1. Population Ecology

2. Study of Populations Population Population Structure
Individuals of a species within a given area
Population Structure
Age distribution of individuals in a population
The way the individuals are spread over the environment
Population Density
Number of individuals of a population per unit of area
Demographic events
Changes of structure
Births, deaths, immigration, emigration

3. Study of Populations Tracking devices
Able to record & transmit information about location, physiology, feeding behavior, & social behavior
Estimate population densities from samples
m2/n2 = n1/N
n1 = number of marked individuals in the first sample (all get marked)
n2 = total number of individuals in the second sample
m2 = number of marked individuals in the second sample
N= estimated size of the total population

5. Study of Populations Birth & death rates can be estimated
N1 – N0 + B – D + I – E
N1 = number of individuals at time 1
N0 = number of individuals at time 0
B = number of individuals born between 0 & time 1
D = number that died between 0 & time 1
I = number that immigrated between 0 & time 1
E = number that emigrated between 0 & time 1

6. Study of Populations Life table
Displays information about birth & death rates in a population
Constructed by
Cohorts
tracking a group of individuals born at the same time
Survivorship
Number that are still alive at later dates
Used to predict future trends

8. Survivorship Curves
Type I curves are typical of populations in which most mortality occurs among the elderly
~ humans in developed countries
Type II curves occur when mortality is not dependent on age
~many species of large birds and fish
Type III curves occur when juvenile mortality is extremely high, life expectancy increases for individuals who survive their risky juvenile period.

10. Age distribution

11. Life History
Describes how an organisms allocates it time & energy among growth, reproduction, & other activities.
Important in understanding how populations grow & are distributed
Vital for designing population management plans

12. Factors that Influence Population Densities
All populations have the potential for explosive growth.
As number of individuals increase, the number of new individuals accelerates.
Graph forms a continuous upward curve
Known as EXPONENTIAL GROWTH

13. Factors that Influence Population Densities
Limited by resources & biotic interactions
Environmental carrying capacity (K)
Determined by the availability of resources
Food, nest sites, shelter, disease, predators, etc.
Growth slows down as it reaches the carrying capacity because of resource limitations
Forms a S-shaped curve
(logistic growth)

15. Factors that Influence Population Densities
Densities influence birth & death rates
Density-dependent (birth & death rates change together). Each additional individual makes things worse for other members.
As species increases, food supply may deplete
Poorer nutrition increase death rate & decrease birth rate
Predator attracted to areas with high densities of prey
Diseases spread more easily in dense populations
Density independent factors
physical or abiotic factors like weather, forest fire, pollutant, etc.

16. Factors why some are more common than others
Species that use abundant resources generally reach higher population densities
Animals that eat plants are more common than animals that eat other animals
Species with small body sizes generally reach higher population densities
Density generally decreases as body size increases
Small bodies require less energy

17. Factors why some are more common than others
Newly introduced species may reach high population densities
May escape factors that normally prevent them from becoming more abundant
Normal predators/pathogens are absent
Complex social organization may facilitate high densities
High social species achieve high population densities