I.
Organisms Ecology – individual species and its needs for survival
a. Interactions Between Organisms – species survival occurs because of
relationships with other species
b. Feeding Relationships –
i. Producers – aka autotrophs – plants, algae, and bacteria that
produce their own food; captures energy from sunlight and raw
material from the environment to produce food.
ii. Consumer – aka heterotrophs – organisms that obtain energy by
consuming other organisms
1. Herbivore – organisms that consume only plants, they
feed directly on producers. Ex) rabbits and squirrels
2. Carnivore – organisms that are meat eaters, they get
food by eating herbivores or other carnivores. Ex)
sharks, wolves, and eagles
a. Scavengers – organisms that eat the remains of
organisms left behind by other animals. Ex) hyenas
and crabs
3. Omnivore – organisms that eat both plants and animals.
Ex) bears, raccoons, people, and skunks
iii. Decomposer – aka detritivores – organisms that
feeds on and break down organic materials and
return nutrients to the soil, air and water. Ex)
bacterium and fungi
II.
Models of Energy Flow – relationships of how energy flows
in an ecosystem; energy and material are converted in form
as it moves through food chains and food webs. In most
ecosystems, energy begins with the sun.
a. Energy flow through an individual organism
i. Gross energy intake – energy enters as food; some is lost in
feces, urine, and sweat. The rest is used, eventually given off
as heat, or stored as fat or as other kinds of tissue.
ii. Existence energy – there are four categories; 1 - standard
metabolism, 2 – specific dynamic action, 3 – thermoregulation, &
4 – the cost of living a free existence.
1. Standard metabolism – the energy used just to stay alive
with minimal activity; it is the energy needed to repair
cells, pump blood, and breathe.
2. Specific dynamic action – the energy used to digest and
assimilate food.
3. Thermoregulation – the energy spent to keep the body
temperature in a narrow range.
4. Cost of living a free existence – Animals that do not live
in a cage with food and water supplied have additional
energy-requiring activities such as traveling from burrow
or roost to feeding grounds, catching food, and escaping
predators.
b. Energy flow through a community / ecosystem
i. Food chain – path of food energy from the sun to the producer
to a series of consumers, in an ecosystem.
1. Trophic level – each step in food chain or food web;
describes the position that an organism occupies in a
food chain, what it eats and what eats it
2. Each organism gets its energy from
the organisms it eats; flow or energy
is always in one direction; organisms
use part of the energy to build new
cells and tissues, remaining energy is
released into environment; sunlight is
the initial energy source; energy is
transferred as heat through trophic
levels
a. Producers
b. Primary consumers – the first organism to feed in
a food chain, they eat producers.
c. Secondary consumers – in a food chain, an organism
that fees on plant-eaters; also called a predator.
d. Tertiary consumers – in an ecosystem, a predator
that feeds on other predators.
ii. Food web – complete model that shows the arrangement of
several overlapping feeding relationships in an ecosystem;
organisms feed on more than one species; consists of many food
chains
1. Most food chains/webs do not have more than 4-5
trophic levels
iii. Pyramid – model to show how energy flows through ecosystems
in three different ways; each level represents a tropic level
1. Energy pyramid - shows amount of energy available at
each trophic level; 90% of the energy is used by the
organisms at each level – used to build cells and tissues,
some released into the environment; only 10% available to
next level
2. Ecological pyramid – amount of biomass consumed by the
level above it
a. Biomass – total mass of living matter at each
trophic level
III.
Symbiosis – two or more organisms the live together in close association, a
close ecological relationship between the individuals of two (or more)
different species.
Sometimes a symbiotic relationship benefits both species, sometimes one
species benefits at the other's expense, and in other cases neither species
benefits. Ecologists use a different term for each type of symbiotic
relationship
a. Mutualism – relationship between two species that live together and
benefit from each other
b. Commensalism – relationship in which one organism is helped and the
other is not harmed or helped
c. Competition – relationship where neither species benefits
d. Parasitism – relationship in which one organism benefits and other is
harmed at a slow rate
e. Predation is when one species (predators) benefits and the other
(prey) is harmed at a fast rate, when one organism is consuming
another organism for food
i. Predator – organism that actively hunts other organisms
ii. Prey – organism that is hunted
Parasitism and Predation are different.
a. Both involve pairs of species in which one species increases its
population at the expense of decreasing the population of the other
species
b. Predators are generally bigger than their prey and kill the prey
instantly
c. Parasites are smaller than their prey and normally kill the prey
slowly, if at all
IV.
Community Ecology – group of interacting populations that occupy the same
area at the same time
a. Organism adapt to the conditions where they live; depend on biotic
and abiotic factors present (quantities)
b. Limiting Factor – biotic or abiotic factors that restrict the numbers,
reproduction, growth or distribution or organism
i. Factors – temperature, light, water availability and soil
(nutrients)
ii. Tolerance – ability of organism to survive when exposed to
biotic or abiotic factors; defined by the conditions in the
environment
iii. Water quality – aquatic organisms may be sensitive to changes
in temperature, pH, dissolved oxygen, nitrates, phosphates, etc.
c. Biodiversity – variety of life in one area determined by number of
different species; indicates the health and stability of an ecosystem
i. Factors that affect biodiversity: availability of natural
resources, climate, geology, and human and natural activities.
ii. As habitats become polluted, diverse life forms cannot exist in
that area and must either move away or die.
iii. Monoculture – only one plant species in large area, require large
amounts of water, pesticides, and fertilizer. ex) corn fields and
monolithic lawns
iv. Adaptation – provided by biodiversity for organisms to survive
and reproduce
V.
Ecological Succession – the process of change where one community
replacing another as a result of changing abiotic and biotic factors over
time.
a. Primary succession – a community that develops in an area of bare
rock, with no top soil into a functioning ecosystem. Examples of
primary succession occur after an event such as lava flow from a
volcano or a new sandbar or mudbar along a river from a flood.
Example: Lava rock – bare rock  lichens/mosses grow first  break
down rock  decaying species  mix with rock  soil develops 
weed plants  plants die, add to soil  seeds brought in by animals,
water, wind  trees/shrubs
i. Pioneer species – first organism to appear in area
ii. Climax community – stable, mature community that is the end
product of succession
b. Secondary succession – succession that occurs after the initial
succession has been disrupted and some plants and animals still exist.
Examples of secondary succession occur after an event such as a
forest fire, abandoned crop land, or a hurricane.
i. Soil is already present
ii. Seeds, roots, and underground vegetative organs of plants may
still survive.
Example: pioneer species begins  annual plants  grasses/herbs 
shrubs  pines  oaks/hickory  climax community