Ecosystems and CommunitiesEcosystems and Communities

Chapter 4

The Role of Climate - Sec. 4.1Organisms vary in their adaptations to

temperature, rainfall, and other environmental conditions.

Species also vary in their tolerances for conditions outside their normal ranges.

Weather – day to day conditions of the Earth’s atmosphere at a particular place and time.

Climate – average, year to year conditions of temperature and precipitation in a particular region.

The Greenhouse Effect The atmosphere traps heat energy and

maintains Earth’s temperature range. Top three gases: carbon dioxide, methane,

water vapor. Sunlight enters the atmosphere as short

wavelength radiation and is converted to long wavelength heat which can not escape back out into space.

Without the greenhouse effect the Earth would be too cold to sustain life.

The Effect of Latitude on ClimateBecause Earth is a sphere that is tilted on

its axis, solar radiation strikes the surface at an angle that varies throughout the year.

The further you move away from the equator the more solar radiation varies during the seasons.

This divides the Earth into three main climate zones:

1. Polar – cold areas where light hits at low angle

2. Temperate – affected by tilt of Earth so seasonal change is great

3. Tropical – near equator from 23.5 degrees north to 23.5 degrees south.

Because the sun is directly overhead year round at the equator climatic conditions vary very little.

Heat Transport in the BiosphereUnequal heating of the atmosphere drives

winds and ocean currents. Warm air rises and cold air sinks.As warm air rises it is replaced by heavier cold

air – creates prevailing winds.Cold water at the poles sinks and flows toward

the equator where it warms and rises.These air and water movements transfer heat

throughout the world.

• Continents and other land masses can also affect winds and ocean currents.

• Winds over the oceans influence currents.

• As air rises over mountains, it cools and often loses its moisture as precipitation.

• This causes a dry area on the leeward side of the mountains = Rain Shadow Effect

Rain Shadow Effect

What Shapes an Ecosystem? – Sec. 4.2

Biotic Factors

- biological influences affecting an organism in its environment

- all of the living organisms in an ecosystem

Abiotic Factors

- physical, or nonliving, factors that affect an organism in an ecosystem

- climate, nutrient availability, soil type, sunlight, rainfall, etc.

Habitat

= where an organism lives

Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.

Niche

- an organism’s habitat and its role in the habitat

- includes biotic and abiotic factors, its role in the food web, its physical tolerances, its reproductive methods, etc.

- no two species can share the same niche in the same habitat. Fig. 4-5

- Many species have similar, but slightly different niches

- Fundamental niche – the complete niche that a species could occupy

- Realized niche – the niche that a species occupies when in competition with other species.

Community Interactions

- refers to interactions between organisms

A. Competition

- occurs when organisms of the same or different species try to use the same resource in the same place at the same time.

- Competitive Exclusion Principle

- no two species can occupy the same niche in the same habitat at the same time

Resource partitioning in Anolis lizards.

A. distichus

A. insolitus

B. Predation

- where one organism eats another

- predator vs. prey

C. Symbiosis

- relationships in which two species live closely together.

A) Mutualism

- both species benefit

B) Commensalism

- one organism benefits and the other has no positive or negative effect

- oxpeckers on grazers

- barnacles on whales

C) Parasitism

- one organism lives on or in another organism and harms it.

- host vs. parasite

Ecological Succession

- ecosystems constantly change in response to natural and human disturbances.

- results in a replacement of one community of species by another community

- as organisms live in an area they make the area better suited to other species

- Primary Succession

- when succession occurs where no soil previously exists

- lava flows, sand dunes, bare rock, etc.

- pioneer species = first species to populate

- lichen are often pioneer species

- composed of a fungus and algae

- begin breaking down rock and forming soil

- prepare the area for small grasses or herbs, which further prepare the area for other species

Secondary Succession

- when disturbance changes an existing community but does not remove the soil

- after fires, cutting forests, abandoned farmland

Secondary Succession

Primary

Succession

Alders to cottonwood

Spruce into Forest

Mount Saint Helens

Biomes – Sec. 4.3

* complex of terrestrial ecosystems that cover a large area and is characterized by certain soil and climate conditions and particular communities of plants and animals.

- organisms are adapted to certain biomes

- an adaptation is an inherited characteristic that increases an organism’s ability to survive and reproduce.

