Speciation Flashcards
Define Speciation
The formation of new and distinct species in the course of evolution
Define Genetic isolation
Genetic isolation is population of organisms that has little genetic mixing with other organisms within the same species.
name two mechanisms that stop gene flow
Prezygotic isolation & Postzygotic isolation
Define Prezygotic isolation
the separation of different species to keep them from creating offspring by preventing the gametes from forming a zygote.
define Postzygotic isolation
occurs after members of two different species have mated and produced a zygote
define morphological species concept
give advantages and problems with it
Species identified based on differences in size, shape, or other morphological features
- Assumes morphological differences arise from genetic isolation
Advantages:
- easy, useful in the absence of data in gene flow
- can be used for fossils and asexuals
Problems:
-Polymorphic species can be classified as multiple species
-Hard to identify cryptic species
Define Monophyletic group
Consists of an ancestorial population and all its descendants. also called a clade or lineage
Define Synapomorphy
Homologous trait found in common ancestor and descendants but not in more distant ancestors.
a species is defined as the smallest monophyletic group on the tree of life
what is allopatric speciation
occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another.
Define Niche
Range of ecological resources that a species can use and a range of environmental conditions that it can tolerate.
Define Disruptive selection
Can cause reproductive isolation through populations adapting to different ecological niches
and are genetically distinct, hybrid offspring will have If two populations have diverged considerably _____ fitness
Lower
