Download Principles of Ecology

Principles of Ecology- Ch. 2
I.
Ecology- study of relationships b/w (between) organisms and their
environment.
A. Biosphere- area of earth where life exists- a thin layer covering the
earth’s surface.
 Lithosphere- the earth’s crust
 Hydrosphere-earth’s water- oceans, lakes, rivers, and
streams.
 Atmosphere- earth’s air- a gaseous envelope
B. Ecosystems- stable environment in which living (biotic) and nonliving (abiotic) things interact and in which materials are recycled.
1. Abiotic (non-living) factors
a. sunlight, climate, non-living substances
2. Biotic (living) factors – are organized into:
a. Populations- a group of organisms, all of the same
species, which interbreed and live in the same area at the
same time.
b. Biological Community- all interacting pop.’s within a
given area at a certain time.
II.
Organisms in ecosystems
A. Habitat- part of the environment where an organism lives.
 Eagle in forest, Mouse in the classroom
B. Niche- way of life, or role of a species in an ecosystem- the how,
when and where an organism obtains its nutrients, its reproductive
behavior, its habitat.
C. Competition
1. In a balanced ecosystem, each species occupies its own niche.
2. Competition arises when the niches of 2 species overlap.
3. Competition between different species is called interspecific
competition.
As resources become more scarce, competition increases
and one of the species will be eliminated.
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4. Competition between members of the same species is called
intraspecific competition.
Population density and available resources affect the
intensity of competition. Poorly adapted individuals will
not survive.
5. Competition is one way species evolve over time.
D. Survival Relationships- some organisms form symbiotic, or
close, permanent relationships:
1. Predation- One individual captures and eats another (the
prey).
Ex: Wolf eats a rabbit
2. Parisitism- one individual (the parasite) feeds another (the
host).
Ex: Tapeworm feeds from human intestines
3. Mutualism- Both species benefit.
Ex: A bee eats nectar from a flower and the flower gets
pollinated.
4. Commensalism- One individual benefits, but the other is
neither hurt nor helped.
Ex: Cattle egrets eat small animals that are forced
out of their hiding places as cattle move through the grass
(the birds hang out on the back of the cattle).
III.
How organisms obtain energy
A. Producers- green plants and algae
 autotrophic provide all the food for higher trophic levels
(primary productivity- how much energy is available).
B. Consumers
 heterotrophic animals, fungi and protists (eat other organisms).
1. First order consumers are herbivores, or animals that
eat plants (eat producers).
 Grasshoppers, mice, deer, rabbits, zooplankton
(animal-like microorganisms)
2. Second order consumersa. carnivores-eat primary consumers (meat)
 snakes, cats, birds of prey, preying mantis
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b. omnivores- eat producers (plants) and consumers
(animals).
 Bears, humans.
c. Scavengers- eat animals that have recently died.
 Vultures, crows
d. decomposers (saprovores)- bacteria and fungi- break
down organic components of dead organisms- use
some for their own food and release the rest to be used
by other organisms.
IV.
Energy flow in an ecosystem.
a. steps by which energy is transferred from the sun to
organisms in an ecosystem is a food chain. Each organism
in a food chain represents a feeding step or trophic level.
Solar Energy
Lettuce
producer
Rabbit
1st order consumer (herbivore)
Coyote
2nd order consumer (carnivore)
Vulture
3rd order consumer (scavenger)
Bacteria
decomposer (saprovore)
A food web is made up of interrelated food chains in an ecosystem.
A. Ecological Pyramids
 amount of energy available in a food web decreases with each
higher feeding level.
 Most energy taken into an organism as food is lost to the
environment as heat (only about 10% is actually used)!
 As you move up the food chain/web (trophic levels), the
number of organisms decreases (as does the biomass- or the
total weight of living matter at each level).
 Because the amount of available energy decreases so
steeply, there are generally no more than 4-5 feeding levels!
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V.
Biogeochemical Cycles- minerals traveling through the abiotic
portion of the environment, such as the atmosphere, into living things
and back again.
a. Water Cycle-includes both fresh and salt water.
1. Evaporation- adds water as vapor to the atmosphere.
2. Transpiration- the release of water through tiny holes in
the leaves of plants (called stomata).
3. Precipitation-the release of water from the atm. (snow,
rain).
b. Carbon Cycle/Oxygen Cycle1. Plants take in CO2, give off O2 (photosynthesis)
2. Animals take in O2, give off CO2 (respiration)
3. Humans have increased CO2 levels greatly by burning
fossil fuels- this causes the Greenhouse Effect- the
gradual rising of the Earth’s temperature.
c. Nitrogen Cycle-Nitrogen is in the air as gas, but plants and
animals can only use it in other forms. Nitrogen is needed to
build proteins, muscle, enzymes, DNA and urine.
1. Plants get nitrogen through:
a. nitrogen fixing bacteria that convert nitrogen gas
from the air into usable forms (nitrogen fixation)
b. decomposers that convert urine & dead plants and
animals into a usable form (ammonification)
2. Animals get nitrogen by eating plants.
3. Nitrogen gas is reintroduced into the atm. by
a. the breaking down of dead organisms and wastes by
bacteria.
d. Phosphorous Cycle- phosphorous is required for growth
and development of all organisms.
a. Plants get it from the soil.
b. Animals get it from eating plants.
c. When organisms die, it is returned to the soil to be
used again.
d. Phosphorous can also be released by rocks over
millions of years.
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