The Ecology of Organisms and Populations

Ecology is the interaction between organisms and their

environments.

Environment can be divided into two parts:

biotic and abioticAbiotic is nonliving • Chemical and physical

factors• Temperature• Light • Air • Water• Minerals• Fire• Wind

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

Do You Think Coral Reefs are composed of Biotic or Abiotic

Components?

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

• Biomes determined by 3 things:– SOIL TYPE

• RANGES FROM CLAY TO SAND AND MANY MIXES

– AMOUNT OF RAINFALL• FROM VERY WET TO VERY DRY

– TEMPERATURE• VARIABLE, STABLE AND EXTREME• 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 Chaparral and Savanna

FOREST BIOMES• Conifer forest

– Mainly pine (evergreen) trees– Highly acidic soils (decaying of pine

needles)– Most productive biome because of

constant p.s.– Pine needles specially adapted to resist water loss from wind

Deciduous ForestRich soils (lots of organic matter decay)Many different types of treesTrees loose leaves in cycles (fall and spring mainly)

Rain (tropical) forest-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

• 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 undisturbed ecosystems, all organisms keep each other in check. Even the top predators control each other.

Ecosystems are complicated networks of trophic Structure

--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 ecosystemphotosynthetic, so they can produce theirown food.

Heterotrophs– organisms that depend on other organisms to feed them.

Heterotrophs are broken down into three categories:Herbivores—eat only plant material and have wideflat teeth adapted for grinding down the plants

Omnivores – eat both plant and animal materialand have both flat teeth for grinding and canineteeth 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 the1920’s many shifts occurred in the food chain:

Elk numbers multiply…their #1 predator is goneQuality of elk declines without predationElk eat many young aspen trees…even manageto completely eliminate some Without aspen, beaver are left without foodBeaver leaves and no dams are made so someaquatic 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 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 treesElk can’t “hang out” here anymore because theyblock the view and cannot see predators

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

Beaver returns because food supply is increasedBeaver dams create new aquatic environments thus inviting new aquatic life…i.e. Boreal toads

Balance is restored to ecosystem.

Do humans cull animals from populations like Natural Selection does?

--what type of animal do humans hunt??--what does mother nature cull

out??