Density-Dependent Limiting Factors

Get yourself into 6 groups of 4-5 students
per group
Once you find your group, sit at a table
You have 30 seconds
Food Station
◦ You will have one piece of “food” to share equally
between you and your group members
◦ 3 stations to go to A,B,C-Rotate through them all
◦ Make notes on your worksheet
Shelter Station
On the ground you will see 3 “shelters”
You must stay in the “shelter” for 3 minutes
If you are loud, you’re out
NO SHOVING! You will be out if you shove anyone
Rotate through all 3 stations
Make notes on your worksheet
Crowded populations mean the individuals
have to compete for food, water, space,
sunlight, or anything else necessary for
survival and reproduction
Some may have enough to survive, but can’t
raise offspring
Some may die of starvation
The more individuals in an area, the faster
resources are used up
Could be between individuals of the same or
different species
Predator-prey relationships tend to fluctuate
(go up and down)
If there is a lot of prey, the predator can eat
more, increasing the number of predators
If the prey decreases too much in population,
there won’t be enough food for predators and
so the population of predators decreases
Plant and herbivore populations fluctuate just
like the predator and prey populations
Parasites and disease causing organisms feed
at the expense of the host
This can weaken or kill the host
The larger the population the easier it is for
the parasite or disease to travel through
Some species will fight amongst each other if
they are overcrowded
This fighting can cause stress leaving
individuals susceptible to disease
In a few species, overcrowding can cause
females to neglect or kill their own offspring
 Organize
the following words
into 3 categories
◦ Density Dependent
◦ Density Independent
◦ I’m not sure
A hurricane
A disease kills half of
the population
A forest is cleared by
a logging company
The plants that one
species really likes
has only grown half
as much as usual
An early frost kills
cherry trees
There is an unusually
large population of
wolves that eat a lot
of rabbits
Territorial lions start
fighting each other
for habitat space
The weather has been
unusually dry so the
watering hole has
dried up
A factor that affects all populations in
similar ways, no matter the population
size or density
 It includes things like:
 Hurricanes
 Droughts
 Floods
 Natural Disasters
So what would happen after a drought?
◦ No water so species will compete for the water
 Sometimes
a density dependent
factor can lead to a density
independent limiting factor like
 What do you think??
We said that something happens to stop
populations from growing.
How do density-independent and dependent
factors play into this?
These limiting factors contribute to what is
called carrying capacity
Defined as: the maximum number of
individuals of a species an environment can
On a sheet of paper, write a paragraph
explaining whether or not you think
that density independent factors
should be considered separate from
density dependent factors.
 Explain your answer using information
from today.