Ecology Notes

What is Ecology??Ecology is the study of the relationships among organisms and their environment. Ecologists study environments at different levels of organization.• Ecology is the study of the interactions among living things, and between

living things and their surroundings.• Every ecosystem includes both living and nonliving factors.

An ecosystem includes both biotic and abiotic factors.• Biotic factors are living things.

– plants– animals– fungi– bacteria

• Abiotic factors are nonliving things. – moisture– temperature– wind– sunlight – soil

Changing one factor in an ecosystem can affect many other factors.• Biodiversity is the assortment, or variety, of living things in an ecosystem. • What ecosystem has the most biodiversity??• Rain forests have more biodiversity than other locations in the world, but are

threatened by human activities. What are the levels of organization??• Organism - An organism is an individual living thing, such as an

alligator.• Population - A population is a group of the same species that lives in one

area.Community - A community is a group of different species that live together in one area• Ecosystem - An ecosystem includes all of the organisms as well as the

climate, soil, water, rocks and other nonliving things in a given area.Biome - A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there

The biosphere is one of Earth’s four interconnected systems. • The biosphere is the portion of Earth that is inhabited by life. The

biosphere includes all ecosystems.– one of Earth’s systems

• There are three other Earth systems.– hydrosphere—water, ice, and water vapor– atmosphere—air blanketing Earth’s solid and liquid surface– geosphere—geologic features above and below Earth’s surface

What is the key factor that determines what the biome (ecosystem) will be?• Climate – is a key abiotic factor that affects the bioshphere• Climate is the long-term pattern of weather conditions.

• average temperature• precipitation• relative humidity

• Key factors shape an area’s climate.• temperature• sunlight• water• wind

Earth has three main climate zones.• The three main zones are the polar, tropical, and temperate climates.

– polar climate: the far northernand southern regions ofEarth

– tropical zone: surrounds the equator

– temperate zone: the wide area in betweenthe polar and tropical zones

Biomes are land-based, global communities of organisms.

Earth has six major biomes.

• Tropical rain forest biomes produce lush forests.• warm temperature• abundant precipitation all year

• Grassland biomes are where the primary plant life is grass.• Temperate grasslands are dry and warm during the summer; most

precipitation falls as snow.• Tropical grasslands are warm through the year, with definite dry and

rainy seasons.• Desert biomes are characterized by a very arid climate.

• very low amount of precipitation• four types: hot, semi-arid, coastal, and cold

• Temperate forest biomes include deciduous forests and rain forests.• Temperate deciduous forests have hot summers and cold winters.• Deciduous trees are the dominant plant species.

The temperate rain forests have a long wet season and relatively dry summer– Ferns and moss cover the forest floor. 

– The taiga biome is located in cooler northern climates.– boreal forest– long winters and short summers– small amount of precipitation

– The tundra biome is found in the far northern latitudes with long winters.– winter lasts 10 months– limited precipitation– permafrost

Polar ice caps and mountains are not considered biomes.• Polar ice caps have no soil, therefore no plant community. • The climate and organisms found on mountains change as the elevation

changes.

Life in an ecosystem requires a source of energy

Producers provide energy for other organisms in an ecosystem.• Producers get their energy from non-living resources.• Producers are also called autotrophs because they make their own food.• Consumers are organisms that get their energy by eating other living or

once-living resources.• Consumers are also called heterotrophs because they feed off of different

things.Almost all producers obtain energy from sunlight.• Photosynthesis in most producers uses sunlight as an energy source.• Food chains and food webs model the flow of energy in an ecosystem. • food chain is a model that shows a sequence of feeding relationships. A

food chain links species by their feeding relationships. • A food chain follows the connection between one producer and a single

chain of consumers within an ecosystem.

Consumers are not all alike– Herbivores eat only plants.– Carnivores eat only animals.– Omnivores eat both plants and animals.– Detritivores eat dead organic matter.– Decomposers are detritivores that break down organic matter into

simpler compounds.Trophic levels are the nourishment levels in a food chain

– Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat herbivores.– Tertiary consumers are carnivores that eat secondary consumers.– Omnivores, such as humans that eat both plants and animals, may be

listed at different trophic levels in different food chains.A food web shows a complex network of feeding relationships.• An organism may have multiple feeding relationships in an ecosystem.• A food web emphasizes complicated feeding relationships and energy flow in

an ecosystem.Matter cycles in and out of an ecosystemWater cycles through the environment.• The hydrologic, or water, cycle is the circular pathway of water on Earth.

Organisms all have bodies made mostly of water.

Elements essential for life also cycle through ecosystems.• A biogeochemical cycle is the movement of a particular chemical through the

biological and geological parts of an ecosystem.• The main processes involved in the oxygen cycle are photosynthesis and

respiration.

• Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients.

• Carbon is the building block of life.• The carbon cycle moves carbon from the atmosphere, through the

food web, and back to the atmosphere.• Carbon is emitted during the burning of fossil fuels.• Some carbon is stored for long periods of time in areas called carbon

sinks.

• The nitrogen cycle mostly takes place underground.• Some bacteria convert gaseous nitrogen into ammonia through a

process called nitrogen fixation.• Some nitrogen-fixing bacteria live in nodules on the roots of plants;

others live freely in soil.• Ammonia released into the soil is transformed into ammonium. • Nitrifying bacteria change the ammonium into nitrate.• Nitrogen moves through the food web and returns to the soil during

decomposition.

Pyramids model the distribution of energy and matter in an ecosystem. An energy pyramid shows the distribution of energy among trophic levels• Energy pyramids compare energy used by producers and other organisms on

trophic levels.• Between each tier of an energy pyramid, up to 90 percent of the energy is

lost into the atmosphere as heat.• Only 10 percent of the energy at each tier is transferred from one trophic

level to the next.

Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.• Biomass is a measure of the total dry mass of organisms in a given area.

2000g/m2producers 2000g/m2

675g/m2

150g/m2

75 g/m2

producers

primaryconsumers

secondaryconsumers

tertiaryconsumers

• A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem.

• A vast number of producers are required to support even a few top level consumers.

Every organism has a habitat and a nicheA habitat differs from a niche.• A habitat is all aspects of the area in which an organism lives.

– biotic factors– abiotic factors

• An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce.– food– abiotic conditions– behavior

Resource availability gives structure to a community.• Species can share habitats and resources.• Competition occurs when two species use resources in the same way.• Competitive exclusion keeps two species from occupying the same niche.

Organisms interact as individuals and as populationsCompetition and predation are two important ways inwhich organisms interact.• Competition occurs when two organisms fight for the

same limited resource.

producers 5,000,0005,000,000

500,000

5000

5

producers

primaryconsumers

secondaryconsumers

tertiaryconsumers

• Predation occurs when one organism captures and eats another.

•There are three major types of symbiotic relationships.• Mutualism: both organisms benefit• Commensalism: one organism benefits, the other is unharmed• Parasitism: one organism benefits, the other is harmed• Parasitism meet their needs as ectoparasites (such as leeches) and

endopaasites (such as hookworms)