Lecture 13: Evolution

Question 1

Where did Darwin spend most of his time on his voyage?

Answer 1

The southern tip of South America in Chile and Argentina because Britain thought it would grow to be a wealthy country

Question 2

What are the five points of Darwin’s Theory?

Answer 2

1) The world is ancient and constantly changing
2) The ongoing change in the planet’s lifeforms is steady and gradual
3) Common descent
4) New species also form gradually and steadily
5) Natural selection

Question 3

What 3 words sum up Darwin’s Theory?

Answer 3

Descent with modification

Question 4

Homology

Answer 4

Similarity in organisms due to common ancestry

Question 5

Monophyletic Group

Answer 5

An evolutionary unit that includes an ancestral population and all of its descendants (also called a lineage, or clade)

Question 6

Synapomorphy

Answer 6

A shared, derived trait

Question 7

Homoplasy

Answer 7

Similarity in organisms due to reasons other than common ancestry

Question 8

Polyphyletic Group

Answer 8

Consists of two or more taxa but not their common ancestor

Based on convergent evolution

Question 9

Paraphyletic Group

Answer 9

Consists of an ancestor and some but not all of its descendants

Question 10

What is natural selection?

Answer 10

Natural selection is a process that occurs whenever certain conditions hold

Question 11

What are the three conditions that must hold for natural selection to occur?

Answer 11

1) Variation in some trait (there is a distribution of traits)

2) Heritability of that trait (inherited from parents)

3) Fitness differences due to that trait

Question 12

Describe natural selection as a process.
3 points from the slide

Answer 12

1) Natural selection occurs whenever there are inherited fitness differences between individuals

2) The process shifts (or maintains) the population frequency of the trait affected by those genes, as well as the population frequency of the genes themselves

3) (natural selection leads to) the frequency distribution shifts due to effects of the trait on fitness (i.e differential and/or reproduction)

Question 13

Explain the peppered moth example for natural selection

Answer 13

A group of the peppered moths gradually become covered in soot to become fully black.

Breeding experiments reveal that the differential is inherited, caused by a single gene (AKA it is heritable)

The dark form became common in industrial areas and the “industrial melanism” hypothesis was formed that the coal burning had darkened tree trunks, making dark coloration advantageous.

This hypothesis was correct: Light coloration is more advantageous for light colored trees; Dark coloration is more advantageous for dark colored trees

This experiment demonstrates all 3 elements of natural selection:
Variation: peppered and dark
Inheritance: Genetics are known
Fitness Differences: Better survival of the more camouflaged form

Question 14

What does directional selection do?

Answer 14

Changes the average value of a trait (shifts the frequency of a trait towards one trait or another–easier to visualize on a graph)

Question 15

Can natural selection reverse?

Answer 15

Yes
See slide 22

Question 16

Directional Selection
1) Effect on phenotype
2) Effect on genotype

Answer 16

1) Favors one extreme phenotype, causing the average phenotype in the population to change in one direction

2) Genetic variation is reduced

Question 17

Stabilizing Selection
1) Effect on phenotype
2) Effect on genotype

Answer 17

1) Favors phenotypes near the middle of the range of phenotypic variation, maintaining average phenotype

2) Genetic variation is reduced

Occurs by selecting against or for a certain trait

Ex. Human babies of average size are most likely to survive

Question 18

Disruptive Selection
1) Effect on phenotype
2) Effect on genotype

Answer 18

1) Favors extreme phenotypes at both ends of the range of phenotypic variation (the middle is selected against)

2) Genetic variation is increased

Question 19

Balancing Selection
1) Effect on phenotype
2) Effect on genotype

Answer 19

1) No single phenotype is favored in all populations of a species at all times

2) Genetic variation is maintained

Ex. Guppies with rare color patterns are favored, changing the favored color pattern over time

Question 20

What type of selection has the opposite effect of stabilizing selection?

Answer 20

Disruptive selection (favors extremes)

Stabilizing selection (favors intermediate–middle– phenotypes)

Question 21

Give the important example of disruptive selection that will definitely be on the exam

Answer 21

Gamete Size
Hypothesis that smaller gametes are more motile and hence do better in locating a partner to fuse with.

Larger gametes have more resources and grow or survive better

This has been proven true because it has evolved independently in many lineages

Question 22

Biological Species

Answer 22

A species is a group of actually or potentially interbreeding populations whose members have the potential to interbreed in nature to produce viable, fertile offspring but do not produce viable, fertile with members of other such groups

(If they do not produce viable, fertile offspring, they are two different species)

Question 23

Morphological species

Answer 23

Based on differences in morphology

Question 24

Morphology

Answer 24

The study of the form and structure of organisms

Question 25

Lineage species

Answer 25

A terminal twig on a phylogenetic tree

Question 26

Speciations results because...

Answer 26

isolated populations follow different evolutionary trajectories. Eventually, they are no longer able to interbreed, even if they come into contact with each other

Question 27

How do new species arise?

Answer 27

Differences begin to accumulate in two groups until they can no longer interbreed. As time passes, different changes take place in the divided environments. Accumulated genetic factors select the populations best able to survive in the new environments

Question 28

As isolation continues and the populations diverge...

Answer 28

barriers to inter-breeding accumulate. If the barrier is later removed, inter-breeding is no longer possible

Question 29

What are the types of prezygotic barriers

Answer 29

Involve individuals of different species Habitat isolation Behavioral isolation Temporal isolation MATING Mechanical isolation Gametic isolation

Question 30

What are the types of postzygotic barriers?

Answer 30

Fertilization Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Viable, fertile offspring

Question 31

Habitat Isolation

Answer 31

A type of prezygotic barrier Occurs before mating Populations live in different habitats and do not meet

Question 32

Behavioral Isolation

Answer 32

A type of prezygotic barrier Occurs before mating Little or no sexual attraction between males and females

Question 33

Temporal Isolation

Answer 33

A type of prezygotic barrier Occurs before mating Mating or flowering occurs at different seasons or times of day

Question 34

Mechanical Isolation

Answer 34

A type of prezygotic barrier Occurs after mating Structural differences in genitalia or flowers prevent copulation or pollen transfer

Question 35

Gametic Isolation

Answer 35

A type of prezygotic barrier Occurs after mating Female and male gametes fail to attract each other or are inviable

Question 36

Reduced hybrid viability

Answer 36

A type of postzygotic barrier Occurs after fertilization Hybrid zygotes fail to develop or fail to reach sexual maturity

Question 37

Reduced hybrid fertility

Answer 37

A type of postzygotic barrier Occurs after fertilization Hybrids fail to produce functional gametes

Question 38

Hybrid breakdown

Answer 38

A type of postzygotic barrier Occurs after fertilization Offspring of hybrids have reduced viability or fertility

Question 39

Monophyletic groups are identified by...

Answer 39

Synapomorphies Trait unique to a particular (monophyletic) group Homologous traits found in a common ancestor and descendants but missing in more distant ancestors

Question 39

How does mate selection affect variation?

Answer 39

Mates will select for or against certain traits, shifting the allele frequency Females are usually the more selective gender because the consequences of the choice matter more

Question 40

What is the phylogenetic species concept?

Answer 40

Identifies species based on evolutionary history based on the rationale that all species are related by common ancestry Based on monophyletic groups

Question 41

Add note about what is required to be two different species in relation to offspring from lab manual