- each species has a range of tolerance for every environmental factor

- microclimate is often very important(insert graph of Law of Tolerances)

Terrestrial Biomes

Climatograph

1. Tropical Rain Forest (pg. 100)

2. Tropical Dry Forest (pg. 100)

3. Tropical Savanna (pg. 101)

4. Desert (pg. 101)

5. Temperate Grassland (pg. 102)

6. Temperate Woodland and Shrubland

7. Temperate Deciduous Forest (pg. 103)

8. Northwestern Coniferous Forest (pg. 103)

9. Boreal Forest (Taiga) (pg. 104)

10. Tundra (pg. 104)

Aquatic Ecosystems – Sec. 4.4Aquatic Ecosystems – Sec. 4.4

- are grouped according to abiotic - are grouped according to abiotic factors which affect them.factors which affect them.

- determined primarily by depth, flow, - determined primarily by depth, flow, temperature, and chemistry of the temperature, and chemistry of the waterwater

- depth determines light penetration- depth determines light penetration

- water chemistry refers mostly to the - water chemistry refers mostly to the amount of dissolved chemicals in the amount of dissolved chemicals in the water – salts, nutrients, and oxygenwater – salts, nutrients, and oxygen

- water covers approximately 75% of - water covers approximately 75% of Earth’s surfaceEarth’s surface

-about 3% of Earth covered by fresh -about 3% of Earth covered by fresh waterwater

Aquatic EcosystemsAquatic Ecosystems

Freshwater EcosystemsFreshwater Ecosystems

- divided based on if water is flowing or - divided based on if water is flowing or stillstill

1. Flowing-water ecosystems1. Flowing-water ecosystems

- rivers and creeks- rivers and creeks

- change along their length- change along their length

- headwaters often cold and - headwaters often cold and turbulent turbulent with lots of dissolved with lots of dissolved oxygen but oxygen but little plant life (trout) little plant life (trout)

- further down soil builds up, water - further down soil builds up, water slows, more plants grow (catfish) slows, more plants grow (catfish)

- organisms are well adapted for speed - organisms are well adapted for speed of of waterwater

2. Standing-water ecosystems2. Standing-water ecosystems

- lakes and ponds- lakes and ponds

- still water is good habitat for - still water is good habitat for planktonplankton

* tiny, free-floating or weakly * tiny, free-floating or weakly swimming swimming organisms in both organisms in both freshwater and freshwater and saltwater saltwater environmentsenvironments

* phytoplankton – single-celled algae * phytoplankton – single-celled algae – – base of most aquatic ecosystem base of most aquatic ecosystem food food chainschains

* zooplankton – planktonic animals * zooplankton – planktonic animals which which feed on the phytoplanktonfeed on the phytoplankton

Freshwater PondFreshwater Pond

3. Freshwater Wetlands3. Freshwater Wetlands

- ecosystems in which water either - ecosystems in which water either covers covers the soil or is present at or near the soil or is present at or near the the surface of the soil for at least part surface of the soil for at least part of of the yearthe year

- often very productive - often very productive

a. bogs – dominated by sphagnum mossa. bogs – dominated by sphagnum moss

- form in depressions where water - form in depressions where water gathers – often acidic soils/water gathers – often acidic soils/water

b. marshes – shallow wetlands along b. marshes – shallow wetlands along rivers rivers

- often contain cattails, reeds, - often contain cattails, reeds, rushesrushes

c. swamps – water slowly flows throughc. swamps – water slowly flows through

- often look like flooded forests- often look like flooded forests

EstuariesEstuaries

* wetlands where rivers meet the sea* wetlands where rivers meet the sea

- mixed fresh and salt water - mixed fresh and salt water

- affected by rise and fall of tides- affected by rise and fall of tides

- often shallow, so they support many - often shallow, so they support many producers and are extremely producers and are extremely

productiveproductive

- detritus feeds many of the lower - detritus feeds many of the lower levels levels of the food chainsof the food chains

- important spawning and nursery - important spawning and nursery areasareas

a. Salt marshesa. Salt marshes

- temperate zone estuaries - temperate zone estuaries dominated dominated by salt-tolerant grasses by salt-tolerant grasses above the above the low-tide line and low-tide line and seagrasses belowseagrasses below

* much of Texas Coast* much of Texas Coast

b. Mangrove swampsb. Mangrove swamps

- tropical wetlands dominated by salt-- tropical wetlands dominated by salt- tolerant trees called mangroves tolerant trees called mangroves

- seagrasses below low-tide line- seagrasses below low-tide line

- valuable nurseries for fish and - valuable nurseries for fish and shellfish shellfish

* coast of Everglades N.P.* coast of Everglades N.P.

