2-Evolution Mechanisms

Question 1

biological evolution

Answer 1

refers to a change in the (heritable) characters of a population over generations

Question 2

microevolution

Answer 2

changes in allele frequencies in a population in a relative short period of time (one generation)

Question 3

macroevolution

Answer 3

evolution that occurs at or above the species level
- how do new species arise
- Typically occurs over longer periods of time

Question 4

current theory for evolution

Answer 4

• all species are related
  
  • Current theory—we all descended from a single called common ancestor (LUCA)
    
    • ~3.7 billion years ago
• Species change over time
• Species do go extinct

Question 5

EVIDENCE THAT ALL SPECIES SPECIES SHARE A COMMON ANCESTOR

Answer 5

• all living taxa are made of Cells
• universality of DNA as the genetic code
• universal flow of Biological information
  
  • DNA to RNA to amino acids/proteins
• Near universality of the Genetic code (codons) and DNA replication and repair

Can
Dogs
Beat
Goats?

Question 6

HOMOLOGIES

Answer 6

EVIDENCE OF EVOLUTIONARY RELATEDNESS
traits present in two or more organisms that were inherited from their common ancestor
- anatomical /structural homologies
- Developmental homolgies
- Genetic homologies

homologies structures may or may not be modified in different taxa
- may not look the same (though they often do)
- Nor may they have the same function in different taxa

Question 7

shared ancestry

Answer 7

allows us to study other organisms and apply that knowledge to help us

Question 8

analogous traits or homoplasies

Answer 8

• arise due to convergent evolution
• Not inherited form a common ancestor
• Streamlined shape and finds represent a similar solution to the same environmental demand (moving efficiently through the water)

Question 9

convergent evolution

Answer 9

Independent soleution to an environmental demand

Question 10

evidence that species have changed with time

Answer 10

• extinctions — in the past (fossils) and today
  
  • Evidence of evolutionary change through time on the fossil record
• Transitional fossils
  
  • Transitional/intermediate forms showing intermediate anatomy between earlier and later forms
• Vestigial traits
  
  • Structures that have reduced function or no function compared to its ancestral from due to evolution
• Real time evidence of charge
  
  • Evolution of antibiotic resistance in bacteria

Question 11

mutation

Answer 11

any change in the nucleotide sequence of the DNA

Question 12

germline mutations

Answer 12

• occur in gametes (eggs or sperm)
• Germline mutations Especially significant for evolution because they can be transmitted to offspring!!

Question 13

Somatic mutations

Answer 13

• occur in other cells in the body
  
  • Not heritable!
  • Confined to one cell
  • May or may not affect individuals during their lifetime

Question 14

what causes high mutation rates?

Answer 14

• organisms that undergo meiosis/mitosis more frequently—higher mutation rates
  
  • Most mutations occur due to errors in DNA replication
• Organisms that reproduce more frequently will pass on those mutations to the next generation at a faster rate if mutation in germline cells

Organisms that invest more in DNA protection and repair will have LOWER mutation rates

Question 15

adaptations definition

Answer 15

a structural, functional, or behavioural characteristic of an organism that helps individual survive/reproduce

Question 16

Evolutionary (Darwinian) fitness

Answer 16

a measure of the relative reproductive success of individuals/an individual’s relative contribution of genotype (or phenotype) to future generations

Individuals that pass more genes to the next generation have a higher evolutionary fitness than individuals that pass fewer genes to the next generations

Question 17

silent mutations

Answer 17

Any mutation in the non-coding region is unlikely to affect the phenotype/fitness of an individual

Question 18

codon

Answer 18

3 letter combinations of nucleotides, writes the genetic code

Question 19

amino acid

Answer 19

building block of proteins, is coded for by more than one codon

Question 20

why are mutations a weak evolutionary mechanism?

Answer 20

• most mutations are silent/neutral with respect to fitness—do not matter to evolution
• Mutations only affect one individual
• Must occur in a germline cell to be passed on to future generations
• It takes other evolutionary mechanisms (natural selection) to increase or decrease the new allele frequency in the population

Question 21

sickle-cell anemia

Answer 21

• genetic disease caused by a recessive allele that produces abnormal hemoglobin proteins in red blood cells
• Reduce oxygen carrying capacity of the blood
• Blood cells break down prematurely, leading to anemia
• But… carriers (heterozygotes) are resistent to malaria

Question 22

gene flow

Answer 22

refers to the movement of alleles between populations caused by dispersal (of individuals or gametes) and subsequent mating

Question 23

what happens if no gene flow?

Answer 23

• genetic divergence of the two populations
• Can lead to speciation

Question 24

who introduced the idea of natural selection?

