Evolution

Question 1

natural selection def’n

Answer 1

mechanism for change in populations that occurs when organisms w/favourable variations for a particular environment survive, reproduce, and pass these variations on to the next generation

Question 2

Lamarck’s Theory of Evolution

Answer 2

• hypothesized that species evolve through the use and disuse + inheritance of acquired traits
• mechanisms he proposed are unsupported by evidence

Question 3

sources of genetic variation

Answer 3

• mutuation: a heritable change in nucleotide sequence of DNA, resulting in an alteration in the products coded for by the gene; can slowly introduce new alleles to a population (harmful, beneficial, or neutral)
• meisos: random alignment of chromosomes or crossing over (exchange of homologous chromosome segments)
• sexual reproduction: combination of alleles of two individuals
• immigration: incoming alleles to a gene pool

Question 4

microevolution vs macroevolution

Answer 4

microevolution: changes within a species that occurs over dozens or hundreds of generations
macroevolution: evolution over long periods of time that involve origin of new species

Question 5

microevolution in large population -> mechs?

Answer 5

• natural selection
• gene flow: the introduction or loss of new alleles into the population through immigration or emigration
• mutation

Question 6

microevolution in small populations -> mechs?

Answer 6

• genetic drift
• founder effect
• genetic bottleneck
• inbreeding

Question 7

genetic drift def’n

Answer 7

random shifts in allele frequences in SMALL POPULATIONS

Question 8

founder’s effect descr.

Answer 8

• small # individuals of a large population migrates, starts new population
• gene pools of new population can change greatly from original population if the new population is small -> loss of genetic variation, can cause inbreeding (rise of homozygosity within a population)

Question 9

genetic bottleneck descr.

Answer 9

• # organisms in a population is drastically reduced
• large populations can become inbred -> ^frequency of harmful recessive alleles in the gene pool
• inbreeding depression: ^homozygosity of a population -> reduction of fertility, survival

Question 10

speciation def’n

Answer 10

origin of a new species
- occurs when interbreeding is prevented
- production of fertile offspring is prevented

Question 11

speciation mechs?

Answer 11

• genetic isolation causes gene pools to become so different, populations can no longer interbreed
• prezygotic and postzygotic isolation

Question 12

prezygotic isolation

Answer 12

• geographical isolation (ex. mountains, canyons, oceans)
• ecological isolation (differed habitats)
• behavioural/reproduction isolation (differences in courtship and/or mating season)

Question 13

postzygotic isolation

Answer 13

• zygotes do not develop properly
• odd chromosome #s in hybrids (mules, ligers, zonies, etc) complicate meiosis
• plants can become polyploid, ^mating difficulty w/plants having the parental # of chromosomes

Question 14

types of evolution

Answer 14

• divergence: single population splits to adapt to different environments
• convergence: unrelated species become similar as they adapt to a similar environment; analogous structures: same use, different form (not evidence of a common evolutionary ancestor)

Question 15

evidence for evolution?

Answer 15

• fossil record
• anatomical relationships
• embryological development
• genetic comparisons