Transcript Bright blue marble spinning in space

organism
population
community
ecosystem
biosphere
Population Ecology
 Population
• group of individuals of same species in same area
at same time
 rely on same
resources
 interact
 interbreed
Population Ecology: What factors affect a population?

Abiotic Factors:
• sunlight & temperature
• precipitation / water
• soil / nutrients

Biotic Factors:
• other living organisms
 prey (food)
 competitors
 predators, parasites,
disease

Intrinsic Factors:
• adaptations
 Describing
a population:
• population range
• pattern of spacing
 density
• size of population
1970
1966
1964
1960
1965
1961
Equator
1958
1951
1943
1937
1956
1970
Immigration
from Africa
~1900
range
density
 Dispersal
patterns within a population:
Provides insight into the
environmental associations
& social interactions of
individuals in population
1. Clumped – grouped
together in clusters
2. Random – spacing has no
pattern
3. Uniform – spacing has even pattern
 Changes
to population
size
• adding & removing
individuals from a
population
 birth
 death
 immigration
 emigration
 Generalized
strategies
1000
Survival per thousand
What do these graphs
tell about survival &
strategy of a species?
Human
(type I)
Hydra
(type II)
I. High death rate in
post-reproductive
years
100
II. Constant mortality
rate throughout life
span
Oyster
(type III)
10
1
0
25
50
75
Percent of maximum life span
100
III. Very high early
mortality but the
few survivors then
live long (stay
reproductive)

K-selected
• late reproduction
• few offspring
• invest a lot in raising offspring
 primates
 coconut

R-selected
• early reproduction
K-selected
• many offspring
• little parental care
 insects
 many plants
R-selected
 The
cost of reproduction
• increase reproduction may decrease survival
 age at first reproduction
 investment per offspring
 number of reproductive cycles per lifetime
Natural selection
favors a life
history that
maximizes lifetime
reproductive
success
Number & size of offspring
vs.
Survival of offspring or parent
r-selected
K-selected
 Characteristic of populations without limiting factors
 introduced to a new environment or rebounding from a
catastrophe
Whooping crane
coming back from near extinction
African elephant
protected from hunting
 Illustrates
a population with carrying capacity
• Carrying Capacity – the number of organisms the
environment can support over a period of time
• Limiting Factors - (food, disease, predators, or lack of
space) will cause population growth to slow over time

As the # of prey
, the # of predators

As the # of predators
, the # of prey

As the # of predators
, the # of prey
 Limiting
factors:
• Density-dependent – factors that limit growth when the
population becomes too large for an area
 competition: food, mates, nesting sites
 predators, parasites, pathogens
• Density-independent – factors that affect all populations no
matter their size
 abiotic factors
 sunlight (energy)
 temperature
 rainfall
competition for nesting sites
marking territory
= competition
swarming locusts
Any
Questions?
2007-2008