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What Are the Factors That Can Affect Various Populations?
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Population Density It is the number of organisms living in a given space. There are four factors that affect the growth (or reduction) of a population
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Can this happen in nature?
Yes Invasive species Uniform habitat No predators No disease Unlimited area Can this happen? 70 miles a year No constraints
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Invasive species An invasive species is one that can be either native and non-native that heavily colonize a particular habitat. Natural, wild species can be threatened with extinction.
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The good ones Asian Oysters- are better at filtering out water pollutants than native oysters. Garlic Mustard- introduced as a means of erosion control
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The bad ones Zebra mussles Waterlettuce is a serious weed of rice crops Burmese python
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#1 ~ Births This is the number of surviving offspring
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#2 ~ Deaths Number of individuals dying from all causes.
limited food supply the buildup of toxic wastes increased disease predation
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#3 ~ Immigration #4 ~ Emigration
Number of individuals entering an area. #4 ~ Emigration Number of organisms leaving an area.
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What Can Affect Each of These Factors?
Climate, Food Availability, Living Space, and Disease can affect each of these factors.
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Carrying Capacity The population remains within the limits that the environment can support This is the largest amount of species that an environment can support There are four factors that can influence Carrying Capacity (K).
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A ~ Materials / Energy Food, water, and other essentials.
If a population continues to grow, it will eventually exceed its food supply (starvation, malnutrition).
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B ~ Food Chains Populations are limited by organisms above them.
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C ~ Competition For food, space, mates, and water.
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D ~ Density There are two types of Density that can affect carrying capacity. Density-independent factors Weather (storms, cold, drought) Density-independent diseases (DDT poisoning) Density-dependent factors Food Space (territories, denning sites, nest cavities) Density-dependent diseases (rabies, SARS)
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Logistic growth is slowed by population-limiting factors http://www
Logistic growth is slowed by population-limiting factors applet
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K Maximum sustainable yield Maximum sustained yield Population size
Carrying capacity r = intrinsic rate of increase. B-D. R=1+r Time, in generations
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The Spread of Shakespeare's Starlings
In 1890, a group of Shakespeare enthusiasts released about 120 starlings in New York's Central Park
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Today: over 100 million starlings, spread over N. America
Current 1955 Current 1955 1945 1935 1925 1945 1905 1915 1925 1935 1925 1935
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The starling population in North America has some features in common with the global human population Both are expanding and are virtually uncontrolled Both are harming other species
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THE HUMAN POPULATION doubled three times in the last three centuries
about 6.1 billion and may reach 9.3 billion by the year 2050 improved health and technology have lowered death rates
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The history of human population growth
Figure 35.8A
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Also reveals social conditions, status of women
The age structure of a population is the proportion of individuals in different age-groups RAPID GROWTH SLOW GROWTH ZERO GROWTH/DECREASE Kenya United States Italy Male Female Male Female Male Female Ages 45+ Ages 45+ Ages 15–44 Ages 15–44 Under 15 Under 15 Percent of population Percent of population Percent of population Also reveals social conditions, status of women
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The ecological footprint represents the amount of productive land needed to support a nation’s resource needs The ecological capacity of the world may already be smaller than its ecological footprint
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Ecological footprint in relation to ecological capacity
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What next?
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