Lecture 9 Flashcards

1
Q

what was the confusion about the link between micro and macroevolution?

A

can processes of microevolution lead to macroevolution?

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2
Q

taxonomic (morphological) species concept

A

based primarily on distinct measurable differences

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3
Q

biological species concept

A

based on inter-fertility among individuals

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4
Q

why is it so hard to define a species?

A

concepts vary among groups of organisms and among scientists. There is no universal species concept.
- geographic isolation alone is NOT sufficient
- isolation does NOT have to be absolute (what cutoff?)

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5
Q

Darwin’s definition of a species

A

groups of organisms that are sufficiently similar in phenotype

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6
Q

Ernst Meyer’s view on distinguishing species

A

reproductive isolation as key to distinguishing species

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7
Q

what species does the BSC not apply to?

A

does not apply well for bacteria, asexuals, highly self-fertilising species…or fossils

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8
Q

allopatric speciation

A

often called geographic speciation
- due to involvement of geographical isolation
- much more common and easier to evolve

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9
Q

stages where reproductive isolation can occur

A

pre-zygotic:
- finding a compatible mate and mating
- fertilisation
post-zygotic:
- development and growth of zygote (F1)
- adult survival & reproduction
- growth, survival, reproduction of offspring (F2)

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10
Q

pre-zygotic barriers

A

prevent mating or fertilisation so no zygote is formed:
- geographical, ecological
- temporal, behavioural (mate recognition)
- mechanical (genital stricture compatibility)
- cellular (sperm-egg compatibility)

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11
Q

use Rhagoletis pomonella (Apple Maggot Flies) as an example of pre-zygotic isolation

A
  • host shift after arrival of domesticated applies in 1800s
  • differences in timing of host planting fruiting (apple vs hawthorn)
  • different timing of fly mating on preferred host plant)
  • reduces fly gene flow by 94% in sympatry (same region)
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12
Q

describe pre-zygotic isolation in abalone

A

binding of sperm lysin protein to egg vitelline envelope receptor (VERL) required for fertilization (molecular lock and key)
Lysin/VERL interaction has coevolved
– Different evolutionary changes in different species
– Causes reproductive isolation due to fertilization
incompatibility

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13
Q

post-zygotic barriers

A

prevent proper functioning of zygotes
once they are formed
* Caused by combinations of genes with low fitness in the
hybrid
* Arise as an indirect byproduct of evolution acting
separately in different populations (cannot be directly
favored by natural selection)

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14
Q

intrinsic post-zygotic barriers vs extrinsic post-zygotic barriers

A

Intrinsic Post‐zygotic Barriers:
* Inviability, sterility, or abnormal development of hybrids
Extrinsic Post‐zygotic Barriers:
* Ecological mismatch of hybrid phenotype to environment

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15
Q

example of intrinsic post-zygotic isolation

A

Mule is a sterile hybrid cross of:
* Male donkey (62 chromosomes)
* Female horse (64 chromosomes)

Hinny is a sterile hybrid of:
* Male horse (64 chromosomes)
* Female donkey (62 chromosomes)

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16
Q

relation between genetic distance and post-zygotic isolation in fruit flies

A
  • The more that fly pairs are genetically differentiated,
    the more likely they are to be reproductively isolated
17
Q

example of extrinsic post-zygotic isolation

A

aposematic helicons butterflies
Hybrids have aberrant colour patterns
* Higher predation risk
* Lower mating success

18
Q

local adaptation by different populations can lead to

A

reproductive isolation and speciation

19
Q

distinct evolutionary responses happen due to

A

different selective pressures

20
Q

is local adaptation necessary for speciation?

A

Local adaptation not absolutely necessary, but accelerates population divergence and
evolution of RI

21
Q

describe sticklebacks in marine and freshwater environments

A

In marine environment:
– Bony armor protects against large fish predation
In freshwater:
– Loss of armor increases growth rate
– Greater winter survival
– Earlier breeding

22
Q

so, can microevolution lead to macroevolution?

A

yes - as populations diverge genetically as a result of evolutionary forces
(mutation, natural selection, genetic drift), they become reproductively
isolate

23
Q

define and describe adaptive radiation

A

The evolution of ecological and phenotypic diversity within a rapidly multiplying lineage
– Originates from a single common ancestor
– The process results in an array of many species
– The species differ in traits allowing exploitation of a range of habitats and resources

24
Q

Four features commonly identify an adaptive radiation

A

1) Recent common ancestry from a single species
2) Phenotype‐environment correlation
3) Trait utility
4) Rapid speciation

25
define ecological opportunity
the absence (or reduction) of competition for resources
25
two things that cause adaptive radiation
ecological opportunity and high propensity for speciation
27
how does ecological opportunity come about?
Colonization of competition‐free regions (e.g., islands, lakes, or continents) Extinction (which can eliminate competitors) Key innovation (evolution of a trait that provides access to new resources)
28
high propensity for speciation
RI evolves more readily in some clades than others
29
define hybridisation
The exchange of genes between species as a result of occasional inter‐species mating – Sometimes can reverse speciation process to merge two groups into one
30
how does hybridisation vary across the tree of life?
common in plants and fish, rare in mammals
31
how can hybridisation result in complex patterns of variation?
Can be evolutionarily significant for speciation, especially by polyploidy
32
define polyploidy
Describes an organism, tissue, or cell with more than two complete sets of homologous chromosomes
33
define and describe allopolyploidy
Allopolyploidy (e.g. AA x A*A* -> AA A*A*) – Arises from duplicated karyotype following hybridization between species – Commonest type of polyploidy
34
define and describe autopolyploidy
Autopolyploidy (e.g. AA -> AA AA) – Arises from duplicated karyotype within a species (e.g. non‐disjunction)
35
describe how allopolyploid hybridisation comes about
1. Two species mate and produce an F1 hybrid offspring (genotype AA*) 2. F1 hybrid offspring produces unreduced diploid gametes (genotype AA*) due to meiotic nondisjunction 3. Diploid gametes combine to produce tetraploid F2 offspring 4. Tetraploid is fertile, but is reproductively isolated from parental species
36
evolutionary significance of polyploidy
Polyploids are reproductively isolated from their diploid parents – Hence a form of sympatric speciation * Polyploids exhibit novel phenotypes – Allows exploitation of new habitats * Polyploids often show hybrid vigor due to heterozygosity, particularly in allopolyploids * Polyploid origin for ~50% of flowering plants – Many crop plants & invasive species Evolutionary Significance of Hybridization© BIO120 Fall 2024
37
draw the speciation continuum