Download Population Ecology - Fulton County Schools

Unit 2 – Lecture 4
Review… Discuss
 What is a population?
 Population –
 a single species in a single location at the same time
Population Growth
 Exponential Growth – number of organisms grows
very quickly
Population Growth – cont’d
 Logistic Growth – begins with a period of rapid growth
[like exponential], then slowly stabilizes
BE CAREFUL WHEN DRAWING THIS GRAPH!!!
Discuss
 Why would a population be able
to grow so quickly like the exponential graph?
 Why would a population stabilize
like the logistic graph?
 Which graph is more realistic?
Population Growth
 Exponential Growth –
 possibly due to lack of predators,
great amount of resources [food, habitat, etc].
Population Growth – cont’d
The population stabilizes in the logistic curve because…
 diminishing resources
 more orgs, less resources for each org
Which growth curve is more realistic? Why?
 Logistic – because resources aren’t unlimited.
Population Growth – cont’d
 Carrying Capacity – the largest number of organisms
that an ecosystem can support.
 influences for carrying capacity include…
 resources [food, shelter…], human influence,
predation, illness, natural disasters, climate, etc…
Population Growth – cont’d
 Which type of curve showed a carrying capacity?
Carrying Capacity
Shown on the graph:
Or, more realistically…
Population Growth – cont’d
 Why does the line of CC waver on the realistic graph?
 births & deaths
[explanation, don’t need
to write this down…]
 as orgs increase, resources decrease
 decrease in resources  decrease
in the number of orgs that can survive
 less orgs surviving  more resources
 more resources  increase in orgs that can survive
Limiting Factors
 Limiting Factor – a factor which limits a population’s
growth
 includes everything that limits the carrying capacity
 resources [food, shelter…], human influence,
predation, illness, natural disasters, climate, etc
Limiting Factors – cont’d
Two Types:
 Density Dependent Factors
 limiting factors that DO depend on the density [#]
of orgs in the area
 Density INdependent Factors
 limiting factors that DO NOT depend on the
density [#] of orgs in the area.
Discuss
 Look back at your warm-up. Each of those items
would be a limiting factor.
 Discuss and label each of the items on your list as
either density dependent or density independent
limiting factors.
Limiting Factors – cont’d
 Density Dependent Factors
 ex: resources, illness, predation…
 Density INdependent Factors
 ex: climate, natural disasters, human interaction…
Limiting Factors – cont’d
Which is which?
 Ask this question:
 Would there be a change in the factor’s effect if
there were 10 orgs in the area compared to if there
were 10,000?
 Examples – Resources vs. Climate


Yes, the factor would change =
density dependent
No, the factor wouldn’t change =
density independent
Homework
 Complete the Kaibob & Carrying Capacity w/s
on page 12-13 of your packet.
 remember –
 use a SCALE
 graph axes go up by even intervals
 every box = the same amount
 use up at least 75% of your graph space!