Populations and Resources Section 2! Text: 2.5. Populations What is a species? Are these 2 animals in the same species?
Post on 29-Dec-2015
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Species A group of similar organisms that can mate
with each other and produce fertile offspring Male donkey + female horse = mule (infertile)
Populations Populations: all the individuals of a species that
occupy a particular geographic spot at the same time South African elephants in Kruger National Park A species of frogs in a pond
Exponential Growth How does a population grow? Exponential growth of a population can occur
under certain circumstances Wealth of resources (Eg. algae) Removal of pressures
Protection from natural predators Protection from hunters (Eg. elephants)
Exponential Growth
Def: accelerating growth that produces a J-shaped curve when the population is graphed against time
Species Re-introduction
The Ontario wild turkey was plentiful prior to the 19th century
Deforestation and hunting were severe and devastated the population
Species Re-introduction
The provincial government re-introduced the wild turkey in the 1980s when southern Ontario’s forests were renewed protection plan was established
From 1980-2000, 4400 turkeys were released By 2001 population was 30 000 By 2008 population was 70 000
(exponential growth)
Exponential Growth and Limiting Factors Exponential growth cannot be sustained
indefinitely Why??
No ecosystem has an unlimited supply of resources Food Water Shelter
These restrictions are called “limiting factors”
Limiting Factors Def: an environmental factor that prevents an
increase in population number or prevents them from moving into new habitats
As a population grows, each individual has less access to resources
This limits the growth of the population
Carrying Capacity
Def: the size of a population that can be supported indefinitely by the available resources and services of an ecosystem
Beyond this capacity, no additional individuals can be supported
Equilibrium
When a population is maintained at its carrying capacity, the size of the population is in equilibrium balance between individuals that join the population and the
number that leave or die = “zero population growth”
Growth Rate: Births – deaths + immigration - emigration x 100 =__%
initial population
Urban Sprawl As humans alter ecosystems to fit their needs,
the carrying capacity changes Urban sprawl is used to describe a city’s
growth as population increases People build new homes and businesses near
outer edges of cities Creates: more dependence on cars decreased farmland decreased carrying capacity for native organisms
Urban Sprawl A city’s growth as it’s population increases
More and more development on the ‘outskirts’ of a city
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