Download POPULATIONS

DO NOW:
• Think of a population of organisms. Describe in
as much detail as you can.
POPULATIONS
Objectives:
1)
Describe the characteristics of populations;
2)
Identify 4 factors that affect population size & growth rate
3)
Compare r-selected and K-selected species
Features of populations
•Density
•Dispersion
Density
• Varies with environment
▫ Can you give an example?
• May vary with season
• May be determined by biotic and abiotic
factors in environment
▫ Explain
Dispersion
• Spacing
• 3 types:
▫ Clumped
▫ Uniform
▫ Random
• What does
dispersion tell us?
Calculate growth rate:
• If a human population of 10,000 has
200 births per year and 100 deaths per
year, what is the growth rate of this
population?
▫ b = 200/10,000 = 20/1,000 = 0.02
▫ d = 100/10,000 = 10/1,000 = 0.01
▫ r = 0.02 – 0.01 = 0.01 or 1% per year
• Per capita growth rate (r):
▫r=b–d
▫ r = (b - d) + (i – e)
• rate of change: ΔN/Δt = N (b – d)
▫ N = # of individuals
▫ t = time
▫ b = birth rate
▫ d = death rate
▫ In our initial example = 10,000 (.01) =
100 people/yr.
• Rate of change at an instant in time
▫ dN/dt = rN
• r may be positive, negative or zero.
▫ What do each of these indicate?
• Every population has an intrinsic rate of
increase (rmax)
▫ Maximum rate at which population can
increase
▫ What influences rmax?
Branch of evolutionary biology and ecology whose goal is to
predict and explain the observed patterns in life histories of
living organisms
Life History
• Life history characteristics are traits that affect
the life table of an organism (Life table =
probability of death)
• Can be imagined as various investments in
growth, reproduction, and survivorship.
▫ https://en.wikipedia.org/wiki/Life_history_theory
Activity:
• You will be given a set of 9 cards, each
describing some characteristics of organisms
related to reproduction.
• Can you find a way to group these organisms?
▫ What characteristics did you base your groupings
on?
▫ What other information (not given) do you think
the organisms in your group might have in
common?
Activity, continued…
• Did you have difficulty grouping any of your
organisms? Why?
• Can you think of 2 or 3 more examples of
organisms and where they would fall?
r selection
• High growth rate (r)
• Characteristics:
▫
▫
▫
▫
▫
▫
Opportunistic
Small
Early maturity
Short life span
Large # of offspring
Little/no parental care
K selection
• Survive in environment near carrying capacity
• What characteristics might you expect to see in a
K-selected species?:
▫ Live in stable environments
▫ Long life spans
▫ Late reproduction
▫ Large body size
▫ Low reproductive rate
▫ Parental care
Reproduction
• Successful reproduction = Fitness
• Different species have adapted different
reproductive strategies:
▫ Semelparous
vs.
Iteroparous
Survivorship Curves
• Can you think of organisms that would fall into
each category?
Journal Questions:
• How do reproductive strategies demonstrate the
relationship between ecology and evolution?
• Why is understanding growth rate important for
both ecologists and evolutionary biologists?