Lecture 2 - Phylogenies and Speciation Flashcards
1
Q
3 Steps to Develop New Trait
A
- Priming (makes it possible)
- Actualization of the trait (makes it manifest)
- Refinement (makes it effective)
2
Q
Priming
A
Step 1: Mutation becomes possible
- Earlier mutations develop a genetic background on which the desired function is accessible
- Primed generations are more likely to develop the mutation
ex: mutation that results in upregulation of Kreb’s cycle so that citrate may be used more effectively
3
Q
Actualization
A
Step 2: Trait manifests
- Mutation occurs that allows trait to actually occur
- Small but significant competitive advantage
4
Q
Refinement
A
Step 3: Makes mutation effective
- Population with the trait begins to thrive
- Small mutation makes the trait more efective
5
Q
Evolution of the Eye
A
Evolution of a complex trait
- known to have evolved independently 50-100 times
6
Q
Stages of Evolution of the Eye
A
- Priming:
- development of light detecting pigments in common ancestor
- other proteins that were already present for other functions were co-opted to function in the eye - Actualization
- now ready to evolve into a basic eye over and over - Refinement
- refined in each lineage to develop complexities such as color, lens, focusing
7
Q
Evolutionary Constraints (5)
A
- evolution can’t produce any trait we want
1. Environment is constantly changing
2. Dependent on a mutation randomly arising
3. Evolution is limited to physical constraints
4. Adaptations are Compromises
5. Evolutions is limited by historical constraints
8
Q
Environment is Constantly Changing (Evolutionary constraint)
A
- Environment influences what traits would be favored if evolving
9
Q
Dependent on a Mutation Arising (Evolutionary constraint)
A
- Dependent on a mutation randomly arising (if an allele for a given trait does not exist , the trait cannot evolve even if it would be favorable)
10
Q
Limit of Physical Constraints (Evolutionary Constraint)
A
- Evolution is limited to physical constraints
ex: limit to how light but strong birds wing bones can be
11
Q
Adaptations are often compromises (Evolutionary constraints)
examples
A
- horses: thinner legs are lighter and faster but more prone to breaking
- snakes that are resistant to newt toxin are also slower…
12
Q
Historical Constraints (Evolutionary Constraints)
Examples
A
- Modifications of PREVIOUSLY existing structures
- Build up what existed before in small steps
- Not going to start over from scratch
Examples
- Appendix is vestigial organ - don’t need to ruminate grass anymore
- hernias arise because we are built to be quadrupeds and it strains our spine to walk upright
- Hiccups are a reflex to make our now non-existent gills begin working when we are low in oxygen - gills are no longer there but still have the reflex
13
Q
Laryngeal Nerve Example
A
Ex: Historical Constraint
- Path: brain, down the neck, loops through arteries in chest, then up neck to larynx
- Indirect –> not logical
- the way it existed originally was in fish with no necks
- As evolution occurred and animals developed neck, the nerve kept the same path
- resulted in a loop
14
Q
Phylogeny
A
The evolutionary history of relationships among organisms or their genes
15
Q
Phylogenic Tree
and features
A
Diagram used to portray phylogenies
- Based on similarities and differences in physical or genetic characteristics
- Lineages joined together in tree have descended from common ancestor
16
Q
Node (Phylogenic Tree)
A
- split that represents point at which lineages diverged
17
Q
Root (Phylogenic Tree)
A
- The common ancestor of all organisms in a tree
18
Q
Taxon
A
- A group of species designated/named
- ex: humans, primates, vertebtrates
19
Q
Clade
A
- Taxon that consists of all the evolutionary descendents of a common tree
- Are subsets fo larger clades
20
Q
Taxon vs Clade
A
- Taxon is ANY group of species we designate or name
- A clade is a taxon that consists of all evolutionary descendents of a root
- Track clade back to the branch point, everything from that point on is included in the clade
- Clade is a taxon, but a taxon is not always a clade
Reptiles = Taxon but not clade
Clade would also include birds
Mammals = Clade
21
Q
Tree of Life
A
- Phylogenic tree that represents the complete evolutionary history of life
- Describes relationships of all life on earth in an evolutionary context
22
Q
Three main “branches” in tree of life
A
- Bacteria
- Eukarya
- Archaea
23
Q
Homologous Traits
A
Any feature shared by two or more species that have been inherited from a common ancestor
ex: whale fin, human arm, lizard leg, bird wing
24
Q
Ancestral Trait
A
A current trait that was present in the ancestor of its current group
25
Derived Trait
A trait found in a descendant that differs from the ancestral trait
26
Synapomorphies
- Shared derived traits
- Shared through a clade
- A newly derived homology
27
Ancestral vs Derived Traits
Depends on point of reference
Ex: Feathers
Ancestral
- Considered ancestral for any group of modern birds
- Homologous but not a synamopomorphy
- In phylogeny of all living vertebrates, feathers are considered derived
- synamopomorphy
28
Continuity of Evolution
- All species are constantly evolving
| - Doesn't make sense to say some are more highly evolved
29
Convergent Traits/Evolution
- Independently evolved traits subjected to similar selection pressures may become superficially similar
- Similar traits in unrelated organisms
30
Homoplasies
Similar traits generated by convergent evolution
31
Ingroup
Focus of phylogenic tree
32
How are phylogenic trees constructed?
