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
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 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
-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 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:
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
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
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
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
Beaver 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??