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Population Dynamics
Populations are studied by looking at changes in:
1) size
2) density
3) dispersion (clumping*,uniform,random)
4) age distribution
? How is population growth measured?
(Births + Immigration) – (Deaths + Emigration) = growth
? What Affects Population Growth?
- Carrying Capacity determines the # of individuals
a habitat can support
- carrying capacity is determined by:
a) Biotic Potential
- how quickly a species can reproduce
b) Environmental Resistance
- limits to a species growth
ex.- space, food, mates, etc.
? What Ways Do Populations Grow?
2 Types of Growth
1) Exponential Growth
- observed in quick reproducing species
- can happen with unlimited resources
2) Logistic Growth
- typical growth pattern for most species
- environmental resistance causes growth
to level off and fluctuate at carrying capacity
? What Affects the Density of Populations?
2 Types of Factors
1) Density-dependent
- limits on growth that only affect very dense
populations
Examples- competition, disease, predation
2) Density-independent
- affects a population regardless of size
Examples- natural disasters, human disturbance
Reproductive Methods
- organisms can reproduce sexually/asexually
- asexual reproduction- requires less energy
- allows everyone to reproduce
- doesn’t allow for diversity
- sexual reproduction- requires more energy
- only females can reproduce
- allows for increased diversity
- males can provide protection
Reproductive Strategies
1) Opportunists (r-selected species)
- put most of its energy into reproduction
- reproduce at a young age
- produce many offspring
- no parental care
- high growth rate
2) Competitors (K-selected species)
- put most of its energy into survival
- reproduce later
- produce few offspring
- provide parental care
- low growth rate
Life Expectancies for “r” & “K” species
“r-selected” species show:
- early loss survivorship curves
- reproductive strategy leads to many deaths
“K-selected” species show:
- late loss survivorship curves
- reproductive strategy leads to fewer deaths
Species with intermediate strategies show:
- constant loss survivorship curves
- reproductive strategy leads to a constant rate
of death
Survivorship Curves
? How do we preserve species?
Conservation Biology measures:
1) size of populations
2) possible changes in size
3) whether sizes are sustainable
Conservation Biology believes:
1) biodiversity is important for survival
2) humans should not alter ecosystems
3) we should protect whole ecosystems
? How do we live more sustainably?
We should understand that:
1) Our lives are dependent on the Earth & sun.
2) Everything on Earth is connected.
3) We should minimize damage & work with nature.