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Bio 1M03 > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Sympatric Speciation

A

Natural selection overcomes gene flow and causes speciation of populations despite no physical isolation

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2
Q

Assortative Mating

A

Favor individuals with similar characteristics to others

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3
Q

What are the two mechanisms of sympatric speciations

A

disruptive selection and polyploidization

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4
Q

Disruptive selection as a mechanism of sympatric speciation

A

natural selection for different habitats or resources cause divergence - must be coupled with assortative mating

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5
Q

Polyploidization

A

genetic isolation is created by formation of polyploid individuals that can breed only with each other

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6
Q

Types of polyploidization

A

Autopolyploidy and allopolyploidy

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7
Q

Autopolyploidy

A

polyploids have duplicate chromosome sets from same species (e.g. a chromosome doubling to produce a tetraploid)

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8
Q

Allopolyploidy

A

polyploids have chromosome sets from different species (they originate with a hybridization event, followed by chromosome doubling)

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9
Q

Explain the example of the Soapberry bug for disruptive selection

A

-bugs use beaks to reach seeds inside fruits
-variation in fruit size between nonnative (small) and native (large) causes the population to diverge into a short beaked population and a long beaked population

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10
Q

Explain the example of the maidenhair fern as it relates to polyploids

A

-Example of autopolyploidy
-this species contains diploid and tetraploid individuals
-tetraploids are the offspring of a diploid gamete that is self fertilized
-tetraploid individuals can breed with other tetraploids but not diploids

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11
Q

How do allopolyploid species form

A

-species 1 and 2 undergo meiosis and produce a hybrid individual
-hybrid individual have less efficient homologous pair recognition causing an increase in chance for error during meiosis
-an error in meiosis causes the formation of an allopolyploid cell which has two copies of each chromosome
-a gamete with the same number of cells as the hybrid individual fuses with another identical cell to form a offspring with twice the ancestral genome (diploid to tetraploid)
-leads to reproductive isolation

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12
Q

How does a polyploid cell lead to isolated reproduction

A

if the polyploid and the original species attempt to mate they will produce a species with an odd number of chromosomes whose gametes rarely contain the same number of each type of chromosome causing dysfunctional number of chromosomes and the inability to reproduce

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13
Q

Why is speciation by polyploidization more common in plants than animals

A

somatic cells of plants that have undergone many rounds of mitosis may then undergo meiosis and produce a polyploid gamete, also self fertilization is more common in plants

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14
Q

Adaptive introgression

A

process in which advantageous genetic variation is transferred from one species (or populatiom) to another

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15
Q

Homogenization

A

When gene flow occurs and may erase distinctions between two populations

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16
Q

Possible outcomes of hybridization

A

homogenization, adaptive introgression, reinforcement, development of hybrid zones and speciation by hybridization

17
Q

What happens when isolated populations come into contact

A

when prezygotic isolation dose not exist, populations may interbreed to produce hybrids

18
Q

Reinforcement

A

Selection for traits that isolate populations reproductively - assortative mating
-occurs because of natural selection
-If two populations of differenct speices are extensively diverged, their hybrid offspring may have lower fitness - incomplete postzygotic isolation

19
Q

Explain the Wolf example from lecture on hybrid speciation

A

Red wolves have mitochondrial DNA that is derived from either the gray wolf or coyotes, they could either be from hybrid origin or there could have been extensive gene flow for mtDNA
-Some wolves have a percentage of coyote DNA
-Red wolves are 24% wolf and 76% coyote
-coyotes are a combination of coyote, wolf and dog DNA

20
Q

Internal Nodes on Phylogenetic tree

A

represent ancestors of the descendant taxa

21
Q

Ancestral Node/ root on phylogenetic tree

A

represents oldest ancestor on tree

22
Q

Polytomy

A

3 way split on a phylogenetic tree where there is not enough data to further classify

23
Q

Homology

A

occurs when traits are similar due to shared ancestry

24
Q

Homoplasy

A

when traits are similar for reasons other than common ancestry

25
Q

Convergent evolution

A

when natural selection favors similar solutions to the problems posed by a similar way of life - common cause of homoplasy

26
Q

How do researchers estimate phylogenies

A

they analyze characteristics of species to infer phylogenetic relationships among species

27
Q

Strategies for estimation trees

A

phenetic (distance), cladistic (maximum parsimony), maximum likelihood and bayesian

28
Q

Synapomorphy

A

a novel trait that a clade of organisms have and that others outside this clade lack

29
Q

What is the purpose of Hox genes

A

to regulate differentiation within the adult and embryo

30
Q

How do we know that Hox genes of humans and fruit flies are homologous

A

similar DNA sequence, similar genomic organization, similar expression patterns during development similar function, other species closely related to fruit flies and humans also have Hox genes Max

31
Q

Maximum parsimony

A

logic that assumes that the best explanation or pattern is the one that implies the least amount of change

32
Q

Cryptic species

A

Many species are not easily distinguished by morphology
animal and plant parts also sometimes not easily identified, most diverse parts of the world are least known

33
Q

DNA barcoding

A

-inventory of biodiversity
-automate and expeditated species identification
-classifies based on DNA sequence of one gene

34
Q

Atavism

A

an ancestral characteristic that is lost but then re-emerges during evolution

35
Q

In situ diversification

A

single ancestor disprses across islands and then diversifies
-each species exploits different aspects of the environment
-Not overly diverse

36
Q

Ecotypes

A

genetic variation within a species that allows it to exploit a particular environment

37
Q

Frog dispersal onto island

A

mainland frogs dispersed and then under went adaptive radiation into different ecotypes

38
Q

Parental care in fanged frogs

A

some carry tadpoles on back others guard eggs, some use internal incubation

39
Q

Did fanged frogs undergo an adaptive radiation

A

-diverse and closely related species that vary in useful trait
-trait variation is correlated with environmental variation
-some adaptive radiations exhibit species for species matching

Bio 1M03 (12 decks)

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