Transcript Ecology Unit

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D. Habitat and Niche – Part III - PreAP
1. Habitat: the place in which an organism
lives out its life.
2. Niche:
a. The role a species plays in a community.
b. A niche is determined by the tolerance/
limitations of an organism, or a limiting
factor.
c. Examples of limiting factors:
i. Amount of water
ii. Amount of food
iii. Temperature
iv. Amount of space
v. Availability of mates
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E. Population Carrying Capacity
1. Limiting factors are categorized into two types:
a. Density-dependent factors b. Density-independent factors
i. Disease
ii. Competition
iii. Predators
iv. Parasites
v. Food
vi. Crowding
1. The greater the
population, the greater
effect these factors have.
i. Volcanic eruptions
ii. Temperature
iii. Storms
iv. Floods
v. Drought
vi. Chemical pesticides
vii. Major habitat disruption
(as in the New Orleans
flooding)
1. Most are abiotic factors
E. Population Carrying Capacity
2. Nearly all populations will tend to grow
exponentially as long as there are resources
available.
3. Two of the most basic factors that affect the
rate of population growth are the birth rate, and
the death rate.
4. Rate of growth = birth rate – death rate
5. If a population does not have any limiting
factor it will exhibit exponential growth
(unrestricted growth).
6. If a population has limiting factors, it will
exhibit logistic growth (limited growth).
E. Population Carrying Capacity
a. In general, no population exhibits the exponential growth
for long.
E. Population Carrying Capacity
a. Exponential growth curve:
population growth plotted against
time.
b. The Exponential curve, also known
as a J-curve, occurs when there is no
limit to population size.
c. As a population gets larger, it also
grows at a faster rate.
d. This is the maximum population
growth under ideal circumstances.
e. Includes plenty of room for each
member, unlimited resources (food,
water) and no hindrances (predators).
E. Population Carrying Capacity
a. Logistic growth: Declining
resources available to populations
as they grow.
b. The Logistic curve, also known as
an S-curve, shows the effect of a
limiting factor.
c. It assumes the birth and death
rates are not constant.
d. As the population grows, births
decline and death rises.
e. Eventually birth = death so the population stops growing;
reach the carrying capacity (K)
f. Carrying capacity (K): the maximum number of
individuals that an environment can support.
E. Population Carrying Capacity
a. r-strategy: high intrinsic
growth rates - focuses on
reproduction, not on
competition with other
individuals in the
population.
b. K-strategy: focuses on
population at or near
carrying capacity—must
be able to compete with
other individuals in the
population.
K-strategy
r-strategy
E. Population Carrying Capacity
Characteristics of contrasting reproductive strategies
Extrinsically Controlled Growth
1.Short life
2.Rapid growth
3.Early maturity
4.Many small offspring
5.Little parental care or protection
6.Little investment in individual offspring
r-strategy
(J curve)
Instrinsically Controlled Growth
1.Long life
2.Slower growth
3.Late maturity
4.Fewer large offspring
5.High parental care and protection
6.High investment in individual offspring
K-strategy
(S curve)
E. Population Carrying Capacity
a. Dynamic equilibrium: community of organisms in
which species and ecosystem diversity remain relatively
stable.
b. Resilience: capacity of an ecosystem to respond to a
disturbance by resisting damage and recovering quickly.
c. Biotic potential: maximum reproductive capacity of a
population if resources are unlimited.
d. Environmental resistance: Factors in
an environment such as predators, climate,
and food availability, that keep its populations from
reaching their maximum growth potential.