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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?