AP Environmental Science Unit 1: The Living World: Ecosystems

Ecosystem

all living & nonliving things in an area (plants, animals, rocks, soil, water, air)

Community

all living organisms in an area

Individual

one organism (elk)

Population

group of individuals of same species (elk herd)

Biome

the plants and animals found in a given region (determined by climate)

Mutualism

relationship that benefits both organisms (coral reef)

Commensalism

relationship that benefits one organism & doesn't impact the other (birds nest in trees)

Competition

organisms fighting over a resource like food or shelter; limits population size

Predation

one organism using another for energy source (hunters, parasites)

Herbivores

(plant eaters) eat plants for energy (giraffe & tree)

True predators

(carnivores) kill and eat prey for energy (leopard & giraffe)

Parasites

use a host organism for energy, often without killing the host & often living inside host (e.g., mosquitoes, tapeworms, sea lamprey)

Parasitoids

lay eggs inside a host organism; eggs hatch & larvae eat host for energy (e.g., parasitic wasps, bot fly)

Symbiosis

Any close and long-term interaction between two organisms of different species

Resource partitioning

different species using the same resource in different ways to reduce competition

Temporal partitioning

using resource at different times, such as wolves & coyotes hunting at different times (night vs. day)

Spatial partitioning

using different areas of a shared habitat (different length roots)

Morphological partitioning

using different resources based on different evolved body features

Tundra

higher latitude biome with low soil nutrients and low water availability

Boreal forest

nutrient-poor biome with frozen soils that limit nutrient availability

Tropical rainforest

biome with nutrient-poor soil due to rapid decomposition and nutrient leaching

Forest

Nutrient-rich soil with lots of dead organic matter, leaves, and warm temperature/moisture for decomposition.

Shifting Biomes

Biomes that change location on Earth as climate changes.

Aquatic Biomes

Biomes that are characterized by water environments.

Salinity

How much salt there is in a body of water, determines which species can survive and usability for drinking (Fresh water vs. estuary vs. ocean).

Flow

Determines which plants and organisms can survive, how much O2 can dissolve into water.

Depth

Influences how much sunlight can penetrate and reach plants.

Temperature

Warmer water holds less dissolved O2 so it can support fewer aquatic organisms below the surface for photosynthesis.

Freshwater: Rivers

Rivers have high O2 due to flow mixing water and air, also carry nutrient-rich sediments.

Freshwater: Lakes

Standing bodies of fresh H2O, key drinking water source.

Littoral Zone

Shallow water with emergent plants.

Limnetic Zone

Where light can reach (photosynthesis); no rooted plants, only phytoplankton.

Profundal Zone

Too deep for sunlight; no photosynthesis.

Benthic Zone

Murky bottom where invertebrates (bugs) live, nutrient-rich sediments.

Wetland

Area with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants.

Benefits of Wetlands

Stores excess water during storms, recharges groundwater, filters pollutants, and has high plant growth rates due to water and nutrients.

Estuaries

Areas where rivers empty into the ocean; mix of fresh and salt water.

Salt Marsh

Estuary habitat along coast in temperate climates; breeding ground for many fish and shellfish species.

Mangrove Swamps

Estuary habitat along coast of tropical climates; mangrove trees with long, stilt roots stabilize shoreline.

Coral Reef

Warm shallow waters beyond the shoreline; most diverse marine biome on Earth.

Mutualistic Relationship in Coral Reefs

Coral takes CO2 out of ocean to create calcium carbonate exoskeleton and provides CO2 to algae; algae provide sugar to coral through photosynthesis.

Intertidal Zones

Narrow band of coastline between high & low tide.

Organisms in Intertidal Zones

Must be adapted to survive crashing waves & direct sunlight/heat during low tide.

Example of Intertidal Organisms

Barnacles, sea stars, crabs that can attach themselves to rocks.

Adaptation to Prevent Desiccation

Shells & tough outer skin can prevent drying out during low tides.

Different Zones

Different organisms are adapted to live in different Zones.

Spiral Wrack

Type of seaweed that curls up & secretes mucus to retain water during low tide.

Open Ocean

So large that algae & phytoplankton of ocean produce a lot of earth's O2 & absorb a lot of atmospheric CO2.

Photic Zone

Area where sunlight can reach (photosynthesis).

Aphotic Zone

Area too deep for sunlight.

Energy Sources in Aphotic Zone

Species rely on detritus from photic zone or chemosynthetic microbes @ hydrothermal vents for energy.

Carbon Cycle Overview

Movement of molecules that contain Carbon (CO2, glucose, CH4) between sources and sinks.

Carbon Sink

Reservoir that takes in more carbon than it releases (e.g., ocean, plants, soil).

