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# 05.3 ecology - populations

## on Feb 07, 2014

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• 5.3.1 – Outline how population size is affected by natality, immigration, mortality and emigration.
• 5.3.1 – Outline how population size is affected by natality, immigration, mortality and emigration.
• 5.3.2 – Draw and label a graph showing a sigmoid (S-shaped) population growth curve.
• 5.3.2 – Draw and label a graph showing a sigmoid (S-shaped) population growth curve.
• 5.3.3 – Explain the reason for the exponential growth phase, the plateau phase and the transitional phase between these two phases.
• 5.3.3 – Explain the reason for the exponential growth phase, the plateau phase and the transitional phase between these two phases.
• 5.3.3 – Explain the reason for the exponential growth phase, the plateau phase and the transitional phase between these two phases.
• 5.3.4 – List three factors that set limits to population increase.
• 5.3.4 – List three factors that set limits to population increase.
• 5.3.4 – List three factors that set limits to population increase.

## 05.3 ecology - populationsPresentation Transcript

• Topic 5.3 - Populations
• Population size can be affected by four primary factors: • Natality = new members due to reproduction • Mortaliaty = members dying • Immigrating = new members arriving from another place • Emigrating = members leaving the population 5.3.1
• immigration natality population mortality emigration 5.3.1
• A population growth curve shows the amount of members of a population over time. It typically shows a sigmoidal shape (s-shape) that has three distinct stages. 5.3.2
• Population S - Curve Phases 1. Exponential Phase (aka logarithmic phase) is when the growth rate exponentially increases. 2. Transitional Phase is 1 2 3 when the population is increasing, but the rate is slowing. 3. Plateau Phase is when the population stabilizes and there is not more growth. 5.3.2
• The exponential growth phase occurs when a population: • Has abundant resources • Little or no competition • Little or no predation or disease • Favorably adapted to environmental abiotic factors. 5.3.4
• The transitional growth phase occurs when the exponential conditions are no longer true. • Increases population size results in competition. • Predators immigrate to the area because the prey population has grown. • Increasing population density expedites spreading of diseases and pathogens. 5.3.4
• The plateau phase occurs when the population size has saturated available resources. Includes requirements: • Immigration and emigration rates are balanced. • Natality and mortality rates are balanced. • Population has reached its carrying capacity (K) 5.3.4
• A population’s carrying capacity is the maximum number of members that a given habitat can support. 5.3.4
• Factors that limit population increase (and therefore the carrying capacity) include: • Availability of resources such as water, food, sunlight, shelter, space, or oxygen • Build of waste such as excrement or excess carbon dioxide • Predation • Disease • Availability of abiotic factors such as temperature, precipitation, etc. 5.3.4
• 5.3.4