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Populations and Resources
Section 2!
Text: 2.5
Populations
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What is a species?
Are these 2 animals in the same species?
Species
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A group of similar organisms that can mate
with each other and produce fertile offspring
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Male donkey + female horse = mule (infertile)
Interesting Species…
+
Male Lion
Female Tigress
Liger!
Interesting Species…
Female lion
+ Male tiger
= Tigon!
Interesting Species…
Leopon!
Interesting Species…
Jaglion!
Populations
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Populations: all the individuals of a species that
occupy a particular geographic spot at the same time
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South African elephants in Kruger National Park
A species of frogs in a pond
Populations
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Community: All the different species that interact in
a specific ecosystem
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Eg. A swamp
Exponential Growth
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How does a population grow?
Exponential growth of a population can occur
under certain circumstances
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Wealth of resources (Eg. algae)
Removal of pressures
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Protection from natural predators
Protection from hunters (Eg. elephants)
Exponential Growth
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Def: accelerating growth that produces a Jshaped curve when the population is graphed
against time
Species Re-introduction
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The Ontario wild turkey was plentiful prior to
the 19th century
Deforestation and hunting were severe and
devastated the population
Species Re-introduction
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The provincial government re-introduced the
wild turkey in the 1980s when
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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
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(exponential growth)
Exponential Growth and Limiting Factors
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Exponential growth cannot be sustained
indefinitely
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No ecosystem has an unlimited supply of
resources
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Why??
Food
Water
Shelter
These restrictions are called “limiting factors”
Limiting Factors
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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
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Def: the size of a population that can be
supported indefinitely by the available
resources and services of an ecosystem
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Beyond this capacity, no additional individuals
can be supported
Equilibrium
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When a population is maintained at its carrying
capacity, the size of the population is in
equilibrium
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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
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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
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Creates:
more dependence on cars
decreased farmland
decreased carrying capacity for native organisms
Urban Sprawl
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A city’s growth as it’s population increases
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More and more development on the ‘outskirts’ of a city
The Golden Horseshoe
West end of Lake Ontario