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ECOLOGY – What is it?

The scientific study of interactions between
organisms and their environments, focusing on
energy transfer

It is a science of relationships.
The environment is made up of two factors:

Biotic factors- all living
organisms inhabiting the
Earth

Abiotic factorsnonliving parts of the
environment (i.e.
temperature, soil, light,
moisture, air currents)
Levels of Organization in Ecology

Organism →Species  Population → Community →
Ecosystem → Biome → Biosphere
Levels of Organization

Species - Group of organisms so similar to one another
that they can breed and produce fertile offspring.


Population - Groups of individuals that belong to the
same species and live in the same area.


Ex - elephant
Ex – herd of elephants
Communities - Assemblages of different populations that
live together in a defined area.

Ex – elephants, zebras, water buffalos, warthogs, hippos
Levels of Organization

Ecosystem – Collection of all living and nonliving things in
a determined place


Biome - Group of ecosystems that have the same climate
and similar dominant communities.


Ex – mud hole, grass, warm temperature, elephants, zebras,
giraffes, insects, sun
Ex – Tropical Savanna (Kenya, Zaire, Tanzania-Africa)
Biosphere – Part of the planet in which all life exists,
including land, water, and air (all ecosystems combined)

It extends from about 8 kilometers above Earth's surface to as
far as 11 kilometers below the surface of the ocean.
Habitat vs. Niche…
 Niche
- the role a species plays in a
community (job)
 Habitat-
the place in which an organism
lives out its life (address)

A niche is determined by the tolerance limitations
of an organism, or a limiting factor.
What is the niche of these animals?
Consumers
1.
2.
3.
4.
5.
Herbivores - eat plants
Carnivores – eat animals
Omnivores – eat both plants and animals
Decomposer – break down dead
organic matter chemically (bacteria)
Detritivores – feeds on plant and
animal remains (crab, earthworm)
Decomposers vs. Detritivores

Decomposers
1.

Bacteria and fungus
Detritivores:
1.
2.
3.
4.
maggots
dung beetles
earth worms
sow bugs
Without them there
would be a lot of dead
bodies lying around!
Leeches and
maggots are now
classified as FDAapproved medical
devices — the first
live animals to earn
that distinction.
Interesting Science!
These maggots are cleaning/removing
the dead tissue from this wound. If the dead tissue is not removed, the
wound will not heal correctly…may end up with a big hole in their heel.
Interesting Science!
All of the yellow tissue is necrotic
(dead) tissue. The pink tissue is granulation (newly formed) tissue. The
dead tissue must be removed for proper wound care or else the tissue
will not grow and fill in the hole
Food Chain vs. Food Web
1.
Food Chains shows how matter and
energy move through an ecosystem
1.
follow just one path as animals find food.
2. Food Webs
shows all
possible feeding
relationships in a
community at
each trophic level
I. follow all possible energy paths
What Do Food Chains and Food
Webs Demonstrate?

Both food chains and food webs show the flow of
energy in an ecosystem.
Energy flows from
the leaf to the
mouse
Energy flows
from the snake
to the hawk
Trophic Levels


Corresponds to the different
levels or steps in the food chain.
Represent a feeding position in
the transfer of energy and matter
in an ecosystem.



Green plants: first trophic level, the
producers.
Herbivores: second trophic level
Carnivores: third and even the
fourth trophic levels.
Food Chains
ALWAYS begin with
plants (producers)!!
Trophic Levels
Tertiary consumerstop carnivores
Secondary consumerssmall carnivores
Primary consumers- Herbivores
Producers- Autotrophs
Matter vs. Energy


Matter – Has mass, takes up space, is usually a “thing”
Energy – Not like matter, does not have mass, does not
take up space,
energy moves
matter

Forms of energy:
light, heat, sound,
motion, and
electricity
How Much Energy is Passed On?


Only 10% is passed on to the next trophic level
The other 90% is lost/given off as heat
100%
10%
1%
.1%
Food Chains: Matter and Energy


As you move up a food
chain, the matter and energy .1% Energy
decreases.
1% Energy
Energy is transferred
upwards but is diminished
10% Energy
with each transfer.
100% Energy
Pyramids are larger at the bottom…more matter
and energy are at the bottom of the pyramid!
Ecological Pyramids

Ecological Pyramiddiagram that shows the
relative amounts of energy
or matter contained within
each trophic level in a food
chain or food web.
Two Types of Ecological Pyramids
1.
2.
Pyramid of Biomass – Represents the biomass at each
trophic level
Pyramid of Numbers – Represents the number of
organisms at each trophic level
Ecological Pyramid: Pyramid of Biomass

Biomass – total amount of
living tissue within a
trophic level

Usually expressed in grams
per unit area.

