Download Evolution - Van Buren Public Schools

Timeline of Earth’s History
Recent History of Life on Earth –
600 millions years ago to the Present
Scientific Theory
– Well-supported testable explanation of something
in nature.
– What do we mean by “testable”?
– In science, nothing is ever proven  ALWAYS
possibility of new discoveries!
Theory of Evolution
• Evolution is the change in the genes of a
population over time
• Process where modern organisms
descended from ancient organisms over time
Changes in the genes
of a population lead to
changes in the
phenotypes … this can
lead to new species
over time!
The new species are
descendants of the
earlier ancestors just
like you are
descendants of your
great great great great
great great
grandparents.
You share a family
history and share
genes but you are not
the same.
Theory of Evolution – KEY to Biology!
• Evolution = the CENTRAL DOGMA in biology
• It explains the patterns we see in living
organisms
Let’s THINK…
How does evolution work??
Genetic Variation
1. Genetic variation = diversity of alleles
(genotype)
2. Leads to diversity in phenotypes
Genetic Variation
1. Genetic variation = diversity of alleles
(genotype)
2. Leads to diversity in phenotypes
3. Variation allows some individuals to succeed
during difficult times or environmental changes
(better adapted!)
4. Allows the population to survive.
Environmental Changes
• Individuals better adapted for environmental
change are more likely to survive and
reproduce
Galapagos Islands tortoises  Shell
structure varies depending on
habitat. The Hood Island tortoise
(left) has a longer neck and curved
shell, which is better for reaching
sparse vegetation. The Isabella
Island tortoise (right) has a domeshaped shell and shorter neck, which
is better for the abundant, close
vegetation.
So… What do we call this genetic
variation within a population??
Gene Pool
1. All the genes in a population
2. Gene combinations change over time due to
forces of evolution
We will talk about these tomorrow!
3. Variation in the gene pool allows for
evolution!
Gene Pool
Genetic variation in the gene pool
allows for the population to change
over time (evolution)…
Which leads to…
Descent with Modification
• Organisms evolve from common ancestors with
changes in genotypes and phenotypes
• Common Ancestor = Species that other
organisms/species have evolved from
Over time, enough changes can occur in a
population to have a new species, descended from
the original ancestor.
What ultimately allows
for evolution to occur
from a common
ancestor to descended
species?
All share a common ancestor…
Evident in the DNA and anatomy!
MANY early scientists and naturalists
set the foundation for our current
understanding of evolution..
However, one naturalist in particular is
credited as the “Father of the Theory
of Evolution”…
Charles Darwin
1. Father of the theory of evolution
2. Observations lead to theories about how life
changes over time
3. Darwin noticed that:
- There are patterns of diversity in natural world
- Living organisms resemble fossils
Darwin’s Finches of the
Galapagos Islands