Download Evolution Basic Forces

Evolution
Basic Forces (what is needed for an
evolvable system)
Evolution – Basic Forces
• Self-replication - reproduction
• Heritability - a system by which characteristics
can be passed from one generation to the
next (here on Earth, DNA is that system).
• Genetic mutation – mistakes in copying DNA
and environmental mutagens.
• Genetic variation
• Natural and artificial selection
What is needed for an evolvable
system?
• Self-replication (Reproduction) – The
organism/molecule is able to reproduce (make
more of itself).
• Heritability - a system of inheritance (such as
DNA or RNA) that allows the passing on of
traits from one generation to the next.
Genetic Mutation
• Mutation results from errors in the
replication of genes and changes caused by
mutagens (such as chemical and
environmental agents)
– Creates new characteristics
– Mutation creates variation (without mutations,
there is no genetic variation).
Genetic Variation
• Genetic Variation describes naturally
occurring genetic differences among
individuals of the same species.
– Differences are hereditary.
– Without variation, selection has nothing on which
to work.
– Variation is the result of genetic mutations.
Genetic Variation
Dogs are the result of
the natural variation
found in the wolf’s
genome plus heavy
selection pressure.
Selection – Evolution’s Creative Force
• Selection results in adaptation – it is the
differential survival of heritable characteristics
through competition (intra and interspecies).
– Natural selection if selective force is the
environment (“nature”).
– Artificial selection if humans are the explicit
selective force.
– Selection is non-random.
Selection – Evolution’s Creative Force
• Due to our impact on the environment, we are
always part of the selective environment
(forces of selection).
Mutation and Selection
http://www.npr.org/blogs/health/2013/11/15/245168252/bacte
rial-competition-in-lab-shows-evolution-never-stops
160 Million Year Old Feathered
Dinosaur
Transitional Bird/Dinosaur Fossil
Note the mix
of bird and
dinosaur
traits. This is
a transitional
fossil. Of
interest, the
front legs are
wing-like
and the
dinosaurian
tail is still
present.
The Chinese Sleeping Dinosaur
The sleeping
dinosaur is 130
million years old and
perfectly preserved.
All of the bones are
present.
The sleeping posture
is that of modern
birds. Also, note the
long tail, which
modern birds have
lost.
A Few Fossils that captured evolution
in action
• Tiktaalik
Better known as the "fishapod", Tiktaalik was
discovered in the Canadian Arctic in 2004. This
375m-year-old creature lived at a crucial time
in history, when fish first left the oceans and
became land dwellers. Tiktaalik looked like a
primitive fish crossed with early four-legged
animals. It had lungs and gills, and fins that
could support much of its weight.
A Few Fossils that captured evolution
in action
• Archaeopteryx
The classic transitional fossil, Archaeopteryx
had feathers like a bird, but teeth, claws and a
bony tail like a dinosaur. The first remains
were discovered in Germany in 1861, only two
years after Darwin published his theory of
evolution. In 1868, Thomas Huxley suggested
that Archaeopteryx was an evolutionary link
between dinosaurs and birds. The animal
became central to the evolution debate.
A Few Fossils that captured evolution
in action
• Amphistium
Amphistium is a 50m-year-old relative of the
flatfish. While modern flatfish, like flounder,
plaice and sole, have both eyes on one side of
the head, the shift in eye position is
incomplete in Amphistium. One eye has begun
to move towards the other. Specimens of
Amphistium had lain in museums for more
than two centuries before their importance
became clear.
A Few Fossils that captured evolution
in action
• Ambulocetus
The evolutionary leap from land to marine
mammals was a problem for Darwin, but
Ambulocetus gave a snapshot of the process
in action. Known as the walking whale,
Ambulocetus was an early whale discovered in
Pakistan in 1992. It could walk on four legs on
land and in water, and heard by picking up
vibrations through its jawbone, just as modern
whales do.
A Few Fossils that captured evolution
in action
• Thrinaxodon
Known from fossils unearthed in Antarctica
and South Africa, this creature lived 245m
years ago. It captures the extraordinary
transition from reptile to mammal. Descended
from reptiles, it had scales and laid eggs, but
like mammals, had whiskers, warm blood and
perhaps a fur coat.