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Ecology
The study of the interactions of
organisms with one another and
with their environment
An Environment Contains…
 Biotic Factors
 “Bio” = Life
 Living factors in an environment
 Abiotic Factors
 “A” in front of a word = Non
 Non-living factors in an environment
 Examples?
How are environments
organized?
 Five Levels of Organization
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1. Organism
2. Population
3. Community
4. Ecosystem
5. Biosphere
1. Organism
 One individual living thing.
 Ex: One individual alligator.
2. Population
 A group of individual organisms of the
same species.
 Ex: a group of alligators.
3. Community
 All species that live
and interact in one
area.
 Ex: alligators, fish,
snakes, and trees
living in a swamp.
4. Ecosystem
 An ecosystem
contains both biotic
and abiotic factors in
an environment.
 Ex: alligators, fish,
snakes, trees, rocks,
water, dirt, etc. that is
found in a swamp.
5. Biosphere
 Contains all ecosystems. This is where
life exists on Earth.
Interactions
Between Organisms and
With the Environment
3 Types of Interactions
Between Organisms:
1. Competition
2. Predation
3. Symbiosis
3 Types of Interactions:
 Competition: When two or more
individuals try to use the same resource.
 Predation: One organisms hunts and kills
another.
 Symbiosis: a close relationship between
two or more species.
3 Types of Interactions
Between Organisms:
1. Competition
2. Predation
3. Symbiosis
Competition
 When two or more individuals or
populations (in the same habitat) try to
use the same resources.
 Let’s Brainstorm! What are some
resources that organisms compete for?
 Resources can be food, water, shelter,
space, sunlight, mates, etc.
 Competition is NOT always a physical
fight!
Competition
 Competition can happen in one of two
ways:
 1. Between individuals within a
population
 2. Between populations in a
community.
Competition
 Competition between individuals within
a population:
 Example:
 The Elks in Yellowstone National Park
 Elks are herbivores (what does that
mean?)
 They compete with each other for the
same food plants
Competition
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Competition between populations:
Example:
Different Species of trees in the forests
What do you think they compete for?
Some trees in the forest grow tall to
reach the sunlight!
 These tall trees are taking away the
sunlight from the shorter trees.
Competition
Competition
 Summary:
 What is the definition of competition?
 The struggle between organisms survive in a
habitat with limited resources.
 What are some examples of resources?
 Food, water, space, sunlight, mates.
 What are the ways in which competition can
happen?
 Between individuals within a population.
 Between different populations.
Standards Check!
 S7L4d Categorize relationships between
organisms that are competitive or
mutually beneficial.
 Describe an example of competition
between organisms in a population.
 Describe an example of competition
between organisms in a community.
Niche-the role an organism
plays in an ecosystem

An organism’s niche includes:
1.
2.
3.
4.
5.
6.
Type of food it eats.
How it obtains its food.
What organisms eat it.
When and how reproduction takes place.
Physical conditions required for survival.
How the organism interacts with other
organisms (its relationships).
TERMS
 LIMITING FACTOR —AN
ENVIRONMENTAL FACTOR THAT
PREVENTS A POPULATION FROM
INCREASING
LIMITING FACTOR
 FOOD—IF THERE IS NOT ENOUGH
FOOD FOR A POPULATION, THE
POPULATION CANNOT REPRODUCE
 SPACE—THERE MUST BE ENOUGH
SPACE IN AN AREA FOR ORGANISMS
TO LIVE AND REPRODUCE
 WEATHER—TEMPERATURE AND
RAINFALL CAN LIMIT A POPULATIONS
GROWTH
 Shelter, water…
Terms
 CARRYING CAPACITY —THE
LARGEST POPULATION THAT
AN ENVIRONMENT CAN
SUPPORT
3 Types of Interactions
Between Organisms:
1. Competition
2. Predation
3. Symbiosis
Predation
 When one organism hunts and kills
another.
 Predator: the organism that kills and
eats all or part of another organism.
 Prey: an organism that is killed and
eaten by another organism.
 Let’s brainstorm! Can an organism be
both a predator and a prey?
Predator/Prey
Predation
 Predation can have a major affect upon
prey populations.
 How? Don’t prey populations produce
new organisms as others die?
 If the death rate exceeds the birth rate….
Populations go down.
 What happens if a predator is suddenly
removed from a habitat?
Predation
 Newsflash! Not all members of an
ecosystem are created equal!
 All organisms have important roles, but
some members are more important to the
ecosystem as a whole.
 We call these important members the
keystone species
 Example: The sea otter in the Pacific
Ocean
Predation
 Sea otters live in the Kelp Forests of the Pacific
Ocean.
 At one point, the otters were hunted to near
extinction. 
 With the otters gone, there was nothing to eat
the sea urchins.
 The sea urchins exploded in number and then
ate all of the kelp  
 The kelp was home to dozens of animals, all of
which disappeared!   
 Eventually, even the sea urchins disappeared.

