CHAPTER 14
Interactions in Ecosystems: Day One
Habitat versus Niche
Review!
• What is a habitat?
• All of the biotic and
abiotic factors in the
area where an
organism lives.
• Examples: grass,
trees, and watering
holes!
• Where it lives!
Habitat versus Niche
Review!
• What is a niche?
• Composed of all of the physical, chemical,
and biological factors that a species needs
to survive
• Niche includes: type of food a species eats,
tolerating certain types of abiotic conditions,
and a species’ behavior.
• How it lives!
• Habitat is like an address in an ecosystem
and a niche is like the job in an ecosystem.
Resource availability
• Provides structure to
communities
• What is a community?
• Different groups of
species
• Many species share
similar habitats and use
some of the same
resources
• Florida Everglades
Competitive Exclusion
• Can present a problem
if two species use the
same resource in the
same way
• One species will
always be better
adapted to the
environment.
Competitive Exclusion
• States that when two species
are competing for the same
resources, one species will be
better suited to the niche, and
the other species will be pushed
into another niche or become
extinct.
• Example:
• In Great Britain, North
American gray squirrel (better
suited) introduced and pushed
out the native European red
squirrel.
• Caused red squirrel population
to decline rapidly.
Other outcomes from competitive
exclusion
• Niche partitioning:
• Divide resources based on competitive
advantages
• Evolutionary response:
• Different sizes of teeth could affect the way they
eat
Competitive Exclusion Principle
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Ecological equivalents
• Are species that occupy
similar niches but live in
different geographical
regions.
• Examples: Mantella frog of
Madagascar and poison
dart frog of South America
• Both have the same niche
in similar habitats, but will
never compete for the
same resources because
they live in different
geographical regions.
Community Interactions
• Competition and
predation are two
important ways in which
organisms interact.
• Competition occurs when
two organisms fight for
the same limited
resource.
Competition
• Two types of
competition:
• Interspecific
competition:
• Competition
between two
different species
(competing for
space)
• Examples: cats
and dogs
Competition
• Two types of
competition:
• Intraspecific
competition:
• Competition
between members
of the same
species
• Examples: male
birds, lions
Predation
• Process by which one organism captures and
feeds upon another organism.
Timber Rattlesnake
More Community Interactions
• Symbiosis:
• Any relationship where two species live closely
together and interact.
• 3 types:
• Mutualism
• Commensalism
• Parasitism
Relationships Between Organisms
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Ticket Out the Door
1. Complete the table about factors that influence
ecosystems.
Type of Factor
Definition
Examples
Biotic Factors
Abiotic Factors
2. When does competition occur?
3. What is a resource?
4. What is the competitive exclusion principle?
5. What is predation?
6. When predation occurs, what is the organism called that
does the killing AND eating, and what is the food source
called?
CHAPTER 14
Interactions in Ecosystems: Day One
Continued…
Mutualism
• Both species benefit
from the relationship.
• Example:
• Ants and aphids:
Ants get a sugary
substance from the
aphid while the aphid
receives protection
from predators.
Commensalism
• One organism benefits
while the other is
unaffected.
• Example:
• Barnacles on whales:
Barnacles “hitch” a ride
on the whale gathering
food during transport; the
whales receives nothing
out of the relationship
Parasitism
• One organism benefits
while the other is
harmed.
• Examples:
• Flea and dog: Flea gets
home/food while the
dog is harmed because
the flea feeds on its
blood!
Parasites
• Two types of parasites:
• Ectoparasite: lives on the outside of an
organism, attaching itself to the outside
of the host
• Examples: fleas, ticks, and leeches
• Endoparasite: found on the inside of
living organisms, feed on nutrients
ingested by their host
• Examples: tapeworms and hookworms
Symbiotic Relationships – Untamed
Science
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in-ecosystems1.html
Ticket out the Door
1.
Determine which ecological factors are a part of a lion’s niche and which are a
part of a lion’s habitat by placing the above items in the correct column.
a.
Items: food, hunting behavior, other lions, trees, watering hole, wildebeast,
zebra, sand, temperature, grass, savanna
Habitat
2.
3.
4.
Niche
What are the three possible outcomes of competitive exclusion?
What are ecological equivalents?
Complete the table about main classes of symbiotic relationships.
Class
Description of Relationship
mutualism
commensalism
parasitism
5.
