Download Populations

Populations
What is a population
• Population - is a set of individuals within a
species living in the same place at the same
time.
• Populations are described in terms of:
– Size, density and dispersion
– Density – the number of individuals per unit of
area or volume
– Dispersion – describes the arrangement of its
individuals in space
• Clumped, even or random
How does a population grow
• The change in the size or a population over a
given period of time is called a ___________
– growth rate
• Growth rates can be positive, negative or even
zero
Change in the
population size
Births
Deaths
How fast can a population grow
• Population growth is directly related to how
fast and how many offspring an organism can
have. This is called reproductive potential.
• Some species have much higher reproductive
potentials than others
– Bacteria can produce 19 million descendants in a
few days
– A pair of whales would take hundreds of years to
have that many descendants
Which organism has a higher
reproductive potential??
Humans
or
Rabbits
Exponential Growth
• Some populations
undergo exponential
growth – which means
they grow faster and
faster.
• Example
– A pair of dogs gives birth to
6 puppies, this is
generation one what
happens for generation 2?
– Each puppy has 6 puppies
it goes to 36 dogs in
generation 2 and so on…
Shape of the graph of number
of dogs over time
Q’n: under what conditions does
exponential growth take place?
Answer:
• Exponential growth takes place when the
populations have plenty of food and space
and have little or no completion or predators
What limits population growth?
• With your partner generate a list of what
would limit population growth
• These things include :
– Resources – food water shelter
– Environmental changes
– Deaths
– Migration
– Natural selection
Carrying Capacity
• Carrying capacity – is the population size
where birth rates and death rates are equal.
Or the maximum population that its
ecosystem can support.
• A population can increase beyond its carrying
capacity but it cannot stay there for long
because of limiting resources
• Example - rabbits in Australia (video)
• http://animal.discovery.com/tv-shows/weirdtrue-and-freaky/videos/outback-rabbitinvasion.htm
What carrying capacity looks like
Your task – on the back of the half
sheet
• Create a carrying capacity comic strip
• Must have at least five different scenes
(boxes).
• Must include the vocabulary terms:
– Carrying capacity
– Resources (food, water shelter etc)
– Population
• Be creative and use
color.