Interactions of Life
Ecology unit: Chapter 9
ECOLOGY: the study of interactions that occur
among organisms and their environments
Birds are a help to the rhinoceros
They feed on ticks and other parasites plucked from the
rhino’s hide. When the birds sense danger, they fly off,
giving the rhino an early warning.
Describe how a familiar bird, insect, or other animal depend
on other organisms
Living Earth
The part of Earth that supports life is the
biosphere
• Includes the top portion of Earth’s crust, all the
waters that cover Earth’s surface, and the
atmosphere that surrounds Earth.

Different Environments in Biosphere
• The biosphere is made up of different
environments that are home to different kinds
of organisms.
Examples
 Desert
 Tropical Rain forest
 Coral Reefs
 Arctic regions
Ecosystems


An ecosystem consists
of all the organisms
living in an area + the
nonliving parts of that
environment
ABIOTIC FACTORS


Non-living parts of the
environment
BIOTIC FACTORS

Living things in the
environment
Abiotic or Biotic?
A)
D)
B)
E)
C)
F)
Pond ecosystem
Populations
• A population is made up
of all organisms of the
SAME species that live in
an area at the same time.
For example, all the bison
in a prairie ecosystem are
one population.
• All the cowbirds are a
different population.

• The grasshoppers make up
another population.
Community
A community is ALL the populations of all
species living in an ecosystem.
• An arctic community might include
populations of fish, seals that eat fish, and
polar bears that hunt and eat seals.

This figure shows how organisms,
populations, communities, and
ecosystems are related.
Habitat


The place in which an organism lives is called
its habitat
An organism’s habitat provides:



the kinds of food and shelter
the temperature
amount of moisture the organism needs to survive.
Habitat
• The salamander’s habitat is the forest floor,
beneath fallen leaves and twigs.
•avoid sunlight
and seek damp,
dark places.
Competition


Competition: when two or more organisms
seek the same resource at the same time
Food and Space

Organisms require food, water and living space,
however sometimes organisms don’t always have
enough
Ex: Woodpeckers
must compete with
each other for
nesting spots.

Growth limits

Competition limits population size



Ex: nesting spaces limited- woodpeckers not able
to raise young
Food becomes scarce- woodpeckers cannot survive
and reproduce
most intense competition is usually among
individuals of the same species

need the same kinds of food and shelter.
Limiting factors
A limiting factor is anything that restricts the
number of individuals in a population.
• Limiting factors--living and nonliving features
of the ecosystem.

• Availability of food, water, living space, mates,
nesting sites and other resources
• EX: Lack of rain
• Limits plant growth-plants produce fewer seedslimiting factor for mice that eats these seeds
limiting factor for hawks and owls (feed on
mice)
Populations
2
Growth Limits
• Competition also takes place among different
species.
• Ex: Gila woodpecker
abandons its nest—
owls, flycatchers,
snakes, and lizards
might compete for
the shelter of the
empty hole.
Populations
2
Carrying Capacity
• Carrying capacity is the largest number of
individuals of one species that an ecosystem
can support over time.
• If a population begins to
exceed the environment’s
carrying capacity, some
individuals will not have
enough resources
• die or be forced to
move elsewhere.
Click image to view movie.
Predator/Prey Cycles

Predator: capture and
eat other consumers
YEARS #of lynx #of
hares

1845
30,000 18,000
Prey: organism that is
10,000 40,000
captured by the predator 1850
1855
30,000 78,000
 EX: HARES
1860
8,000
21,000
1865
67,000 71,000
1870
7,000
12,000
1875
40,000 99,000
1880
12,000 9,000


(consumers: organisms that
eat other organisms)
EX: LYNX
Graph of Data
Series1
Predator prey cycles
# organisms (1000's)
Series2
110
100
90
80
70
60
50
40
30
20
10
0
1840
1845
1850
1855
1860
1865
1870
1875
1880
1885
Year
What is the pattern between the population numbers of the
lynx and the hares?
What happens when a population exceeds carrying capacity?
Questions

What is the pattern between the population numbers
of the lynx and the hares?

# of hares increase, # of lynx increases-- # hare
decreases, # of lynx decrease

What happens when a population exceeds carrying
capacity?

May not be enough resources to support all members
of the population. Its likely that members will begin
to die from lack of resources such as food and water.
Interactions within communities

All organisms need ENERGY (chemical bonds in
food-mostly sugar)

How do they obtain this energy?

How do producers get energy different than
consumers?
Producers vs. Consumers
Producers
Use the sun to make foodPHOTOSYNTHESIS or
chemicalsCHEMOSYNTHESIS
-Plants
-Some bacteria
-Some protists
Consumers
Get their food and energy
by eating OTHER
organisms
Animals (Herbivores,
Omnivores, Carnivores)
- Fungi (decomposer)
-
4 categories of consumers

Herbivores: Eat only plants (vegetarians)

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Carnivores: Eat other animals

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EX: Frog and spiders (eat insects)
Omnivores: Eat plants and animals

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EX: rabbits, deer
EX: pigs and most humans
Decomposers: Eat waste and dead organisms (Absorb
and break down dead matter and recycles it back into the environment)

EX: fungi, bacteria, earthworms
SYMBIOTIC RELATIONSHIPS

Symbiosis: Any close relationship between species
Mutualism (+/+)
Both organisms benefit

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Commensalism (+/0)
One organism benefits and the other is unharmed
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Parasitism (+/-)
One organism benefits and the other is harmed

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Mutualism
(+/+)

EX: Bee and a flower

Bees fly from flower to flower gathering nectar, which they
make into food, benefiting the bees. When they land in a
flower, the bees get some pollen on their hairy bodies, and
when they land in the next flower, some of the pollen from the
first one rubs off, pollinating* the plant. This benefits the
plants. In this symbiotic relationship, the bees get to eat, and
the flowering plants get to reproduce.
Commensalism
(+/o)
-Clown fish and
Sea Anemones

Anemones use their tentacles to capture shrimp, fish,
and other small animals to eat. The clown fish can
swim among the tentacles without being harmed. The
anemones tentacles protect the clown fish from the
predator. Clown fish are protected but the anemones
is not helped or hurt
Parasitism (+/-)

Parasite (+) / Host (-) can affect its growth,
ability to reproduce, and survival.

EX: Tapeworm and
Humans (intestines)

Tapeworms are segmented flatworms that attach
themselves to the insides of the intestines of animals
such as cows, pigs, and humans. They get food by eating
the host's partly digested food, depriving the host of
nutrients. The tapeworm benefits, while the host
(human) is harmed

Niches

An organisms role in its environment

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How do Predator and Prey fit in a niche?

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how it gets its food, shelter, finds a mate, cares for its
young and avoids danger
Predators hunt and captures the prey. Prey’s niche includes
how it avoids being eaten (hiding, camouflage)
How do species in a niche cooperate?

Cooperation occurs when organisms work together in ways
to improve survival

Warning/Alerting other organisms of danger, living groups to care
for young, hunting in packs
Describe the habitat and niche

An aquarium with snails and algae

Habitat: aquarium-freshwater for
both organisms
Snails niche: feeds on algae,
shelters under rocks or in aquarium
plants
Algae niche: uses photosynthesis,
obtains nutrients from water.
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