 Otter became protected animals, and grew in
number. Over time, the different populations
returned!        
Predation
Predation
 An organism’s adaptations allow it to
survive
 Organisms develop adaptations
(changes) over time in response to their
environment.
 This is called natural selection.
 Does this apply only to predators? Only
to prey? Or to both??
Predation
 Predator Adaptations
 A predator must be able to catch their
prey!
 Predators have developed a wide variety
of methods and abilities in order to
effectively and efficiently hunt their prey.
 Let’s brainstorm! Can you think of some
ways that predators have adapted to be
able to hunt their specific prey?
Predation
 Predator Adaptations
 Examples: speed, sharp teeth, sharp
claws/talons, poisonous venom, night
vision, “radar”, coloring
 The cheetah
 The cheetah’s speed gives it an advantage
over predators competing for the same prey!
 The Goldenrod Spider
 Blends in with the goldenrod flower. All it has
to do is wait for its next insect dinner!
Predation
Predation
 Prey Adaptations
 Prey must be able to avoid being eaten!
 Prey have developed methods and
abilities to keep from being eaten.
 Let’s brainstorm! Can you think of any
prey adaptations?
Predation
 Prey Adaptations
 Examples: speed, protective coverings,
warning coloration, mimicry, camouflage,
false coloring, defensive chemicals.
 Staying in groups can also benefit prey:
 Schools of Fish/ Herds of Animals
 More eyes, ears, and noses
 Earlier notification of a predator
presence!
Predation
 Prey Adaptations
 Camouflage
 Coloration that helps an organism to blend in with its
surroundings.
 Makes an organism harder to see.
 Rabbits
 Brown Rabbits, White Rabbits
 Walking Sticks
 Insect that looks just like a twig.
 Some even sway to look like they were a stick being
blown by a slight breeze!!
Predation
Predation
 Prey Adaptations
 Warning Coloration
 A way to advertise their defensive chemicals
 Predators avoid animals that have colors
and patterns they associate with pain
 Most common warning colors: bright shades
of red, yellow, orange, black, and white.
 Fire Salamander
 Bright yellow and black
 Sprays a chemical that burns
Predation
Predation
 Prey Adaptations
 Pretenders
 Don’t have defensive chemicals, but use
warning coloration
 Scarlet King Snake vs. Coral Snake
 Same coloring, but only the coral snake is
poisonous.
 What might happen if there were more
pretenders than there were animals with
real defensive chemicals??
Predation
Standards Check!
 S7L5 Students will examine the evolution
of living organisms through inherited
characteristics that promote survival of
organisms and the survival of successive
generations of their offspring.
 What is camouflage, and how does it
prevent an animal from being eaten?
3 Types of Interactions
Between Organisms:
1. Competition
2. Predation
3. Symbiosis
Symbiosis
 Some species have very close
interactions with other species.
 Symbiosis is a close, long-term
association between two or more
species.
 There are 3 types of symbiosis
(relationships):
 1. Mutualism
 2. Commensalism
 3. Parasitism
Symbiosis