- Can focus on any trait that is genetically determined, and therefore heritable
33
Sources of data for phylogenic trees (5)
Sources of data:
- morphology
- development
- behavior
- paleontology
- molecular data
34
Morphology
Q: Do they look similar?
- presence, size, shape and other attributes of body parts
- Limitations: 1. some diverse species look similar (leopard frogs), 2. hard to compare very distant species (earthworms and humans)
35
Development
Q: Do they have similar traits early in life?
- Similarities in developmental patterns
- Ex: frog larva and seq squirt larva look similar
36
Behavior
Q: Do they behave similarly?
Ex: Flight animals
37
Paleontology
- Fossils provide information about where organisms lived and what they looked like
- Help determine derived ancestral traits and when lineages diverged
- Information on extinct species is often critical to understanding the large divergences among surviving species
Limitations: fossil record is fragmentary and missing for some groups
38
Molecular Data
- Heritable variation is encoded in DNA
- most widely used data for constructing phylogenic trees
- also use mitochondrial, chloroplast and nuclear DNA
- mathematical models to describe how DNA sequences change over time
39
How did self-fertilizing flowers arise?
- Convergent evolution
- NOT members of the same species
- ability arose independently three different times
40
How is the "molecular clock" used to date divergent species?
- Use average rate at which mutations accumulate in a given gene or protein to gauge the timing of divergences
41
Significance of HIV and evolution
- molecular clock can be used to datetransmission of HIV-1 from chimps
- Data suggests the virus was transmitted from chimps to the original human around 1930
42
Binomial Nomenclature
two name system
genus + species
43
Hierarchical Classification (acronym...)
```
Kingdom
Phylum
Class
Order
Family
Genus
Species
```
"King Phillip came over for great spaghetti"
44
"Species"
Typically groups of organisms that mate with one another and produce fertile offspring
(not always clear cut)
45
Species Concepts (3)
- Morphological
- Lineage
- Biological
46
Morphological
- Individuals that look alike
limitation:
- not all members of a species look alike (males, females, juveniles)
- cryptic species morphologically indistinguishable but do not interbreed
47
Lineage
- Species is considered a branch on the tree of life
- speciation is process by which one species splits into two or more daughter species that evolve as distinct lineages
- each lineage starts as a speciation even and ends in extinction or another speciation event
- concept of a species over evolutionary time
48
Biological
Species are groups of inter-breeding natural populations that are reproductively isolated from other groups
49
Reproductive isolation
2 populations no longer exchange genes
50
Polar Bear vs. Brown Bear
- considered to be two different species within genus Ursus
- diverged 4-5 million years ago (lineage concept)
- Can interbreed, produce fertile offspring, have intermittently mated during warming periods (biological concept)
- Cannot survive long in each others climates, have different morphologies, metabolism, social and feeding behaviors (morphological concept)
- most brown bears have 2% polar bear DNA, up to 5/10%
51
Dog vs. Wolf
- dogs were domesticated from the grey wolf (lineage concept)
- both in genus "Canus"
- all breeds of dogs considered same species (biological, not-reproductively isolated = can mate)
- dogs and wolves can also interbreed
- husky looks more like a wolf than a chihuahua but WERE not considered same species
- NOW considered a sub-species of the grey wolf
52
How do new species arise?
