Ecology EOC Review
Biotic vs. Abiotic Factors
– Biotic = living (plants, animals, bacteria, fungus,
protists)
– Abiotic = non-living (temp, water, soil, weather,
rocks, sunlight, etc)
Ecological Organization
– Organism ~ one member of one species
– Population ~ all members of one species in a given
area
– Community ~ all populations in a given area
– Ecosystem ~ all members of community plus
abiotic factors in the area
– Biome ~ group of ecosystems with same climate
and organisms
The Water Cycle
The Carbon Cycle
The Nitrogen Cycle
Succession
– Primary Succession = colonization of NEW land by
pioneer species until a climax community is
reached.
• Lava flow  lichens  mosses  grasses  shrubs 
trees
– Secondary Succession = existing community is
destroyed and a new one begins to form
• Occurs more quickly than primary succession because
soil is already present and seeds were left behind
• Forest  Fire  mosses  grasses  shrubs  trees
Ecosystem Relationships
– Niche vs. Habitat
• If an organism’s habitat is its address, its niche is its
occupation.
– Competition
• Organisms of same or different species try to use same
resource at same place during same time.
• Competition can be reduced by developing different niches.
• Ex. 3 species can easily live in same tree if one eats leaves,
one eats bark and another eats the flowers.
– Predator-Prey
• Organism doing killing = predator
• Organism being killed = prey
Symbiosis
• Mutualism – both species benefit from the relationship
–Flowers may feed on insects, which may in turn
disperse pollen to other flowers
• Commensalism – one species benefits and the other is
unaffected by the relationship
–Barnacles attach to the skin of a whale to catch more
food particles
• Parasitism – one species benefits and the other is
harmed by the relationship
–Tapeworms live inside a human intestine and feed
from the human
Energy Flow
– Producers (autotrophs)
• Use sunlight to make their food and energy through
photosynthesis or chemosynthesis
• Only plants and some bacteria/algae are autotrophic
– Consumers (heterotrophs)
•
•
•
•
•
•
Must acquire their energy from other organisms
Herbivores = eat plants only
Carnivores = eat animals only
Omnivores = eat both plants and animals
Scavengers = eat dead or decaying plants and animals
Decomposers = break down dead or decaying plants or
animals
Feeding Relationships
• Food Chains = series of steps in which organisms
transfer energy by eating and being eaten
–Arrow shows the direction of energy transfer in
the food chain
–Ex. Grass  Grasshopper  Mouse  Snake 
Hawk
Feeding Relationships
• Food web = links all food chains together in an ecosystem
Trophic Levels
–Producers – get energy from sun & use some for own
metabolism
–Primary Consumers – get 10% of original energy
from producers and use some for own metabolism
–Secondary Consumers – get 10% of energy from
primary consumers and use some for own
metabolism
–Tertiary Consumers – get 10% of energy from
secondary consumers and use some for own
metabolism
Ecological Pyramids
Populations
– Population Growth
• If birth rate is larger than death rate = growing
• If birth rate is smaller than death rate =
shrinking
• Immigration = movement into a population
• Emigration = movement out of a population
Populations
– Exponential Growth (J-shaped Curve)
• Occurs when individuals reproduce at a
constant rate (ex. every individual has 2 kids)
• Will occur under ideal conditions with
unlimited resources
Populations
– Carrying Capacity (S-shaped Curve)
• A population’s growth slows or stops following
a period of exponential growth
• Carrying capacity = largest number of
individuals that a given environment can
support
Populations
– Limiting Factors
• A factor that causes a population’s growth to
decrease
• Competition, predation, disease, climate extremes,
human disturbance
– Density-dependent vs. Density-independent
• Density-dependent = limit a population according to
population size
–Competition, predation
• Density-independent = affects all populations the
same, regardless of size
–Natural disasters
Human Environmental Impacts
– Human population is growing exponentially with
no slowing in sight because of technological
advances in medicine.
– Humans are clearing habitats of plants and
animals to have more room for cities & suburbs as
well as space to grow more food for the growing
populations.
Human Environmental Impacts
• Ozone depletion
–Ozone protects us from harmful UV
radiation from the sun
–Chlorofluorocarbons (CFCs) destroy the
ozone layer
–CFCs are banned, but their affects are lasting
as the ozone layer slowly heals itself
Human Environmental Impacts
• Global Warming
–Burning of fossil fuels adds excess carbon
dioxide in the atmosphere
–Carbon dioxide is an insulator and traps heat
in the atmosphere causing the global
temperature to slowly rise.
–Higher global temperatures could have
devastating effects such as melting of
glaciers and changes in weather patterns.
Human Environmental Impacts
• Pesticide Use
–DDT and other pesticides are dangerous
because they can contaminate groundwater
and other water sources.
–Biological magnification – concentrations of a
harmful substance increase in organisms at
higher trophic levels in a food web or a food
chain.
»Ex. algae pick up toxin from water they live
in – plankton eat much algae to survive –
small fish eat the plankton – large fish eat
the large fish  there is much more DDT in
the large fish than the plankton because it
has concentrated up the food chain.
Practice Questions
1.
Which situation would result in the
greatest increase in the human
population?
A.
B.
C.
D.
decreased birth rate and
increased death rate
increased infant mortality and
decreased death rate
decreased death rate and
increased birth rate
increased birth rate and
increased infant mortality
2. In a forest ecosystem, which is an abiotic
factor?
A.
B.
C.
D.
the amount of rainfall
the size of the deer
the type of trees
the number of birds
3. In the carbon cycle, atmospheric carbon
dioxide is converted into organic material
by which process?
A.
B.
C.
D.
cellular respiration
decomposition
photosynthesis
transpiration
4. Why do ecosystems rarely contain more
than a few trophic levels?
A.
B.
C.
D.
Energy transfer efficiency is high.
Energy transfer efficiency is low.
Energy amounts remain constant.
Energy cannot flow through levels.
Practice Questions
5. Recent climate data suggests a global
warming trend. The most likely cause
could be an increase in which gas?
A.
B.
C.
D.
A community is studied and
several interactions are
observed and recorded.
oxygen
carbon dioxide
nitrogen
hydrogen sulfide
6. Silt and nutrients from eroding
farmland flow into a lake. As a result,
which will most likely increase first?
A.
B.
C.
D.
7.
fish population
shore vegetation
algae growth
dissolved oxygen
Which type of interaction could
illustrate the process of
mutualism?
A.
B.
C.
D.
interaction A
interaction B
interaction C
interaction D