LECTURE 9: EVOLUTIONARY PROCESSES AND LARGE-SCALE EVOLUTION

Question 1

introduction

Answer 1

if genetic drift, mutation and natural selection are the mechanisms for evolution, are they the reason for taxonomical diversification (macroevolution)?

Question 2

Nagging Doubts by Early Researchers

Answer 2

1. How do organisms diverge and diversify?
2. How can we explain variation across species?
3. If genetic drift, mutation and natural selection are the mechanisms for evolution, can the explain taxonomic diversification

Question 3

The species problem

Answer 3

the problem that arises due to the fact that there are many theories about what a species is

Question 4

Four Factors of Taxonomic Species Concept

Answer 4

1. Phenetic
2. Genetic
3. Ecological
4. Phylogenetic

Question 5

Four Factors of Biological Species Concept

Answer 5

1. Recognition
2. Cohesion
3. Darwinian
4. Evolutionary

Question 6

TWO MAIN SPECIES CONCEPT

Answer 6

TAXONOMIC: looks at the variation of distinct morphologies and phenotypes of species
BIOLOGICAL: looks at inter-fertility and crossability of organisms

Question 7

Original Species Concept

Answer 7

organisms that look alike are the same species

Question 8

Ernst Mayr

Answer 8

Biological Species Concept
SPECIES: a group of interbreeding individuals that are reproductively isolated from other groups of interbreeding individuals

Question 9

Jerry Coyne and Allan Orr

Answer 9

When we understand the origin of reproductive isolating mechanisms, we can begin to understand the origin of species

Question 10

Biological Species Concept: Some Points

Answer 10

• We look at reproductive rates between group of individuals
• Geographical Isolation does not play a key role due to the fact that we are looking at a reproduction
• The isolation does not have to be absolute
• Must be able to see interbreeding in the wild. Not conclusive of anything if these experiments are done in the lab
• Does not apply to bacteria, asexuals

Question 11

Allopatric Speciation (Geographic Speciation)

Answer 11

When a population of individuals split into groups due to geographic isolation and begin adapting in different directions resulting in variation between the two and reproductive isolation as the byproduct of natural selection and evolutionary processes

Question 12

Sympatric Speciation

Answer 12

When species begin to arise within a continuous range without the imposition of a geographic barrier

Question 13

Where can Reproductive Isolation Occur

Answer 13

Finding a mate, Mating and fertilization, The formation of the gamete and its development, the adult growth and survival, the reproductive potential

Question 14

Premating Isolating Mechanisms

Answer 14

• Geographic, ecological (separated by distance)
• Temporal Behavioural (different mating tactics)
• Mechanical, prevention of gamete fusion

Question 15

Maggot Flies on Apple trees and Hawthorn Trees

Answer 15

Due to the different trees having different flowering times and the flies burrowing into the trees, the fly’s mating period coincides with the flowering time of its trees. This, the two populations of flies begin to diverge due to the fact that they are unable to interbreed as well as due to the implication of genetic flow due to the small population

Question 16

Prezygotic Isolation in Alabone

Answer 16

There are proteins in the sperm (lysin) and proteins in the egg (VERL) and they have coevolved in different directions thus imposing reproductive isolation to the species

Question 17

Postmating Isolating Mechanisms

Answer 17

• Inviability, Sterility and abnormal development of zygotes

- There is a genetic incompatibility between the two parents forming the hybrid

Question 18

Intrinsic Postmating Isolating mechanism

Answer 18

Prevents the exchange of genes between groups

Question 19

Extrinsic Postmating Isolating mechanisms

Answer 19

physical barriers that prevent the effective mating between groups

Question 20

Sterility: Intrinsic

Answer 20

Mule: male donkey and a female horse who have become genetically incompatible thus making a hybrid that is unfit

Question 21

Mullerian Mimicry: Extrinsic

Answer 21

If two different species breed and they have similar patterns, they will create a hybrid with an ineffective pattern and thus will increase its predation rates and reduce its viability

Question 22

Is the evolution of adaptation required for speciation

Answer 22

Since local adaptation arises from divergent selection, it can be reasonably inferred that this will cause reproductive isolation and thus speciation. Current research is aiming to find a speciation gene

Question 23

EDA

Answer 23

the three-spined stickleback fish has bony armor in the ocean but loses it when it is introduced into the freshwater. The gene of speciation that separates the two is known as EDA

Question 24

Adaptive Radiation

Answer 24

the evolution of ecological and phenotypic variation within a multiplying lineage that arises through speciation
- happens from a common ancestor and the difference is genes stems from geographic isolation typically

Question 25

Four Factors of Adaptive Radiation

Answer 25

1. recent common ancestry from a single species
2. Environment-Phenotype correlation
   3 Trait Utility
3. Rapid Speciation

Question 26

What Cause Adaptive Radiation?

Answer 26

1. Ecological Opportunity - if there is an environment with an abundance of resources and a lack of competition
2. High speciation characterizes the clade - in essence certain species, don’t have to rapidly diversify nor have the ability to. they don’t want to move to new areas or just haven’t recognized the opportunity
3. Key innovations - innovations of traits that can further evolution in the future

Question 27

Hybridization

Answer 27

The exchange of genes between species due to occasional interspecific mating
- causes great variation and the potential of speciation, especially with pollyploidy

Question 28

Polyploid

Answer 28

• an organism, tissue or cell that has more than two sets of homologous chromosomes
• Autopolyploid - (AAAA) - reproduces with itself
• Allopolyplloidy (AABB) (reproduces with other polyploids because the conflict of genes is eliminated as AA reacts with the two A alleles present. the same goes for BB)

Question 29

Allopolyploid Complex

Answer 29

• A diploid organism produces haploid gametes
• the haploid gametes of one species interbreed with haploid gametes of another species (AB)
• the chromosomes duplicate themselves and now the polyploid gametes can reproduce with other polyploid gametes from different species

Question 30

Significance of the Evolution of Polyploid

Answer 30

• New species formed as the new populations cannot reproduce with the parent population
• New individuals have unique phenotypes
• The species have a one-up over the parents because of their heterozygosity (hybrid vigor)
• Especially Significant in plants and asexually reproducing individuals - half of flowering plants are due to polyploid origin