3. Big Idea #2
Populations cannot grow indefinitely
because resource are limited and there is
competition for those resources
4. Population Dynamics
The study of how
Distribution
Age structure
Population Size
Population Density
These things change in response to
changes in the environment
5. Some species count more than others
Changes in the growth rate of
Invasive species
Keystone species
Ecosystem engineers
Has a greater impact on the biodiversity
of an area than other species
7. Population Dynamics
For example:
How disease affects a population
How the introduction of a nonnative species affects a
population
How the presence of chemicals like pesticides affect
populations
Studying these things helps us identify keystone
species
10. Why clump?
1. Cluster where there are resources
2. More likely to find resources if they
work together
3. Protection from predators
4. Teamwork to catch prey
5. Mating group and/or help raising
young
11. Uniform
Especially in plants
Secrete chemicals that prevent others
from growing nearby
Increases chances of getting the water and
soil nutrients it needs
16. Biotic Potential
A population’s capacity for growth
under ideal conditions
General rule of thumb:
Big things have low biotic potential
Little things have high biotic potential
Blue whale &
calf
ants
E. O. Wilson
studied ants
mostly
Give an example of an
organism with low biotic
potential and an organism
with high biotic potential
17. Intrinsic Rate of Increase (r)
The rate at which a population
would grow if it had unlimited
resource
Species with high “r” usually:
Reproduce early in life
Have short generations
Can reproduce often
Have lots of offspring each time
So what’s the difference between biotic potential and
intrinsic rate of increase?
19. Reproductive Strategies
K-selected species
Low biotic potential
Few offspring
Lots of parental care
Usually competitive species
22 mo. Gestation, 522 mo. Gestation, 5
years between birthsyears between births
9 mo. Gestation,9 mo. Gestation,
8 years between8 years between
birthsbirths
21. Species can’t keep growing and
growing…
There are limiting factors that prevent
this
Competition for resources
Predators
Disease
22. How do you feel about what you
are learning?
A. Happy
B. Frustrated
C. Suspicious
D. Love-struck
E. Confused
F. Overwhelmed
G. Other? _________________
Check all that apply
28. Environmental Resistance
The combination of all the factors that limit the
growth of a population
Together these factors determine the carrying
capacity (K) of the population
The maximum number of a species that can survive in a
given area
The combination of all the factors that limit the
growth of a population
Together these factors determine the carrying
capacity (K) of the population
The maximum number of a species that can survive in a
given area
32. Genetic Diversity
Difference in genes among
members of a population
A very important factor in
the long term health and
survival of a population
33. The Founder Effect
Founder Effect - a small
group of individuals
becomes separated from
the larger population.
They may have less
genetic diversity than the
larger population
34. The Bottleneck Effect
When only a small
group survives some
change in the
environment
Lack of variation
means less
adaptability
Humans sometimes
create bottlenecks in
other species
35. Small populations may experience
genetic drift
Fluctuations in gene frequencies in a
small population from one generation
to the next
The smaller the size of the population,
the more likely there is to be a major
shift in allele frequencies
36. Example
If I flip a penny 100 times, how
many heads should I get?
If I flip a penny 10 times,
would it seem really weird that
I got 7 heads and only 3 tails?
Why not?
38. Minimum viable population
The minimum number of individuals
needed to maintain a species for the
long term (so no inbreeding!)
39. How do you feel about your knowledge
of genetics and population dynamics at
this point?
How do you feel about your knowledge
of genetics and population dynamics at
this point?
0 – not even with prompting can I
explain this topic
1 – with some prompting I could explain
some of it
2 - I get the basics
3 – I understand it beyond just basic info
without help
4 – I can apply what I know to a test
question
0 – not even with prompting can I
explain this topic
1 – with some prompting I could explain
some of it
2 - I get the basics
3 – I understand it beyond just basic info
without help
4 – I can apply what I know to a test
question
44. LE 52-18
1960
Year
Moosepopulationsize
2,500
Steady decline probably
caused largely by wolf
predation
2,000
1,500
1,000
500
0
1970 1980 1990 2000
Dramatic collapse caused by severe
winter weather and food shortage,
leading to starvation of more than
75% of the population
Irregular
50. Quick Think
What are the pros and cons of:
Rapid population growth?
No population growth?
Declining population?
Economic
Social
Environmental
51. Choose 1:
Would you rather…
Sleep in a bed of rats.
Catch a porcupine thrown from a 2nd
story
window.
Be sprayed by a skunk.
Let a rattle snake slither across your body.
Let bumble bees cover you from head to feet.
Let a tarantula walk across your face.
Give a speech to the student body with only
your underwear on
Shave off your head hair and eyebrows for
the rest of the semester
Would you rather…
Sleep in a bed of rats.
Catch a porcupine thrown from a 2nd
story
window.
Be sprayed by a skunk.
Let a rattle snake slither across your body.
Let bumble bees cover you from head to feet.
Let a tarantula walk across your face.
Give a speech to the student body with only
your underwear on
Shave off your head hair and eyebrows for
the rest of the semester
52. Stump the class
• Work in teams of 2-3
• Each person write one multiple choice
or short answer question on your index
cards from Ch. 4 or 5
• Question on one side, answer on the
other
• Share your questions with your team
and revise if necessary
• Give your cards to Beck to share with
the class