1. Characteristics of a Population
Population - individuals inhabiting the same area at the same time
Population Dynamics: Population change due to
Population Size - number of individuals
Population Density - population size in a certain space at a given time
Population Dispersion - spatial pattern in habitat
Age Structure - proportion of individuals in each age group in population

2. Population Size Natality Mortality
Number of individuals added through reproduction
Mortality
Number of individuals removed through death

3. Population Density
Population Density (or ecological population density) is the amount of individuals in a population per unit habitat area
Some species exist in high densities - Mice
Some species exist in low densities - Mountain lions
Density depends upon
social/population structure
mating relationships
time of year

4. Population Dispersion
Population dispersion is the spatial pattern of distribution
There are three main classifications
Clumped: individuals are
lumped into groups

5. Population Dispersion
Uniform: Individuals are regularly spaced in the environment
tips/2002/clover611.htm
Random: Individuals are randomly dispersed in the environment

6. Age Structure
The age structure of a population is usually shown graphically
The population is usually divided up into prereproductives, reproductives and postreproductives
The age structure of a population dictates whether is will grow, shrink, or stay the same size

7. Population Growth Population growth depends upon
birth rates
death rates
immigration rates (into area)
emigration rates (exit area)
Pop = Pop0 + (b + i) - (d + e)

8. Population Growth Populations show two types of growth Exponential
J-shaped curve
Growth is independent of population density
Logistic
S-shaped curve
Growth is not independent of population density

9. Exponential Growth Graph

10. Population Dynamics and Carrying Capacity
Basic Concept: Over a long period of time, populations of species in an ecosystem are usually in a state of equilibrium (balance between births and deaths)

11. Carrying Capacity (K)
Exponential curve is not realistic due to carrying capacity of area
Carrying capacity is maximum number of individuals a habitat can support over a given period of time due to environmental resistance (sustainability)

13. Logistic Growth
Because of Environmental Resistance, population growth decreases as density reaches carrying capacity
Graph of individuals vs. time yields an S-curved growth curve
Reproductive time lag causes population overshoot
Population will not be steady curve due to resources (prey) and predators

14. Density Dependent Limiting Factor
Only affects a population when it reaches a certain density (size).
Competition
Fighting for resources
Predation
Increase of predators in an area will limit the growth of prey

15. More…
Disease
High densities make it easier for parasites and diseases to find a host and spread.
Parasitism
More animals for the parasites…more parasites that are there to harm the host
Crowding
Over-crowding can cause a depletion of resources, disease and stress
Stress
Makes organisms weak and prone to diseases

16. Density Independent Factors
Affect a population no matter what the density is
Natural disasters
Droughts, floods, tornadoes, fires, hurricanes…they don’t care how many organisms are in an area
Temperature
Determines which organisms can survive
Sunlight
Can only penetrate up to 30 m of water.

17. More… Human Activities Physical Characteristics Behaviors
Habitat destruction, hunting, pollution…
Physical Characteristics
adaptations
Behaviors
Migration, societies, feeding areas…

19. Reproductive Strategies
Goal of every species is to produce as many offspring as possible
Each individual has a limited amount of energy to put towards life and reproduction
This leads to a trade-off of long life or high reproductive rate

20. Conservation Biology
Careful and sensible use of natural resources by humans
Originated in 1970s to deal with problems in maintaining earth's biodiversity
Dedicated to protecting ecosystems and to finding practical ways to prevent premature extinctions of species

21. Conservation Biology Three Principles
Biodiversity and ecological integrity are useful and necessary to all life on earth and should not be reduced by human actions
Humans should not cause or hasten the premature extinction of populations and species or disrupt vital ecological processes
Best way to preserve earth’s biodiversity and ecological integrity is to protect intact ecosystems that provide sufficient habitat

22. Habitat Fragmentation
Process by which human activity breaks natural ecosystems into smaller and smaller pieces of land
Greatest impact on populations of species that require large areas of continuous habitat
Also called habitat islands

24. Habitat fragmentation in northern Alberta
Habitat fragmentation in northern Alberta

25. Human Impacts Fragmentation and degrading habitat
Simplifying natural ecosystems
Strengthening some populations of pest species and disease-causing bacteria by overuse of pesticides
Elimination of some predators

26. Human Impacts Deliberately or accidentally introducing new species
Overharvesting potentially renewable resources
Interfering with the normal chemical cycling and energy flows in ecosystem