The organism from which a parasite obtains nutritional needs is called a(an)
_________________________.
CHAPTER 14
Interactions in Ecosystem: Day Two
Populations
• What is a population?
• A group of the same species of
organism living in the same place.
Characteristics of Populations
• How do populations grow?
• Four important characteristics of a population are:
• Geographic distribution
• Population density
• Growth rate
• Age structure
Geographic Distribution
• May also be called it’s
range
• Describes the area
inhabited by a
population
• Varies in size
depending upon the
type of organism
Geographic dispersion
• Shows how individuals in a population are
spaced
• Allows ecologists to study population
dispersion
• Way in which individuals of a population are
spread in an area or a volume
• Three types of population dispersion:
• Clumped dispersion
• Uniform dispersion
• Random Dispersion
Clumped dispersion
• Individuals live
close together in
groups in order to
facilitate mating,
gain protection, or
access food
Uniform dispersion
• Individuals living at
specific distances from
one another
• Caused by territoriality
and intraspecific
competition
Random dispersion
• Individuals are
spread
randomly within
an area or
volume
Population Dispersion
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Population density
• Number of individuals per unit area
(defined space)
• Varies greatly depending on the species
and ecosystem
• Measures the “crowdedness” of an area
• Population density =
# of individuals
area (units2)
Population growth
• Affected by three factors
• Number of births
• Number of deaths
• Number individuals
that enter and leave the
population
• Immigration – movement
INTO an area
• Emigration – movement
OUT of an area
Ticket Out the Door
1.
2.
3.
4.
5.
6.
7.
What are four main characteristics of a population?
What is a population’s geographic distribution?
Another term for geographic distribution is
____________________.
What is population density?
What three factors affect population size?
If more individuals are born than die in any period of time,
how will the population change?
Complete the table about changes in population size.
Type of Change
Immigration
Emigration
Definition
Resulting
Change in Size
CHAPTER 14
Interactions in Ecosystem: Day Two
Continued…
Population growth based on
available resources
• Growth is a function of
the environment
• Directly determined by
the amount of resources
available
• Two distinct types of
population growth
• Exponential
• Logistic
Exponential growth
• Population has abundant
space and food
• Occurs when the individuals
in a population reproduce at
a constant rate
• Lack of limiting factors
(causes population growth to
decrease)
• Shown as a J-shaped curve
in a graph
• Examples: bacteria!
More on exponential growth
• When a population has unlimited
resources and continues to grow
to its full living potential, it is
called its biotic potential.
• A population that has reached
biotic potential has reached its
maximum reproductive
capacity.
• That means it has reproduced
as much as it can!
Logistic Growth
• Occurs when the population’s
growth slows or stops following
a period of exponential growth
• Most realistic
• Caused by resources becoming
less available
• Influenced by limiting factors
• Can slow down when birthrate
decreases or death rate
increases
• Represented as an S-shaped
curve
Carrying Capacity
• Represented as K
• Largest number of
individuals that a
given environment
can support
• Can change when
the environment
changes
•Region A= very close to
exponential growth
•Region B= declining birthrate;
inc. death rate
•Region C= pop. reaches K;
usually fluctuates around
Carrying Capacity
Limiting factors
• Is a factor that causes population growth to
decrease
• Two types of limiting factors:
• Density-dependent
• Density-independent
Density-Dependent Factors
• Depends on population size
• Becomes limiting only when the
population density reaches a
certain level
• Density is the number of
organisms per unit area
• Best seen when population is large
and dense
• Do not affect small, scattered
populations
• Examples: competition, predation,
parasitism, and disease
Competition
• Occurs if crowded organisms compete for food,
water, space, sunlight, and other essentials
• Can occurs between members of the same
species
• Can also occur between members of different
species…remember no two species can occupy
the same niche in the same place at the same
time
Effect of Predation
• Population size often
controlled by
predation
• Takes place in the
predator-prey
relationship
• Best mechanism of
population control
Parasitism and Disease
• Limit growth of
population
• Take nourishment at
the expense of their
hosts often
weakening them and
causing disease and
death
Density-Independent Factors
• Affect all populations
regardless of size
• Examples: unusual weather,
natural disasters, seasonal
cycles, and human activities
• Can see a population crash
• Dramatic decline in the
population size over time
Age Structure
• Population growth depends on how many
people of different ages make up a given
population.
