Population Ecology Chapter 4. GPS SB4 Students will assess the dependence of all organisms on one...
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Transcript of Population Ecology Chapter 4. GPS SB4 Students will assess the dependence of all organisms on one...
Population Ecology
Chapter 4
GPS
• SB4 Students will assess the dependence of all organisms on one another and the flow of energy and matter within their ecosystems.
• d. Assess and explain human activities that influence and modify the environment such as global warming, population growth, pesticide use, and water and power consumption.
A biological community is a group of interacting populations that occupy the same area at the same time.
A desert oasis
• Organisms within a community adapt to the conditions in which they live.
• These conditions are often abiotic factors
• Communities are often stable but may evolve and change over time.
Keeps a population in check.
Doesn’t allow unlimited growth.
Limiting factors include:
Food, water, shelter/ habitat, mates
Organism compete for these limited resources
Population Dynamics
Populations of species are described by density,
spatial distribution, and growth rate
Population Characteristics
Population Density
The number of individuals per unit area
Spatial Distribution
The pattern of spacing of a population
Population Ranges
• Populations can not live in all environments
• Abiotic conditions effect the range of environments in which a population can live
• A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region.
Population Limiting FactorsThere are two categories of limiting factors
1. density-independent factors Any factor in the environment that does not depend
on the number of members in a population per unit area
2. density-dependent factorsAny factor in the environment that depends on the
number of members in a population per unit area
Disease
Temperature
Competition
Parasites
Storms
Food
Habitat disruption
Drought
Environmental limits to population growth
Density-dependent factors
disease, competition, parasites, and food
Density-independent factors
temperature, storms, floods, drought, habitat disruption
• An upper limit and lower limit that define the conditions in which an organism can survive
• The ability of any organism to survive when subjected to abiotic factors or biotic factors is called tolerance.
Population Growth Rates
Exponential growth
As the population gets large it also grows faster
Reasons this occurs:
1. Initial increase is slow because few breeding individuals
2. As individuals mature, reproducing individuals increases.
Time
Pop
ulat
ion
size
Exponential growth is not realistic
Populations tend to grow until some environmental condition stops growth
Time
Pop
ulat
ion
size
This is called Logistic Population Growth!!
Carrying capacity and Limiting factors
Keeps a population in check.
Doesn’t allow unlimited growth.
Limiting factors include:
Food, water, shelter/ habitat, mates
Organism compete for these limited resources
Reproductive patterns
Species of organisms vary in:
the number of births per reproduction cycle
the age that reproduction begins,
the life span of the organism
What causes a population to grow
Number of births is greater than the number of deaths
Immigration exceeds Emigration.
What causes a population’s numbers to decrease?
Number of births is less than the number of deaths
Emigration exceeds immigration.
2 Reproductive Patterns• K-strategist
– Little environmental change– Generally large organisms– Long life spans– Few offspring with extended parent care
• R-strategist– Fluctuating abiotic factor occur– Generally small organisms– Short life span– Many offspring
Elephants
Bacteria
Mice
Humans
Cows
Termites
Lions
Rabbits
• Demography- the study of human population growth characteristics.
• Age structure-proportions of a population that are at different age levels.
Predator prey relationships