3 types of symbiotic relationships:
1. Mutualism: both species benefit.
2. Commensalism: one species benefits, the
other species is unaffected.
3. Parasitism: one species benefits, the other
species is harmed.
Symbiosis
 What is the definition of symbiosis?
 A close, long-term relationship between two
species.
 What are the three types of symbiotic
relationships?
 Mutualism, Commensalism, Parasitism
 What do all three “isms” have in common?
 At least one species benefits from the
relationship.
Symbiosis
 Mutualism: what is the definition?
 A relationship between two species in which
both species benefit.
 Bacteria and You
 Bacteria in your instestines- they get food from you
and produce vitamins for you!
 Coral and Algae
 Algae receive a place to live through their
relationship with coral. The coral receives the extra
food that the algae produce from photosynthesis.
 BOTH SPECIES BENEFIT- IT’S MUTUAL!
Symbiosis
 Commensalism: what is the definition?
 A relationship between two species in which one
species benefits and the other is unaffected (does not
benefit, is not harmed).
 Remoras and Sharks
 Remoras “hitch a ride” on sharks by attaching themselves.
They feed on the scraps of the shark’s meal.
 The remoras benefit, the shark neither benefits nor is harmed
by the relationship.
 Golden Trevally and Whale Sharks
 The smaller fish travel in front of the whale shark, right in front
of his mouth. They receive protection from the much larger fish
(even though the whale shark is a filter feeder!)
 The whale shark is unaffected by the trevally traveling with
them
Symbiosis
Symbiosis
 Parasitism: what is the definition?
 A relationship between two species in
which one species benefits while the
other is harmed.
 The parasite is the organism that benefits
from the relationship.
 The host is the organism that is harmed
by the relationship.
 The parasite gets nourishment from its
host, while the host is weakened.
Symbiosis
 Parasitism
 Tapeworms in human intestines
 Tapeworm takes food from the host and multiply in
number
 The human gets malnourished and may eventually
die
 Fleas on dogs
 Fleas feed on the blood of the dogs
 The dog is physically weakened by the loss of blood
 Let’s brainstorm! Can you think of any other
examples of parasitism?
Name That Relationship!
 Acacia ants live on the bullhorn acacia
tree, which provides the ants with food
and shelter. The ants deter grazing
animals from eating the tree, ultimately
protecting it.
 What type of symbiotic relationship is
this?
 Mutualism! Both species benefit from the
relationship!
Name That Relationship!
 Plants called epiphytes, such as certain
orchids, live on other plants, which
provide only a place to grow. Epiphytes
absorb sunlight, water, and nutrients from
their surroundings and make their own
food.
 What type of symbiotic relationship is
this?
 Commensalism! The epiphyte benefits by
having a place to grow. They do not harm
the plant they grow on.
Name That Relationship!
 There is a tiny wasp that lays its eggs in
a variety of other insects, such as
caterpillars, spiders, aphids, and flies.
The wasp larvae feed on the host insect
and eventually kill it.
 What type of relationship is this?
 Parasitism! The wasp larvae benefit by
having a food source and a place to
grow. The host insect is harmed and
eventually killed by the wasp larvae.
Coevolution
 Relationships between organisms
change over time.
 Interactions between organisms can also
cause a change in the organisms
themselves!
 Coevolution is when a long-term change
takes place in two species because of
their close interactions with one another.
 These changes happen over a very long
period of time.
Coevolution
 Coevolution and Flowers
 Pollinators are organisms that carry pollen from
one flower to another.
 What is an example of a pollinator?
 Pollination is necessary for reproduction in
most plants.
 Over millions of years, flowers have changed
to attract certain pollinators!
 Flowers attract pollinators with their color, odor,
or even nectar.
Standards Check!
 S7L4 Students will examine the
dependence of organisms on one
another and their environment.
 Why do flowers need to attract
pollinators?
Interactions Between
Organisms
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Competition
Predation
Symbiosis
This leads us to the term….. Niche.
What is the definition of niche?
Niche: an organism’s unique role in the
ecosystem.
So now we know…..

How organisms interact with each
other!
1. Competition
2. Predation
3. Symbiosis
-
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Mutualism
Commensalism
Parasitism
We also know how those relationships
can change over time…. Coevolution!
But now we need to
know….

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How organisms interact with their
environment
Organisms interact with their
environment through:
1. Limiting Factors
2. Carrying Capacity
Interactions with the
Environment
 Limiting Factors
 The environment contains a limited
amount of food, water, living space, and
other resources.
 A resource that is so scarce that it limits
the size of the population is called a
limiting factor.
 Food becomes a limiting resource when
a population becomes too large for the
amount of food available.
Interactions with the
Environment
 Carrying Capacity
 The largest population that an
environment can support is known as the
carrying capacity.
 When a population grows larger than its
carrying capactity…. What happens?
 Limiting factors in the environment cause
the individuals to die off or leave.
 The population will decrease and return
to a size that the environment can
support.
Summary….
 Organisms interact both with each other and
with their environment.
 Interactions with the environment:
 Limiting factors
 Carrying capacity
 Interactions with each other:
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Competition
Predation
Symbiosis
Coevolution