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
Ecology- The scientific study of
interaction between organism and their
environments.
◦ Environments:
 Biotic factors –all the living
organism that inhabit an environment
 Abiotic factors – the nonliving parts
of the environment
Ex: air currents, temperature,
moisture, light, and soil

Population – is a group
of organisms of one
species that interbreed
and live in the same
place at the same time
◦ Organisms compete
for food, water,
mates.
 Determines how
large each population
can become

EcosystemThe
interacting
system of a
biological
community
and its
nonliving
environment.

Community – is a collection of interacting
populations
◦ A change in one population in a
community will cause changes in the
other populations

Habitat- Place where an organism lives;
◦ Even in the same ecosystem, different
organisms differ in their habitats.

Producer- Organisms that
produce their own food are
called autotrophs.
Ex: Plants
all of the species of the
ecosystem depend on
autotrophs for nutrients
and energy.
 Consumer- They obtain food by
eating other organisms.
All the organisms that cannot
make their own food (and need
autotrophs) are called
heterotrophs.
◦ There are different
levels of consumers:
 Those that feed
directly from
producers, i.e.
organisms that eat
plant or plant
products are called
primary
consumers.
 Niche_= a role that an organism
has in the environment (based on
what they EAT!)
1. Herbivores- consumer that eats only
plants
◦ Ex: grasshoppers, mice, rabbits, deer,
beavers, moose, cows, sheep
2. Carnivores- consumer that eats only
other animals.
◦ Ex: Foxes, frogs, snakes, hawks, and
spiders.
3. Scavengers – consumer that eats the
remains of dead animals.
◦ Ex: vultures, buzzards, crows, ants,
beetles
4. Omnivores- eats both plants (acting as
primary consumers) and meat (acting as
secondary or tertiary consumers).
◦ Ex: Bears --They eat insects, fish,
moose, elk, deer, sheep as well as
honey, grass
5. Decomposers- organisms that break
down the remains of other organisms.
◦ Found at the bottom of the food web.
◦ Ex: Bacteria, yeast, fungi, worms and
many insects

Symbiosis – permanent, close
association between two or more
organisms of different species
1. Commensalism – one species benefits
and the other species is neither
harmed nor helped
◦ Ex: an orchid growing on the branch
of a larger plant
2. Mutualism – relationship that is
beneficial to both species
◦ Ex: acacia trees (provides
food/shelter for ants) and ants
(protect tree by attacking any
herbivore)
3. Parasitism – one species benefits at
the expense of the other species
◦ Ex: ticks, tapeworms live on or in the
organism

Food Chain- Show one preypredator relationship and
how each living thing gets its
food.
◦ Some animals eat plants and
some animals eat other
animals.
◦ Ex: Trees/shrubs 
giraffes  lions


Each link in this
chain is food for
the next link.
Always starts with
plant life and ends
with an animal.

Trophic levels-link represented by each
organism in a food chain;
◦ Represents a feeding step in the
transfer of energy and matter in an
ecosystem.

All energy in an ecosystem originates
with the sun.
◦ Plants transform solar energy into
chemical energy (food) via
photosynthesis
◦ This is consumed by plant-eating
animals, which are in turn consumed as
food.

The total energy transfer from one
trophic level to the next is only about
10 %, the other 90% is lost as heat

Heat is lost by:
1) Organisms fail to capture and eat
ALL food available at the trophic
level below them
2) Not all food that is captured and
eaten gets digested
3) Digested food is used by the
organism as a source of energy.

Food web- model used
to express feeding
relationship among the
members of a
community.
◦ A group of
interlinked food
chains

Illustrates:
1. Who eats who?
2. Arrow = Energy flow through the
community
3. Functional feeding groups
4. Important ecological interactions
1)
Food chains ONLY show one
prey-predator relationship. The
source of food is also often
seasonal with many animals
adapting to changes in the season
by eating different types of
food.
2)
Food webs show a better picture
of interrelationships between
plants and animals.

Biomagnification = The process of
increasing a chemical concentration
through the food chain (Examples:
DDT and PCB)
◦ Animals that eat other animals have
HIGHER levels of contaminants
than animals that eat plants.
◦ Some contaminants are persistent once they are in the animal's body,
they stay there for a long time.


So when smaller animals are
eaten by bigger animals, all
the contaminants stored in
their tissues are then passed
on to the bigger animal.
The result of biomagnification
is that animals at the "top"
of their food chain have
higher contaminant levels
than animals at the
"bottom".

