lecture 6 Flashcards
what does speciation means?
biological, morphospecies, and phylogenetic
how does speciation affect biodiversity
increases it
what is the main criteria for identifying species?
reproductive isolation
what is the difference between prezygotic and postzygotic isolation?
pre zygotic- isolation before mating
post zygotic- not able to produce offspring that can survive
biological species
reproductive success
morphospecies
new and different species
phylogenetic species
identifies or separates species based on their evolutionary history
allopatry-
populations geographically separated
How does allopatric speciation differ in Dispersal
versus Vicariance?
the movement of organisms from one location to a new location
How does this differ from sympatric speciation?
separation despite living in same area
external events
disruptive selection
internal events
chromosomal mutations
Autopolyploidy
created when mutation leads to double chromosomes all from same species
polyploidy
have more than one set of chromosomes
Allopolyploidy
two different species mate and an error in mitosis occurs creating a viable, non sterile offspring with twice the usual chromosomes
What does Phylogeny actually mean?
evolutionary history of a group of organisms
phylogenetic trees
graphical representation of this history
what is an outgroup
sister group that shares a common ancestor with the taxa being studied but it is not focus of study
ancestral traits
traits in common ancestor
derived traits
traits not present in common ancestor
synapomorphy
trait found in most recent common ancestor but not the older distant ancestors
How do autapomorphies differ from synapomorphies?
autapomorphies only found in a single taxa such as humans
monophyletic group
evolutionary unit that includes an ancestral population and all of its descendants but no others
polyphyletic
are groups that do not include most recent ancestor
paraphyletic
would be a group that include ancestor and most descendants but put all descendants
homology
when traits are similar due to shared ancestry
homoplasy
when traits are similar for reasons other than common ancestry
convergent evolution
common cause of homoplasy
fossil
any physical remains of an organism that has extinct in the past
fossil record
total or complete collection of all fossils found around the world so far
what are the 4 main limitations
- habitat bias
2.taxonomic and tissue bias - temporal bias
4.abundance bias
Cambrian explosion
went from unicellular organisms to major villa a emerged into a short period of time
what is Cambrian explosion an example of
adaptive radiation
What are 4 hypotheses that can
explain how Cambrian Explosion happened?
- higher oxygen levels
- evolution of prediction
- new niches
- new genes
mass extinction
a wide spread event that wipes out the majority of living plants and animals
background extinction
refers to the normal extinction rate
how many big pass extinctions have there been
5