2. • In 1850, about two dozen rabbits from
Europe were introduced to Australia. The
rabbits had plenty of vegetation to eat, no
competition and no predators. Their
numbers increased rapidly. By the 1950’s,
there were 600 million rabbits!!! The
rabbits ate so much vegetation that the
numbers of native plants and animals
declined and crops were damaged.
3. • As Australia learned,
understanding
populations is
important in
protecting
ecosystems!
• A population is group
of organisms of the
same species that
live together in the
same place
4. • Understanding
population grown
is important
because
populations of
different species
interact and
affect one
another, including
human
populations
5. • How do populations
grow and shrink?
• Biologists use
population models to
track population
growth
• Population growth
depends on: births,
deaths, immigration
and emigration
6. • Immigration is
the movement of
organisms INTO
a population
• Emigration is the
movement of
populations OUT
(Exit) of a
population
7. • Exponential growth:
occurs when number
increase by a certain
factor in each
successive time
period
Example: When a
population is small, its
growth is also small,
but as it gets bigger…
it grows even faster!
8. • Logistic Growth: A
population growth that
starts with a minimum
number of individuals
and reaches a
maximum number of
individuals depending
on the carrying
capacity of the habitat
9. • Populations do not grow unchecked forever. Factors such
as food, predators and disease limit the growth size of a
population.
• Carrying Capacity: the largest population that an
environment can support at any given time
10. • Anything that
limits the size of
a population:
• Availability of
food
• Shelter
• Space
• Sunlight
• Water
• Mates
• Disease
11. ABIOTIC FACTORS BIOTIC FACTORS
•Climate: temperature •Food (plants and
and rain animals)
•Sun exposure •Predators (animals that
•Availability of water eat other animals)
•Fertile soil •Finding a mate
•Earth factors: wind, •Natural resources for
tornadoes, volcanoes, living: nest making,
earth quakes trees for living, brush for
•Space and shelter hiding…)
12. • Today the world
population is more
than 6 billion people
and increasing!
• Better sanitation and
hygiene, medicine,
disease control and
agricultural technology
have decreased the
death rate of the
human population
13. • For most of human history there has been fewer than 10
million people.
• In 1700 there were 10 million people but due to more
modern technology… the population has grown to over 6
billion in 300 years!
• Scientists believe the world population will be 9 billion in
another 50 years!
• How many people the earth can support depends on how
humans take care of the earth, along with science and
technology
14. • Interactions in communities take many forms.
Predators and prey are locked in a struggle
for survival. Organisms with the same needs
compete for food. Parasites and hosts try to
get ahead of one another and some
organisms depend on other organisms for
their own survival…
15. • Mutualism: a
relationship in
which both
organisms benefit
from one another
(good/good)
These two species of fish have
evolved a mutualistic • Example: A shark
relationship: the grouper fish gets cleaned by
allows the cleaner fish to eat cleaner fish. (shark
food trapped between its teeth: gets parasites out of his
a free lunch in exchange for gills, cleaner fish get food…
good for both)
some dental hygiene.
16. • Commensalism: a relationship
in which two organisms live in
a community, one organism
benefits while the other is
unharmed. (good/nothing)
• Example: Lion kills a zebra,
when the lion is done eating,
birds come and eat the rest
(good for the birds, does not
effect the lion)
17. • Parasitism: a
relationship between
two organisms in
which one benefits
and the other is
harmed (good/bad)
• Example: Human Bot
Fly needs to grow under
the skin of the human
stealing blood and
nutrients and causing the
human pain
18. A. Predator: An
animal that hunts,
kills and eats
another animal
B. Prey: the animal
that is hunted and
killed by the
predator
