ECOLOGY
(Chapters 19, 21, 22, & 23)
1. Organisms cannot exists alone. Ecologists study how organisms live together in
relationship with each other & their environment.
2. We begin by looking at our biosphere - which is the area of the earth where
life exists. Within this biosphere are specific ecological units called biomes.
Each can be identified by temperature, rainfall, soil, plants, & animals.
3. Ecologists study all features of an environment & the organisms living there.
a) abiotic factors - nonliving things such as air, water, rocks, sunlight,
rainfall, slope of land, temperature, etc.
b) biotic factors - living plants, animals, & microorganisms competing for
food, water, space, & other resources
4. We will organize our study of biomes in this way:
a) organism - focus on adaptations that allow an individual species to
overcome challenges of their environment
b) organisms of the same species make up a population
c) populations of different species interact as communities
d) communities of plants, animals, & microorganisms that interact with &
depend upon each other & their environment for survival are an
ecosystem
5. The specific place within an ecosystem where an organism lives out its life is
known as its habitat.
6. Species who share a habitat each occupy a role or position called a niche for
how it meets its needs for food, shelter, reproduction, etc.
7. To increase their chances of survival some species form close & permanent
relationships with a different species. This “living together” is called
symbiosis.
a) commensalism - 1 species benefits & other is unaffected (Spanish moss,
orchids, cows & egrets)
b) mutualism - both species benefit (termite & protist, pollinators, lichen,
cows & cowbirds)
c) parasitism - 1 species benefits & other is harmed (ticks, fleas, bacteria)
8. Other interactions within ecosystems:
a) competition - various species strive for same limited resources such as
food, water, mate, & shelter
b) limiting factors - anything that restricts existence, numbers,
distribution, or reproduction of species (food, predators/prey, weather,
shelter, water)
c) carrying capacity - maximum # of 1 species environment can support will
determine whether population will increase or decrease as nature seeks
to maintain balance between number of individuals & available resources
d) predator/prey – since the prey will be eaten & the predator will die if it
does not get food, these animals both have whatever adaptations are
necessary for survival (speed; stealth; camouflage; good sense of smell,
sight, or hearing; defenses or kill tactics such as mouth & other body
parts, sounds, & poisons)
e) invasive non-native species – plants, animals, or other organisms that
are introduced to an area outside their original habitat that cause harm
in their new harm because they have no natural enemies to limit their
reproduction – they are then able to take over the habitats of native
species
9. Energy enters ecosystem from sun & flows in a sequence of transfers called
trophic levels.
a) producers - autotrophs (plants, algae, & some bacteria) create their own
food sunlight or chemicals - manufacture all nutrients for an ecosystem
b) consumers - heterotrophs (animals, protozoa, fungi) must get energy
from other organisms - they are classified according to food source:
1) primary consumers/herbivores - eat producers
2) secondary consumers/carnivores - eat other consumers
3) omnivores - eat both producers & consumers
4) scavengers - eat animals that have already died
5) decomposers - break down dead & decaying animals & plants into
simpler molecules that are absorbed by decomposer or returned to
soil or water
10. A food chain is a specific sequence of interactions in which organisms
produce & consume energy in an ecosystem - this energy originally came from
the sun. In nature, many food chains interlink & overlap in food webs as
many consumers eat more than 1 type of food & more than 1 species of
consumer may feed on same organisms.
11. An ecological pyramid shows how energy flows through an ecosystem.
a) base represents autotrophs & higher trophic levels are layered on top
b) energy transfer from 1 trophic level to next is only about 10% because
organisms fail to capture & eat all food available at trophic level below
c) energy from food is used for metabolism, for building tissues, some is
given off as waste, & energy lost enters the environment as heat
d) only energy used to build body tissues is available for use by consumers
e) energy decreases as trophic levels increase
f) biomass expresses the weight of living material at each trophic level & is
calculated by finding the average weight of each species & multiplying by
estimated number of organisms in each population
12. Bioaccumulation/biomagnification refers to the way pollutants enter a food
chain & then tend to become more concentrated as they move upward from 1
trophic level to the next.
