Evolution. What We Now Know. The “Theory” of Evolution. Humans have come a long way!. Have you ever stopped to wonder what mechanisms fueled our evolution? Why have we inherited some traits from our parents and lost others?
What We Now Know
The early ideas about the natural world were heavily influenced by Plato and Aristotle. Early Christians built upon this idea, and concluded from the biblical account of creation that God had created each species individually.
The traditional Judeo-Christian version of creationism was strongly reinforced by James Ussher , a 17th century Anglican archbishop of Armagh in Northern Ireland. By counting the generations of the Bible and adding them to modern history, he fixed the date of creation at October 23, 4004 B.C.
The Creation of Adam is a section of
Michelangelo’s fresco on the ceiling of the Sistine Chapel painted in 1511.
Charles Darwin and Alfred Russel Wallace had not thought of Natural Selection.
Jean-Baptiste Lamarck’s inheritance of acquired traits was the most commonly accepted mechanism for evolutionary change.
Early believers may have been wrong about how it happened but give them credit for at least understanding that it did happen.
Evolution is the process in which significant changes in the inheritable traits (genetic makeup) of a species occur over time.
Includes actual bones, shark’s tooth, petrified wood, frozen mammoth, insects in amber.
English geologist William Smith (1769-1839) realized that certain fossils always showed up in the same kinds of rocks, even if they were found in different locations.
3. Biogeographic distribution of living species gave scientists clues to the patterns of evolution
If a group of related species all descended from a common ancestor,
they should share many similarities even if they evolved different
Two short bones
1) Salamander, 2) Frog, 3) Turtle, 4) Aetosaurus, 5)Pleisiosaurus, 6) Ichthyosaurus, 7) Mesosaurus, 8) Duck.
the tetrapod limb
The wing of a dragonfly and the wing of a butterfly are homologous — they were both inherited from an ancient flying insect.
Not all homologies are obvious if they have been adapted for different roles. For example, the chomping front teeth of a beaver look quite different than the tusks of an elephant. Each is a modification of the basic incisor tooth structure
Homologies show that Divergent Evolution takes placeDivergent Evolution: A common ancestor evolves into new species, which continue to evolve and become less and less alike over time due to differences in the demands driven by the environment.
Smilodon, the saber-toothed cat,
which is a placental mammal
a marsupial mammal
analogysimilarity due to convergent evolution not common ancestryCONVERGENT Evolution: When two separate groups of animals evolve to have similar structures
How do analogies evolve?Often, two species face a similar problem or challenge. Evolution may then shape both of them in similar ways — resulting in analogous structures.....like the saber teeth.
While sugar gliders (marsupials) superficially resemble the placental flying squirrels of North America, the ability to glide through the air evolved independently in these unrelated mammals.
HOMOLOGY vs. ANALOGY
5. Embryonic Development – Embryos of different organisms can have homologous features
6. Vestigial Features- Structures which serve no useful function in a living organism
For aficionados of gigantic Ice Age mammals, woolly mammoths provide a cool example of how gene sequencing reveals information about the evolution of elephants and their relatives. In 2006 an international group of scientists sequenced genes from extinct wooly mammoths—itself a remarkable feat. Mammoths are often found in permafrost, extremely cold soil, which provides ideal conditions for preserving DNA. The research team compared mammoth gene sequences to two different kinds of elephants living today: modern Asian and African elephants. They discovered that the closest living relatives of mammoths are Asian elephants. In other words, mammoths and Asian elephants share more of their DNA and a more recent common ancestor than modern Asian and African elephants.