Post on 23-Feb-2016
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Populations in Ecology
Lesson # 27
ECOLOGY
It is the study of the interaction that living things have with each other and with their environment
Importance of Ecology
It provides the information base that society can use to make decisions about the environment
E C O L O G Y
All the members of a single species that live together in a specific geographic region.
The population of all species living in a single region.
It is the community plus all the non-living elements that interact with it (rainfall, chemicals nutrients, soil).
1- Population
2- Community
3- Ecosystem
4- The BiosphereIt is the interactive collections of all the Earth’s ecosystems.
For Ecology, life is organized into:
Arithmetic growth
4,000
13,000
25,000
7,000
16,00019,000
22,000
10,000
1,000
13 197 251 4 10 16 22
Populations: Size and Dynamics
Water flea Daphnia
Exponential growth32,000
64,000
128,000
16,0008,000
13 197 251 4 10 16 22
256,000
Populations growth exponentially because each living thing is capable of playing part in giving rise to more units.
Logistic growth: Population starts growing exponentially, but eventually the rate of growth slows and finally ceases altogether, stabilizing at a certain level (K).
Environmental Resistance
Charles Darwin: “There is not exception to the rule that every organic being naturally increase at so high a rate, that, if not destroyed, the Earth would soon be covered by the progeny of a single pair”.
Factors that limit population growth
2- Food supply
3- Living space
4- Diseases
5- Predators
6- Wastes produced by the organisms
1- Water supply
Environmental Resistance
All the forces of the environment that act to limit population growth.
Carrying capacity (K)
Environmental Resistance
It is the maximum population density of a given species that a defined geographical area can sustain over time.
When species stabilize their rate of growth to a certain level they are known as “equilibrium species”
The growth of the population of equilibrium
species is limited by carrying capacity (K)
In contrast to equilibrium species, other species like houseflies tends to fluctuate greatly in reactions to variations in its environment
Favorable weatherAbundant food supply
Fly population increases enormously
Change in temperatureFood is gone
Fly population decreases enormously
When population size tends to fluctuate greatly in reactions to variations in its environment they are
known as “opportunistic species”
The population sizes of these species tend to be only limited by their reproductive rate ( r ).r-selected species: Species whose population sizes tend to be limited by reproductive rate.
Limited by carrying capacity (K) Limited by reproductive rate ( r )Density dependent Density independentRelatively stable Relatively unstable
POPULATION SIZE
ORGANISMS
Larger, long-lived Smaller, short-livedProduce fewer offspring Produce many offspringProvide greater care for offspring Provide no care for offspring