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ECOLOGY &
FOODWEBS
S7L4
• Students will examine the dependence of organisms
on one another and their environments.
– a. Demonstrate in a food web that matter is transferred
from one organism to another and can recycle between
organisms and their environments.
– b. Explain in a food web that sunlight is the source of
energy and that this energy moves from organism to
organism.
– c. Recognize that changes in environmental conditions can
affect the survival of both individuals and entire species.
– d. Categorize relationships between organisms that are
competitive or mutually beneficial.
EQ’s to be answered in this unit:
• How is life like a web?
• Why is it necessary for everything in an
ecosystem to work together?
• How do YOU fit into the larger world?
• How does a change in temperature and/or
precipitation affect the living things in the
environment?
• Why can’t there be a lone survivor?
• What effect does the environment have on
organisms?
• How does the environment affect us?
Chapter 20, Section 1 p.675
• We’ve learned about biomes, and about the
characteristics of living things. Now we are
gong to tie these things together by looking at…
p. 675 Habitats
• An environment that provides the things the
organism needs (food, water, shelter) to live,
grow, and reproduce
• One area may contain many habitats
• Organisms live in different habitats because
they have different requirements for survival.
p. 675 Factors
• An organism interacts
with both the living
and nonliving parts of
its habitat.
• P.675 - Biotic
factors: living parts
of a habitat. Ex:
grass, plants, hawks,
ferrets, badgers,
worms, fungi, bacteria
P.676 – Abiotic factors – Nonliving parts of
an organism’s habitat.
• Water – Organisms require water to carry on life’s
processes, and water makes up a large part of
organisms’ bodies.
• Sunlight – Needed for photosynthesis; without it, few
organisms can survive.
• Oxygen – Can be obtained from the air or from water,
and is essential for life.
• Temperature – help determine the types of organisms
that can live in an area.
• Soil - contains rock fragments, nutrients, air, water, &
decaying remains; type of soil determines plants, and
for many organisms, soil is used as a home.
p.677 Levels of Organization
• 1) Species – a
group of organisms
that are physically
similar and can mate
with each other and
produce offspring
that can also mate
and reproduce.
2) Populations
• all the
members of
one species
in a
particular
area.
3) Communities
• all the
different
populations
that live
together in
an area.
p. 678
4) Ecosystems
• The
community of
organisms that
live in a
particular area
along with their
nonliving
surroundings.
BRAIN POP
http://www.brainpop.com/science/population
sandecosystems/ecosystems/zoom.weml
p.681 Studying Populations
Sometimes we need to
know the size of a
population of organism
in a particular
ecosystem. We use
several different ways to
determine the
population:
p.682 Direct Observation
• Counting all of the members in a
population
• Ex: Counting all the crabs in a tide pool
p.682 Indirect Observation
• Observing signs of organisms rather than the
organisms themselves
• Ex: Counting entrance holes to swallow nests
p.682 Sampling
• Making an estimate (an approximation of a
number, based on reasonable assumptions).
• Ex: Counting number of organisms in a small
sample area, then multiplying to find the
number in a larger area
p.683 Mark-and-Recapture
Studies
• Marking an organism,
releasing it back into the
wild, then returning at a
later date to see how many
organisms have marks,
and how many do not.
• Ex: marking turtles, then
coming back in 2 weeks
and counting the number
of marked turtles.
p. 684 Changes in
Population Size
• Populations can change in size when new
members join the population or when
members leave the population.
p.684 Births and Deaths
• The birth rate of a
population is the number
of births in a population
in a certain amount of
time (ex: 600 per year)
• The death rate is the
number of deaths in a
population in a certain
amount of time (ex: 400
per year)
p.684 The Population
Statement
• If birth rate > death rate, population size
increases.
• If birth rate < death rate, population size
decreases
p.684 Immigration and
Emigration
• The size of a population can also change when
individuals move into or out of the population.
• Immigration means moving INTO a population
• Emigration means leaving a population
p.684 Graphing Changes in
Population
• X axis shows time
• Y axis shows number of organisms
p.685 Population Density
• The number of individuals in an area of a
specific size
• population density = Number of individuals
Unit area
p.685-7 Limiting Factors
• An environmental factor that
causes a population to decrease
– Food and Water – often in limited
supply
– Space - if it gets too crowded,
organisms don’t survive because
their needs aren’t met.
– Weather – temperature and rainfall
can limit population growth
• Carrying Capacity – the largest
population that an area can
support
BrainPop
• Population Growth
p.700 Changes in Communities
– Succession– the
series of
predictable
changes that
occur in a
community over
time.
p.701 – Primary Succession
• The series of changes
that occur in an area
where no soil or
organisms exist.
– Pioneer species– the
first species to populate
the area, carried by wind
or water. They help
break up rocks, building
soil. Ex: mosses, lichens
Primary Succession
p.702 – Secondary Succession
• The series of changes that occur in an
area where the ecosystem has been
disturbed, but where soil and organisms
still exist. Ex: fires, hurricanes, farming,
logging, mining
Climax Community
• an ecological community that has reached
the final stage of ecological succession.
