Zusammenfassung der Ressource
Speciation and
Macroevolution
- macroevolution
- is
- measured as change in allele
frequencies in a population
over generations, evolution
on a large scale
- another concept is the
- biological species concept
- relies primarily on reproductive isolation
rather than trait differences or shared
evolutionary history to define the species
- reproductive isolation before fertilization
- is called
- prezygotic isolation
- and after fertilization is
- postzygotic isolation
- a
- zygote
- is the
- first cell that results
when the egg is fertilized
- but
- reproductive isolation
- is when
- physiological, behavioral, and genetic
processes that inhibit interbreeding
- there are mechanisms such as
- prezygotic isolating
mechanisms
- that
- prevent reproductive attempts or
make it unlikely that fertilization will
be successful if mating is attempted
- these isolating mechanisms
make highly unlikely
- hybridization
- or the
- mating between 2 species
- postzygoitic isolating mechanisms
- operate after formation of the
zygote, prevents hybrid
offspring from developing
- reinforcement
- is given
- to the process of the natural
selection that reinforces
reproductive isolation
- speciation
- is
- the splitting of one species
into two or more species
- scientists define species based
on many types of evidence
- a
- taxonomist
- a scientist that classifies organisms into groups,
makes a working hypothesis about whether they are
different species based on the evidence provided
- we can study
- species concepts
- different ways in which
a species is defined
- Linnaeus
- is the
- father of taxonomy
- identified new species by
differences in their appearances
- which is
- morphology
- in the
- morphological species concept
- each species is defined by one or
more distinct physical characteristic
- called
- diagnostic traits
- some organisms look so similar that
they appear to ve the same species
- these are
- cryptic species
- species that look almost
identical but are very
different in other traits
- then there was
- the evolutionary species concept
- it was proposed to explain
speciation in the fossil record
- the there was the
- phylogenetic species concept
- an evolutionary "family tree" or
phylogeny used to identify species
based on a common ancestor
- in a phylogeny there is
- a monophyletic
- a branch that contains all of the
descendants of a common ancestor