1. Next Lab IV: Student-Driven Project 1
Complete Homework 6 at home:
Correlation/Regression
Bring 3 abstracts to trade with group + TA
Complete SDP1 Proposal Worksheet 1
Use pg

2. Next lecture: Ch 10: Life Histories and Evolution

3. The hierarchical nature and processes of different levels of ecological systems:

4. Individual organism: How do structure, physiology, and behavior lead to the individual’s survival and reproduction?
Population: What determines the number of individuals and their variation in time and space?
Community: What determines the diversity and relative abundance of organisms living together?
Ecosystem: How do energy and matter move in the biotic and abiotic environment?
Biosphere: How do air, water, and the energy and chemicals they contain circulate globally?

5. Today: Ch 16: Population Genetics
Population Ecology
Genetics
Evolution
Pop genetics = brtanch of ecology dealitn with mechanics of selection and genetic responses of organisms.
Darwin’s finches…

6. Objectives Define (micro)evolution and its relation to genetics
Sources of genetic variation
Forces causing change in gene frequency in pop
Small population size
Assortative mating
Gene flow
Natural selection
Which force(s) maintain vs. eliminate genetic
variation?
Which force is strongest in plants? animals?

7. ***Sample exam question. A species of scale insects extracts fluids from
branches of pine trees. They have very limited
movement. In an experiment, these insects were
transplanted 1) between branches of the same pine
tree, and 2) from one pine tree to another pine tree
of the same size.

8. State the hypothesis/prediction that was being
tested as an “If…then…”
Summarize the results in one concise sentence.
Do the results support the hypothesis?
Predict whether gene flow or natural selection would be a more powerful force affecting the genetic structure of this insect. Explain your choice.
5. Predict whether the genetic makeup of populations of the insect on adjacent trees would be homogeneous or differentiated. Explain your choice.

9. Genetic structure (differentiation) of populations is determined by ecological factors, e.g. heavy metals from mines.
C23.1 mine tailings: heavy metal tolerance

10. *** A ‘pre-test’ on adaptation, natural selection, evolution, fitness…
Copper from mine in soil
of plant subpopulation
Non-Cu-
resistant
Cu-resistant
individuals
TIME

11. Mutation, a change in nucleotide in DNA
*** What is definition of (micro)evolution? Change in allele frequency in a population through time… ***What must be present for natural selection to cause evolutionary change? Genetic variation ***What is the ultimate source of genetic variation?
unless there is genetic variation in a population.
Mutation, a change in nucleotide in DNA
---> change in amino acid it specifies
---> change in phenotype of organism

12. A change in just one nucleotide can have phenotypic effects.
A single-nucleotide mtuation in gene for human hemoglobin changes structure of hemoglobin and cuases RBCs to assume a sickle shape. Severe anemia if have two copies of mutant gene.; if one copy --> resistant to malaria.
Natural selection acts on phenotypic variation.
Evolution occurs if the phenotypic variation is underlain by genetic variation.

13. Genetic variation revealed via electrophoresis
SS19.5 Electrophoretic gel studied under UV light

14. What do different patterns of coloration (different phenotypes) represent in the population?
C pg 445 population of marine snales; differnet patterns of colaration represent genetic variation in pop.If predators feed preferentially on snails having a particular coloration, then the proportion of individuals with that coloration probably will decline from one generation to the next because such snails will produce fewer offspring. Thus, it is the population, not the indivuidal that evolves. Some characteristics become more common in the overall population, while other characteristics decline.

15. ***How much genetic variation exists? ***Why is genetic variation important?
In changing environments, the reservoir of genetic variation may take on positive survival value.
Rapid environmental change by humans may exceed the capacity of a population to respond by evolution --> extinction
30% of human genes in population are variable; 10% of an indiviudal’s genes are heterozygous.

16. Are most mutations beneficial. Are most mutations dominant
***Are most mutations beneficial? Are most mutations dominant? What happens to harmful mutations?
Most mutations are harmful and recessive; natural selection weeds out most deleterious genes, leaving only those that suit organisms to their environments.
Mutations are likely to be beneficial when the relationship of the organism to its environment changes.
Selection for beneficial mutations is the basis for evolutionary change, enabling organisms to exploit new environmental conditions.
5 lethal recessives/ individual human…

17. Genetic variation is also produced by chromosome recombination during 1)meiosis and by 2) fertilization.

18. How does sexual reproduction rapidly produce new combinations of genes--> abundant variation for natural selection to work on?
Crossing over during meiosis…
Random new combinations
from fertilization

19. The gene pool represents the total genetic variation in the population = genotypes (alleles) of all individuals.
***Does evolutionary change occur through sexual reproduction itself?

20. Hardy-Weinberg Equilibrium:
C23.3a Hardy-Weinberg theorem
Gene pool: generation 1: p = q = .2

21. Gene pool: generation 2: p = .8 q = .2
Hardy-Weinberg equilibrium: frequencies of alleles and genotypes stay constant through time…unless additional forces operate.
Sexual
reproduction
C23.3b Hardy Weinberg theorem
Gene pool: generation 2: p = q = .2

22. ***Does evolutionary change occur through sexual reproduction itself?
No (Hardy-Weinberg Law).
Changes in allele and genotype frequencies (= evolution) can result only from additional forces acting on the gene pool of a species.
Understanding the nature of these forces and their relative importance is one goal of evolutionary biology.

23. ***What forces can cause change in genotype frequency?
Effects of small population size
a) Genetic drift
b) Founder effect
c) Population bottlenecks
2) Assortative (non-random) mating
3) Gene flow (= dispersal/migration) --> homogenizes subpopulations
4) Natural selection --> differentiates subpopulations
Other forces that make it difficult to change genotype frequency:
heterosis (heterozygote superiority)
pleiotrophy (genetic correlation of traits)
epistasis (> 1 gene affects a trait)

24. Genetic drift: 5 of 10 plants 2 of 10 plants
leave offspring leave offspring
C23.4 genetic drift
Genetic drift: Change in allele frequencies due to random variation in fecundity and mortality-->decrease in genetic diversity
When all but one allele for a particular gene disappears ---> remaining allele becomes fixed.
Generation 1 Generation 2 Generation 3p p =.7, q = p = .5, q = p = 1.0, q = 0
Change in allele frequency due to random variation in
births and deaths.

25. Population Bottleneck: period of small pop. size.
C23.5 bottleneck effectPopulation bottlenecks: A period of extremely small population during which a population is vulnerable to loss of genetic diversity through genetic drift.
…subject to genetic drift