• Watch this to see succession at work:
Succession video!
ENERGY FLOW
• Energy is transferred from
one organism to another.
• Three methods of transfers
–Food Chain
–Food Web
–Energy Pyramid
FOOD CHAIN
• Shows how energy passes from one
organism to another.
–A producer will ALWAYS be first.
Producers make their own food through
photosynthesis. (ex: plants, algae, some
bacteria)
– CONSUMERS will be next:
• A herbivore will be second.
–An organism that eats only
plants (ex: rabbit, deer)
• A carnivore will be next.
–An organism that eats other
animals (ex: hawk, wolf)
• An omnivore can also be
next.
–An organism that eats both
plants and animals (ex:
bear, human)
• A scavenger can also be
next.
– A carnivore that feeds
on the bodies of dead
organisms. (ex: catfish,
vultures)
• A decomposer can also
be next.
– An organism that breaks
down wastes and dead
organisms and returns
the raw materials to the
ecosystem (nature’s
recyclers!). (ex: worms,
mushrooms, bacteria)
EXAMPLE
GRASS
RABBIT
Producer
Herbivore
WOLF
Carnivore
Example of a Food Chain
Grass  Grasshopper 
Frog  Snake  Hawk
• GRASS (is eaten by a) GRASSHOPPER
(which is eaten by) a FROG (which is eaten by
a) SNAKE (which is eaten by a) HAWK
Food Web
• Each living thing in an
ecosystem is part of multiple
food chains. Each food chain
is one possible path that
energy and nutrients may take
as they move through the
ecosystem. All of the
interconnected and
overlapping food chains in an
ecosystem make up a food
web.
ENERGY PYRAMID
• Shows how much energy is at each level
of food chain
• Pyramid Levels
– 1st level is carnivores
• Larger animals
• least energy
– 2nd level is carnivores
– 3rd level is herbivores
– 4th level is producers
• Plants
• Most energy
ENERGY PYRAMID
Carnivores
(Larger Animals)
Least Energy
Carnivores
Herbivores
Producers
(Plants)
Most Energy
Let’s Review!
• Watch this video about
ENERGY PYRAMIDS
• Do ENERGY PYRAMID
ACTIVITY
Where Does Energy
Comes From?
•SUN
–Provides energy for life on Earth
BRAIN POP
http://www.brainpop.com/science/population
sresourcesandenvironment/foodchains/zo
om.weml
p.694
How Living Things Interact
• There are three major types of
interactions among organisms:
competition, predation, and
symbiosis.
p.694 - Competition
• If two species occupy the
same niche, one of the
species will eventually
die off.
• Competition is the
struggle between
organisms to survive as
they attempt to use the
same limited resource.
p.695 Predation
• An interaction in which one organism
kills another for food
• Predator - The organism that does
the killing.
• Prey – the organisms that is killed.
p.696 Adaptations
• Predator Adaptations
– Help them catch and
kill their prey. Ex:
cheetah can run very
fast.
• Prey Adaptations –
Helps organisms avoid
being killed. Ex: Skunk
spray
p.697 Defense Strategies
• Mimicry– Having a strong
resemblance to other
predators
• Protective Coverings– Shield
the organism from predators
• False Coloring– Scare
potential predators away
• Warning Coloring– Bright
colors warn predators not to
eat them
• Camouflage – Hide from
predators
SYMBIOSIS
• Relationship between species
• Types:
–Mutualism: both benefit
–Commensalism: one benefits,
the other is not affected
–Parasitism: one benefits, the
other is harmed
Mutualism – Bees & Flowers
Commensalism – Fish &
anemones
Parasitism – Ticks
BrainPop Time Again!
• http://www.brainpop.com/science/livingsyst
ems/symbiosis/
NICHE-Organism Survival
• Every organism has a variety of adaptations
that are suited to its specific living conditions:
– How does it find food and shelter?
– How does it avoid danger?
– How does it care for its young?
– Does it have predators?
– Can it cooperate with other animals?
– Can it find prey (food)?
• A Niche is the role of an organism in its habitat, or
how it makes its living.
Your Challenges: Show how you
have mastered the standards:
a) Draw a food web containing at least 10 organisms
that shows matter being transferred and recycled.
b) Show/Explain how the energy from sunlight moves
from organism to organism. Include at least 5
organisms.
c) Explain how a change in an environmental condition
would affect the survival of an individual organism,
the population, the community, and the ecosystem
d) Describe 3 examples in your own life of relationships
between organisms that are competitive and 3 that
are mutually beneficial.
Let’s see if you can answer the EQ’s:
• How is life like a web?
• Why is it necessary for everything in an
ecosystem to work together?
• How do YOU fit into the larger world?
• How does a change in temperature and/or
precipitation affect the living things in the
environment?
• Why can’t there be a lone survivor?
• What effect does the environment have on
organisms?
• How does the environment affect us?