5 - Modern Synthesis

Question 1

Evolution

Answer 1

Changes in gene frequencies in populations between generations

Question 2

Evolutionary change in a phenotype

Answer 2

Reflects changes in underlying genetic composition of the population

Question 3

Level of natural selection

Answer 3

Individuals

Question 4

Level of evolution

Answer 4

Populations

Question 5

Population genetics

Answer 5

Study of changes in gene frequencies in populations under natural selection

Question 6

Modern synthesis

Answer 6

The synthesis of genetics and Darwinian evolutionary theory

Question 7

DIscontinuous

Answer 7

If a trait controlled by one gene with 2 alleles, will not not be continuous (yellow or geen)

Question 8

Continuous variation

Answer 8

If trait is controlled by multiple genes (e.g. human height)

Question 9

Environmental variation

Answer 9

• Phenotypes will be
  affected differently by development and
  environment (e.g.,
  prenatal nutrition)
• Overlap in range of variation for phenotypes
  of discrete genotypes
• Explains blending of
  phenotypes without
  blending genotypes

Question 10

Maintenance/generation of variation

Answer 10

• Mutation
• Recombination
• Sexual reproduction

Question 11

Mechanism of inheritance

Answer 11

• Discontinuous (e.g. Mendelian traits)
• Continuous (multi-locus or polygenic traits)

Question 12

Mechanisms of evolution

Answer 12

• Natural selection (reduces variation, removes disadvantageous ohenotypes)
• Mutation (increases variation)
• Gene flow (maintains variation)
• Genetic drift (changes allele frequencies through chance, usually decreasing variation)

Question 13

Evolutionary constraints

Answer 13

• A factor limiting the adaptive potential of the phenotype
• A limit on the direction, nature, rate and amount of evolutionary change
• Can prevent evolution of optimal adaptations, leading to maladaptive traits

Question 14

Three broad types of evolutionary constraints

Answer 14

• Historical constraints
• Developmental/genetic constraints
• Material constraints

Question 15

HIstorical constraints

Answer 15

• The adaptive potential of a population depends on the history of that population
• e.g. Genetic drift, disequilibrium, local and global optimal adaptations

Question 16

Fixation

Answer 16

All individuals have identical alleles at a locus

Question 17

When is genetic drift most rapid

Answer 17

If small populations are isolated

Question 18

Founder effect

Answer 18

Establishment of a new population by a few original founders which carry only a small fraction of the total genetic variation of the parental population (not indicative of the original population)

Question 19

Example of founder effect

Answer 19

• Remote south atlantic island colonised by british then abandoned
• Gene pool traces to 15 individuals
• One carried allele recessive eye disease
• Disease became common due to inbreeding

Question 20

Is genetic drift selection

Answer 20

no, is unpredictable

Question 21

Disequilibrium

Answer 21

• Selection produces optimal adaptations only at equilibrium (reach stabilizing selection for an optimum)
• Populations may still be undergoing selection

Question 22

Disequilibrium example

Answer 22

• Hunter gatherers had little access to fat, salt and sugar
• Agriculture and trade make these nutrients more readily available (Change in the environment where trait originally evolved)
• Excess salt, fat, sugar causes health problems

Question 23

Local vs global optima

Answer 23

• Small improvements to existing phenotype, based on which phenotype increases fitness
• Existing phenotype a function of phylogenetic
  history
• Change occurs until an optimum is reached
• Once reached, cannot get to another optimum
  without steps that reduce fitness
• That optimum may be
  local, not global

Question 24

Pleiotropic

Answer 24

• Genes that affect multiple aspects of the phenotype
• Causes certain characters to be correlated

Question 25

Developmental constraints

Answer 25

• Variation is patterned by normal genetic and
  developmental processes
• Some processes are used multiple times over the course of an organism’s development
• Genes that affect multiple aspects of the phenotype are pleiotropic

Question 26

Material constraints

Answer 26

• Adaptive potential is limited by the laws of
  chemistry and physics,
• Requires organisms to be able to function properly in their environments (e.g. gravity)

Question 27

Material constraints example

Answer 27

• To provide the same support as an animal half that size, bones must be over 4-times thicker
• Places upper limit on size of animals on land, as the bones quickly become too heavy to move!