Exam 2 Powerpoints Flashcards
Analogous traits
similarities that are independently evolved or convergent
not used in cladograms
branch points
speciation events
Darwin described…
a “Great tree of Life”- the beginning of phylogenies- linked embryology, genetics, medicine, etc.
Organisms united by shared ancestry
Pros & Cons of the Analysis of Fossils
P: Direct
C: fragmentary, hard to interpret
phylogenetic analysis
compare similarities of organisms (molecular)
construct cladograms
systematics
classification to reflect the phylogeny of organisms
monophyletic
shared derived trains
an ancestor and all of its descendant
polyphyletic
convergent similarity
analogous structures
paraphyletic
an ancestor and some of its descendants
Goal of Phylogenetics
monophyletic groups- accurately describe relationships
Two Cladistic Methods
- out group analysis
2. Parsimony
taxon
group of similar and related individuals
phylogeny
patterns of lineage branching produced by the truth evolutionary history of the organisms being considered
cladistics
school of systematics using only homologous, shared derived characteristics
clade
monophyletic groups- a group of species that includes an ancestral species and all of its descendants
speciation
the origin of new species, is at the focal point of evolutionary theory
microevolution
consists of changes in allele frequency in a population over time
macroevolution
refers to broad patterns of evolutionary change above the species level
species concept
members have the potential to interbreed
some hybridization is i.k. as long as it is natrual
ecological
viewed in terms of a niche
pre zygotic barriers
prevent formation of a zygote or fertilized egg
post zygotic barriers
prevent development of viable or fertile offspring
What separates species? (Prezygotic)
- habitat isolation
- temporal (timing) isolation
- behavioral isolation
- mechanical isolation
- Gametic Isolation
Habitat Isolation
Pre.
may occupy the same range and be potentially able to hybridize, but prefer different habitats so never (or rarely) mate.
(i.e. maggots)
Temporal Isolation
Pre.
may potentially interbreed, but are :ready” at different times
(i.e. breeding times in frogs)
behavioral isolation
pre.
species may encounter each other, but do not mate because of differences in courtship or other behaviors
(i.e. bird courtship & songs, firefly blink pattern)
mechanical isolation
pre.
differences in anatomy
especially in flower and insects
Gametic Isolation
pre.
gametes do not recognize each other due to different receptors
What separates species post zygotically?
- reduced hybrid viability
- hybrid infertility
- hybrid breakdown
reduced hybrid viability
post
hybrid offspring do not develop
hybrid offspring do not survive as well
(i.e. stickleback: Benthics vs. Limnetics)
hybrid infertility
post
the hybrids are not fertile
(i.e. mules, Tigons etc.)
STERILE
hybrid breakdown
post
1st generation hybrids are fertile, but 2nd generation are sterile or weak (i.e. in some plants)
How do differences arise?
- allopatric speciation
2. sympatric speciation
allopatric speciation
physical barrier divides population (vicariance)
(i.e. rise of a mountain range, formation of a river/valley, changes in sea level, or migration to an island or a new habitat)
adaptive radiation
(speciation on islands)
evolution of many diversely adapted species from a common ancestor
Populations become different due to..
founder effect at outset (especially if one or both of the new populations are small) through genetic drift
- natural selection under different conditions. May result in physical or behavioral differences that inhibit breeding even if contact is restored.
Reinforcement
hybrid offspring have lower survival, so selection favors assortative mating
hybrids gradually cease to form
fusion
large areas of hybridization and highly fit hybrids may fuse the two species back into one
Re-contact may overwhelm differences acquired in isolation
sympatric speciation
no physical barrier separating diverging populations (ecological isolation, auto and allopolyploidy)
allopoloploidy
hybridization and errors in meiosis lead to polyploid offspring with chromosomes from 2 different species
Evolution is a tinkerer
when evolution gives something a function…. turns a leg into a wing or a part of a jaw into ear pieces
macroevolutionary patterns
broad-sale patterns of change, diversification and extinction in the fossil road
macroevolutionary patterns
- gradualism
2. punctuated equilibrium
gradualism
classic darwin
generally slow and constant change
distinction among fossil species fairly arbitrary
claims that gradual change is a predominant pattern
punctuated equilibrium
emphasizes periods of stasis interspersed with periods of “rapid” change
emphasizes that most change occurs at speciation
what causes stasis?
stabilizing selection
variable directional selection
genetic/ developmental constraints
6 origins of evolutionary novelty
- exaptation
- duplication
- serial homology
- heterochrony
- lateral gene transfer
- homeotic genes and pattern formation
exaptation
evolution is a tinkerer
(i.e.
