Transcript Divergent Evolution - MAH-SBHS

 Fossil: Any non-living object obtained from the ground
indicating the former presence of a living thing in a broad sense
is a FOSSIL
 Rock strata can be aged, the succession of fossils in the layers
shows the most primitive forms are in the oldest strata
 The progression of fossils follows he evolution of life as we
know if from other sources
For example: Fish in the oldest strata, then amphibians,
then reptiles etc.
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Homologous structures
 Similar characteristics resulting from common
ancestry
 Different functions but same basic anatomy due to
same ancestor
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Analogous structures
 Same function but different ancestry
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Vestigial Organs
 Organs that have become reduced or lost their
function
Comparative Anatomy. Examples of homologous organs.
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Have the same function but a different
ancestry
 The wing of a bird and wing of insect give the
ability to fly but have no structural relationship
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Vestigial structures are evidence for evolution
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Vestigial organs are organs that have become
reduced or have lost their function
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E.g. tail bones in humans, the wing bones in
the kiwi, the leg bones in a snakee
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On the surface, these animals look very
different, but the relationship between them
is easy to demonstrate.
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Except for those bones that have been lost
over time, nearly every bone in each
corresponds to an equivalent bone in the
other.
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The early embryonic stages of all vertebrates
are very similar, even though the adults are
very different
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Gives the appearance of a relationship
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Species which are close in evolutionary terms
have only small differences in their DNA and
proteins
Example: haemoglobin
- Sequence of 300 amino acids in haemoglobin is identical to
that in chimpanzees
- Gorilla: 2 are different
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http://evolution.berkeley.edu/evolibrary/sear
ch/topicbrowse2.php?topic_id=46
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http://sci.waikato.ac.nz/evolution/Homology.
shtml#Homology
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http://www.buzzle.com/articles/divergentevolution.html
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The evolution of species from different taxonomic
groups toward a similar form; the development of
similar characteristics by taxonomically different
organisms.
When organisms that aren't closely related evolve
similar traits as they both adapt to similar
environments. There are a finite number of effective
solutions to some challenges, and some of them
emerge independently again and again
 Handout
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Bird and bat wings are analogous—that is,
they have separate evolutionary origins, but
are superficially similar because they evolved
to serve the same function. Analogies are the
result of convergent evolution.
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Compare how a human foot evolved to be very different from a monkey's
foot, despite their common primate ancestry.
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It is speculated that a new species (humans) developed because there
was no longer was a need for swinging from trees.
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Upright walking on the ground required alterations in the foot for better
speed and balance. These differing traits soon became characteristics
that evolved to permit movement on the ground.
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Although humans and monkeys are genetically similar, their natural
habitat required different physical traits to evolve for survival.
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Divergent evolution occurs when a group
from a specific population develops into a
new species. In order to adapt to various
environmental conditions, the two groups
develop into distinct species due to
differences in the demands driven by the
environmental circumstances.
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Divergent evolution is the process by which
related lineages develop different biological,
genetic, and behavioral traits over time.
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Natural selection, sexual selection, genetic drift,
gene flow, and mutation are the processes that
drive these changes.
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Observe the development of the limbs in
vertebrates
The vertebrate arm in a human, the side fin
of a whale (a mammal), the wing of a bat and
the paws of a cat - all these evolved from one
primal stock of ancestors!
One can see how it has undergone change in
form and function over millions of years,
adapting according to the need.