Ecosystems and Communities

Chapter 4 & 5 Notes

• Every organism affects its environment, and in turn is affected by its environment.  Ecosystems are affected by two kinds of factors– abiotic factors, or non-living factors: examples

include temperature, soil, precipitation, etc. – biotic factors, or living factors: examples

include organisms of the same species and organisms of different species

Biotic or Abiotic?

• Predators

• Hot weather

• Acid rain

• Wood from trees

• Your parents

• The river flow

• The leeches found in the river

The Role of Climate

• Weather: day-to-day conditions of the Earth’s atmosphere at a particular time and place– Temperature– Wind– Precipitation– Humidity– Specific weather

patterns

Weather for Sugar Land, TX

Sunday Sept. 16, 2007

The Role of Climate

• Climate: it is the average conditions in a region over several decades; affects the soil, and in turn the vegetation, and in turn other organisms in an area. It is described by:– temperature– precipitation

The Role of Climate• Temperature is determined by latitude/

angle of sunlight.

The Role of Climate

• Polar: 90-66.5º N or S (within the Arctic and Antarctic circles)

• Temperate: from the lines of Tropic of Cancer and Capricorn to 66.5 º N or S, respectively

• Tropical: between the Tropic of Cancer and Tropic of Capricorn

Polar (blue)Temperate (green)Tropical (red)

Other determinates of weather and climate:

• Coastal or central to the continent?

• Wind and ocean currents are driven by unequal heating of land and water

Other determinates of weather and climate:

• Upwelling: flow of denser cold water from the poles parallel to the ocean bottom and eventually rising in warmer regions

Diagram illustrating the principle of equatorial upwelling. Winds along the equator (dotted line) create currents, which are then diverted north and south by the Coriolis force. The cold, deep waters from below rise to the surface to replace these diverted waters, causing upwelling.

http://earthguide.ucsd.edu/virtualmuseum/climatechange1/11_2.shtml

• Greenhouse Effect: the natural situation in which heat is retained by the greenhouse gases (CO2, methane, water vapor, etc.) is called the greenhouse effect. If these gases were not present, the Earth would be 30º C cooler and unlivable

Biomes• -a collection of ecosystems with the same

climate and dominant communities; 2 main areas of biomes– Aquatic- in water– Terrestrial- on land

Aquatic

• Photic zone- where light penetrates (shallow water)

• Aphotic zone- no light (deep water)

• Estuary- where fresh and salt water meet (end of a river)

• Tidal zone- beach front

Tidal Zone

Photic Zone

Aphotic Zone

Photic Zone

Great Barrier Reef, Australia

Aphotic Zone• Photo credit: Edith Widder/HBOI

Estuary

Louisiana swampy areas

Tidal Zone

• From low tide to high tide

Tropical Rainforest

Costa Rica

Tropical Dry Forest

Fiji

Tropical Savanna

African Savanna

Desert

Sonoran Desert, Arizona

Temperate Grasslands

Temperate Woodland and Shrubland

Temperate Forest

Kauri Forest in North Island of New Zealand

Northwestern Coniferous Forest

Canadian Rockies

Taiga/ Boreal Forest

Alaska

Tundra

Community Interactions

• Habitat- place an organism lives• Niche- the role of an organism in an ecosystem,

every organism has a specified role it fulfills• Competition- competing for resources, shelter,

space, mates, etc.– Interspecific competition: between members of

different species– Intraspecific competition: between members of the

same species

• Predation- an organism hunts and feeds on another organism, ex: lion eats a zebra

Community Interactions

• Symbiosis- the relationship of organisms from DIFFERENT species living closely

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Community Interactions

• Mutualism- both species benefit from the relationship (ant live on an acacia tree, ant protects tree from harmful plants, tree gives ant a home)

Clownfish live within sea anemones, which normally sting other fish. The fish gets protection, and the anemone benefits because the clownfish keep it clean of bacteria.

Community Interactions

• Parasitism- one organism gains benefits at the other’s expense (fleas or ticks on a dog; flea gets a home, sucks the dog’s blood and is bothered by it)

Leech sucks the blood of a human

Community Interactions

• Commensalism- one species benefits and the other is not hurt nor helped (moss growing on trees)

Epiphytes are plants that grow on other plants without harming them. They never set root in the ground!

Factors Affecting Populations

• Three things affect population size:– # of births– # of deaths– # of individuals immigrating (entering) or

emigrating (leaving)

Types of Growth

• Exponential Growth- if a population has abundant space and food, no disease or predators; it will grow at an exponential rate. It is a J-shaped curve resembling y = ax2 + b

Types of Growth

• Logistic Growth- population growth slows then stops (stays stable) after a period of exponential growth once resources become less available. The number at which the environment can support this population is known as the carrying capacity.

Limiting factors

• factor that causes a population to decrease in size

• Two types…

Limiting Factors

• Density dependent- relies on how many organisms in a define space are in that population; can include things like competition, predation, parasitism, and disease

• Notice the pattern of population size with predator/prey relationship of hares and lynxes

Limiting Factors

Density independent- affect all populations in similar ways, regardless of the population size. Unusual weather natural disasters seasonal cycles certain human activities

Ecological Succession

o After such disasters, a community can start anew by a process called ecological succession (series of predictable changes that occurs in a community over time); there are two types

Succession

Primary succession- a community start where no soil is present (after a volcanic eruption/ glacier retreats)

Succession

Secondary succession- a community starts where soil is present (after a fire, disease, natural disaster)