Population Ecology. Ecologists study life at many levels, from individual organism to the entire...
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Transcript of Population Ecology. Ecologists study life at many levels, from individual organism to the entire...
Ecosystems include both biotic and abiotic factors. Biotic factors are parts of the ecosystem that are living.
Describing Populations….
The OVERALL health of a population can often be monitored by tracking how its size changes.
Population size describes the number of individual organisms present in a given population at a given time.
Population Ecology
Deals with the # of individuals of a particular species that are found in an area and how and why those numbers change or remain fixed over time.
Population ecologists study…
How populations respond to its environment
Competition for resources, predations, disease and other environmental pressures
Determine population size by sampling. Instead of counting every individual, ecologists count every organism in a small area than estimate the number of individuals in the larger area.
Population density describes the number of individuals within a population per unit area.
For example: 1500 golden toads per 4 sq. kilometers
High population density can make it easier to find mates and group together. However, it also leads to more competition for resources.
Age structure diagrams show the number of males & females in different age groups within a population.
All things being equal, when a population birthrate is greater than its death rate, population size will increase.
Immigration – movement of individuals into a populationEmigration – movement of individuals into a population
Birthrate – number of live births per 1000 in a given yearDeath rate – number of deaths per 1000 in a given year
Exponential growth is when a population increases by a fixed percentage each year.
Exponential growth occurs in nature only when the starting population is small & the environmental conditions are ideal.
This type of growth usually does not last long. Most populations are constrained by limiting factors.
Limiting factors are characteristics of the environment that limit population growth. Limiting factors determine a population’s carrying capacity.
Logistic Growth describes how a population’s initial exponential increase is slowed & finally stopped by limiting factors.
Carrying capacities are not fixed. Carrying capacity is the largest population size a given environments can sustainably support.
Limiting factors have more of an effect in dense populations & other limiting factors affect all populations in the same way.
Biotic potential is based on…
• Age at which reproduction takes place
• % of life span that an organism can reproduce
• Number of offspring in each reproduction period
• Generally larger animals have a lower biotic potential than microscope organisms.