Populations Studying Populations Scientists look at multiple factors

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Populations

Populations

Studying Populations • Scientists look at multiple factors • Geographic Range: the spaces where

Studying Populations • Scientists look at multiple factors • Geographic Range: the spaces where it lives • Density/Distribution: number of individuals/unit area and how they’re spread across their range • Growth Rate: bigger smaller or the same size • Age Structure: number of males and females of each age in the population

Population Growth • Size of the population changing based on individuals moving in or

Population Growth • Size of the population changing based on individuals moving in or out • Birthrate: individuals born • Death Rate: Individuals die – If one is higher than the other, the size changes accordingly • Immigration: Individuals moving in • Emmigration: Individuals moving out. – If one is higher than the other, the size changes accordingly

Syrian Refugee Crisis • Since 2011, the start of the civil war: – 5.

Syrian Refugee Crisis • Since 2011, the start of the civil war: – 5. 6 million people have fled. – 6. 1 million are displaced within the country – Roughly 400, 000 have died • The population before the war: Roughly 23 million

Exponential Growth • The growth of a population with no inhibitors. • Population with

Exponential Growth • The growth of a population with no inhibitors. • Population with full access to resources and space, no predators, no disease, and no waste. • Reproduction at a constant rate

Logistic Growth • When exponential growth is slowed • Creates a standard S-shaped curve

Logistic Growth • When exponential growth is slowed • Creates a standard S-shaped curve • Caused by an increased death rate, slowed birth rate, increased emigration

Carrying Capacity • The largest number of individuals that a given environment can support.

Carrying Capacity • The largest number of individuals that a given environment can support. • Generally represented by the flat line of the S-Curve

Limiting Factors • The primary productivity of an ecosystem can be reduced when there

Limiting Factors • The primary productivity of an ecosystem can be reduced when there is an insufficient supply of a particular nutrient. • Ecologists call such substances limiting nutrients.

Limiting Factors • A limiting nutrient is an example of a more general ecological

Limiting Factors • A limiting nutrient is an example of a more general ecological concept: a limiting factor. • In the context of populations, a limiting factor is a factor that causes population growth to decrease.

Density-Dependent Factors • A limiting factor that depends on population size is called a

Density-Dependent Factors • A limiting factor that depends on population size is called a density-dependent limiting factor.

Density-Dependent Factors – Density-dependent limiting factors include: • • competition predation parasitism disease

Density-Dependent Factors – Density-dependent limiting factors include: • • competition predation parasitism disease

Density-Dependent Factors – Density-dependent factors operate only when the population density reaches a certain

Density-Dependent Factors – Density-dependent factors operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense. – They do not affect small, scattered populations as greatly.

Density-Dependent Factors – Competition • When populations become crowded, organisms compete for food, water

Density-Dependent Factors – Competition • When populations become crowded, organisms compete for food, water space, sunlight and other essentials. • Competition among members of the same species is a density-dependent limiting factor.

Density-Dependent Factors • Competition can also occur between members of different species. • This

Density-Dependent Factors • Competition can also occur between members of different species. • This type of competition can lead to evolutionary change. • Over time, the species may evolve to occupy different niches.

Density-Dependent Factors – Predation • Populations in nature are often controlled by predation. •

Density-Dependent Factors – Predation • Populations in nature are often controlled by predation. • The regulation of a population by predation takes place within a predator-prey relationship, one of the best-known mechanisms of population control.

Density-Dependent Factors Wolf and Moose Populations on Isle Royale Moose Wolves

Density-Dependent Factors Wolf and Moose Populations on Isle Royale Moose Wolves

Density-Dependent Factors – Parasitism and Disease • Parasites can limit the growth of a

Density-Dependent Factors – Parasitism and Disease • Parasites can limit the growth of a population. • A parasite lives in or on another organism (the host) and consequently harms it.

Density-Independent Factors • Density-independent limiting factors affect all populations in similar ways, regardless of

Density-Independent Factors • Density-independent limiting factors affect all populations in similar ways, regardless of the population size.

Density-Independent Factors – Examples of density-independent limiting factors include: • unusual weather • natural

Density-Independent Factors – Examples of density-independent limiting factors include: • unusual weather • natural disasters • seasonal cycles • certain human activities—such as damming rivers and clear-cutting forests

5 -2 – A limiting factor that affects all populations in similar ways regardless

5 -2 – A limiting factor that affects all populations in similar ways regardless of their size might be • • drought. disease. predation. crowding.

5 -2 – Which of the following would be a limiting factor affecting the

5 -2 – Which of the following would be a limiting factor affecting the panda population of China? • programs that educate people about endangered species • capture of some pandas for placement in zoos • laws protecting habitat destruction • a disease that kills bamboo plants

5 -2 – Density-dependent factors operate most strongly when a population is • •

5 -2 – Density-dependent factors operate most strongly when a population is • • large and dense. large but sparse. small and sparse. small, but growing.

5 -2 – Within a limited area, if the population of a predator increases,

5 -2 – Within a limited area, if the population of a predator increases, the population of its prey is likely to • • increase. decrease. remain about the same. become extinct.

5 -2 – Which of the following is a densityindependent factor affecting populations? •

5 -2 – Which of the following is a densityindependent factor affecting populations? • • predation disease a destructive hurricane parasites

END OF SECTION

END OF SECTION

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