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Ch 17, 18.2, 19.2 Guided Notes (Evolution) Name _________________________
Review
• Heritable traits are controlled by genes carried on chromosomes  changes
in genes and chromosomes generate ___________________________.
Population
• _______________________________ – group of the same species living in
the same area that mate together and produce fertile offspring.
• Individual organisms don’t evolve  ________________ evolve over generations.
• Variation within a population  genetic changes ________________ fitness.
Gene Pool
• Gene Pool – ___________ genes (including all alleles for each gene) present
in a population.
• Populations ____________________________  same gene pool.
• Changes in the frequency of alleles in a population over time  ______________.
Favorable Phenotypes Increase Chance of Survival
Examples of _______________________ traits that enhance reproduction success:
–
–
–
–
–
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Biological Evolution
• Genetic variation is _______________ and ensures that each new generation
results in individuals with unique genotypes and phenotypes  evolution.
• Factors that influence genetic variability within a population:
1.
2.
3.
4.
5.
1) Genetic Drift
• Genetic Drift – _____________________ change in the frequency of alleles
of a population over time.
– Alleles will “________________” from generation to generation
– Due to ____________________
– ______________________ populations have greater chances of losing
alleles and changing phenotypes
– Rare alleles will decrease  ________________________
– Common alleles will increase  _______________________
• Type of Genetic Drift: _____________________________________
– Population of organisms is almost wiped out but then surviving
individuals repopulate.
– Problem: _______________________________ variation of alleles
– Caused by ____________________________ or ___________________
2) Gene Flow
• ______________________ - movement of genes into or out of a population.
– Due to ____________________ (IN) or _____________________ (OUT)
– Animals move and they take their genes  introducing new genes into
a population
– _____________________________ genetic variability
3) Non-Random Mating
• Choosing mates is ____________ random; mates are often chosen based on
certain criteria.
• Most individuals breed with others of the ____________________________
that share the same ecosystem  increased inbreeding.
• Limits the frequency of the expression of certain alleles.
4) Mutations
• Increase the frequency and type of allele changes within population.
• DNA can _____________ and these changes are nearly impossible to predict.
– DNA mutations are caused by: crossing over, sexual reproduction, basepair changes, mutagens.
– Mutations can _________________ or ______________ an individual’s
chance of survival.
5) Natural Selection
• Allows for the most _________________________ phenotypes to survive
and be passed on to future generations.
Genetic Equilibrium
• Evolution will not occur in a population if allele frequencies are not acted
upon by forces that cause _______________________.
• Hardy-Weinberg Principle – allele frequencies remain constant unless they
are affected by a factor that causes change  ________________________.
Hardy-Weinberg Principle
• ALL ______ required conditions must be met to maintain genetic equilibrium:
1. Population must be very _________________  no genetic drift
2. No movement into or out of population  _____ gene flow
3. _____________ mating
4. No ____________________ within the gene pool
5. No _______________________________________
Speciation
• _______________ – group of similar organisms that breed & produce fertile
offspring.
• ______________________________ – process of forming a new species by
biological evolution from a preexisting species.
– Large population is divided into smaller groups
– Smaller groups don’t mix with others  reproductively _____________
 interbreed
– Over time, small group exhibits unique traits and can no longer
reproduce with original group  different _______________________
6 Kingdoms of Life
• 6 Kingdoms 
Domains of Life
• 3 Domains 
Phylogeny
• Phylogeny – evolutionary _____________ of a species or group of related species.
– Phylogenetic Tree (or cladogram) – scientific diagram used to
represent the evolutionary history of organisms.
• Classifies organisms into ____________________ groups (taxa)
• Shows how organisms descended from common ancestry using
______________________ characteristics.
• __________________________  branching of family tree
• __________________________  loss of tree branch
Derived Traits
• ____________________________________________ – trait that appears in
recent organisms but not in its older members.
Adaptation and Extinction
• Throughout history organisms have faced ________________ environments.
• When environment changes  some species ____________ to new
condition & thrive but some species fail to adapt and become ____________.
Patterns of Evolution
1.
2.
3.
4.
5.
6.
– Gradual Extinction
– Mass Extinction
1) Gradualism
• Gradualism – _____________________ changes of a species in a particular
way over long periods of time.
– Rate of evolution is ________________ and ______________________.
2) Punctuated Equilibrium
• ______________________________________ – evolution occurs with
relatively sudden periods of speciation followed by long periods of stability.
– ____________________ changes are sporadic and cause major change.
3) Adaptive Radiation (or Divergent Evolution)
• Adaptive Radiation (or divergent evolution) – number of different species
diverge from a common ancestor  ______________________ over time.
– Many generations over time organisms evolve a variety of
characteristics which allow them to survive in different niches 
species compete evolving into ____________________ species.
4) Convergent Evolution
• Convergent Evolution – different groups of organisms living in ____________
environments produce species that are similar in appearance and behavior.
– Produces ____________________________ structures
5) Coevolution
• _________________________________ – two or more species living in close
proximity change in response to each other.
– Different species form an _________________________ relationship.
6) Extinction
• Extinction – _______________________________ of a species; occurs when
species cannot adapt to change in its environment.
– ________________________ Extinction – occurs slowly and may be
due to other organisms, changes in climate, or natural disaster.
– _________________ Extinction – occurs rapid and due to a catastrophic
event (volcanic eruption, meteor) suddenly changing the environment.
Read Chapter 17 (section 2 & 3; pages 487-497)
Read Chapter 18.2 (pages 516-522)
Read Chapter 19.2 (pages 546-551)