Post on 11-May-2015
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CHAPTER 22 DESCENT WITH MODIFICATION
By Charith Samarasena
Vocabulary
Fossils: the remains or traces of organisms from the past
Strata: layers of sediment Paleontology: the study of fossils Catastrophism: the principle that events in the past
occurred suddenly and were caused by mechanisms different from the present
Gradualism: mechanisms of change occur gradually over time
Uniformitarianism: mechanisms of change are constant over time
Adaptations: characteristics of an organism that enhance their survival and reproduction in specific environments
Vocab cont’d
Natural Selection: the process in which individuals with certain inheritable traits leave more offspring than individuals with other traits
Artificial Selection: the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits
Homology: similarity of characteristics resulting from a shared ancestry
Vestigial Structures: historical remnants of structures that had important functions in ancestors but no use in current organisms
Evolutionary Tree: a branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms
Vocab still cont’d
Convergent Evolution: the evolution of similar features in independent lineages
Analogous: having characteristics that are similar because of convergent evolution, not homology
Biogeography: the study of past and present distribution of species
Plate Tectonics: theory of how landmasses move along the earth’s crust
Endemic: where a species of plant or animal is only found in one particular location
Theory: a hypothesis that is supported by evidence and has been tested repeatedly with success
What is Evolution and why is important?
Evolution is the process in which species have modifications of certain traits that allow them to adapt to changes in environments
It’s important because it helps explain how some species in one location don’t look like other species in another location
It’s also explains why current organisms don’t resemble their ancestors
Carolus Linnaeus
He developed a two-part system of naming organisms according to genus and species
Georges Cuvier
Largely developed the field of paleontology
Observed that older layers of strata contain fossils of organisms that are more and more dissimilar to today’s organisms
Also came up with the principle of catastrophism
James Hutton
Proposed that Earth’s geological features could be explained by gradual mechanisms in the past that still occur today (ex. Continental drift)
Charles Lyell
Came up with the principle of uniformitarianism and also thought that this process still occurred today
Jean-Baptiste de Lamarck
Observed that older to younger fossils lead to living species
Hypothesized that structures that are used more frequently than others grow larger and stronger, and the structures that aren’t used deteriorate over time
Also hypothesized that organisms could pass on these modifications to offspring
Also thought that evolution occurs because organisms have an innate drive to become more and more complex
Charles Darwin
Proposed the idea of descent with modification by natural selection
Observed this in various finches while exploring the Galapagos Islands
What did Charles Darwin conclude after his voyage on the H.M.S. Beagle?
The Five Points of Evolution: 1. Organisms produce more offspring than necessary. 2. There is a variation in the offspring’s traits. 3. Competition among offspring cause many to die
out (as do the lack of food and resources). 4. Natural Selection favors the traits of the offspring
that survive. 5. Evolutionary changes in organisms occur over
time.
NOW WHAT EVIDENCE IS THERE THAT SUPPORTS THESE POINTS?
The Fossil Record
Fossils of past organisms show that there have been evolutionary changes over time to shape organisms into the forms of today
Homology
Homologous and Vestigial structures show similarities of structures in different species
DNA & RNA
The genetic code is essentially universal in all organisms; this shows evidence of common ancestry
Biogeography
Distribution of organisms allows paleontologists to figure out where fossils will be
Also shows similarities of species in different areas