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14.1: Habitat & Niche
 Key concept: Every organism has a habitat and
a niche.
What’s the difference
between a habitat and
niche?
 Habitat: All of the biotic & abiotic factors in the
area where an organism lives (i.e. grass, trees,
watering hole)
 Niche: All of the physical, chemical, and
biological factors that a species needs to survive,
stay healthy, and reproduce (i.e. type of food
species eats, temperature it can tolerate, time of
day it is active)
 Habitat is where a species lives (“address”), niche
is how it lives there (“job”)
Living things need food,
water, and shelter to be
successful
 Competitive exclusion principle: when two
species are competing for the same resources,
one species will be better suited to the niche,
pushing the other species to another niche or
extinction.
 Other outcomes
 Evolutionary response
 Example: selection for different tooth size in
different squirrel species, allowing each to eat
different food in the same area.
 Niche partitioning (next slide)
 Ecological equivalents are species that occupy
similar niches but live in different geographical
regions.
https://www.youtube.com/watch?v=z31y-ZtegZ8
STOP & REVIEW
 What is the difference between a habitat & a
niche?
 A habitat is where a species lives, a niche is how it
lives there/what it needs to survive
 What are the possible outcomes when two
species are competing for the same resources?
 One species moves to another niche, one species
becomes extinct, an evolutionary response, or niche
partitioning.
14.2: Community
Interactions
 Key concept: Organisms interact as individuals
and as populations
Competition and predation
are two important ways in
which species interact.
 Competition: Two organisms fight for the same
limited resources.
 Intraspecific: members of the same species
 Interspecific: Two different species
 Predation: One organism captures and feeds
upon another organism.
Symbiosis is a close ecological relationship
between two or more organisms of
different species that live in direct contact
with one another.
 Mutualism: Both species benefit from one
another. Example: bat & cactus
 Commensalism: One species benefits from the
other, the other is neither helped nor harmed.
Example: Humans & demodicids
 Parasitism: One organism benefits while the
other is harmed. Ex.: Tapeworms
 Endoparasite: Live in the tissues and organs of the
host
 Ectoparasite: Lives on the exterior of the host
 https://www.youtube.com/watch?v=zSmL2F1t81Q
STOP & REVIEW
 What is the name for a close ecological
relationship between two or more organisms of
different species that live in direct contact with
one another?
 Symbiosis
 What type of relationship exists between two
organisms when one is benefiting from the
relationship and the other is neither helped nor
harmed?
 Commensalism
14.4: Population Growth
Patterns
 Key concept: Populations grow in predictable
patterns.
Population Size Changes
 Increased Population
 Immigration: Movement of individuals into a
population from another population
 Births
 Decreased Population
 Emigration: Movement of individuals out of a
population and into another population
 Deaths
 The rate of growth for a population is directly
determined by the amount of resources
available.
Types of Population Growth
Exponential Growth – occurs when
individuals reproduce at a constant rate under
ideal conditions; population size increases
dramatically over a period of time.
 Examples: J-curve, human population
Fruit Fly Population Growth
Number of Fruit Flies
600
500
400
300
Series1
200
100
0
0
20
40
Days
60
Types of Population Growth
 Logistic Growth – population rises
exponentially and then growth slows when it
reaches its carrying capacity.
 Carrying capacity: The maximum number of
individuals of a particular species that the
environment can normally
Rabbit Population Growth
and consistently support.
Number of Rabbits
 S-shaped Curve
16000
14000
12000
10000
8000
6000
4000
2000
0
-50
Series1
0
50
100
Days
150
200
STOP & REVIEW
 In a logistic growth model, the population grows
exponentially until it reaches the ______________,
then the growth will level off.
 Carrying capacity
 The carrying capacity refers to the maximum
number of individuals of a particular species that
the environment can:
 Normally and consistently support.
What affects the carrying
capacity of a population?
 Factors that have the greatest effect at keeping
down the size of a population are called limiting
factors.
 They can be density-dependent or densityindependent.
Density-dependent limiting
factors
 Affected by the number of individuals in a given
area (population density)
 Examples: Competition, predation, parasitism,
disease
Density-Independent
Limiting Factors
 Aspects of the environment that limit population
growth regardless of population size.
 Examples: Unusual weather, natural disasters,
human activities.
STOP & REVIEW
 This aspect of the environment will limit
population size regardless of the initial population
size.
 Density-Independent Limiting Factors
 Examples of density-dependent limiting factors
include:
 Competition, predation, parasitism, disease.
14.5 Ecological Succession
 Key concept: Ecological succession is a process
of change in the species that make up a
community.
Succession occurs following
a disturbance in an
ecosystem.
 Succession: the sequence of biotic changes that
regenerate a damaged community or create a
community in a previously uninhabited area.
 https://www.youtube.com/watch?v=V49IovRSJD
s
Primary Succession
 The establishment and development of an
ecosystem in an area that was previously
uninhabited.
 Can begin due to melting glaciers, volcanic
eruptions, or landslides.
 First organisms to live in a previously uninhabited
area are called pioneer species.
 Examples: lichens and mosses that can break rock
down into smaller pieces.
Secondary Succession
 The reestablishment of a damaged ecosystem in
an area where the soil was left intact.
 Plants and other organisms that remain start the
process of regrowth.
 Small disturbances start the process again and
again.
 Example: forest fire, tree falling
STOP & REVIEW
 This type of succession can happen again and
again in the same ecosystem.
 Secondary