The top predators at the end of a long
food chain may accumulate
concentrations of a toxic chemical high
enough to cause serious deformities or
death even though the concentration of
the chemical in the open water is
extremely low.
◦ The concentration of some chemicals
in the fatty tissues of top predators
can be millions of times higher than
the concentration in the open water.

Ex:
Mercury,
DDT,
PCB’s,
arsenic
1. Water cycles between the oceans,
atmosphere and land.
A. Water enters the atmosphere as
water vapor, a gas, when water
evaporates from the ocean or other
bodies of water.
◦ Evaporation—the process by which
water changes from a liquid to a gas.
B. Water can also enter the
atmosphere by evaporating from the
leaves of plants—Transpiration.
C. Precipitation--rain, snow, sleet, or hail
◦ The sun heats the atmosphere.
◦ Warm, moist air rises and cools.
◦ Eventually, the water vapor condenses
into tiny droplets that form clouds.
◦ When the droplets become large enough,
the water return to Earth’s surface.
D. Run-off—Precipitation runs along the
surface of the ground until it enters a river or
a stream that carries the run-off back to an
ocean or lake.
E. Seepage—Rain also seeps into the soil, some
of it deeply enough to become ground water.
Water in the soil enters plants through the
roots, and the water cycle begins anew.
Condensation
Condensation
Precipitation
Precipitation
Transpiration
Seepage
Ground Water
Evaporation
Surface Run-off
1. Every organic molecule contains the
element carbon.
A. Carbon and oxygen form carbon
dioxide gas (CO2), an important
component of the atmosphere.
B. Carbon dioxide is taken in by plants during
photosynthesis and is given off by plants and
animals during cellular respiration.
◦ Cellular respiration is a process where cells
transform chemical energy (sugar) into a
useable form of energy (ATP).
2. Four main types of processes move carbon through
its cycle:


Biological processes, such as photosynthesis, cellular
respiration, and decomposition, take up and release
carbon and oxygen.
Geochemical processes, such as erosion and volcanic
activity, release carbon dioxide into the atmosphere
and oceans.


Mixed biogeochemical processes, such as the burial
and decomposition of dead organisms and their
conversion under pressure into coal and petroleum
(fossil fuels), store carbon underground.
Human activities, such as mining, cutting and burning
forests, and burning fossil fuels (car emissions,
electricity), release carbon dioxide into the
atmosphere.
Burning of
Fossil Fuels
Coal & Petroleum
CO2 in atmosphere
Cellular
Respiration
Decomposition of
dead organisms
Photosynthesis
1. All organisms require nitrogen to make
amino acids, which in turn are used to build
proteins.
A.
Nitrogen gas makes up 78% of Earth’s
atmosphere.
B. Nitrogen containing substances such as
ammonia (NH3), nitrites (NO2-), and nitrates
(NO3-) are found in the wastes produced by
many organisms and in dead and decaying
organic matter
C. Nitrate is major component of plant
fertilizers.
2. Nitrogen gas is the most
abundant form but only certain
bacteria can use this form.
A. Such bacteria live in the soil and
on the roots of plants.
B. These bacteria convert nitrogen
gas into ammonium--nitrogen
fixation
C. Other bacteria in the soil
convert ammonia into nitrites and
nitrates.
3. Once the nitrites and nitrates are
available, producers (plants) can use them
to make proteins.
◦ Consumers then eat the producers and
reuse the nitrogen to make their own
proteins.
4. When organisms die, decomposers return
nitrogen to the soil as ammonia.
5. Other soil bacteria convert nitrates into
nitrogen gas--denitrification. This process
releases nitrogen into the atmosphere once
again.
Nitrogen in atmosphere (N2)
Denitrification
Nitrogen
Decomposers
return ammonia to
soil
Nitrates
(NO3-)
Nitrites
(NO2-)

Succession = orderly, natural changes
that take place in the communities of
an ecosystem
◦ The community of organisms
inhabiting an area gradually changes.
◦ Difficult to observe since it can take
decade or centuries for one type of
community to completely succeed
another.
Figure 1: Succession of plant species on abandoned fields in North
Carolina. Pioneer species consist of a variety of annual plants. This
successional stage is then followed by communities of perennials
and grasses, shrubs, softwood trees and shrubs, and finally
hardwood trees and shrubs. This succession takes about 120 years
to go from the pioneer stage to the climax community.
 Primary succession =establishment of a
community in an area of exposed rock that does
not have any topsoil.
◦ Ex: Lava flowing from a volcano destroys
everything in its path, but when it cools it
forms new land
◦ Ex: Streams gradually deposit silt
along their banks, creating new soil in
which plants can take root.
◦ After some time, primary succession
slows down, and the community
becomes fairly stable.
 A stable, mature community that
undergoes little of NO succession is
called a climax community.