As you move up a food
chain, both available
energy and biomass
(matter) decrease.

Energy is transferred
upwards but is diminished
with each transfer.
Pyramid of Numbers
As you go further
down a food chain,
the numbers of
organisms decrease
because there is less
energy available (like
in this meadow)!
Other Pyramid of Numbers
If you have a large
producer (such as a
tree in a forest), the
pyramid of numbers
may look diamond in
shape.
A large tree
supports a lot of
organisms.
Population Changes in Food Chains

What would happen to this bird if the population of
caterpillars decreases?
Population Changes in Food Chains

What would happen to this bird if the population of
caterpillars decreases?

The bird population would decrease also because he
would have less food.
Population Changes in Food Chains

What would happen to the bee population if the flower
population exploded?
Population Changes in Food Chains

What would happen to the bee population if the flower
population exploded?

The bee population would also increase.
Population Changes in Food Chains

If the snake population
decreases, what would happen
to the other organisms in the
food chain?
Population Changes in Food Chains
• If the snake population
decreases:
– The hawk population
decreases also (less food)
– The frog population
increases (less predators
eating them)
– More frogs eating the
grasshoppers, so less
grasshoppers
Carrying Capacity and Predators
Carrying Capacity

Number of species that can be supported by an
ecosystem. (Average growth rate = zero)
Population Growth is Represented With an S-Curve
Population Growth

Exponential - individuals in a
population reproduce at a
constant rate (Ideally happens IF
there are unlimited resources)
(J-curve)

Logistic – The growth of a
population slows or stops as
resources become less available
(S-curve)
.
3 Factors that affect population size:

1. # of births





Populations will grow if birthrate > death rate
Populations will shrink if birthrate < death rate
Populations will stay the same birthrate = death rate
2. # of deaths
3. # of individuals that enter or leave a population


Immigration = movement of individuals INTO an area (growth)
Emigration = movement of individuals OUT of an area (shrink)
 Limiting
factor- any biotic or abiotic
factor that restricts the existence of
organisms in a specific environment.
Limiting Factors: Limit Population
Growth
Limiting factors:
a. Density independent: factors that affect all members
of the population equally if population is dense or not.
 Natural disasters: floods, earthquakes, wildfires,
tornadoes, mudslides, pollution, habitat
destruction
b. Density dependent: factors that affect crowded
populations
 EX: competition, predation, crowding and stress,
parasitism, and disease
Competition

Competition – A rivalry between organisms for the same
resources; The fitness of one of the organisms is lowered by
the presence of another.

Limited supply of at least one resource used by both organisms is
required

Example:Animals compete for
food, mating, or territory and
plants can compete for water,
food, minerals, sunlight.
Predators

Organism that hunts and kills other organisms

Can be carnivores or omnivores
The Importance of Predators
We need them to control populations



Without predators, certain species like mice would crowd
out other species and would also destroy their habitat.
They also get rid of weak, crippled, stupid, stunted, and
diseased organisms (survival of the fittest)
Predator Prey Graph
Large Predators

The number of large
predators is decreasing.
Wild Rabbits in Australia

Early 1900's, wild rabbits were taken from England to
Australia to be used for hunting.


Since then, rabbits have multiplied exponentially and have
severely affected the ecosystem where they live.
Damages include:
1.
2.
3.
Loss of vegetation from rabbit
grazing – threatens the
survival of native animals that
rely on plants for food and
shelter
Wild rabbits compete with
livestock for available pasture
and kill young trees & shrubs.
The holes they dig contribute
to soil erosion by removing
vegetation and disturbing soil.
Symbiotic Relationships:

Interactions between two or more organisms; Two
different species start a relationship (interact) in order to
ensure survival
Predation

The capturing of prey as a means of maintaining life


One organism benefits
One organism is killed
Parasitism
One organism (the
parasite) benefits
and the other (the
host) is harmed, but is
still alive
Because the
parasite needs
the host to
remain alive, it
is typically
advantageous
for the parasite
NOT to kill its
host
A tomato hornworm is
covered with cocoons of
pupating braconid wasps
Mutualism

Relationship that benefits both species.
Examples of Mutualism



Pollination
Seed Dispersal
Anemones
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Hippo and fish
Commensalism

One species benefits and the second species is
unaffected
Barnacles and Cattle Egrets

Barnacles and Algae
Interactions Summary
Type of
Interaction
Predation
Parasitism
Mutualism
Commensalism
Organism 1
Organism 2
Is Killed
Still Alive
“It’s Mutual.”