The evolution of living things
Transcript of The evolution of living things
The Evolution of Living Things
Section 1: Change over Time
Section 2: How does Evolution Happen?
Section 3: Natural Selection in Action
Change Over Time Adaptation: a characteristic that helps an
organism survive and reproduce in its environment
Species: a group of organisms that can mate with one another to produce fertile offspring
Population: groups of individuals of the same species living in the same place
Evolution The process in which inherited
characteristics within a population change over generations such that new species sometimes arise
Fossils The remains or physical evidence of an
organism preserved by geological processes
Fossil record: a historical sequence of life indicated by fossils found in layers of the Earth’s crust
Evidence of Ancestry
Adapted from "A Simplified Family Tree of Life" in The Evidence of Evolution by Nicholas Hotton III, Smithsonian, c1968.
Examining Organisms Evidence of Whale Evolution (p. 170, Fig. 7)
Pakicetus: Scientists think that whales evolved from land-dwelling mammals that could run on four legs; one of these ancestors may have been Pakicetus, which lived about 50 mya
Ambulocetus: This mammal lived in coastal waters about 49 mya; could swim by kicking its legs and using its tail for balance
Dorudon: This mammal lived in the oceans about 40 mya; resembled a giant dolphin with tiny hind limbs that could not be used for swimming or walking
Modern toothed whale: Forelimbs are flippers; no hind limbs, but do have tiny hip bones; range in size from 1.4 m porpoises to 33 m blue whales
Comparing Organisms Comparing Skeletal Structures: similarities
in arrangement of bones suggests that cats, dolphins, bats, and humans had a common ancestor
Comparing DNA: every organisms inherits the traits determined by DNA; if two species have similar DNA, the hypothesis suggesting common ancestry is supported
Charles Darwin (1809-1882) Took a five-year voyage around the world on
the HMS Beagle in an effort to study nature and to explain HOW evolution happens
Studied finches on the Galapagos islands
Thomas Malthus (1766-1834)"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus
on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-
continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable
variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to
work".
Charles Darwin, from his autobiography. (1876)
Charles Darwin – Theory of Natural Selection As random genetic mutations occur within an
organism's genetic code, the beneficial mutations are preserved because they aid survival -- a process known as "natural selection." (Descent with Modification) These beneficial mutations are passed on to the next generation. Over time, beneficial mutations accumulate and the result is an entirely different organism (not just a variation of the original, but an entirely different creature).
In 1859, Darwin published his famous book, “On the Origin of Species by Means of Natural Selection”
Natural Selection in Action In 1930, about 99% of the male elephants
in one area had tusks; today, because of hunting for ivory, only 85% of the male elephants in that area have tusks
Insecticides – insects developing resistance Antibiotics – bacteria developing resistance Peppered moths – industrial melanism
Forming a New Species Speciation: the formation of new species
as a result of evolution Separation Adaptation Division
The Evolution of the Galapagos Finches Some finches left the mainland and reached one
of the islands (separation) The finches reproduced and adapted to the
environment (adaptation) Some finches flew to a second island (separation) The finches reproduced and adapted to the
different environment (adaptation) Some finches flew back to the first island but
could no longer interbreed with the finches there (division)
This process may have occurred over and over again as the finches flew to the other islands
Review When a single population evolves into two
populations that cannot interbreed anymore, __________________ has occurred.
speciation
Review Darwin’s theory of
______________explained the process by which organisms become well-adapted to their environment.
natural selection
Review A group of organisms that can mate with
each other to produce offspring is known as a(n) ________________________.species
Review The _____________provides information
about organisms that have lived in the past.fossil record
Review In ________________, humans select
organisms with desirable traits that will be passed from one generation to another.
selective breeding