Download Population Ecology

Population Ecology
Science 10
Definitions
Population- a group of individuals of the same
species living within a particular area or volume.
Population dynamics- changes in a population
characteristics determined by a number of
possible outcomes. Ex: mortaility, immigration
Characteristics of Population
• Habitat- the place where an organism or
species normally lives.
• Species- organisms that resemeble one
another in appearance, behaviour, genetic
make-up.
• Niche – the way an organism occupies a
position in an ecosystem including all the
necessary biotic and abiotic factors.
Population Size and Density
• Population Size is the number of individuals of
a certain species occupying a certain
area/volume at a given time.
• Population Density is the number of
individuals of the same species that occur per
unit of area or volume
Calculations
Formula: D= N/S
D- Population Density
N- Total Number “Count” of that species
S- Space occupied by the population
Examples:
1. 480 moose living in a 600 hectare(ha) region.
D= N / S
D=480 moose / 600 ha
D= 0.8 moose/ha
2. What is the density of a population of
bacteria if there are 1000 bacteria in a testtube
of 10mL?
Changes in population
There are two types of factors which can effect a
population:
1. Density independent factors – any factor
which does not depend on density eg.
extreme storms, fires and floods.
2. Density dependent factors – any factor which
does depend on the density eg. Disease, lack
of food, predation, and competition.
*** Read pages 288-289 Questions 1-4 page 290
Measuring and Modeling Population
Change
• Carrying capacity is the maximum number of
organisms that can be sustained by available
resources over a given period of time.
• the largest population of a species that an
environment can support.
• Eg. – 100,000 white tailed deer in Nova Scotia
• These are often shown in graphs
- Complete graph on page 291
Four main factors that determine carrying capacity
1. Materials and Energy – energy from Sun, water, carbon
2. Food Chains – populations are limited by food supply
3. Competition – demand for resources among individuals
4. Density – amount of available space.
Two types of competition
Intraspecific Competition – competition among members of the same
species – wolves competing with wolves
Interspecific Competition – competition between species – lions and
tigers competing for food - seals and dolphins competing for food
Different types of populations
Open population- a population in which change
in number and density is determined by births,
deaths, immigration, and emigration.
Closed population- a population in which
change in size and density is determined by
birth and death rates!
Population Growths
A closed population will exhibit exponential
growth- a pattern of population growth where
organisms reproduce continuously at a constant
rate.
Open Population Growth
• An open population will show the following
type of growth which is referred to as an Scurve – a pattern of exponential growth at
first then a leveling off once carrying capacity
is reached.
Human Population and Carrying
Capacity
• What is happening to the human population
of earth?
• http://www.npr.org/2011/10/31/141816460/
visualizing-how-a-population-grows-to-7billion
• Read pages 293-294 Questions 5-7 page 295
Ecological footprints
• Ecological footprints: is a measure of the
impact of a human individual or population on
the environment.
• Unsustainable: large ecological footprints and
dependence on fossil fuels.
• Sustainability: modern societies must seek to
establish ecological footprints which use water
and land at levels which can continue forever.