Ecosystems & Communities

Chapter 4

The Role of Climate

Chapter 4-1

III. EcosystemDefinition: the combination of biotic and biotic and

abiotic components abiotic components through which energyenergy flows and materials cycle flows and materials cycle (usually a self-contained unit, such as a pond, swamp, meadow, or woods)

A. Energy Flow 1. Ultimate source - SUN - 50% of suns energy that

collides with earth actually reaches the surface of earth

- 0.1 % of that ends up in living organisms

The Role of ClimateClimate is caused by the interplay of many

factors:Trapping of heat by the atmosphereLatitudeTransport of heat by winds and ocean

currentsThe amount of precipitation that resultsThe shape and elevation of landmasses

Maintenance of Earth’s Temperature RangeHeat energy is trapped by atmospheric

gasesCarbon dioxideMethaneWater vaporOther gases like CFCs, ozone, NO

Without this greenhouse effect, Earth would be 30o Celsius cooler.

Greenhouse Effect

The Effect of LatitudeDifferent parts of Earth’s surface receive

varying amounts of solar radiationsolar radiationAs a result of differences in latitude and differences in latitude and

thus the angle of heatingthus the angle of heating, Earth has three main climate zones:TropicalTropical- receives direct- or nearly-direct

sunlight year-roundPolarPolar- near North and South poles, receive

rays at a low angle

The Effects of Latitude cont’dTemperate zones: between the other two

zones, receive sunlight at changing angles throughout the year

Latitude

WindUnequal heating of Earth’s surface causes

warm air at equator to rise, and cooler near warm air at equator to rise, and cooler near poles to sinkpoles to sink

This creates windsEarth’s rotation rotation develops patterns called

currentscurrents (example: Gulfstream current, Arctic current)

Wind

Ch 4-2 Biotic & Abiotic Factors

Together determine the survival & growth of an organism as well as productivity of ecosystem in which the organism lives

Biotic Factors

Biological influences on organisms

Birds, trees, mushrooms, bacteria- the ecological community

Abiotic FactorsTemperaturePrecipitationHumidityWindNutrient availabilitySoil typeSunlight

The NicheHabitat = address. Doesn’t tell much about the individual.

Niche = full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions.

The NichePlace in the food webRange of temperatures it needs to survive

Tells when and how it reproduces

Determined by biotic and abiotic factors

Bay-Breasted WarblerFeeds in the middlepart of the tree

Yellow-Rumped WarblerFeeds in the lower part of the tree andat the bases of the middle branches

Cape May WarblerFeeds at the tips of branchesnear the top of the tree

Spruce tree

Figure 4-5 Three Species of Warblers and Their Niches

Community InteractionsCommunity interactions such as competition, predation, and various forms of symbiosis can powerfully affect an ecosystem.

Community InteractionsCompetition- occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time

Community Interactions

Resource- any necessity of life, such as water, nutrients, light, food or space

Competitive exclusion principle- no two species can occupy the same niche In the same habitat at the same time

Community InteractionsPredation- an interaction in which one organism captures and feeds on another

Community InteractionsSymbiosis- any relationship in

which two species live closely togetherMutualism

Both species benefit. Example: bees and pollen/nectar

MutualismMutualism: both organisms benefit from

living in close association. Example: ants and acacia trees.

Community Interactions

CommensalismOne benefits, other unaffected. Example: barnacles on a whale

Parasitism- when one organism lives in or on another organism, obtaining from its host all or part of its nutritional needs

Commensalism

Example: shark and pilot fish, moss and trees

ParasitismParasitism: one organism benefits at

the expense of the other. Usually they do not kill the host. Example: ticks and fleas on dogs, mosquitoes on humans.

Disturbance & SuccessionEcosystems are constantly changing in

response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. Called ecological succession.

Ecological successionEcological succession- the succession of communities that follows the disturbing of an area.

Characteristics 1. Increase in total biomass 2. Gradual decrease in net productivity 3.Mature systems have a greater capacity to

entrap and hold nutrients 4. Number of species increase 5. r-species early K-species late

Climax communityClimax community = final s = final stable stagetable stage

1

2

5

10

20

Causes of SuccessionMay result from slow changes in the

environment that cause predictable shifts in living communities. Example: Freshwater pond fills with sediments and becomes a marsh.

Can also be caused by sudden natural disturbance, like hurricane or fire. Example: fire on the prairie

Primary & Secondary SuccessionHappens slowly because living organisms

modify their environment a little at a time.

Primary successionThe colonization of new sites by colonies

of organisms is called primary succession. Usually occurs on newly exposed surfaces.

Eventually, repopulating slows down and becomes stable. If little or no succession is occurring this is called a climax community.

Secondary SuccessionIf a natural disaster or human action destroys a

community without destroying the soil it is secondary succession.

Community of organisms gradually changesNew species replace pioneer speciesClimax community reached more quicklyExamples: land plowed and cleared for

farming, lightning fire on prairie