Download Evolution-

Name________________________
EVOLUTION AND NATURAL SELECTION NOTES
Evolution- _____________ in the heritable (genetic) traits of a population over time
Note: When we talk about evolution, we are talking about _____________________ changing, not
individuals
Natural selection- The main _________________ by which evolution occurs
Four conditions required for natural selection:
1. Variation- Individuals in a population are not _______________ to each other.
2. Inheritance- Traits are passed to _________________; traits have a genetic basis
3. Environmental population limits- Environmental ________________ ____________ prevent all
individuals from surviving to reproduce; some die young.
4. Environmental selection Individuals in the population with more _____________ (advantageous) traits are the ones that
survive to reproduce.
 Individuals without advantageous traits ______ before reproducing.
How does natural selection cause evolution of a population?
1. Variation- Members of a population are similar but not identical to one another:
Variation in Height Within a Population
Example graph:
2. Inheritance- DNA determines the ____________ of individuals
 Individuals inherit __________ from their _______________
 This causes the traits of the offspring to resemble the traits of the ______________
WITH limiting factors (reality)
Population
Population
3. Environmental population limitsNO limiting factors (not natural)
Time
Time
Examples of limiting factors:
4. Environmental selection
Individuals without advantageous traits ______ before reproducing.
Individuals with advantageous traits survive to reproduce.
Frequency
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•
Characteristic
Populations change, not individuals• The “average” characteristic or other measure of the _____________ changes over
___________________
The environment is the ___________ ______________ behind evolution
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•
•
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The ________________ determines which characteristics are favorable (advantageous)
Characteristics are said to be “selected for”
Because the environment changes over time, the characteristic that is more __________ for a
population changes
Therefore, characteristics of the population change, or evolution occurs
GENETIC VARIATION
1. Why is genetic variation in a population important?
• A population without much variation limits a species’ ability to further _________. (Variation is
one of the 4 factors required for natural selection to cause evolution)
• If populations do not adapt to their environment, they may become ____________.
2. What are the sources of genetic variation in a population?
1. Sexual reproduction
A. Meiosis – one copy of a gene is passed on from each ___________, combination may
be different than someone else
B. Random fertilization – only one of the millions of sperm involved in mating will
fertilize the egg.
2. Mutations:
Mutation means a change in _________A sequence.
- Can happen when DNA is copied during cellular replication
A new DNA sequence can result in new variation (not always).
– Many mutations produce traits that are ____________ (e.g. Huntington’s disease)
– Some mutations produce traits that are neutral (neither helpful nor harmful)
– Very, very few mutations produce traits that are ________________
Natural Selection:
• Individuals with advantageous genes survive to reproduce and pass on these genes to their
offspring.
• Individuals without advantages genes do not survive to reproduce, and these genes do not get
passed on in the population.
• “Survival of the Fittest” – best _____ (able to survive and reproduce) in the environment
• Natural Selection leads to ______________!!!
Conclusion:
• Mutation does NOT ____________ evolution
– it is only a source of variation (just one of the factors required for natural selection)
• Natural selection determines if the frequency of traits will change within a population.
• Change in traits in a population = __________________
Name________________________
THEORY, HYPOTHESIS, AND PREDICTION (SCIENTIFIC PROCESS)
Hypothesis-
Prediction-
Theory-
How are predictions used to test hypotheses?
What is the relationship between a hypothesis and a theory?
EVIDENCE FOR THE THEORY OF EVOLUTION
6 areas of evidence for evolution:
1. Fossils-
2. Vestigial structures-
3. Biogeography-
4. Homologous structures-
5. Embryology-
6. DNA/protein sequences (macromolecules)-
Determining the age of fossils:
Relative dating-
Radiometric dating-
Half-life-