EstuariesEstuaries

Marine Ecosystems – pg. 109Marine Ecosystems – pg. 109

Marine EcosystemsMarine Ecosystems

* Photic Zone – area where light * Photic Zone – area where light penetratespenetrates

- photosynthetic producers- photosynthetic producers

* Aphotic Zone – below light * Aphotic Zone – below light penetrationpenetration

- chemosynthetic producers and - chemosynthetic producers and detritusdetritus

1. Intertidal zone1. Intertidal zone

- area between high and low tide - area between high and low tide

- organisms adapted to being exposed - organisms adapted to being exposed for for part of the daypart of the day

- clear - clear zonationzonation of organisms of organisms

Marine EcosystemsMarine Ecosystems

2. Coastal Ocean2. Coastal Ocean

- extends from low-tide mark to outer - extends from low-tide mark to outer edge of continental shelfedge of continental shelf

- often all in the photic zone- often all in the photic zone

- kelp forests- kelp forests

3. Coral Reefs3. Coral Reefs

- warm, shallow tropical waters- warm, shallow tropical waters

- coral animals’ hard calcium carbonate - coral animals’ hard calcium carbonate skeletons make up the reef baseskeletons make up the reef base

4. Open Ocean4. Open Ocean

- low productivity, but huge area makes - low productivity, but huge area makes it important for worldwide it important for worldwide photosynthesisphotosynthesis

5. Benthic Zone5. Benthic Zone

- ocean floor ecosystem- ocean floor ecosystem

- usually depends on detritus - usually depends on detritus “raining “raining down”down”

- benthos – organisms which live on - benthos – organisms which live on the the ocean floorocean floor

Characteristics of PopulationsCharacteristics of Populations1. Population Density1. Population Density

- number of individuals per unit of area- number of individuals per unit of area

2. Geographic Distribution2. Geographic Distribution

- range- range

- the area inhabited by a population- the area inhabited by a population

3. Growth Rate3. Growth Rate

- depends on birth rates, death rates, and the - depends on birth rates, death rates, and the number number of individuals moving into or out of a of individuals moving into or out of a populationpopulation

Populations in nature grow in two Populations in nature grow in two ways:ways:

1. Exponential Growth 1. Exponential Growth

- occurs in populations with - occurs in populations with abundant abundant space, resources, and space, resources, and few predators or few predators or diseasedisease

- individuals in a population - individuals in a population reproduce at reproduce at a constant rate.a constant rate.

- at first population grows slowly, - at first population grows slowly, but but steadily increases at an steadily increases at an accelerating accelerating speed.speed.

Exponential Growth – Whooping Exponential Growth – Whooping CranesCranes

2. Logistic Growth2. Logistic Growth

- after a period of exponential - after a period of exponential growth, growth, resources become resources become limited and limited and population growth population growth slows or stops.slows or stops.

- slows due to decrease in birthrate, - slows due to decrease in birthrate, increase in death rate, or bothincrease in death rate, or both

- eventually the population reaches a - eventually the population reaches a maximum size that the maximum size that the

environment environment can support = can support = Carrying CapacityCarrying Capacity

Logistic Population GrowthLogistic Population Growth

Limiting factors cause population growth to Limiting factors cause population growth to decrease.decrease.

Density-Dependent FactorsDensity-Dependent Factors

- limiting factors that depend on population size- limiting factors that depend on population size

- become limiting only when the population density - become limiting only when the population density reaches a certain level and as population grows reaches a certain level and as population grows the factor becomes more limiting.the factor becomes more limiting.

* competition, predation, parasitism, disease* competition, predation, parasitism, disease

Density-Independent FactorsDensity-Independent Factors

- affect all populations in similar ways, regardless - affect all populations in similar ways, regardless of population sizeof population size

* weather, natural disasters, seasonal cycles, and * weather, natural disasters, seasonal cycles, and human activitieshuman activities

Human Population growth has historically been exponential.

Age-structure diagrams give a view of what a population is like now and what might happen in it in the future.