Download 6A Population Ecology 2015

Population
Ecology
Chapter 6, pp.149-160
Populations and Communities
 Population:
A group of organisms of a
single species that live in a given area
 Metapopulation: a group of populations
of the same species that exchange
individuals occasionally
 Community: All the populations living in a
given area
True or False: a population
made up of individuals of
different species
A.
B.
True
False
How can we describe a
population?
 Size
(N) = number of individuals
 Density = number of individuals per unit
area (or volume in aquatic ecosystems)
 Distribution = random, clumped, or
uniform
 Sex ratio = ratio of males to females
 Age structure = number of individuals in
various age categories
A scientist samples a 10
hectare field and estimates
that the population of field
mice is 350. What is the
population density of field
mice?
Type your answer into your Qwizdom
Density-Dependent Factors
 Factors
that influence growth and survival
depending on how large the population is
 Examples:





Food
Disease
Space
Sunlight
Water
Limiting Resources
 Resources
that occur in smaller amounts
than a population needs to grow in size
 If the amount of limiting resource declines,
so does the size of the population
All of the following are densitydependent factors EXCEPT
A.
B.
C.
D.
Food supply
Habitat
Disease
Temperature
Carrying Capacity (K)
 The
maximum number of individuals that
can be supported in an environment
 Changes based on resource availability
The number of individuals of a
given species that can be
supported by an ecosystem is
A.
B.
C.
D.
Age structure
Population density
Limiting factor
Carrying capacity
Density-Independent Factors
 Factors
that influence individuals
regardless of population size
 Example:





Tornados
Hurricanes
Floods
Fires
Temperature
How do populations grow?
Exponential Growth
 Intrinsic
growth rate (r) =
maximum possible
growth rate for a
population in ideal
conditions

Based on litter size and
gestation time
 With
no resource
limitations populations
grow exponentially (J
curve)
How do populations grow?
Logistic Growth
 When
population size
approaches carrying
capacity growth follows
logistic model (S curve)
 Density-dependent
factors limit growth
When a population’s growth is
limited by environmental
factors, the growth model is
A.
B.
C.
D.
Logistic, or S-shaped curve
Exponential, or J-shaped curve
Mitigated, or sine curve
Value-added
Overshoots and Die-offs
 Populations
that exceed their carrying
capacity (overshoot) then experience a
large or small crash (die-off)
Predator-Prey Relationships
 Predator
and prey populations oscillate
over time in some ecosystems

Each population affects the size of the other
Reproductive strategies

K-selected species (K-strategists)



Low reproductive rate, abundance determined
by carrying capacity
Large, reproduce relatively late, long gestation,
few large offspring, nurturing parent
r-selected species (r-strategists)


High intrinsic growth rate, overshoot & die-off
Small, frequent reproduction, large litters, short
gestation, little parental care
You discover a new species of bird
that lays eggs once per year and
spends approximately 6 months
raising its offspring. This bird is an
example of a
A.
B.
C.
D.
R-strategist
K-strategist
Density independent factor
Niche specialist