13. Biogeochemical cycles impact organisms in ecosystems as materials move
from air or soil into living organisms & back again.
a) water cycle - plant absorption & transpiration + animals eat or drink &
exhale, perspire, or excrete + evaporation from bodies of water +
precipitation
b) nitrogen cycle - lightning & nitrogen-fixing bacteria in soil convert
atmospheric nitrogen into ammonia (form plants & animals can use
to build proteins) - animal waste & decomposition return nitrogen to soil
c) carbon cycle - during photosynthesis plants take in carbon dioxide from
air & release oxygen - plants, animals, & decomposers use oxygen during
cellular respiration & release carbon dioxide
14. Ecologists can predict a specific & gradual pattern of change in plant &
animal populations known as succession.
a) primary succession - area has not previously supported life (bare rock or
sand dune) & may require 1000 years or more.
b) secondary succession - destroyed by natural disaster or human activity but not totally stripped soil & vegetation.
15. Pattern of forest succession:
1st: pioneer community - grass & lichens are first species to be established
2nd: as soil develops new species such as dandelions, other weeds, & shrubs
establish themselves
3rd: soil, climate, & other abiotic factors eventually lead to establishment
of stable long-lasting climax community
16. Pattern of lake succession:
1st: clear water, low in nutrients, few species of organisms
2nd: murky water, increase in species, vegetation appears along shore,
buildup of sediment
3rd: increasing buildup of sediment creates marsh -> swamp -> dry land ->
forest
17. Earth’s terrestrial biomes:
a) tundra:
1) near North Pole in northern N. America, Europe, Asia
2) snow-covered in winter & brief summer with ponds, bogs, mud
3) thin layer of topsoil low in nutrients covers permanently frozen
ground called permafrost - very little rainfall
4) treeless, woody shrubs, mosquitoes, ducks, fox, reindeer, owls
b) taiga:
1) south of tundra across Canada, Northern Europe, Asia
2) evergreen cone-bearing trees (pine, fir, spruce, cedar) provide
shelter for moose, bear, wolves, lynx - many hibernate or migrate
3) long, cold winters & short summers - wetter, nutrient-poor soil
c) temperate deciduous forest:
1) eastern U.S., parts of Europe, Asia, S. America, Africa, & Australia
2) noticeable seasons with warmer winters & longer summers &
rainfall throughout year
3) trees lose leaves in fall (oak, maple, hickory, willow)
4) rich soil supports mice, raccoons, foxes, rabbits, deer, bears, &
birds
d) grassland:
1) large areas of N. America, Asia, Europe, Australia, S. America
2) rich soil, but too little rain to support trees - dominated by grasses
& small plants (cereal grain bread basket - oats, rye, wheat
3) herds of grazing herbivores, rodents, insects, birds, & reptiles
4) known as savannas in Africa where they are more tropical & have
scattered trees & shrubs
e) desert:
1) large areas of N. Africa, Australia, southwest N. America, E. Asia
2) less than 10” annual rainfall & ranging from hot to below freezing
3) plant & animal species adapted to dry climate & sandy, nutrientpoor soil (cactus & scattered grasses, burrowing reptiles & insects,
& coyotes, hawks, owls)
f) tropical rain forest:
1) near equator in Asia, Africa, S. America, & C. America
2) warm temperatures, plenty of rainfall, year-around growing season
- greatest diversity of plant & animal species
3) treetops form continuous layer called the canopy - little sunlight
reaches the ground where soil is thin, moist, & nutrient poor
18. Earth’s aquatic biomes: (producers are plants, algae, & plankton)
a) marine biomes: zone shallow enough for sunlight to penetrate is photic &
zone too deep to receive sunlight is aphotic zone
1) ocean - pelagic zone - open ocean & benthic zone - ocean bottom
2) intertidal zone - along shore where tides rise & fall - life here is
adapted to periodic exposure to air & force of crashing waves
3) estuaries - where freshwater rivers & streams flow into the sea varying temperature & salinity allow for great biodiversity
4) neritic zone - ocean area over continental shelf with nutrient-rich
waters that are shallow enough for photosynthesis - diverse in
plankton, fish, sea turtles, crustaceans, mollusks & coral reefs
b) freshwater biomes:
1) lakes & ponds - those rich in organic matter & vegetation have
murky water are called eutrophic - those with little organic matter
have clear water & rocky or sandy bottom & are called oligotrophic
2) rivers & streams - bodies of water flows swiftly down a slope
toward a mouth - organisms are adapted to powerful or slow waters