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

Natality Number of individuals added through

reproduction

Mortality Number of individuals removed through death

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

Population dispersion is the spatial pattern of distribution

There are three main classifications

Clumped: individuals are lumped into groups

http://www.johndarm.clara.net/galleryphots/

Uniform: Individuals are regularly spaced in the environment

http://www.calflora.net/bloomingplants/creosotebush2.html

www.agry.purdue.edu/turf/ tips/2002/clover611.htm

Random: Individuals are randomly dispersed in the environment

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

Population growth depends upon birth rates death rates immigration rates (into area) emigration rates (exit area)

Pop = Pop0 + (b + i) - (d + e)

Populations show two types of growthExponential

J-shaped curve Growth is independent of population

densityLogistic

S-shaped curve Growth is not independent of

population density

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)

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)

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

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

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

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.

Human Activities Habitat destruction, hunting, pollution…

Physical Characteristics adaptations

Behaviors Migration, societies, feeding areas…

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

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

Three PrinciplesThree Principles1. Biodiversity and ecological integrity are

useful and necessary to all life on earth and should not be reduced by human actions

2. Humans should not cause or hasten the premature extinction of populations and species or disrupt vital ecological processes

3. Best way to preserve earth’s biodiversity and ecological integrity is to protect intact ecosystems that provide sufficient habitat

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

1949 1964

Habitat fragmentation

in northern Alberta

1982 1991

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

Deliberately or accidentally introducing new species

Overharvesting potentially renewable resources

Interfering with the normal chemical cycling and energy flows in ecosystem