Download File - Ms.Holli

BELL RINGER:
WHAT IS A POPULATION?
A group of organisms of the same
species.
HOW DO POPULATIONS GROW?
Reproduction (sexual or asexual)
Objective: Identify and understand the
trends and limiting factors that affect
growth within an ecosystem.
2 Kinds of Population Growth
Exponential Growth
Logistic Growth
• Occurs when individuals
in a population
reproduce at a constant
rate, and the population
keeps growing and
growing.
• Occurs when individuals
reproduce at a constant
rate until a limit is
reached, when growth of
the population stops.
Exponential Growth
• Occurs under ideal conditions with unlimited
resources.
• The following is a real life example of exponential growth:
Chat Chum Questions
1. How many wild rabbits were originally brought in from
England?
2. What conditions allowed the rabbit population to
reproduce?
3. Look at the graph. Describe in words what happens to the
rabbit population over 0-15 weeks.
4. Based on the graph, describe in words what happens to the
rabbit population over 15-30 weeks.
5. What biotic and abiotic factors would be necessary to stop
the growth of the rabbit population?
6. What do you think would happen to the numbers of the
rabbit population in this case?
Limiting Factors
• Many factors can limit population size and stop populations from
growing exponentially. These factors are called limiting factors.
• Examples of limiting factors:
• Density Dependent factors (depend on # of organisms):
• Competition (with other organisms for food, water,
sunlight, space)
• Predation
• Parasitism
• Disease
• Density Independent factors (don’t depend of # of
organisms):
• Unusual weather/ natural disasters
• Seasonal cycles
• Certain human activities
• IN REALITY, most populations are limited by these factors, and
only grow exponentially until they reach the ecosystem’s
carrying capacity.
• Carrying capacity is defined as:
The number of organisms of one species
that an environment can support
indefinitely.
Logistic Growth
• As populations reach carrying capacity, its growth
slows/stops.
Chat Chum Questions
1.
2.
3.
4.
5.
In this sample population,
how many hours of growth
does it take to reach the
carrying capacity?
Describe in words what
happens to the number of
organisms from 0-12 hours.
Describe in words what
happens to the number of
organisms from 12-30
hours.
Describe in words what
happens to the number of
organisms from 30-42
hours.
Does a population stay at
its EXACT carrying capacity?
Explain why.
Exit Questions
• The Human Population
• What type of growth represents the human
population?
• Why do you think this is?
• Has the Earth reached its carrying capacity?
• Will we ever run out of room? Where will
people go once we run out of room?