BIOL 180 Exam Review: Mendelian Genetics, Evolution, Biodiversity and Ecology

Terms in this set (31)

1. Mendel's law of segregationEach individual has two alleles for a gene, which separate during gamete formation so each gamete carries only one.
2. Mendel's law of independent assortmentAlleles of different genes assort into gametes independently of one another, as long as the genes are on different chromosomes or far apart on the same one.
3. Genotype vs phenotypeGenotype is the allele combination an organism carries. Phenotype is its observable trait, which results from genotype and environment.
4. Expected ratios from a monohybrid cross Aa x AaGenotypes 1 AA : 2 Aa : 1 aa; phenotypes 3 dominant : 1 recessive.
5. Expected phenotype ratio from a dihybrid cross AaBb x AaBb9 : 3 : 3 : 1, assuming complete dominance and independent assortment.
6. What is a testcross?Crossing an individual with the dominant phenotype to a homozygous recessive. If any offspring show the recessive phenotype, the parent was heterozygous.
7. Incomplete dominance vs codominanceIncomplete dominance: heterozygote is intermediate (red x white gives pink). Codominance: both alleles fully expressed (AB blood type).
8. Why are X-linked recessive traits more common in males?Males have one X chromosome, so a single recessive allele produces the trait; females need two copies.
9. How does meiosis create genetic variation?Crossing over between homologous chromosomes in prophase I, independent assortment of homologs in metaphase I, and random fertilization.
10. Mitosis vs meiosis outcomeMitosis gives two genetically identical diploid cells. Meiosis gives four genetically different haploid gametes.
11. Linked genes and recombination frequencyGenes close on a chromosome tend to be inherited together. Recombination frequency (recombinant offspring / total) estimates distance: 1% = 1 map unit.
12. Darwin's natural selection in four pointsIndividuals vary, variation is heritable, more offspring are produced than survive, and individuals with advantageous traits leave more offspring, so those traits increase over generations.
13. Fitness in evolutionary biologyAn individual's relative reproductive success: how many offspring it contributes to the next generation compared with others.
14. Hardy-Weinberg equationsp + q = 1 for allele frequencies and p^2 + 2pq + q^2 = 1 for genotype frequencies (AA, Aa, aa).
15. Five Hardy-Weinberg assumptionsNo mutation, random mating, no natural selection, very large population (no drift) and no gene flow.
16. Mini-problem: 16% of a population shows a recessive trait. What is q?q^2 = 0.16, so q = 0.4 and p = 0.6. Heterozygotes are 2pq = 0.48.
17. Genetic drift, and the bottleneck vs founder effectDrift is random change in allele frequencies, strongest in small populations. Bottleneck: a population sharply shrinks. Founder effect: a few individuals start a new population.
18. Directional, stabilizing and disruptive selectionDirectional favors one extreme; stabilizing favors intermediate phenotypes; disruptive favors both extremes over the middle.
19. Biological species conceptA species is a group of populations whose members can interbreed in nature and produce fertile offspring, and are reproductively isolated from other groups.
20. Allopatric vs sympatric speciationAllopatric: populations are separated geographically and diverge. Sympatric: new species arise in the same area, for example through polyploidy in plants.
21. Homologous vs analogous structuresHomologous structures share common ancestry (human arm and whale flipper). Analogous structures have similar function from convergent evolution (bird and insect wings).
22. What is a monophyletic group (clade)?An ancestor and all of its descendants. Paraphyletic groups leave out some descendants, such as traditional reptiles without birds.
23. The three domains of lifeBacteria, Archaea and Eukarya. Bacteria and Archaea are prokaryotes; Archaea share some molecular features with eukaryotes.
24. Population growth: exponential vs logisticExponential: dN/dt = rN, a J-shaped curve with unlimited resources. Logistic: dN/dt = rN(K - N)/K, an S-shaped curve leveling off at carrying capacity K.
25. r-selected vs K-selected speciesr-selected: many offspring, little care, fast maturity (often in unstable habitats). K-selected: few offspring, high parental care, near carrying capacity.
26. Types of species interactions with their +/- effectsCompetition (-/-), predation and parasitism (+/-), mutualism (+/+), commensalism (+/0).
27. Competitive exclusion principleTwo species competing for the exact same limiting resources cannot coexist indefinitely; one will outcompete the other or they will partition resources.
28. What is a keystone species?A species whose effect on community structure is far larger than its abundance suggests, like sea otters controlling urchins and protecting kelp forests.
29. Why is only about 10% of energy passed between trophic levels?Most energy is lost as heat in metabolism or remains in unconsumed or undigested material, which limits the length of food chains.
30. Major threats to biodiversityHabitat loss and fragmentation, invasive species, overharvesting, pollution and climate change.
31. Why does small population size threaten conservation?Small populations lose genetic diversity through drift and inbreeding, lowering fitness and adaptability, which can create an extinction vortex.