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Interactions Among Living Things
Adapting to the Environment
• Natural Selection – a characteristic that makes an
individual better suited to its environment may
eventually become common in that species.
• Natural selection results in adaptations or
behaviors and physical characteristics that allow
organisms to live successfully in their
environments.
• (you will hear more about this during Evolution)
Interactions Among Living Things
Organisms have adaptations that
help them survive in their
environment
All organisms have their own Niche.
Niche is the role of an organism in its environment or how
it makes its living.
NICHE INCLUDES:
• type of food the organisms eats
• how it obtains this food
• which other organisms use this organism as food
• when and how it reproduces
• physical conditions it requires to survive
Three types of Interactions among
Organisms
• Competition
• Predation
• Symbiosis
COMPETITION
• The simultaneous demand by two or more
organisms for limited environmental
resources, such as nutrients, living space, or
light.
PREDATOR/PREY
• Predator- organisms that obtain their nutritional energy by
killing and eating other organisms.
• Prey – Any creature that is hunted and caught to be eaten
for food.
Symbiosis
Organisms within a community interact with each other in many
ways. Some are predators, some are prey. Some compete with one
another, some cooperate. Some species form symbiotic relationships
with other species:
Mutualism
benefits both
Commensalism
benefits one, other unaffected
Parasitism
benefits one, harms other
SYMBIOTIC RELATIONSHIPS
• MUTUALISM-An association between
organisms of two different species
in which each member benefits.
•
EXAMPLE
Example: Rainforest ants and the Whistling Thorn and Bullhorn Acacia
trees.
ants nest inside the plant's thorns.
ants protect acacias from attack by herbivores (which they frequently
eat, introducing a resource component to this service-service
relationship)
• Commensalism- the relation between two
different kinds of organisms when one
receives benefits from the other without
affecting or damaging it.
•Barnacles adhering to the skin of a whale or shell of a mollusk:
barnacle is a mollusks that benefits by finding a habitat where
nutrients are available. (In the case of lodging on the living organism,
the barnacle is transported to new sources of food.)
•The presence of barnacle populations does not appear to hamper or
enhance the survival of the animals carrying them.
PARASITISM
• symbiosis in which one organism lives as a
parasite in or on another organism and usually
does some harm to it.
Ticks on
a bird
• Hosts is the
organism that the
parasite lives
on
Competition
• It is the struggle between organisms as they
attempt to use the same limited resource
• Occurs when two species occupy
the same niche
• Why can’t two species occupy the same niche?
– If two species occupy the same niche, they will
compete directly against each other and one species
will eventually die off
• In Australia Rabbits compete with herbivores
like the western Quoll which became extinct
• Rabbits were brought in; they were an
invasive species whose destruction of habitats
is responsible for the extinction or major
decline of many native animals such as the
Western Quoll.
Predation
• The interaction in which one organism kills
another for food is called predation
• The organism that does the killing is the predator
• The organism that is killed is the prey
Adaptations
• Predator adaptations
– Help them catch and kill prey
• Cheetah can run very fast for a short time
• Jellyfish’s tentacles contain a poisonous substance that
paralyze tiny water animals
• Prey adaptations
– Help them avoid becoming prey
• Alertness and speed of an antelope help protect it from its
predators
• Smelly spray of a skunk
Predation and Population Size
• Predator and prey populations rise and fall in related cycles.
Predation
Defense Strategies
False Coloring
Mimicry
Protective Covering
Warning Coloring
Camouflage
Changes in Communities
Ecosystems are always changing…
Primary Succession – a series of changes that occur in an area where
no soil or organisms exist.
In a barren area, a new community is established with pioneer species
(first species in the area), like mosses, that do well with little or no soil.
Mosses eventually give way to coniferous trees.
Ecosystems are always changing…
Secondary Succession – a series of changes that occur in an area
where the ecosystem has been disturbed.
When a disturbance (fire, flood, or tornados) damages a community
but soil remains, the community gets reestablished from seeds and
roots left behind. Grasses grow, then small shrubs, and eventually
trees.
Types of Succession
Primary
• 1st time plants
or animals are
established
• New island
• Volcanoes
• Bare soil, rock
Secondary
• After a “blowout”
• Re-establish a
community
• Already had living
organisms
• Fire, flood, human
disruption
Pioneer species:
• Are the first plants
to grow in an area
• Lichens (algae &
fungi) break apart
rock to make soil
• Grasses
• Annual flowers
• Mosses
Succession communities:
1. Pioneer 2. Intermediate
species
species
3. Climax
community
Intermediate Community
Is
characterized
by trees that
grow fairly fast
like pine trees
that needs
lots of sun.
CLIMAX COMMUNITY
Plant community that no longer
undergoes changes in species
composition due to succession.
Hard
woods like
oak &
maple trees