Summary
BIO 101 Theory of Evolution Summary
- Course
- Biology 101
- Institution
- Tidewater Community College
This is a comprehensive and detailed summary on Theory of Evolution for Bio 101.
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Charles Darwin● From 1831 to 1836, Darwin traveled around the world on H.M.S. Beagle, including stops
in South America, Australia, and the southern tip of Africa
● During stops on island chains, Darwin observed species of organisms on different
islands that were clearly similar, yet had distinct differences
● Darwin imagined that the island species might be species modified from one of
the original mainland species
● He realized that the varied beaks of each finch helped the birds acquire a specific
type of food
● This lead to his idea of natural selection
● The more prolific reproduction of individuals with favorable traits that survive
environmental change because of those traits
● Also known as “survival of the fittest,”
3 Principles Lead to Natural Selection
● Most characteristics of organisms are inherited, or passed from parent to offspring
● Even though genes and genetics were unknown at the time, this was a common
understanding
● More offspring are produced than are able to survive, so resources for survival and
reproduction are limited
● There is competition for those resources in each generation
● This principle came from reading an essay by the economist Thomas Malthus
who discussed this principle in relation to human populations
● Offspring vary among each other in regard to their characteristics and those variations
are inherited
● Offspring with inherited characteristics which allow them to best compete for
limited resources will survive and have more offspring than those individuals with
variations that are less able to compete
Alfred Wallace
● Darwin was not alone in developing these ideas
● Alfred Russell Wallace was also a naturalist who traveled to island chains and made
similar observations
● Papers by Darwin and Wallace presenting the idea of natural selection were read
together in 1858 before the Linnean Society in London
The Theory of Evolution
● Natural selection can only take place if there is variation, or differences, among
individuals in a population
● These differences must have some genetic basis
, ● Genetic diversity in a population comes from two main mechanisms: mutation and
sexual reproduction
● Mutation, a change in DNA, is the ultimate source of new alleles, or new genetic
variation in any population
● Sexual reproduction also leads to genetic diversity: when two parents reproduce,
unique combinations of alleles assemble to produce the unique genotypes and
thus phenotypes in each of the offspring
Evolution Requires Adaptation
● A heritable trait that helps the survival and reproduction of an organism in its present
environment is called an adaptation
● Whether or not a trait is favorable depends on the environmental conditions at
the time
● The same traits are not always adaptive because environmental conditions can
change
● Sometimes, evolution gives rise to groups of organisms that become tremendously
different from each other
● When two species evolve in diverse directions from a common point, it is called
divergent evolution
● Convergent evolution occurs where similar traits evolve independently in species
that do not share a recent common ancestry
Physical Evidence for Evolution
● Fossils provide solid evidence that organisms from the past are not the same as those
found today, and fossils show a progression of evolution
● Anatomy shows the presence of structures in organisms that share the same basic form
as well as the convergence of form in organisms that share similar environments
● Embryology shows structures that are absent in some groups often appear in their
embryonic forms and disappear by the time the adult or juvenile form is reached
Biological Evidence for Evolution
● Biogeography
● The geographic distribution of organisms on the planet follows patterns that are
best explained by evolution in conjunction with the movement of tectonic plates
over geological time
● Molecular biology
● Like anatomical structures, the structures of the molecules of life reflect descent
with modification
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