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Theory of Evolution
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Theory of Evolution
 Evolution: the process in which populations gradually change over
time.
 Population: all of the individuals of a species that live together in an
area
 The theory of evolution was developed by a man named Charles
Darwin.
Charles Darwin
 Darwin collected birds from
the Galapagos Islands. He
noticed that the birds on
various islands differed slightly,
but he realized they were all
finches. The most obvious
difference between them was
the shape of their beaks. This
was most likely due to their
diets.
What else influenced Darwin’s ideas?
Organisms pass on traits to their
offspring. A trait is a form of an
inherited characteristic (Ex: a bird’s
feather size)
Humans select certain animals and
plants to breed based on desired
traits. We call this artificial
selection.
Natural Selection
 Darwin proposed that most evolution happens
through natural selection.
 Natural Selection is the process by which
organisms that inherit advantageous (helpful,
most useful, strongest) traits tend to reproduce
more successfully than others.
 Within species, there are natural differences.
We call this variation. (Ex: two jaguars can have
different jaw sizes, dogs can have different
color fur)
https://www.youtube.com/watch?v=vnktXHBvE8s
Adaptation
 An adaptation is an inherited trait that
helps an organism survive and reproduce
in its environment. Adaptations can help
organisms to reproduce, find food, protect
itself etc.
 (Ex: A large jaw size helped jaguars
survive when food was hard to find)
 What adaptations does this frog have to
help it survive?
https://www.youtube.com/watch?v=S6iiuFj5hzo
Extinction
 Some species may not adapt well to
their environment as it changes. If
adaptation is not taking place, then
it may become difficult for a species
to survive.
 Extinction is when all of the
members of a species have died.
Competition, predators,
environmental changes, and loss of
habitat can lead to extinction.
Reflection (Left Side)
Write a paragraph (minimum 5 sentences) answering the
following questions. Make sure to write in complete
sentences. Underline vocabulary words that you use.
 Why do organisms change over time?
 How have organisms changed over time?
 What is an example of a species changing over time to
adapt to its environment?