Download Changes Over Time - Effingham County Schools

• The central ideas of evolution are that life has a
history. It has changed over time and that
different species share common ancestors.
Evolution only occurs when there is a
change in gene frequency within a
population over time.
1st generation of Beetle
population
Many generations later
of the same population
Gene Pool
Any change made
in the gene pool
over time
contributes to
evolution
What can cause these
changes?
Mutations- Any
change (error) made
in DNA during
replication
Mutation
• Mutations are
important in how
populations
change over time
because they
result in genetic
changes to the
gene pool.
Mutations can cause changes
over time, if they cause an
inheritable beneficial trait.
What can cause these
changes?
Migration
(Gene Flow)An individual
travels to a new
population and
introduces a
new trait.
What can cause these
changes?
Genetic DriftRandom event
that changes
the allele
frequency in a
population
What can cause these
changes?
Natural Selectionprocess of
evolution in which
traits that result in
better fitness of
an individual
survives to the
next generation.
The evolution of insecticide resistance is an
example of natural selection in action
Chromosome with gene
conferring resistance
to insecticide
Additional
applications of the
same insecticide will
be less effective, and
the frequency of
resistant insects in
the population
will grow
Insecticide
application
Survivor
Natural Selection
• the survival and reproduction of the
individuals in a population that exhibit
the traits that best enable them to
survive in their environment.
• The Survival of the Fittest
What can cause these
changes?
Mutation
Migration/ Gene Flow
Genetic Drift
Natural Selection
Charles Darwin’s Theory
of Evolution:
1. Members of a
population have
inheritable
variations.
(Inheritance of
traits)
Why Genetic Variation?
If a population was 100% the same…
natural selection and genetic drift would
have NO effect because the genetic
make-up would never change.
Sexual Reproductionbrings together a new
combination of genes.
• Introduces new
combinations of
genes every
generation.
2. In a population, more individuals are
produced than the environment can
support. They compete for food and
shelter. (overproduction- struggle for
survival).
3. Some individuals have adaptive
characteristics that enable them to
survive and reproduce better than other
individuals (survival of the fittest).
4. An increasing number of
individuals in succeeding generations
have these adaptive characteristics
(natural selection)
• Evolution takes place
through a set of
processes that
include:
–
–
–
–
mutation,
adaptation,
natural selection,
extinction.
When humans choose organisms with
specific characteristics as breeding
stock, they are performing the role of
the environment
• This is called “selective breeding”
Example of selective
breeding in plants: five
vegetables derived from
wild mustard
Selective breeding in Animals: Dog Breeding
German
shepherd
Yorkshire terrier
English springer
spaniel
Hundreds to
thousands of years
of breeding
(artificial selection)
Ancestral dog
Mini-dachshund
Golden retriever
Evidence of
Evolution
How do we know there has
been changes?
• The study of fossils provides strong
evidence for evolution.
Hominid skulls
Petrified Trees
Younger
Older
Relative Dating
Relative Dating
Ammonite casts
Fossilized organic
matter in a leaf
Scorpion in amber
“Ice Man”
Human
Homologous Structures provide
evidence of evolution
Cat
Whale
Bat
Vestigial Structures
EX.: appendix
in humans,
whale pelvis,
tiny snake
pelvic and limb
bones, and the
eyes in cavedwelling
salamanders
and fish that
are completely
blind.
Provide evidence that organisms
evolved from a common ancestor
• The central ideas of evolution are that life has a
history. It has changed over time and that
different species share common ancestors.