Syllabus | Notes | Practice Tests
BIOLOGY

---

9.1
• Evolution is a change in species over time.
• Since the beginning of the earth, about 4.5 billion years ago, it has gone through many changes.
• Creationists do not believe that species change slowly.
• Before his 5 year voyage on the Beagle, Darwin believed in creationism (he had a theology degree).
• Darwin conducted much of his research on the Galapagos Islands.
• Darwin’s book, The Origin of Species in 1859, presented 2 major ideas:

 > species change over time
 > this change occurs by natural selection.
• Darwin’s theory of evolution included ideas such as:

 > species change slowly over time
 > some organisms reproduce at greater rates than others
 > some organisms become less suited to their environment than others
 > evolution occurs due to natural selection.
• Darwin’s studies included finches, who had a common ancestor, but had evolved differently.
9.2
•  Radioactive substance have a characteristic known as half-life ... that is the length of time it takes for one half of the substance to deteriorate.
• The half life of carbon-14 is 5730 years.  So for a sample of carbon-14, it will be half gone in 5720 years, there will be 1/4 of the original amount in 11460 years, there will be 1/8 of the original amount in 17180 years, and so on.
• Evidence for evolution includes:

 > the fossil record
 > homologous structures
> similarities/differences in the protein and DNA sequences of organisms.
• Darwin predicted that transitional fossils would be found that would show intermediate stages in the fossil record.
• The fossil record of the horse, for example, from the small dog-sized creature of 60 million years ago into today’s horse shows the slow, gradual pace of evolution.
• The age of fossils can be determined by:

 > where they were found relative to other fossils
> the amount of radioactive material in fossil remains.
• A bone becomes fossilized when its calcium is replaced by harder minerals.
• Homologous (similar) structures in organisms suggest that organisms had a common ancestor.
• Two organisms with  homologous structures may show DNA nucleotide sequences that are similiar.
• Structures that have become smaller as the years have gone by (because they are no longer used) are called vestigial.  Examples include small internal leg bones in snakes, the appendix in humans, and hip bones in whales.
• A human embryo exhibits gill pouches, a coat of fine fur, and a bony tail for a certain amount of time.
• The theory of evolution says that:

 > as organisms are more similiar, their amino acid sequences in their proteins are more similar
 > if species have changed over time, their genes will have changed as well
> as organisms are more similiar, their nucleotide sequences are more similiar.
9.3
•  Steps in the process of natural selection:

 > variation is the raw material for natural selection
 > living things face a constant struggle for existence
 > only some individuals survive and reproduce
 > natural selection causes genetic change
> species change to fit their environment (called adaptation).
• Natural selection is the process by which organisms better suited to their environment reproduce at a faster rate than those not as well adapted to that environment.
•  Organisms that are suited to their environment reproduce faster than those less suited to that environment.
• Organisms often produce more offspring than can survive.
• The evolution of the long necks of giraffes is an example of directional selection.
• Natural selection could not occur without genetic variation in species.
• Natural selection can change the physical appearance and genetic makeup of a species.
• Natural selection causes changes in the frequency of certain alleles in a species population.
• Balancing variation occurs when two opposing forces affect the frequency of an allele in a population.
• Kettlewell conducted experiments with peppered moths that showed that moths whose color matched the tree trunks were more likely to survive.
• People heterozygous for the sickle cell allele are less susceptible to malaria.  This means that they have an advantage for survival if they live in Africa, but are disadvantaged in they live in the U.S.
•  Genetic variations in species is the raw material for natural selection.
• Populations of the same species living in different places become more and more different as each becomes adapted to its own environment.
• Populations of the same species that differ genetically because they have adapted to different environments are known as ecological races.
• Punctuated equilibrium is a theory that says that evolution occurs at an irregular rate over time.  Things change in big steps instead of gradually.
Go to the Ch 9 Practice Test