The ecology of organisms and populations
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The Ecology of Organisms and Populations. Ecology is the interaction between organisms and their environments. Environment can be divided into two parts: biotic and abiotic. Abiotic is nonliving Chemical and physical factors Temperature Light Air Water Minerals Fire Wind.

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The ecology of organisms and populations

The Ecology of Organisms and Populations

Ecology is the interaction between organisms and their environments.

Environment can be divided into two parts biotic and abiotic
Environment can be divided into two parts:biotic and abiotic

Abiotic is nonliving

  • Chemical and physical factors

  • Temperature

  • Light

  • Air

  • Water

  • Minerals

  • Fire

  • Wind

Biotic is living or at one time was living
Biotic is living or at one time was living

  • Includes all currently living organisms from smallest to largest

  • Also includes any dead or decaying organisms such as tree stumps, bones, bacteria

The biotic part of the earth lives in a zone called the biosphere
The biotic part of the Earth lives in a zone called the BIOSPHERE:

  • All areas on Earth where life exists

  • Atmosphere: air up to about 17,000 feet

  • Lithosphere: land

  • Hydrosphere: water down to about 300 feet…although life is found in many areas previously thought uninhabitable by living things

  • If we compared Earth to an Apple…how

    thick do you think the Biosphere would be?

Lithosphere is divided up into biomes grasslands forests deserts
Lithosphere is divided up into BIOMES…grasslands, forests, deserts

  • Biomes determined by 3 things:







      • HOT AND COLD

Grassland biomes

  • Rainfall enough to support extensive grass family but not enough to support many trees

  • Tundra—coldest grassland, short growing season, characterized by permafrost, reindeer, ptarmigan, arctic hare

  • Prairie—central of US, most used for farming now, both tall and short grass…tall grass in east, short in west

  • Savanna—African grassland, supports world’s largest number of herbivores, characterized by Acacia tree (symbiotic relationship with ants)

  • Chapparal—found only in California and Argentina, characterized by scrub brush and frequent fires

Tundra and Prairie deserts

Chaparral and Savanna

Forest biomes

  • Conifer forest

    • Mainly pine (evergreen) trees

    • Highly acidic soils (decaying of pine


    • Most productive biome because of

      constant p.s.

    • Pine needles specially adapted to resist water loss from wind

      Deciduous Forest

      Rich soils (lots of organic matter decay)

      Many different types of trees

      Trees loose leaves in cycles

      (fall and spring mainly)

Rain (tropical) forest deserts

-up to 300+ inches of rain per year

-large trees-100’s of feet tall

-largest diversity of organisms of any biome

-divided into two parts; upper canopy above the

tree tops and forest floor

-trees will lose leaves during

“dry” period

DESERTS deserts

  • Sahara – world’s largest desert

  • Sandy soils

  • Very little rain

  • High daytime temps, low nighttime temps

  • Animals and plants specially adapted to extreme temps and drought

    • Kangaroo Rat—excretes mainly ammonia, very little water in urine

    • Cacti and other plants have reduced leaves and succulent stems to store water.

Aquatic biomes

  • Estuary—where river meets ocean, often called “nurseries of the sea,” fishermen harvest shrimp, lobster, salmon here

  • Pelagic Zone – top layer of ocean, part where boats cruise

  • Benthic Zone – bottom of the ocean, very little life except along rift zones

  • Intertidal Zone – “beach” where tide comes in and out, many types of organisms bury into sand when tide is “out” to keep moist

Intertidal Benthic Estuary Pelagic

In Estuary Pelagic undisturbed ecosystems, all organisms keep each

other in check. Even the top predators control each


Ecosystems are complicated networks of trophic


--the pattern of feeding levels that determines

energy flow and chemical cycling in an ecosystem.

Tropic levels include:

Autotrophs—plants and plant material

the producers in an ecosystem

photosynthetic, so they can produce their

own food.

Heterotrophs– organisms that depend on other

organisms to feed them.

Heterotrophs are broken down into three categories: Estuary Pelagic

Herbivores—eat only plant material and have wide

flat teeth adapted for grinding down the plants

Omnivores – eat both plant and animal material

and have both flat teeth for grinding and canine

teeth for tearing.

Carnivores – eat only (mainly??) meat and have

canine teeth allowing them to grasp and tear flesh

Detrivores decompose organic matter and speed

up the process of returning nutrients to soil.

Most bacteria act as detrivores.

When wolves were exterminated from the West in the Estuary Pelagic

1920’s many shifts occurred in the food chain:

Elk numbers multiply…their #1 predator is gone

Quality of elk declines without predation

Elk eat many young aspen trees…even manage

to completely eliminate some

Without aspen, beaver are left without food

Beaver leaves and no dams are made so some

aquatic life suffers…

All because the wolf was removed from the ecosystem

Ripple effect is felt throughout the food chain.

Return wolf to environment in 1995 and 1996 Estuary Pelagic

wolves from Canada released in YNP (31) and central Idaho (35)

current numbers as of Dec. 2008 from USFWS data (GYA-449) (CID-803)

Subsequent increase in number of young aspen trees Estuary Pelagic

Elk can’t “hang out” here anymore because they

block the view and cannot see predators

Wolves prey on old and sick elk…reduce overall #’s

Beaver returns because food supply is increased Estuary Pelagic

Beaver dams create new aquatic environments thus inviting new aquatic life…i.e. Boreal toads

Balance is restored to


Do humans cull animals from populations like Natural Selection does?

--what type of animal do humans hunt??

--what does mother nature cull out??