Transcript Interactions in the Ecosystem

Interactions in the Ecosystem
Chapter 5 (pg 72-87)
Mrs. Paul
5.1 HABITATS AND NICHES

Habitat: the place where an organism
lives.
◦ Each organism is adapted to its habitat.
 Have special ways of gathering food, reproducing,
avoiding predators.
◦ Ecosystems contain many different habitats
and organisms.
Niches

Niche: the role of an organism in the
ecosystem.
◦ What an organism does within its habitat.
◦ Includes biotic and abiotic factors (food
sources, predators/temperature, amount of
sunlight and water).
◦ All members of a species adapted to same
niche---2 species may NOT share the same
niche.
Example: Anolis lizard
All of this type of lizard
vary ONLY by the size of
insects that they eat.
 Large jaws eat large
insects.
 Small jaws eat small
insects.
 Occupy DIFFERENT
niches.

What if 2 species try to share the same
niche?
Compete for resources (some will get
more of what they need to survive and
some will get less).
 Competitive Exclusion:the extinction of a
population due to direct competition with
another species for a resource.

Example: The actions of species A influences the niche of species B!
Species A Chthamalus stellatus
Species B Balanus balanoides

There is a difference between the role a
an organism CAN fill in the environment
vs. the role it actually fills when it
interacts with other species in the
environment.
◦ Fundamental niche: the theoretical role an
organism plays in its habitat.
◦ Realized niche: the actual role the organism
plays in its environment.
Fundamental niche vs. Realized niche…
Niche Diversity

Determined by the abiotic factors in the
environment.
◦ If the physical conditions of a place are fairly
constant, then there will be less diversity.
◦ Differences in temperature and moisture.

Predator: an organism that actively hunts
other organsims.
◦ Can increase niche diversity.
◦ Decrease population size of their prey species,
then more resources become available for
another species.
Example: remove sea stars from tide pools
and mussels increased until they
“outcompeted” other species.
Number of species in tide pool decreased
from 15 to 8.

Keystone predator: a predator that causes
a large increase in the diversity of its
habitat.
Check for Understanding:
1.
2.
3.
How is a niche different from a habitat?
What is competitive exclusion? How is it
related to the concept of the niche?
What might happen to an ecosystem if all
the carnivores were removed? Explain your
answer.
Homework – review worksheet 5.1
Class Activity
Maps in Action “Bats and Insects”
 Answer questions in journal.

5.2 EVOLUTION AND ADAPTATION
A change in the environment affects all the
organisms in the environments and their
niches.
 If a niche disappears, a species may become
extinct.
 Evolution: change in a population of organisms
over time.

◦ One way populations respond to a changing
environment.
Evolving to the Niche

May change for several reasons:
◦ To adapt to niches in environment.
◦ Avoid competition with another species.
◦ Example: 5 species of Warblers eating insects
in spruce trees…

Each of the 5 species has evolved into a
narrow niche (they eat insects in different
parts of the spruce trees)
◦ Specialized niche: an organism with a small or
very specific role in the habitat.
 Example: giant panda only eats bamboo leaves
 Vulnerable to extinction-can’t deal with change in
environment.
◦ Generalized niche: an organism with a wide or
more general role in the habitat.
 Example: mice or cockroaches.
CONVERGENT EVOLUTION
Organisms living in similar ecosystems
with similar niches may become alike as
they adapt to the similar conditions.
 Convergent evolution: the development of
similar adaptations in two species with
similar niches.

◦ Example: wings of birds and bats, dolphin and
ichthyosaur.
Coevolution
Organisms that interact closely may have
evolutionary responses to each other.
 Coevolution: species that interact closely
may adapt to one another.

◦ May be between predator and prey (plants
and caterpillar), species that cooperate (acacia
trees and the stinging ants that live on them).
Check for Understanding:
1.
2.
3.
Why do species such as the warblers in Figure
5.5 evolve avoid competition with other
species?
Explain convergent evolution and give one
example. Why does convergent evolution
happen?
What would happen to the ant colony living on
an acacia tree if that tree was chopped down?
What does your answer imply about the effect
of destroying an organism’s habitat?
Homework – review worksheet 5.2
Case Study

Darwin’s finches
5.3 POPULATIONS
Population: a group of organisms of the
same species that live together in an area
and interbreed.
 As the environment changes, the size of
the population changes.

Population Growth

Thomas Malthus
◦ Observed that human population can quickly
grow beyond what the environment can
support.
 Result in famine and disease
Populations have the ability to grow very
quickly.
 Exponential growth: population growth in
which the rate of growth in each
generation is a multiple of the previous
generation.
 In reality, a population cannot continue to
grow like this due to limited resources.

Carrying Capacity
As a population increases, available
resources decrease (water, food, space,
etc).
 Competition increases as there is no
longer enough for everyone.

◦ Those who don’t get resources die (death
rate increases, birth rate decrease…having
babies requires a lot of resources).
◦ Population growth slows down.

Population growth = population death
◦ The population is no longer getting bigger.

Carrying capacity: number of individuals
that can be supported by an ecosystem.
◦ Resources that are available will determine
the carrying capacity.
◦ Carrying capacity is the maximum population
size.
Limiting Factors

Limiting factors: forces that slow the
growth in a population.
◦ Examples: natural disasters, human
disturbance, water availability, living space,
food competition, disease, parasitism,
predation, climate.

Two types of limiting factors:
◦ 1. Density-dependent limiting factors
◦ 2. Density-independent limiting factors.
Density-Dependent Limiting Factors
Limiting factors that are dependent on
population size.
 Affect a population more strongly as the
population gets bigger.
 Examples: lack of food, predation, disease

Density-independent Limiting
Factors
Limiting factors that affect the same percentage of
the population, no matter how big the population
becomes.
 Affect a population the same amount each time.
 Examples: natural disasters, human habitat
damage.

Human Populations
Growth of human population is
exponential.
 Caused by many factors: advances in
agriculture, technology, and medicine.

Check for Understanding:
1.
2.
What is exponential growth? Under what
conditions do populations grow
exponentially?
What is the difference between densitydependent and density-independent limiting
factors?
Lab Activity

Predator/Prey Interactions