Evolution
Darwin’s Theory of Evolution
1. Individual organisms in nature differ
from one another. Some of this variation is
inherited.
Natural variation –
differences among
individuals of a species
•Darwin also saw that when humans choose organisms
with specific characteristics as breeding stock, they are
performing the role of the environment
–This is called artificial selection
–Example of artificial
selection in plants: five
vegetables derived
from wild mustard
–Example of artificial selection in animals: dog
breeding
German
shepherd
Hundreds to
thousands of
years
of breeding
(artificial
selection)
English springer
spaniel
Golden retriever
Yorkshire
terrier
Minidachshund
Ancestral dog
2. Organisms in nature produce more offspring
than can survive.
Leopard Frog
3. Because more organisms are produced
than can survive, members of each species
must compete for limited resources.
4. Because each organism is unique, each
has different advantages and disadvantages
in the struggle for existence.
Peppered Moths
5. Individuals best suited to their environment
survive and reproduce most successfully. The
characteristic that make them best suited to their
environment are passed on to offspring.
Individuals whose characteristics are not as
well suited to their environment die or leave
fewer offspring.
6. Species change over time. This is natural
selection.
Over long periods of time,
natural selection causes
changes in the
characteristics of a
species, such as in shape
and form. New species
arise, and other species
disappear.
7. Species alive today have descended with
modifications form species that lived in the past.
Jackal
Thousands
to
millions of
years
of natural
selection
•These five canine
species evolved from a
common ancestor
through natural selection
African wild
dog
Fox
Fox
Coyote
Wolf
Ancestral canine
8. All organisms on Earth are united into a single
tree of life by common descent.
C
A
B
A is more closely related to B than to C
Phylogenetic Tree – Hand out Phylogenetic
Tree and Homologous Structures Worksheet
1. Which two modern
organisms are likely to be
most closely related?
2. What was the most recent
common ancestor of
organisms 2 and 3?
3. Now do this one on your own. Then complete the
rest of your worksheet.
The End!!!