Transcript Population growth

Population growth
Can we grow forever?
• No, because…
• Yes, because…
Global Human population
Population growth patterns
Changes in population occur when
individuals are added to or removed from
a population.
Population growth=(birth+immigration)– (deaths+emigration)
Carrying Capacity
1. Ultimately all
populations are limited
by the amount of usable
energy from sun, water,
carbon
2. Populations are limited
by their food supply.
Entire food web is
affected if there is a shift
in available organisms to
feed on.
Cont’d
3.
Limits on population
1. Biotic potential: The maximum number of
offspring that a species could produce.
2. Carrying capacity: The maximum number of
individuals of a species that can be supported
indefinitely by an ecosystem.
3. Law of minimum: Where the nutrient in least
supply is the one that limits growth.
4. Law of tolerance: an organism can survive
within a certain range of an abiotic factor.
Factors that cause changes in
population
• Density independent
factors: (affect population
regardless of density)
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Flood
Fire
Spraying of pesticides
Change in climate
Change in temperature
Destruction of habitat
drought
• Density dependent
factors: (affect population
because of the density)
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Food storage
Competition for mates
Breeding areas (habitat)
Disease caused by a
microorganism or parasite
– Introduction of an exotic
species
– Increased predation
– Competition for water and
other resources.
Plotting yeast cell growth
• Yeast are single-celled
fungi that use sugar as a
food supply. When
deprived of oxygen, they
convert sugar to carbon
dioxide gas and alcohol.
This reaction releases
energy, and the yeast use
that energy to grow and
reproduce rapidly.
Graph the following
Time
(days)
Number
of yeast
cells
(per mL)
1.
2.
3.
4.
1
2
3
4
5
6
7
8
9
2
3
8
19
33
68
44
12
0
Use the data to plot a line graph of time (on the horizontal axis)
against the number of yeast cells (on the vertical axis).
Describe the shape of the graph.
Explain and give reasons for the population pattern from days 1-6.
Explain what might have caused the change in the growth pattern
from day 7 through day 9.
What information needs to be on
your graph
Graph #
Appropriate title
Label
axis
with
units
Label axis with
units