Biology 108- Systematics
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What is phylogeny?
grouping or naming organisms based on evolutionary history.
What is a Cladogram?
branching diagrams that illustrate evolutionary relationships.
What is a Clade?
a group of organisms related through evolution.
Ingroup vs. Outgroup?
The ingroup is the group that is being studied. The outgroup is related to the ingroup but diverged through evolution.
What is an "Event"?
A change from the ancestral state. Either a loss or gain of a trait.
Derived vs. Ancestral in building a cladogram
Derived=1 (Has the characteristic) different than the outgroup
- Ancestral=0 (Doesn't have the characteristic)
- is an outgroup state
What is Synapomorphy?
- shared derived characteristics.
- Ex. both a turtle and leopard have an amniotic egg.
- Useful in creating phylogenetic relationships
What is a Symplesiomorphy?
- Shared, Ancestral state by two or more taxa therefore not useful in determinig
- can NOT be used in phylogeny.
Homology vs. Homoplasy
Homologous: look the same and have the same evolutionary origin.
Analogous/Homoplasy: appear the same, evolve independently. Do NOT use in tree
What is Convergent evolution?
- Features that different species posses that have a similar structure but there is no common ancestor. Usually caused by similar environments.
- Creates analogous features.
- Ex. birds and bats
Polyphyletic vs. Paraphyletic
- Polyphyletic: accidentally placing species on a cladogram that don't care a common ancestor.
- Ex. Bats and Birds
- Paraphyletic: accidentally removing a species from a clade that does have a common ancestor.
- Ex. birds removal from the Reptilia clade
- Often due to species appearing different from rest if clade.
Molecular Phylogenetics-How do you know the degree of relatedness of species?
- Look for matching bases in the gene sequences. More matches= more closely related.
- Become increasing dissimilar as they evolve from their common ancestor.
What is a taxon (or taxa) ?
a group of one or more populations of organisms that can be considered similar/together
What is a monophyletic clade?
It is an ideal taxon, descended from a single organism.
What did Cuvier believe?
- Species do not change over time.
- A catastrophe wipes a species out and then a new species moves in to that area (explanation for fossils)
What did Lamarck believe?
- inheritance of acquired traits.
- Giraffes necks stretched and passed that trait on.
What did Darwin conclude?
- Natural Selection. Species change over time, descent with modification (evolution)
- studied finches on Galapagos Island
Genotypic vs. Phynotypic
- genotypic: genetic makeup
- phynotypic: form, function, behavior.
What's a vestigial structure?
- structures or attributes that have lost their function throughout evolution. A result of evolution rather than intelligent design.
- Ex. pelvic bones in whales and snakes.
How is meiosis a source of variation? (steps)
Mutation (random changes in DNA) -> Recombination (crossing-over) ->Independent assortment (of chromosomes) -> Fertilization (sexual reproduction)
Define a gene
- combination of two alleles
- -in diploid individuals
- There is one allele per chromosome (one from each parent in sexual reproduction)
- Blending of two alleles.
- Ex. a white and red snapdragon create a pink snapdragon.
proportion/% or a specific genotype within a population.
proportion/% of specific allele within a population.
Define evolution in terms of alleles.
Change in alleles in a population between generations.
Can populations and individuals evolve?
Only populations can evolve, individuals cannot.
List the four factors that can change allele frequency.
- 1. Mutation
- 2. Genetic drift
- 3. Gene flow
- 4. Natural selection
What causes a mutation?
- An error in DNA replication, structural damage (ex. radiation), or it can be random.
- -result can be positive, negative or neutral
What is Genetic Drift?
changes in allele frequency due to chance (not caused by natural selection). Have a greater effect in small populations.
Genetic drift: Founder Effect
A small part of the population is separated (usually geographical). There are less different genes in this new gene pool.
Genetic drift: bottleneck effect
Natural disaster( human activity etc) wipes out a portion of the population. The remaining population has different gene frequencies than the previous one. Often results in inbreeding.
What is gene flow?
- transfer of genes/alleles between populations.
- Ex interbreeding and migration
Extreme phenotypes are favored, often a response to constant change in environment.
Extremes are favoured. Results in polymorphism (2 or more divergent phenotypes)
- Intermediate/common phenotypes are favoured. (opposite of disruptive, selection against extremes)
- -little/no evolutionary change
Frequency Dependent Selection.
- Rare genotypes are favoured
- advantage can come and go
evolution at the population level, occurs mainly through selection or drift.
- Evolutionary change above species level.causes speciation
What is the Biological species concept?
Individuals that can interbreed but don't have the same appearance.
What is the Ecological species concept?
Species adapted to the same niche in an environment.
What is the Phylogenetic species concept?
- A species share a common ancestor and have certain defining characteristics.
- not as restrictive as biological, don't have to interbreed.
List the five types of Prezygotic isolation:
- 1. Ecological (habitat)
- 2. Temporal ex. different mating schedules
- 3. Behavioral
- 4. Mechanical isolation (incorrect genitalia)
- 5. Gamete isolation (sperm can't fertilize egg)
List the three types of postzygotic isolation.
- 1.zygote death
- 2. hybrid sterility (offspring can't reproduce)
- 3. fitness (can't reproduce therefore lower fitness)
How do hybrids speed up reproductive isolation and speciation?
When different hybrid species mate they produce offspring with lower fitness making it beneficial for them to avoid mating outside of their "hybrid group"
- forms without geographic barrier.
- Includes: habitat selection, temporal isolation and assortive isolation.
Explain the two "paces" of evolution.
- 1. slow- gradual differentiation by natural selection
- 2. rapid change followed by long periods of stasis.
- Neither are right, both can occur.
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