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Chapter 20

Chapter 20

Course Code
BIOL 1001
Tamara Kelly

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Chapter 20 Notes
20.1: Recognition of Evolutionary Change
-Natural history: the branch of biology that examines the form and variety of organisms
in their natural environment
-Aristotle believed that both inanimate objects and living species had fixed characteristics
and created a ladder-like classification of nature from simplest to most complex
-In the 14th century it was thought that everything had been created by a god, that species
could never change or become extinct and that new species could never arise
-Natural theology was a belief that knowledge of God may be acquired through the
study of natural phenomen and sought to name and catalogue all of God’s creation.
Careful study of each species would identify its position and purpose in the Great Chain
of Being (Scala Naturae)
-Biogeography: the study of the geographic distribution of plants and animals
-Comparative morphology: analysis of the structure of living and extinct organisms
-George-Louis Leclerc noticed the existence of body parts with no apparent function and
proposed that some animals must have changed since their creation.
-Vestigial structure: An anatomical feature of living organisms that no longer retains its
function but may have been useful for ancestors of a species
-Cuvier developed the theory of catastrophism: the theory that earth has been affected
by sudden, violent events that were sometimes worldwide in scope. Local organisms
would die, form a fossil layer and then somewhat different species would recolonize the
area until the next catastrophe.
-Lamarck proposed the first theory of biological evolution and stated that there is a
metaphysical “perfecting principle” that caused organisms to become better suited to
their environment, become more complex and move up the ladder of life.
Principle of use and disuse: something used more often will be larger (like a
muscle) and something not will be smaller
Inheritance of acquired characteristics: changes that an animal acquires during its
lifetime are inherited by its offspring
-He theorized that an animal that stretches their legs or uses their muscles to enlarge
them will pass this on to the offspring who will make their legs even longer or
muscles bigger
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Lamarck made 4 important contributions to the evolutionary world-view:
He proposed that all species change through time (very important for Darwin)
He recognized that changes are passed from one generation to the next
He suggested that organisms change in response to their environments
He hypothesized the existence of specific mechanisms that caused
evolutionary change
20.2: Changes in Earth
-Hutton proposed the theory of gradualism: the view that Earth and its living
systems changed slowly over its history. Slow and continuous processes, acting
over long periods of time, produced Earth’s major geological features
-Lyell proposed the theory of uniformitarianism: the concept that the geological
processes that sculpted Earth’s surface over long periods of time are exactly the
same as the processes observed today
20.3a: Darwin’s Voyage
-Darwin noted that the animals on different Galapagos Islands differed slight in
form and that many species resembled those on the distant South American
-Hypothesized that the plants and animals on the islands were descended from
South American ancestors and that each species had changed after being isolated
on a particular island
20.3b: Selective Breeding and Hereditary
-“Like begets like”: offspring resemble their parents
-Artificial selection: selective breeding of animals or plants to ensure thar certain
desirable traits appear at higher frequency in future generations
20.3c: Survival of the Fittest
-Malthus noted that the population grows much faster than the agricultural
capacity, that individuals had to compete for food and that some would obviously
-Darwin applied this to nature: species produce more offspring than are needed to
replace the parent generation. Despite this, some members of each population de
without reproducing, while others do survive and reproduce
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