economic evolutionary domain (macroevolution) · economic evolutionary domain (macroevolution)...
TRANSCRIPT
What 2 things are necessary to define a species?
Economic Evolutionary Domain (Macroevolution)
Overall outcomes of evolution creates (and destroys/extinction) 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
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.
So what happens after they are separated and enough time goes
by…..
Sympatric Mechanisms Are Always Required to MAINTAIN
Speciation
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.)
Harris’ antelope squirrel White-tailed antelope squirrel
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
http://www.youtube.com/watch?v=eI_quJRRGxk&t=138s
http://www.youtube.com/watch?v=VDhNutbXpFE
http://www.youtube.com/watch?v=L54bxmZy_NE&feature=related /
http://www.youtube.com/watch?v=VjE0Kdfos4Y&t=115s
http://www.youtube.com/watch?v=GPbWJPsBPdA
https://www.youtube.com/watch?v=1XkPeN3AWIE 1:49
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
Gary Larson
The Cretaceous/Tertiary Mass Extinction
The Linnaean
Hierarchical
Classification System
ADD DOMAIN!
A Better Way to Classify Organisms
Ideally, classification is based on establishing the evolutionary relationships
between organisms.
Cladistics is the method
of classification based
on establishing
phylogenies (i.e. getting
at evolutionary
relationships.
The evolutionary relationship between organisms is their phylogeny.
Cladistics proceeds by
comparing shared
ancestral and shared
derived characters
between sets of
organisms.
Results of Cladistic Analyses Sometimes Run Counter to Classical
Classification Schemes
Which pair is more closely related? A lizard/crocodile or bird/crocodile?