Answer 24

charles darwin and. Alfred Russell Wallace. Introduced idea in 1800s

Question 25

natural selection

Answer 25

non-random differences in the survival and reproduction o f individuals with certain genotypes and the associated phenotypes in a population over time, generations

Question 26

three requirements for natural selection to occur

Answer 26

1. variation in trait/phenotype in population 2. Diffferences in fitness associated with the difference in phenotypes 3. Phenotype must be heritable (genetic component)

Question 27

outcome of natural selection

Answer 27

- increase in frequency with the advantageous phenotype in population over generations - Increase in frequency of the beneficial allele - Population becomes more well adapted to the environment - If environment changes, so can the direction of selection

Question 28

ADAPTATIONS (OR ADAPTIVE TRRAITS)

Answer 28

Refer to a heritable trait that increases the ability of an individual to survive and reproduce compared to ppl without that trait

Question 29

when is something NOT an adaptation?

Answer 29

- not heritable - No function - Does not affect fitness

Question 30

directional selection

Answer 30

favours individuals with a phenotype at one end of the distribution of a trait outcome: frequency distribution of the trait in the subsequent generation is shifted in one direction from where it was in the parental generation - average value for a trait is CHANGED!! - variation (genotypic/phenotypic) tends to DECREASE

Question 31

2. STABILIZING SELECTION

Answer 31

selects against extreme phenotypes at both ends of the frequency distribution favours intermediate phenotypes, removes extreme phenotypes outcome: - average value of the trait remains the SAME - phenotypic/genotypic variation is REDUCED

Question 32

3. DISTRUPTIVE SELECTION

Answer 32

both extremes are favoured at the expense of intermediate phenotypes - average value of the trait remains the SAME - increase in phenotypic variation (?) - often drives speciation!!!

Question 33

THEORY OF SEXUAL SELECTION

Answer 33

certain conscpicuous traits that potential decrease survival could be selected for if they gave an individual an advantage for reproduction, either by: - enabling an individual to outcompete rivals for access to a mate - increasing the likelihood that an individual would be able to woo a prospective mate

Question 34

sexual dimorphism

Answer 34

distinct differences in size/appearance/behaviour/physiology between males and femals

Question 35

the two mechanisms of sexual selection

Answer 35

**intrasexual selection** - competition for mates - male-male interactions (mostly) **intersexual selection** - mate choice - female mate choice (mostly)

Question 36

Intrasexual selection COMPETITION FOR MATES—DIRECT MALE-MALE INTERACTIONS

Answer 36

- males may physically combat each other - males may evolve “weapons” that give them an advantage in a fight - but... does not always involve direct combat! maybe ornaments and behaviours? maybe mimicry? etc.

Question 37

Direct benefit

Answer 37

*males can signal that they would provide good parental care* - providing shelter from the environment - protecting female and/or young from threats such as predators - can provide resources to the female by bringing gifts

Question 38

indirect benefit

Answer 38

*male’s phenotype is an indicator or advertisement for good genes/high fitness that can be passed to the female’s offspring* - usually means the signal has to bear some cost to the female - LOOKING BEAUTIUFUL? MEANS DISPLAYING THEIR GOOD GENES! - healthy—no parasites - good immune system - non-damaged DNA, etc

Question 39

Artificial selection

Answer 39

people, instead of nature select which individuals get to reproduce and pass their alleles onto the next generation

Question 40

GENETIC DRIFT

Answer 40

changes in allele frequencies in a population over time due to random differences in survival and/or reproduction changes in allele frequencies are not a function of whether the alleles are harmful or beneficial - occurs in all populations that are not infinite in size - outcome is due to chance!—sampling error

Question 41

genetic drift on small populations vs large populations?

Answer 41

- random fluctuations in allele frequencies tend to be more pronounced in smaller populations than larger populations - small populations tend to lose genetic diversity more quickly than larger populations

Question 42

the opportunities for genetic drift

Answer 42

1. (population) bottleneck event 2. founder event - both events involve a change in population size - new population smaller than original population - allele frequencies in a population can ALSO change by due to chance events with no change in population size

Question 43

Population bottleneck Event

Answer 43

population size is greatly reduced (often over a short time period) for at least one generation (usually due to a catastrophe such as wildfire, flood, etc)

Question 44

founder event:

Answer 44

occurs when a new population is founded by a few individuals

Question 45

Transitional fossils

Answer 45

Transitional/intermediate forms showing intermediate anatomy between earlier and later forms

Question 46

Vestigial traits

Answer 46

Structures that have reduced function or no function compared to its ancestral from due to evolution

Question 47

how to tell when something is an adaptation?

Answer 47

Heritable – It has a genetic basis Functional Adaptive - Trait must increase the fitness of the organism compared to organisms lacking the trait Current function – The trait evolved at the same time as the current function.