Population biology and speciation Big IDEA #1 (Evolution) & #4 (Interactions) Chapter 24 & 53
What is a species? • Biological species concept… • Interbreed and produce viable, fertile offspring • Does this apply to all living organisms?
What are barriers to reproducing? • Prezygotic barriers-- • Habitat Isolation • Temporal Isolation • Behavioral Isolation • Mechanical Isolation • Gametic Isolation • If you were given an example, can you recognize that these are pre-zygotic barriers?
Postzygotic barriers to reproduction • Reduced hybrid viability • Reduced hybrid fertility • Hybrid breakdown
How does speciation occur? • Allopatric speciation: • Speciation based on geographic separation. • How do these experimental results with flies support this idea?
Other mechanism for speciation • Sympatric speciation: • Speciation within the same geographic location • Figure 24.10 & Figure 24.19
Population: • Ecologists observe species to determine the health of an ecosystem. • Population: group of organisms of the same species in a specific place. Discussion: What happens as populations decrease in size? What happens as emigration occurs in a particular population? What happens when other species compete for the same resources?
Estimating Population Size • Capture/Recapture Technique 53.2 X = s nN • N=overall population size • S=initial amount of individuals tagged • n=population size at second sampling • x=individuals at second sampling that were tagged If 180 endangered dolphins were tagged off the coast of New Zealand and then two months later 44 dolphins were located and of those 44, 7 was tagged, what is a reasonable estimate of the population size?
Do all populations look the same? • Patterns of dispersal differ: clumped, uniform, random
Do reproductive strategies link to surviorship? • R-selection: • Lots of offspring; low parental investment • Important: must be density independent! • K-selection: • K- “Kare”: few offspring; high parental investment
Comparing growth Models • What is the 1,500? • What happens as the graph approaches 1,500 • What affects the rate of growth?
Population growth computer models • Population growth simulation: • http://ats.doit.wisc.edu/biology/ec/pd/pd.htm • Can you use some of your math skills to identify informaiton about 2 populations: • Zebra mussels • Elephants • This above simulation walks you through the math that you can do along with your calculator!!! You will document this activity in your ecology lab notebooks.
What does population growth actually look like • Why does an actual growth model fluctuate around the carrying capacity?
What factors lead to changes in growth: • Density independent • Affects large and small populations equally • Natural disasters, climate change • Density dependent • Effect is magnified as population reaches carrying capacity • Disease, nutrient limitation, competition
Predator-Prey population dynamics • Explain the dynamic relationship between predator and prey population growth: