Unit 7: Speciation, Phylogenetics, and Evidence of Evo. Flashcards
Define
Convergent evolution
Two species that share similar traits due to environmental pressure and not common ancestry
Define
Divergent evolution
Two species with traits that differ due to unique selective pressures but share common ancestry
Define
Punctuated equilibrium
Periods of genetic equilibrium interspersed by rapid periods of evolutionary change
Define
Gradualism
Pattern of slow, continuous evolution
Define
Adaptive radiation
Rapid divergent evolution that occurs when one group enters an area that is unoccupied by similar groups
Explain the term
Common Ancestry
Two groups that diverged from a single ancestral species;
Ultimately, all species are thought to have arisen from one single common ancestor
Define
Phylogeny
Evolutionary history of species
List
Three major “branches” on phylogenetic tree of all life
Domains:
- Archaea (Archaebacteria)
- Bacteria (Eubacteria)
- Eukarya
Describe
Homologous structures
Physical structures that are similar between species who share a common ancestor, but may have different functions
Provide examples of
Homologous structures
Limbs of all tetrapods, which usually have a single long bone, a pair of long bones, many short bones, and digits
Ex: Human arm, cat’s leg, bat’s wing, whale’s fin
Define
Analogous structures
Physical structures that share common functions but evolved via convergent evolution (and thus are not due to common ancestry)
Provide examples of
Analogous structures
A bird’s, bat’s, and butterfly’s wing
Define
Theory
A well-supported explanation of why a particular phenomenon occurs
Define and give an example of
Vestigial structures
Structures that have no function but are present because they served a function in the ancestor;
ex: human appendix function is greatly reduced but was used by ancestors for aiding in the digestion of fibrous foods
Explain
Fossil Dating
- compare fossil to known age of rock layer
- Carbon-14 dating, where carbon isotopes (C-14) have a known rate of decay and can be measured to approximate age of the organism
Describe
Molecular homologies
as a source of evidence for evolution
Groups with most recent common ancestor tend to have fewer differences between their DNA sequences (less time for mutations to accrue)
Comparing DNA or amino acid sequences can be used to determine when two species shared a common ancestor
Describe
Embryologic development
as a source of evidence for evolution
Controlled by genes which are shared among descendents of common ancestors.
Closely related organisms undergo very similar embryonic developmental stages.
Similar development also helps account for homologous structures
List
Evidence of common ancestry in eukaryotes
-Linear chromosomes
-Membrane-bound organelles
-Genes with introns
Define
Biogeography
The geographic distribution of species and fossil evidence of those species’ ancestors
How does biogeography support evolution?
Divergence of groups can be traced to movement of Earth’s land masses (techtonic plate movement, changes to terrain);
Groups that diverged most recently are most clustered together, whereas those with distant common ancestors are more widely distributed, because all continents were once joined together
Describe how to
Construct a cladogram and/or phylogenetic tree
Compare traits of each group;
Place those with similar traits closest together to maximize parsimony;
Limit the independent emergence of traits in separate lineages
Define
Speciation
The divergence of one species into separate species
Define
Species
(Biological Species Concept)
A group of organisms that are capable of reproducing and making fertile offspring
What is wrong with the biological species concept?
Not very “neat”
-Ring species may exist, where populations A and B can mate, and B and C can mate, but A and C cannot
-Does not apply to extinct species
-Does not apply to species that reproduce asexually
-Difficult to apply to groups that are physically separated but could potentially mate
Define
Sympatric speciation
Speciation that occurs without physical separation of the groups
Define
Allopatric speciation
Speciation that occurs due to the physical separation of groups
What condition is necessary for speciation to occur?
Reproductive isolation
State two types of
Reproductive isolation
Pre-zygotic and post-zygotic
Define and give examples of
Pre-zygotic isolation
The separation of two groups that prevents the formation of a zygote
Examples: Habitat, temporal, behavioral, mechanical, and gametic isolation
Define and give examples of
Post-zygotic isolation
Processes that prevent a hybrid zygote from contributing to the gene pool
Examples: low hybrid viability, hybrid infertility, hybrid break-down
Define and provide an example of
Geographic isolation
Reproductive isolation due to physical barriers between species
Example: Squirrels on the north and south ridges of the Grand Canyon
Define and provide an example of
Habitat isolation
Reproductive isolation due to different habitats
Example: Lions and tigers, whose habitats differ so they rarely encounter one another
Define and provide an example of
Temporal isolation
Reproductive isolation from different mating times / seasons
Example:
Define and provide an example of
Behavioral isolation
Answer
Define and provide an example of
Mechanical isolation
Answer
Define and provide an example of
Gametic isolation
Answer
Define and provide an example of
Hybrids
Answer
Define and provide an example of
Low hybrid viability
Answer
Define and provide an example of
Hybrid infertility
Answer
Define and provide an example of
Hybrid breakdown
Answer
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