characteristics of a population
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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