1. Chapter 53

2. Ecology is the study of how organisms (biotic) interact with each other and their environment (abiotic)

3. Populations
A population consists of individuals of a species living together at the same place at the same time.
Most species have a limited geographic range.
organism’s environment (abiotic) include:
temperature
water
sunlight
soil

4. Population Dispersion
Randomly spaced
Uniformly spaced - competition for resources
Clumped spacing - unequal resources

5. Population Dispersion
Human effect
Dispersal mechanisms
light seeds (wind)
hooks and hairs (animal fur)
fruits (animal digestive systems)

6. Demography - statistical study of populations Survivorship curves
Survivorship is the percentage of an original population that survives to a given age.
Type I - full life span
Type II - mortality unrelated to age
Type III - early susceptibility

7. Cost of Reproduction
A life history is the complete life cycle of an organism.
cost of reproduction
Due to limited resources, increased reproduction may decrease survival
Natural selection will favor the life history that maximizes reproductive success.
number of offspring vs size
size may affect chances of survival

8. Cost of Reproduction
Reproductive events per lifetime
semelparity - organisms focus all reproductive efforts on a single, large event
iteroparity - organisms produce offspring several times over many seasons
Age at first reproduction
Longer-lived animals tend to reproduce later, and provide more parental care than shorter-lived animals.

9. Biotic Potential
Exponential growth model - J curve
Rate at which a population will increase when no limits are placed on the rate of growth.

10. Biotic Potential Carrying capacity
Carrying capacity (K) is the maximum number of individuals the resources in a given area can support.
Logistic growth
As a population approaches carrying capacity, its growth rate slows as resources become depleted.
sigmoidal (S curve) growth curve

11. Population Growth Density-dependent population controls
As populations approach their carrying capacity, competition for resources can be severe, leading to decreased birth rate and increased risk of mortality.

12. Linked Population Cycles
snowshoe hares
Food plants (willows) and predators (lynx) both control the population.

13. Population Growth and Life History Models
K-selected species tend to produce relatively few, large offspring.
large investment in parental care
r-selected species tend to produce many, small offspring.
small investment in parental care