EOC Packet #3
Evolution
 Defined as a change in a species over time
 What key scientist is credited with the bulk of out
understanding?

Charles Darwin
Evidence for Evolution
 Anatomy:
 Homologous- same structure/different function
 Example: bone structure in human arm and cat leg
 Embryology:
 Earlier stages of development look similar
 Biochemical:
 Similarity in DNA and proteins

ALL OF THIS EVIDENCE POINTS TO A COMMON
ANCESTOR!
Natural Selection
 Organisms with the best traits will survive
 Example: An environment used to be very cold/snowy but has
become warmer and all the snow melts. Based on the principle
of natural selection would a rabbit with white fur or brown fur
have a better chance of survival?
Requirements for Natural Selection
 Overpopulation- more offspring produced than can
survive
 Survival of the Fittest
 Variation
 Adaptations
Genetic Variation
 Promotes evolution because a variety of species are
produced and the environment chooses the trait that
is best suited for that environment
Does a population have to become a separate
species in order to be evolving?
 No- because traits can evolve but organism will still
belong to the same population (ex: fur color may
change but still considered to be a rabbit)
Basic Information
 DNA contains the master copy of all our information.
 This information is broken up into sections called genes.
Each gene contains the directions to make a single
protein by linking together the proper sequence of
amino acids.
 Before building a protein, a temporary copy of the single
recipe must be made. This copy is called mRNA.
 Ultimately it is the gene that gives you the trains that we
have and the genetic code that teaches us how to make
them.
Where is DNA kept in the cell?
 DNA is found in the nucleus (also called chromatin)
 What is the name of the little structure of wound up
DNA?

Chromosomes
What is a mutation?
 A mutation is a change in DNA sequence.
 Cause of mutations could be:
 Diseases
 Environment
 Types of changes considered mutations:
 Insertion (insert extra nucleotide)
 Deletion (delete nucleotide)
 Substitution (substitute one nucleotide for another)
If a piece of DNA is mutated how can that affect
future cells?
 The mutation can be inherited
 Mutations are not always negative
Genetic Variations
 A genetic variation is a variation in alleles, genes, or
both in a population.
 It is important because it allows the stronger
variations to become more prevalent within an
environment.
 Causes of variation: change in environment,
mutation, crossing over during meiosis
(infinite number of different children)