Download interactions in the ecosystem

INTERACTIONS IN THE
ECOSYSTEM
CHAPTER 5
Habitats and Niches
Every organism is adapted to life in the habitat
or ecosystem in which it lives
 The role of an organism in the ecosystem is
called its niche (pronounced neesh)
 Niche made up of:
abitoic factors: sunlight, temperature, water
biotic factors: food source, position in the food
chain, etc
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More About Niches
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Competitive Exclusion - the
extinction of a species due to
direct competition for the
same resources.
The species that is better at
getting the resources will
force the other species to
leave, change their niche or
die
Niche diversity is determined
by the abitotic factors in a
habitat
Predator/Prey
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A predator is an
organism that hunts
other organisms for
food (prey)
Predators can be a
limiting factor in
niche diversity
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Keystone Predator A predator that causes a large
increase in habitat diversity
(Ex: a seastar in a tidepool
Evolution and Adaptation
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Ecosystems change over time
All species adapt to niches in their environment
The way many populations respond to
environmental changes is by evolving or
changing in response to changes in their
environment.
Evolution and Adaptation
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Evolution is defined as a change in a
population of organisms over time
Organisms have three options in response to
changes in the environment:
adapting to different niches in the same
habitat to avoid competing for the same
resources
move to a new habitat to avoid competition
die (and possible extinction)
Convergent Evolution
Convergent Evolution
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Similar ecosystems often have similar niches.
Organisms from both ecosystems will also have
similar adaptations
Ex: Wings on a bee, a bird and a bat. The insect wing, bird
wing and mammal wing all serve the same purpose but are very
different on each organism. Sharks (fish) and dolphins
(mammals) look similar, both have fins, but their bodies are very
different in structure.
Coevolution
Species that are dependant
on and adapt to suit
each other
•
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Monarch caterpillar eats only
poisonous milkweed leaves –
which make the adult butterfly
poisonous to its predators.
Acacia tree and ants - the
trees have sharp thorns provide ants with both food
and a place to build their
nests. Ants keep otherinsect
pests away from the trees.
Populations
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The size of the population of any organism is
dependent on the abiotic and biotic factors that
shape each niche.
Population size changes as the conditions in
the niche change.
Thomas Malthus (1798) studied human
populations
Charles Darwin (1859) studied plant and
animal populations
Populations
Exponential Growth – the growth rate of each
generation is a multiple of the parent
generation
 Plants: corn, rice, wheat, oak trees
 Animals: like sea turtles, alligators, mice,
spiders, goldfish, robins, dogs and cats
All have many babies – not all
babies survive to become
adults.

Growth Rate
Darwin – noticed that most
organisms produce
many more offspring than will
Actually survive into adulthood (some babies do
die)
Abiotic factors like water and
land (space) limit population
size and reproduction rate
Population Size

Carrying Capacity – The number of individuals
in any species that can be successfully
supported by their ecosystem.
Ex: The number of lynx
that survive the Arctic winter
depends on the number
of snowshoe hare that
available to eat.
Black bears in NJ have exceeded
the carrying capacity of the forest
Populations
Limiting Factors – The forces
that slow the growth in any population
Density-Dependent factors:
predators, food, disease
Density-Independent factors:
water, climate, living space,
natural disasters,
human disturbance
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Limiting Factors
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Elephants are limited in population growth
because the resources like water, food and land are
limited in their African savanna habitat.
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There is a long dry season (with no rain) followed by a shorter
rainy season.
Elephants eat many tons of plants each day and need a lot water
to drink and cool themselves with.
Only one female in each family has a baby – the rest of the
females help care for the young
CHAPTER 5 VOCABULARY
(You Should Know)
Niche
Keystone
Predator
Evolution
Convergent
evolution
Prey
Extinction
Adaptation
Coevolution
Exponential
Growth
Carrying
Capacity
Competitive
Exclusion
Evolve
Habitat
Ecosystem
Migration
Limiting
factor