Secondary succession = the sequence of
community changes that takes place when
a community is disrupted by natural
disasters or human actions
 Ex: Hurricanes, forest fires, farmers
abandoning fields


Biomes = a large group of ecosystems
that share the same type of climax
community
Two factors that will determine which
biome will be dominant on land:
1. Temperature
2. Precipitation


Characteristics: treeless, long cold
winters, little winter sun, poor soil, little
rain (less than 5 in)
Permafrost – permanently frozen ground

Location: Canada, Russia, Alaska

Vegetation: grasses, moss, lichen

Animals: insects, fox, rodents, caribou,
reindeer

Characteristics: coniferous forest, poor soil, long
severe winter

Location: Canada, N. Europe, N. Asia

Vegetation: pine, fir, hemlock, spruce

Animals: rabbits, lynx, caribou, moose, woodpecker

Characteristics: deciduous trees, 4 seasons,
vegetation exhibits seasonal changes
◦ Deciduous – trees lose leaves in winter

Location: East US, Europe

Vegetation: Maple, Oak, Birch, Hickory

Animals: bear, deer, robin, raccoon



Characteristics: warm, wet,
humid, most diversity, up to
17 feet of rainfall annually
Location: islands, equatorial
regions
Vegetation: broad lush
plants, flowers, vines,
palms, fruit trees
◦ lush with many layers in
the canopy that support
an incredible diversity of
life.

Animals: monkey, sloth, frogs, snakes,
parrots

Characteristics: ideal growing
season, good soil quality, little
precipitation does not support trees,
but grasses and herbs are present in
great abundance.

Location: central regions

Types:
◦ Prairie – US
◦ Steppe – Russia
◦ Savanna – Serengeti
◦ Pampas - Argentina


Vegetation: grass, grains, crops,
wildflowers
Animals: bison, prairie dogs, birds, lions,
elephants

Characteristics: dry & arid, less than 10 in
of rainfall

Location: SW US, N. Africa, Middle East
◦ Hot- Mojave, Sahara
◦ Cold- Gobi

Vegetation: Plant cover is sparse, and
characterized by drought tolerant
brushes, succulent (cacti, creosote
bushes)

Animals: rodents(gerbils,
jerboas and kangaroo rats),
snakes, lizards, scorpions,
turtles, hawks


All species occur in groups called
populations
Limiting factors = factors that are
biotic or abiotic that keep a population
from continuing to increase indefinitely

2 types of Population-Limiting Factors:
• density-independent factors
• density-dependent factors

Density-independent factors = Any factor in the
environment that does not depend on the number
of members in a population per unit area

Usually abiotic (natural phenomena)

Ex:

Weather events (tornadoes, floods, hurricanes)

Fire

Human alterations of the landscape

Air, land, and water pollution

Density-dependent factor = Any factor in the
environment that depends on the number of
members in a population per unit area

Usually biotic

Ex:
◦ Predation
◦ Disease- (high population density--> disease
quickly spreads)
◦ Parasites
◦ Competition – food, space limitations

The population growth rate (PGR)
explains how fast a given population
grows.


Exponential growth
occurs when the
growth rate is
proportional to the
size of the
population.
All populations grow
exponentially until
some limiting factor
slows the population’s
growth.

The population’s growth slows or stops
following exponential growth, at the
population’s carrying capacity.

A population stops increasing when the
number of births is less than the
number of deaths or when emigration
exceeds immigration.

Carrying capacity = The maximum
number of individuals in a species that
an environment can support for the long
term.
◦ limited by the energy, water, oxygen,
and nutrients available.
◦ Population exceeds carrying capacitydeaths outnumber births because
resources are not available to support
all individuals

If the major food source of seals declines due to pollution or
overfishing, which of the following would likely occur?
a)
The carrying capacity of seals would decrease, as would
the seal population.
b)
The carrying capacity of seals would decrease, but the
seal population would remain the same.
c)
The number of seal deaths would increase, but the
number of births would also increase, so the population
size would remain the same.
d)
The carrying capacity of seals would remain the same, but
the population of seals would decrease.