Transcript Ecology - Part 3

Ecology – Part 3 – General Biology
• Carrying Capacity
• Population Growth
• Human Population
• Biodiversity
What is a population?
Groups of individuals that belong
to the same species and live in
the same area.
Exponential Growth
• Populations grow if the birthrate
is greater than the deathrate.
• Under ideal conditions with
unlimited resources, a population
will grow exponentially. This is
called exponential growth.
Exponential Growth
• This is represented by a J-shaped
curve.
Exponential Growth Curve
Population Growth of Houseflies
Population size
1 million
500,000
100
One year
Carrying Capacity:
the largest # of individuals that a
given environment can support
indefinitely.
• Exponential growth does not
occur in natural populations for
long. Eventually resources (food
and space) become less available
and growth slows down. This is
called logistic growth.
• The J-shaped curve levels off as
the population reaches carrying
capacity (K).
• This is represented by an Sshaped curve.
• In an undisturbed environment
(no human intervention),
populations will fluctuate around
carrying capacity (equilibrium).
Carrying Capacity vs.
Exponential Growth
• J-shaped curve
S-shaped curve
Carrying Capacity
• The maximum number of organisms of a
particular type that can be supported in an
area…
Carrying Capacity
• This graph shows an Scurve
• As the population size
approaches the carrying
capacity (dashed-line),
the growth slows down
(note the blue arrows)
Population
Time
Figure 52.19 Population cycles in the snowshoe hare and lynx
• What limits population growth
and maintains balance
(equilibrium) in an ecosystem?
• Density-dependent and densityindependent limiting factors
Limiting Factors
• Limit the organisms that can live in an
area:
• can be biotic
• can be abiotic
• What are some factors that would keep the
population at a steady level?
• Competition
- organisms struggling for limited resources
Competition
1. Competition: when the demand for
resources such as food, water, space,
and other essentials exceeds the
supply.
• Some organisms avoid competition
by migrating seasonally to areas
where climate is better and more
food is available
Predator-prey relationships:
controls numbers of predators and
prey
Figure 41.9 Bulk-feeding: a python
Parasitism and Disease:
crowding leads to an increase in
parasitism and resistance to
disease.
Other limiting factors:
1. Unusual weather: such as extreme
hot or cold temperatures
2. Natural disasters: such as
hurricanes, tornados, floods, or
droughts.
3. Human activity: such as damming
a river or clear-cutting a forest.
PBL Task #3
• List some ways that the climate would have to change in
order for your organism to display a J-shaped growth
curve.
• Do they at least represent an S-shaped growth curve right
now? Please explain why or why not.
• Explain how the biodiversity of your organism’s
environment has changed in the last 20-30 years.
• Look at the slides about Human Population and do the
Age Structure Activity with your group members.
•Everyone must have their OWN graph!
Human Population
• Demography – the study of human
population size
– Census
– Birth rate (live births/1000 people)
– Death rate (deaths/1000 people)
Human Population
Human Population (con’t)
Age Structure Graph – number of people at
each different age
- see p.103 in textbook
Age Distribution Graphs Activity
• You will get this from your teacher.
Really cool Population Website!!
Population Biology
Biodiversity
• A wide range of different species of
organisms living in an ecosystem
• More biodiversity = More stability in the
ecosystem
– Biodiversity – forest
– No biodiversity – corn field
• Biodiversity allows ecosystems to better
survive a catastrophic environmental event
• Loss of Biodiversity can lead to:
– Extinction, endangered species, & threatened
species
Figure 53.21 Which forest is more diverse?
Biodiversity Smart Board
• See p.8, 9
Biodiversity – True or False?
• Answers
–
–
–
–
–
–
–
9. true
10. false
11. false
12. true
13. false
14. true
15. true
Complete the Age Distribution
Graphs Activity
• At some point you need to answer any
questions from the back of the paper and
turn yours in!
• Then begin ppt #4