• Populations with large numbers of young
offspring have greater potential for rapid
growth
• Population Pyramids or Age-Structure
Diagrams show age structure in a population.
Patterns of Population Growth
• The scientific study of human populations is
called demography
• Examines the characteristics of human
populations and attempts to explain how
those populations will change over time
• Birthrates, death rates, and the age
structure of a population help predict why
some countries have high growth rates
while other countries grow more slowly
Human Population Growth
• It took from the beginning of mankind to
around 1800 for the human population to
reach 1 billion.
• In the last 200 years, the human population
has reached just over 6 billion.
• The U.N. estimates the world’s population to
be 12.5 Billion by 2050.
• What effects will these numbers have on the
Earth? Other forms of life?
The Demographic Transition
• Over the past century, population growth in the
US, Japan, and much of Europe has slowed
dramatically.
• One hypothesis as to why these countries have
slowed in their growth is the demographic
transition (a dramatic change in birth and
death rates).
• As countries modernize, there are advances in
nutrition, medicine, and sanitation.
• These result in more children surviving into
adulthood and more adults living to old age.
• These changes lower the death rate and
begin the demographic transition.
Population Biotic Potential
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Ticket out the Door
1.
2.
3.
4.
5.
6.
7.
How will a population change if there is abundant space and food and if the
population is protected from predators or disease?
When does exponential growth occur?
When does logistic growth occur?
Word Bank:
Births
Emigration
Deaths
Immigration
When resources are abundant in a particular area, individuals may move
into the population of this area. This movement of individuals into a
population from a different population is called __________________.
A very cold winter has left many deer in a population hungry and sick. By
the end of the winter, this population will likely decrease because of
____________________.
A deer population experiences growth when the rate of reproduction
increases. This change in population size is due to ___________________.
As humans move into their territory, many members of a deer population
move away and join other herds. This movement of individuals out of a
population into a new population is called _______________________.
CHAPTER 14
Interactions in Ecosystems: Day Three
Ecological succession
• Succession means the
sequence of biotic
changes that regenerate a
damaged community in a
previously uninhabited area
• Ecosystems are constantly
changing in response to
natural and human
disturbances.
• When an ecosystem
changes, older organisms
gradually die out and new
organisms move in.
Ecological succession
• Can result from slow changes in the
physical environment
• Sudden natural disasters or human
activities also play a role in ecological
succession
• Ecological succession can be
• Primary
• Secondary
Primary succession
• Establishment and development of an
ecosystem in an area that was previously
uninhabited
• Occurs on land where no soil exists
• Occurs on surfaces formed as volcanic
eruptions build new islands or cover the
land with lava rock or volcanic ash
• Can also occur on bare rock
Primary succession
• First, lichens that do not
need soil to survive grow on
rocks
• Lichens are made up of
fungus and algae; helps
break up rocks
• Next, mosses grow to hold
the newly made soil
• Each of these are known as
a pioneer species
• Meaning these are the first
species to populate an area
Primary succession
• Soil starts to form as
lichens, weather, and
erosion help break down
rocks into smaller pieces
• When lichens die they
decompose, adding
organic matter to the
rock to make soil
Primary succession
• Simple plants like mosses and ferns can grow in the
new soil
Primary succession
• Simple plants die, adding more nutrients to the soil
• Soil layer thickens
• Grasses and wildflowers begin to take over
Primary succession
• Grasses and wildflowers will die, adding nutrients to
the soil
• Shrubs and trees can survive now
Primary succession
• Insects, small birds, and mammals begin to move
into the area
• What was once bare rock, can now support an area
of life
Secondary succession
• Begins in a place that already has soil and
was once the home of living organisms
• Occurs faster and has different pioneer
species than primary succession
• Often see this after a natural disaster such
as a forest fire or volcano
Climax community
• A stable group of plants and animals that is the end
result of the succession process
• Final and stable community
• Does not always mean big trees
• Grasses in prairies
• Cacti in deserts
Climax Communities
Climax Communities
Ecological Succession
Ticket Out the Door
1. What is ecological succession?
2. What is primary succession?
3. The first species to populate an area when primary
succession begins are called _________________.
4. When a disturbance changes a community without
removing the soil, what follows?
5. An area that was once referred to as a climax
community without removing the soil, what follows?