Genetic Variability
factors:
Gene flow
(321), Genetic
Drift (322),
Non-random Mating
(sexual selection) (323), mutations,
Natural Selection
(324) Hardy-Weinberg
Equilibrium: READ
In order for
there to be NO evolution, the following assumptions must be met (in
reality, only hypothetical):
· The population must be very large, no genetic drift occurs
· There must be no movement into or out of a population
· There must be random mating
· There must be no mutations within the gene pool
· There must be no natural selection
(read
more...)
Speciation
(326-331), gradualism and
punctuated equilibrium (330)
Adaptive Radiation
(309)
Divergent Evolution
(309)
(flightless birds)
(How do YOUR parts match up with other creatures?)
Convergent Evolution
(309)
Coevolution (310)
Gradual Extinction: usually
occurs at a slow rate and may be due to other organisms, changes in
climate, or natural disasters. Speciation and gradual extinction
occur at approximately the same rate.
Mass Extinction:
usually occurs when a catastrophic event changes the
environment very suddenly (such as a massive volcanic eruption, or a
meteor hitting the earth causing massive climatic changes). It is
often impossible for a species to adapt to rapid and extreme
environmental changes.
Scientific evidences, sources of
data for Evolution:
Field of Anatomy
(305)
ESKELETONS
* Scientists study homologous structures as one form of evidence to
determine the possible relationship between the evolutionary paths
of two species.
> Organisms which have diverged from a common ancestor often
have homologous structures
(similar characteristics resulting from common
ancestry). The greater the numbers of shared structures between two
species, the more closely the species are related.
> Many species have vestigial
organs (structures with little or no
function to the organism) that are remnants of structures that had
important functions in ancestors of the species. The vestigial
organs of one species are often homologous with structures in
related species where the structure has remained functional.
* Also, the study of the anatomy of species located in different
geographical locations reveals that species living in different
locations under similar ecological conditions developed similar
structures and behaviors.
* If a species encountered a different ecosystem due to a change in
geographical location,favorable anatomical traits become
established. A new species evolves with a shared common ancestor
from the original population. See also
Phylogeny (307).
Field of Embryology
(305)
Watch this!
* Sometimes similarities in patterns of development
or structures that are not obvious in adult organisms become evident
when embryonic development is observed.
* The embryos of vertebrates are very similar in appearance early in
development but may grow into different structures in the adult
form.
Field of Biochemistry
(306)
The more similar the DNA and amino acid sequences in
proteins of two species, the more likely they are to have diverged
from a common ancestor.
* Biochemistry provides evidence of evolutionary relationships among
species when anatomical structures may be hard to use. For example,
>when species are so closely related that they do not
appear to be different, or
>when species are so diverse that they share few
similar structures.
Field of Paleontology
(302)
* The fossil record provides
valid evidence of life forms and environments along a timeline and
supports evolutionary relationships by showing the similarities
between current species and ancient species.
* Comparing current and ancient species shows a pattern of gradual
change from the past to the present.
* Examining the fossil record of Earth reveals a history that tells
a story of the types of organisms that have lived on Earth
(including those that are extinct) and the relative ages of those
fossils.
* The fossil record is not complete because most organisms do not
form fossils. Many of the gaps in the fossil record have been filled
in as more fossils have been discovered.
* The older the fossils, the less resemblance there is to modern
species.
Geographic Distribution
(Also, read here)
"Another clue to
patterns of past evolution is found in the natural geographic
distribution of related species. It is clear that major
isolated land areas and island groups often evolved their own
distinct plant and animal communities. For instance, before
humans arrived 60-40,000 years ago, Australia had more than 100
species of kangaroos, koalas, and other
marsupials
but none of the more advanced terrestrial
placental mammals
such as dogs, cats, bears, horses. Land mammals were entirely
absent from the even more isolated islands that make up Hawaii
and New Zealand. Each of these places had a great number of
plant, insect, and bird species that were found nowhere else in
the world. The most likely explanation for the existence of
Australia's, New Zealand's, and Hawaii's mostly unique biotic
environments is that the life forms in these areas have been
evolving in isolation from the rest of the world for millions of
years."
from
Evidence of Evolution
http://anthro.palomar.edu/evolve/evolve_3.htm
Field of Ichnology
(What?! Eeewww...)
Phylogenetic Trees (307)
site 1
site 2
Wow,
site 3...
The tree of life.
Click to download this pdf, then
enlarge.
The rise of the modern horse...
What was
Archaeopteryx?
Interesting insight from a blogger,
godot
Genes coding for enzymes are hard to mutate, its too
easy to break one of these molecular machines, so gene control here would be a
light-toggle that sometimes sparks.
But many developmental traits are controlled not so much by protein sequence,
but by the timing/amount of their production. Much variation in dog breeds can
be accounted for by varying repeats of what was once thought "junk" DNA between
the transcribed gene and promoter sequences upstream.
http://www.pnas.org/content/101/52/18058.full
Repetitive DNA is commonly miscopied during meiotic crossover, so there's a
built-in source of variation that is more akin to a fader than a toggle. Its
easy to imagine an isolated population drifting/being selected by "fader"
increments till it was behaviorally or physiologically unlikely to interbreed
with the parent population, and speciation occurs. If it outcompetes the parent
species, Voilla! the paleontological punctuated equilibrium is explained.
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Evolution