Carbon Source

Reservoir that releases more carbon than it takes in (e.g., fossil fuel combustion, animal agriculture, deforestation).

Photosynthesis

Process done by plants, algae, and phytoplankton to remove CO2 from the atmosphere and convert it to glucose.

Cellular Respiration

Uses O2 to break glucose down & release energy, releasing CO2 into the atmosphere.

CO2 Sink

Removes CO2 from the atmosphere.

Direct Exchange of CO2

CO2 moves directly between atmosphere & the ocean by dissolving into & out of ocean water at the surface.

Ocean Acidification

Increasing atmospheric CO2 also increases ocean CO2, leading to ocean acidification.

Calcium Carbonate Exoskeletons

Coral, mollusks, and some zooplankton take CO2 out of the ocean to make calcium carbonate exoskeletons.

Sedimentation

Calcium carbonate precipitates out as sediment & settles on ocean floor.

Burial Process

Over long periods of time, pressure of water compresses C-containing sediments on ocean floor into sedimentary rock.

Fossil Fuels Formation

Formed from fossilized remains of organic matter into coal or oil; decomposition produces natural gas (CH4).

Extraction & Combustion

Digging up or mining fossil fuels & burning them as energy source; releases CO2 into atmosphere.

Nitrogen Cycle

Movement of N-containing molecules between sources & sinks/reservoirs.

N reservoirs

Hold N for relatively short periods of time compared to C cycle.

Atmosphere

Main N reservoir where N exists mostly as N2 gas, which is not usable by plants or animals.

Nitrogen Fixation

Process of N2 gas being converted into biologically available NH3 (ammonia) or NO3- (nitrate).

Biotic fixation

Certain bacteria that live in the soil or in symbiotic relationship with plant root nodules convert N2 into ammonia (NH3).

Rhizobacteria

Bacteria that live in root nodules of legumes (peas, beans) & fix N for them in return for amino acids from the plant.

Abiotic fixation

Lightning converts N2 gas into nitrate (NO3-) and FF combustion converts N2 gas into ammonia (NH3).

Assimilation

Plants & animals taking N in and incorporating it into their biomass.

Ammonification

Soil bacteria, microbes & decomposers converting waste & dead biomass back into NH3 and returning it to soil.

Nitrification

Conversion of NH4 into nitrite (NO2-) & then nitrate (NO3) by soil bacteria.

Denitrification

Conversion of soil N (NO3) into nitrous oxide (N2O) gas which returns to atmosphere.

Human Impacts on N Cycle

N2O (nitrous oxide) is a greenhouse gas which warms earth's climate, produced by denitrification of nitrate in agricultural soils.

Leaching & Eutrophication

Synthetic fertilizer use leads to nitrates (NO3) leaching, causing algae blooms that block sun & kill other aquatic plants.

Phosphorus Cycle

Movement of P atoms & molecules between sources & sinks/reservoirs.

P cycle speed

Very slow compared to C/H2O/N cycles; takes a long time for P minerals to be weathered out of rocks.

Limiting nutrient

Because it cycles so slowly, P is often a limiting nutrient, meaning plant growth in ecosystems is often limited by P availability.

Phosphorus Sources

Major natural source of P is weathering of rocks that contain P minerals.

Weathering

Wind & rain break down rock & phosphate (PO4-3) is released and dissolved into water.

Synthetic sources of P

Mining phosphate minerals & adding to products like synthetic fertilizers & detergents/cleaners.

Assimilation & Excretion/Decomposition

P is absorbed by plant roots & assimilates into tissues; animals assimilate P by eating plants or other animals.

Geological uplift

The process of tectonic plate collision forcing up rock layers that form mountains.

Eutrophication

The excess of nutrients (N & P) in aquatic ecosystems leading to algae growth.

Algae bloom

A rapid increase in algae that covers the surface of water, blocking sunlight.

Dissolved oxygen

The amount of oxygen available in water, crucial for aquatic life.

Positive feedback loop

A cycle where less O2 leads to more dead organisms, causing more decomposition and further reducing O2.

Hydrologic Cycle

The movement of H2O in different states between sources and sinks.

Evaporation

The process where liquid water becomes water vapor in the atmosphere.

Evapotranspiration

The amount of H2O that enters the atmosphere from transpiration and evaporation combined.

Infiltration

The process where precipitation trickles through soil down into groundwater aquifers.

Runoff

The flow of precipitation over the earth's surface into a body of water.

Primary Productivity

The rate that solar energy is converted into organic compounds via photosynthesis over a unit of time.

Units of Primary Productivity

Measured in kcal/m2/yr, indicating energy over time and area.