Transcript Phylogeny - Teaching Biology Project

Phylogeny
Version: 2.0
Phylogeny and Taxonomy
The evolutionary history of a group of related species
is called phylogeny.
Reconstructing phylogenies
involves identifying and
classifying species to show
their evolutionary relatedness:
a scientific discipline (or area
of study) called taxonomy.
Common Ancestors
http://evolution.berkeley.edu/evolibrary/print/printable_template.php?article_id=evo_05&context=0_0_0
The central idea of biological
evolution is that all life on Earth
shares a common ancestor, just as
you and your cousins share a
common grandmother.
Through the process of descent
with modification, the common
ancestor of life on Earth gave rise
to the fantastic diversity that we
see documented in the fossil
record and around us today.
Evolution means that we're all
distant cousins: humans and oak
trees, hummingbirds and whales.
Understanding phylogenies
Understanding a phylogeny is a lot like reading a family
tree.
The root of the tree represents the ancestral lineage, and
the tips of the branches represent the descendents of that
ancestor. As you move from the root to the tips, you are
moving forward in time.
When a lineage splits (speciation),
it is represented as branching on a phylogeny.
When a speciation event occurs,
a single ancestral lineage gives rise to two or more
daughter lineages.
Phylogenies trace patterns of shared ancestry between
lineages.
Each lineage has a part of its history that is unique to
it alone and parts that are shared with other lineages.
Similarly, each lineage has ancestors that are unique to
that lineage and ancestors that are shared with
other lineages — common ancestors.
Plate Tectonics and
Continental drift
Plate Tectonics
The movement of the plates that
make up the surface of the Earth
that contributes to continental
drift.
Continental drift
http://itsyourexperiment08.files.wordpress.com/2008/10/plate-tectonics1.gif
The crust of the Earth is in
constant motion, moving whole
continents and sea floors.
The movement of continents, at
times joining and at other times
separating, has had a powerful
effect on the distribution of
organisms
http://earthscience.files.wordpress.com/2007/04/gondwana.gif
Evolution by natural selection
Darwin concluded that natural selection could explain how
organisms gradually change and evolve into new species.
At the time of publishing Darwin found it difficult to get his
theory accepted, as it was difficult to prove.
Other scientists at the time wanted Darwin to provide an
explanation to how individuals passed on their characteristics to
their offspring.
Since Darwin’s time advances in our understanding of genetics
have provided evidence to support and extend Darwin’s theory.
Evolution through natural selection involves:
• The consequence of this is what
Darwin described in his book as a
“struggle for existence”. The
weakest are eliminated in this
struggle. The fit survive. The
survivors pass on their traits to
their offspring. Over enough time,
these differences in
characteristics will lead to the
formation of a new species
What is Natural selection?
Natural selection is the process of evolutionthe mechanism which allows the organisms
that are better adapted to survive in the
environment in which they are living, to
reproduce more successfully - thus
spreading their genes throughout the
population.
This is what Charles Darwin meant by
“survival of the fittest”
How does Natural Selection work?
Natural selection works by
tiny mutations (changes) in
the genes that are always
happening during sexual
reproduction- when a
mutation is beneficial to
survival of the organism it
eventually, generation after
generation, becomes more
dominant in the population,
and a new species is
formed.
What determines natural selection?
Thus the ENVIRONMENT
naturally selects those genes that
increase the chances of survival to
adulthood and therefore
reproductive success.
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