Download 1859

Presenting Darwin’s Case
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In 1859, Charles Darwin published the The
Origin of Species.
He compiled years of travels and observations
and used them to explain why species or
groups of organisms change.
Darwin wanted to publish his findings before
Alfred Wallace, who was working on similar
findings
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First, Darwin explained that species are NOT
perfect and unchanging.
Instead within the same species, each
individual organism is different from the
others. This is known as Natural Variation.
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Darwin explained that
humans had already
taken advantage of
these variations to
improve crops and
animal performance.
Crossing animals that
had desirable
characteristics to make
more is known as
Artificial Selection
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Labradoodle
 Schnoodle
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Nature “selects” the desirable characteristics
within a species causing change and
evolution
This works because of a few key ideas.
1. All species have some variation in their
inherited characteristics.
2. Species are always undergoing a struggle for
existence. This is caused by competition for
food, shelter and other resources.
3. The ability of an individual to survive and
reproduce despite this struggle is known as
fitness.
4. Adaptations or inherited characteristics
sometimes increased the fitness of an
individual.
5. When certain individuals with specific
characteristics survive and reproduce more,
this is known as the survival of the fittest and
this is what causes Natural Selection
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There is variation among individuals and some of that
is inherited.
Many species produce more offspring than can
survive, creating a limitation on resources.
Some individuals will have advantages over others,
allowing them to survive better with limited resources
and produce more offspring.
Because they make more offspring, more individuals
in the future generation will have this advantage and
continue to produce more offspring.
Over time (many generations) this species will change
and more individuals will have this survival
advantage.
1. What is it called when humans decide which
individuals make offspring?
1. Natural Selection 2. Artificial Selection
2. What is the name for an individual’s ability
to survive and reproduce.
1. Fitness
2. Adaptation
3. What helps an individual increase it’s fitness
1. Adaptations 2. Natural Selection
4. Adaptations are
1. Learned
2. Inherited
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Each living species has descended, with
changes, from other species over time.
Common descent: all species – living and
extinct – were derived from common
ancestors. Therefore, a single “tree of life”
links all living things
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As the fossil record became more complete,
Darwin could see more similarities or
intermediate species between ancient species
and those present today.
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Darwin’s theory of Natural
Selection also is supported
by species on different parts
of the world having similar
adaptations when their
environments are similar.
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Looking at bone structure in fossils and
current living species, Darwin could see
similarities in body development.
This is known as homologous structures.
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The organs of many animals are so reduced
in size
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Homologous structures can be traced
back to similarities in embryology
(development of the embryo).
1. What is the term for structures in different
organisms that come from the same embryonic
tissues
1. Heterozygous structures
2. Homologous structures
2. What type of evidence shows how organisms
have changed throughout the history of the
earth?
1. Fossils
2. Geographical Distribution