Economic Evolutionary Domain (Macroevolution) Overall outcomes of evolution creates (and destroys/extinction) species. What 2 things are necessary to define a species? These are members of different species - eastern (left) and western (right) meadowlark.
How many species is this?
.
What mode of selection leads to the development of a new species? WHY? Disruptive/Diversifying!
Timing of speciation Branching pattern called punctuated equilibrium (branching) is the widely accepted model called cladogenesis. (Gradualism called anagenesis, is not supported with any evidence!) This means that organisms are relatively static (stable) in their phenotypic expression until a drastic environmental force occurs, then there are periods of great phenotypic change again followed by periods of calm.
Reproductive isolation ends in speciation as if you can t get to each other, you can t interbreed! Two ways to stop gene flow. (Isolate): Externally (extrinsic) separate meaning due to an outside force and then once separated 2) Internally (intrinsic) separate meaning due to reproductive isolating mechanisms. (Which has to happen first?) Geographic isolation (vicariances) are the causes of extrinsic separation. There are 2 types of this; 1) Allopatric speciation- separation caused by a physical barrier 2) Parapatric speciation separation caused by unique habitat adaptations. (Niches)
Allopatric Speciation Harris antelope squirrel White-tailed antelope squirrel
So what happens after they are separated and enough time goes by.. Once populations are separated, each population/species continues to evolve independently of the other group. Therefore even if they were allowed physical contact, they don t recognize each other as mates. Recognition means economic or codical recognition! The mechanisms that maintain the integrity of a species are called Sympatric speciation mechanisms. These mechanisms preserve the 2 species and maintain their separation. (Internal mechanisms). Isolation can cause rapid exaptations as organisms face new challenges in new environments.
Sympatric Mechanisms Are Always Required to MAINTAIN Speciation Harris antelope squirrel White-tailed antelope squirrel Internal mechanisms involve changes to organisms that prevent Interbreeding, EVEN if they try!! Once either allopatric or parapatric speciation occurs (external), than internal mechanisms come into play. (AFTER the populations are physically/habitat separated.)
2 areas where sympatric speciation mechanisms can be actively maintaining the separateness of each species: 1) Pre-zygotic-pressures/mechanisms that keep fertile/viable offspring from developing BEFORE a zygote is formed 2) Post-zygotic-pressures that keep fertile/viable offspring from developing AFTER a zygote forms
4 PREZYGOTIC Mechanisms 1) Behavioral- courtship rituals do not match up. 2) Mechanical- anatomical differences. 3) Gametic- chromosome # too different 4) Temporal- Breeding seasons do not match
https://www.youtube.com/watch?v=1xkpen3awie 1:49 http://www.youtube.com/watch?v=gpbwjpsbpda http://www.youtube.com/watch?v=vje0kdfos4y&t=115s http://www.youtube.com/watch?v=ei_qujrrgxk&t=138s http://www.youtube.com/watch?v=l54bxmzy_ne&feature=related / http://www.youtube.com/watch?v=vdhnutbxpfe
POSTZYGOTIC MECHANISMS- Occur after the egg and sperm fuse, but no new species made! http://www.youtube.com/watch?v=1zowyj59bxi&t=87s
Species Come and Go Evolutionary process does NOT produce the perfect organisms for all time. It produces the best possible for a given set of standards. (environmental) Best estimates from the fossil record indicate that greater than 99% of species that have ever existed are now extinct. A typical lifetime for a species is about 1 million years.
Mass Extinctions Are a Fact of Life
The Cretaceous/Tertiary Mass Extinction Gary Larson
The Linnaean Hierarchical Classification System ADD DOMAIN!
Cladistics proceeds by comparing shared ancestral and shared derived characters between sets of organisms. A Better Way to Classify Organisms Ideally, classification is based on establishing the evolutionary relationships between organisms. The evolutionary relationship between organisms is their phylogeny. Cladistics is the method of classification based on establishing phylogenies (i.e. getting at evolutionary relationships.
Results of Cladistic Analyses Sometimes Run Counter to Classical Classification Schemes Which pair is more closely related? A lizard/crocodile or bird/crocodile?