Example: Glucose (C₆H₁₂O₆) and proteins are organic molecules.

Pool

A storage area for a nutrient within an ecosystem.

• Example: The ocean is a large pool of carbon.

Reservior

A natural place where a nutrient or element is stored for a long time.

• Example: The atmosphere is a reservoir for nitrogen gas (N₂).

Rhizobium Bacteria

A type of bacteria that lives in plant roots and helps with nitrogen fixation.

• Example: Rhizobium bacteria in pea plant roots convert nitrogen into a usable form.

Weathering

The breakdown of rocks into soil and minerals by wind, water, and temperature changes.

• Example: Rainwater slowly dissolves limestone, releasing minerals into the soil.