1. Reproductive isolation
2. Allopatric Speciation
3. Sympatric speciation
53
Reproductive Isolation
- Requires evolution of reproductive isolation within a species whose members formerly exchanged genes
- As they diverge genetically, they become more reproductively isolated
- May take millions of years or only generations for isolation to develop
54
Allopatric Speciation
* PHYSICAL, aka geographical speciation
- Results when a population is divided by a physical barrier
- Evolve differences because environments are different
- Barrier can form
- Species can cross barrier (founder effect)
55
Prezygotic Reproductive Barriers (5)
- Act BEFORE fertilization to prevent individuals of different species from mating
1. Habitat Isolation
2. Temporal Isolation
3. Mechanical Isolation
4. Behavioral Isolation
5. Gametic Isolation
```
Harry
Took
My
Big
Gun
```
56
Postzygotic reproductive barriers (3)
- Act AFTER fertilization to prevent development of viable offspring or reduce the offspring's fertility
1. low hybrid zygote viability
2. low hybrid adult viability
3. hybrid infertility
57
Habitat Isolation
- Different species have evolved genetic preferences for different habitats to live or mate in
- Never come into contact during mating periods
58
Temporal Isolation
- Different species have distinct mating seasons
| - Different times of year or times of day
59
Mechanical Isolation
- Different sizes and shapes of reproductive organs prevent fertilization
(tiger and house cat...)
60
Behavioral Isolation
- Reject or fail to recognize individuals of other species as potential breeding partners
ex:
- different mating cals
- pollination by specific insect or bird that is not drawn to other types of flowers
61
Gametic Isolation
- sperm of one species does not attach to eggs of another
| - chemically incompatible: attractive signals from egg or ability of sperm to penetrate egg
62
low hybrid zygote viability
- zygote fails to mature normally
- develops abnormalities
- most do not survive birth
63
low hybrid adult viability
- hybrid offspring have lower survivor-ship than purebred offspring
- some different species of salamanders can mate with one another but the hybrid offspring are frail
(ligers?)
64
hybrid infertility
- hybrids may mature normally but are infertile
| ex: mules - healthy but sterile
65
Outcomes in "hybrid zones"
1. Gene pools re-mix and combine into one species
2. Reinforcement
3. Formation of narrow hybrid zones
66
gene pools re-mix and combine
- if hybrids are as fit as individuals of each species
- hybrids will mate with individuals of both parental species
- gene pools will gradually become mixed, resulting in one species
67
reinforcement
- Post-zygotic reproductive barriers reinforce pre-zygotic barriers
- hybrid offspring are less fit --> leads to reproductive isolation
- natural selection favors evolution of pre-zygotic
68
formation of narrow hybrid zones
- hybrid offspring are less fit but reinforcement is not complete
- does not expand because of selective pressure against hybrids
- continues to exist because the two parent species continue to move into it
69
adaptive radiation
- rapid proliferation of species from a single ancestor to fill a variety of ecological niches in a new habitat
- resulting species differ in the characteristics they use to exploit those environments
ex: Hawaiin Islands
- 10,000 species of insects from about 400 immigrant species
- 100 species of birds from 7 immigrant species
- 28 species of silversword plant
70
Sympatric Speciation
- without physical isolation
- species have a preference for certain microhabitats where mating takes place
ex: apple maggot fly
- historically deposited eggs on hawthorn fruits
- 150 yrs ago apple trees introduced, some flies began depositing eggs there
- flies began mating with other flies that preferred apples
ex: Horseshoe bats
- different echolocation call frequencies isolate bats
71
Allopatric vs Sympatric Speciation
Allopatric - species physically cannot get to each other
Sympatric - species, for some reason, choose not to mate with one another
72
Hybrid Zones
- when reproductive isolation is incomplete
- reproductive barriers do not completely prevent individuals from mating
- closely related species may form hybrids in areas where ranges overlap
73
Example of Adaptive Radiation
ex: Hawaiin Islands
- 10,000 species of insects from about 400 immigrant species
- 100 species of birds from 7 immigrant species
- 28 species of silversword plant
74
Rate of Speciation
- occurs at different rates
- the more specialized a species is, the higher the rate of speciation
- subtle differences lead to isolated groups diverging from original
- higher in groups with poorer dispersal abilities
75
Synapomorphies vs Homoplasies
Synapomorphy
- is synonymous with homologous trait
- shared derived trait
Homoplasy
- Traits generated by convergent evolution
- similar environmental pressures allow similar traits to arise in different, unrelated animals
- ex wings in bats and birds - very different structures actually
