Download 5.3 Populations

5.3
Populations
Factors Affecting Population Size
• Populations are affected by:
– Natality – number of new
species due to reproduction
– Mortality – number of deaths
– Immigration – members
arriving from other places
– Emigration – members
leaving the population
Population Growth Curve
Exponential Growth Phase
a) The number of
individuals is
increasing at a fast
rate due to higher
natality compared to
mortality, abundant
resources (little/no
limiting factors),
little/no disease and
predators, more
immigration than
emigration
Transitional Phase
b) a slowing but still
high growth rate
because limiting
factors are starting to
take effect which
increases
competition, natality
falls and/or mortality
rises, increases in
number of
predator/diseases
Plateau Phase
c) population remains
constant over time
because natality +
immigration =
mortality +
emigration, the
limited resources and
predators/diseases
keeps population at
carrying capacity
Limiting Factors
1.
2.
3.
4.
5.
Shortage of food or prey
Disease/Parasites
Accumulation of waste
Predation
Availability of resources like water, food,
sunlight, shelter
The Human Population Graph
What part of the
Population
Growth Curve are
human
populations
currently under?
What will be the
limiting factors
that affect the
human
population?