Download Populations Population Species

Populations
I. Demography
Defining populations
Distribution
Counting populations
(size/density)
Age structure
Sex ratio
II. Population growth
Exponential growth
Logistic growth
Population
• What is a population?
– A group of organisms of
the same species
occupying a particular
space at a particular
time.
• Problems
– How big is a particular
space?
– When is the particular
time?
– A group of organisms, of a
single species, with equal
probability of breeding with any
other individual.
Species
• What is a species?
1
Population Characteristics
• Species
Equus caballus
Equus asinus
Population Characteristics
• Species
– A group of
organisms
capable of
interbreeding
A cross between a male donkey
(jack) and a female horse (mare)
produces a mule. A cross between a
female donkey (jennet or jenny) and
a male horse (stallion) produces a
hinny.
Population Characteristics
• Species
– A group of
organisms capable
of interbreeding and
producing fertile
offspring.
– Isolated gene pools
• Isolation
–
–
–
–
Temporal
Spatial
Mechanical
Behavioral
Genes go in
but they don’t
Come out!
2
LIMITATIONS TO DISTRIBUTION
SPECIES ABSENT BECAUSE OF:
AREA
INACCESSIBLE
YES
DISPERSAL
YES
HABITAT SELECTION
PREDATION
PARASITISM
COMPETITION
DISEASE
YES
NO
BEHAVIOR
OTHER SPECIES
NO
PHYSICAL FACTORS
TEMP, LIGHT, SOIL, FIRE
CHEMICAL FACTORS
WATER, OXYGEN, SALINITY, pH,
NUTRIENTS
(A) Original distribution
of the Gypsy moth in
Eurasia.
(B) Spread of the Gypsy
moth in the northeastern
United States after
accidental introduction at
the end of the 19th cent.
Time
• Less
complicated
• Depends on the
species
Genus Magicicada
http://insects.ummz.lsa.umich.edu/fauna/Michigan_Cicadas/Michigan/Index.html
3
Space
• more complicated
• local population
(Deme)
Space
• more complicated
• local population
(Deme)
Distribution Patterns
• Dispersal
• Dispersion
4
Dispersion
• Clumped
– High density in small
areas surrounded by
large areas with very
low (or zero) density
Dispersion
• Random
– No pattern to where
organisms occur
Dispersion
• Uniform
– Equal spacing
between individuals
across an area.
5
Dispersion
• What is the influence
of scale?
Dispersion
What is the influence of
scale?
Distribution Pattern Depends on
Scale
6
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
Genes go in
but they don’t
Come out!
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
7
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
• Species
– A group of organisms
capable of
interbreeding and
producing fertile
offspring.
– Isolated gene pools
•
•
•
•
Temporal
Spatial
Mechanical
Behavioral
• Population
– A group of organisms,
of a single species,
with equal probability
of breeding with any
other individual.
• Distribution
– Clumped
– Random
– Uniform
8
Distribution Patterns
• What influences dispersion patterns?
• Which dispersion pattern is most
common?
Dispersion
• Most species exhibit a
clumped distribution
• How does one test for type of
dispersion?
• Poisson Distribution - a
mathematical description of
infrequent, random events
– sample mean (x) = sample
variance (s2)
• Mean = average
• Variance =
• Populations with a random
distribution will follow a
Poisson distribution
–
i.e., x/s2 = 1
Dispersion
x/s2
• If
< 1 then distribution is
clumped
2
• If x/s > 1 then distribution is
Uniform
• We can test this using the
following equation:
– Critical value = [(n1)s2]/x
– Where: n = number of
samples (plots)
• This function has a Chi
square distribution i.e., use
a Chi square table with n-1
degrees of freedom
9
Chi Square Table
[(n-1)s2]/x
=
[(25-1)2.68]/1.48 = 43.5
27 November 2001 by NASA satellites
Notice the aggregated distribution
LIMITATIONS TO DISTRIBUTION
SPECIES ABSENT BECAUSE OF:
AREA
INACCESSIBLE
YES
DISPERSAL
NO
YES
HABITAT SELECTION
PREDATION
PARASITISM
COMPETITION
DISEASE
BEHAVIOR
NO
YES
PHYSICAL FACTORS
TEMP, LIGHT, SOIL, FIRE
OTHER SPECIES
NO
CHEMICAL FACTORS
WATER, OXYGEN, SALINITY,
pH, NUTRIENTS
10
10 Truths About Ecology
1. Distribution of species is limited by barriers and
unfavorable environments.
2. No population increases without limits
3. Good and poor places exist for every species
4. Overexploited populations can collapse
5. Communities can rebound from disturbance
6. Communities can exist in several stable
configurations
7. Keystone species may be essential to a
community
8. Natural systems recycle essential materials
9. Climates change, communities change
10. Natural systems are products of evolution
11