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Evidence for Evolution

part of 5.4 in the IB Syllabus

Angela De Jong

on 20 September 2017

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Transcript of Evidence for Evolution

Comparative Anatomy
It involves identifying the largest, best or most useful of the progeny for the intended purpose and using them as the parents of the next generation.
By “selecting” those traits most desired, the genetic makeup of a population changes rapidly.
Evidence for Evolution
Evolution in Action
Let the evidence speak for itself.
Pesticides are substances used for destroying insects or other organisms harmful to cultivated plants or to animals. Pest populations have evolved resistance to these chemicals, and, as such, they are losing their effectiveness. This can be seen as an example of artificial selection, as humans have caused it.
Pesticide Resistance
Bacteria cause many illnesses in humans. Antibiotics are drugs which block specific steps in bacterial metabolic pathways, resulting in death of the bacteria. Since World War II, many bacteria have become resistant to antibiotics, and the former “wonder drugs” are now ineffective against certain strains of bacteria.
Fossils are the preserved remains or traces of prehistoric life. Examples include:
Petrified wood or bone (turned to stone when internal cavities and pores are filled with mineral matter)
Impressions such as leaf prints, footprints, and the like
Coprolites (petrified feces)
Insects in amber (hardened tree sap)
Frozen mammoths in the Arctic
Mummified corpses in peat bogs
Comparative Anatomy looks at similarities and differences among the physical structures of organisms. One key piece of evidence for evolution is the pentadactyl limb of vertebrates:
The Fossil Record
Selective Breeding of Domestic Animals
The fossil record is incomplete, however, there is evidence to show how some species have evolved:
Fossils show changes in organisms over time. For example, there are fossils of horse ancestors dating to 53 mya, and many intermediates.
Fossilized organisms are different from existing ones, yet they share features with existing organisms. These shared features are called homologous structures.
English Sheepdogs, Dachshunds, Weimaraners and Saint Bernards, all examples of
Canis familiaris
, show obvious differences that make us question their classification.
Comparative Embryology looks at the embryonic development of different species. In the early stages of life, there are many similarities among vertebrates:
homologous structures are evidence of divergent evolution, while analogous structures are evidence of convergent evolution
homologous structures
analogous structures
are similar in fundamental structure
are similar in position and development
are similar because of common ancestry
resemble each other in function
differ in their fundamental structure
illustrate only superficial resemblances
It only takes one mutant bacterium with resistance to become a resistant strain... many bacteria reproduce themselves every 20-30 minutes!
This suggests common ancestry.
Fossils can show intermediate stages in evolution of groups.
Fossils of "missing links" such as Archaeopteryx (birds and reptiles) and Tiktaalik (fish and amphibians) have been found.
Artificial selection is the process by which all plants and animals used by humans have been derived from wild organisms.
Staphylococcus aureus
is a common bacterium found living on the skin. It is usually harmless, but under some circumstances can enter the bloodstream, infect tissues in the kidneys or bones, and could become fatal. There are some strains of
S. aureus
that are resistant to all known antibiotics. These bacteria are of grave concern to hospitals, where patients have died of a simple Staph infection, once treatable by antibiotics.
For example, millions of rats aren't even getting sick from pesticide doses that once killed them. In one county in England, these "super rats" have built up such resistance to certain toxins that they can consume five times as much poison as rats in other counties before dying.
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