Download Unit 8 (Microevolution) Study Guide KEY

Pre-AP Biology - Evolution Review - KEY
1. Explain what each scientist below did that was significant to the Theory of Evolution.
 Redi – Did experiment showing that maggots come from flies and not from meat
o Remember: Redi = Red meat

Needham- Tried to PROVE spontaneous generation (only guy who did that)
o Boiled broth in a flask and WAITED TO COVER IT UP until after it had cooled (that was
the problem with his experiment)
o bacteria entered flask as it cooled
o Saw bacteria return to flask
o Thought this proved spontaneous generation
 Remember = Needham “needs” to get a better experiment

Spallanzani – Did basically the same experiment as Needham but was trying to disprove
spontaneous generation
o Difference was that he covered up the flask immediately so no bacteria came back
o People argued that he killed the “life force” of the air so they didn’t accept his results
 Remember his as the “air murderer”

Pasteur – Did same experiment as Needham and Spallanzani but came up with a flask that
allowed AIR TO ENTER BUT BACTERIA COULD NOT
o This set up would’ve allowed the “life force” of the air to reenter
o Still, there were no bacteria that returned to the flask
o Proved biogenesis to be true (and spontaneous generation to be false) once and for all
 Pasteur = put spontaneous generation in the “past”

Malthus - Gave Darwin idea that populations produce more offspring than can survive
because populations increase faster than earth can support
This would mean that natural selection would be “the survival of the fittest” because there
were not enough resources for every organism to survive.

Wallace – Came up with idea of correct idea of evolution at same time as Darwin but Darwin
published his book first
Lamarck – Believed in Evolution (populations change over time) before Darwin, but his ideas
on how it worked were wrong.

1. Simple forms of life eventually develop into more complex forms
2. Inheritance of Acquired Characteristics by Means of Use or Disuse (Traits gained in life
by experience or behavior could be passed on to offspring)
(Ex. Bodybuilder parents
Bodybuilder baby)
2. What is spontaneous generation? Life can come from non-living things
3. What is the biological definition of evolution? A scientific theory that states that living species
are descendants of ancestral species that were different from present day ones (the genetic
changes in a population over generations)
4. What is the gene pool of a population? All the genes in a population; EVOLUTION OCCURS
WHEN A POPULATION’S GENE POOL CHANGES.
5. What was the name of Darwin’s book? On the Origin of Species by Means of Natural Selection
6.
Darwin had 2 main themes in his book. Identify these 2 themes and explain what is meant by both terms.
a. Descent with Modification – All life has originated from life before them and has been
modified over time. This is evolution.
b. Natural Selection - The process by which individuals that are better suited to their
environment survive and reproduce most successfully. That is the process that CAUSES
evolution.
7. Contrast Lamarck’s and Darwin’s ideas about changes in organisms over time.
8.
9.
Define the word adaptation.
A naturally occurring, heritable trait that improves an organism’s fitness (survive longer, reproduce
more). It IS NOT an organisms “adapting” or “trying to change” to fit their environment.
What is fitness?
a. Which of the 2 factors of fitness is not actually required for it to be considered an adaptation.
1) Survive Longer, 2) Reproduce More  3) Future is more like you
Survival is not actually required (must only survive long enough to reproduce)
10. Give the steps that are required for natural selection to occur.
Organisms produce more offspring than can survive.
Genetic Variation - Individual organisms in a population have slight variations or adaptations
(WORD MEANING??).
Competition - Individuals struggle to survive, those with adaptations best suited to the
environment are more likely to survive.
Survivors pass on genes for the adaptations to their offspring.
Gradually, the population’s gene pool changes and the population evolves.
11. For each of the following types of natural selection include 3 pieces of information: a) what
phenotypes are chosen against, b) what does the resulting population look like after the selection,
c) draw a graph showing what the population would look like before selection and after selection
 Stabilizing
Selection against the extreme phenotypes (physical type)
This causes average phenotype to become much more common (the look of the population is very
similar and average)
Ex. Human weight at birth

Directional Selection
favors one extreme phenotype (physical type)
This causes this particular extreme phenotype to become much more common (the look of the
population is pushed in 1 direction)
Ex. Peppered Moths

Disruptive/Diversifying
Selection that favors both extreme phenotypes (physical type)
This causes extreme phenotypes to become much more common (the look of the population shows
extreme differences)
Ex. Darwin’s Finches
12. What is artificial selection?
Evolution that occurs because of human interference (the evolution is “artificial”)
Ex. Dogs or crops
13. What is convergent evolution, and what are analogous structures?
These species do NOT have a common ancestor. They have merely evolved to look similar.
Convergent evolution – process by which different species evolve similar traits
(SAME FUNCTION, DIFFERENT ANCESTOR)
Example: Birds, bats, and moths have wings, but they did not evolve from a recent common
ancestor.
 Caused by:
◦ living in similar habitats / performing similar functions
Analogous Structures:
 Structures with closely related function but do not come from the same ancestral structure
◦ Same function, different structure
 Example: Birds, bats, and moths have wings, but they did not evolve from each other.
a. How is convergent evolution different from divergent evolution?
Convergent evolution causes organisms that DO NOT have a common ancestor to appear
similar (have analogous structures). Divergent evolution causes that DO have a common
ancestor to appear different.
14. Explain how each of the following gives evidence that supports evolution.
 Fossils-
We can see the change in a population over time through the fossils; Can also use relative
dating (strata) and absolute dating (carbon dating in fossils) to see what time period the
species were alive

Homologous structures – Ex. Whale fin, Human hand, Cat paw, and Bat wing
Divergent evolution- build up of differences between groups which can lead to the development of a
new species
 In other words, two different species that evolved from the same ancestor.
 Caused by populations of the same species:
1. moving to two different environments or..
2. specializing in different areas of the same environment
Homologous Structures:
 Structures in different species that originated from common ancestor
 May have different function but similar structure

Molecular Biology (DNA and amino acid sequences - proteins) – Note: This is the most
important type of evidence proving evolution.
The closer 2 different species DNA is to one another, then the closer those 2 are related.
All living things use DNA and RNA.
The genetic code amongst all living things is universally the same. (In other words, the fact
that the RNA codon AUG gives the amino acid MET in humans is seen in every other living
thing as well)

Vestigial structures
Structures that once had a use but no longer are used (they are still present because there is
no evolutionary selection against having them)

Biogeography
study of the distribution of species and ecosystems in geographic space and through
geological time.

15. Genetics and Molecular Biology (DNA  mRNA  proteins) are the mechanism that gives a population
its physical traits. Through natural selection, the environment then chooses which of those traits are most
fit. To be able to understand how evolution works, you must be able to recall the information learned in
these units. Define the following terms:
a. Chromosome
1 strand of DNA
b. Homologous Chromosome
Chromosomes that are the same size, shape, and carry the same genes. 1 from mom and 1 from dad.
c. Gene
Enough DNA to make one protein
d. Allele
Different versions of a gene (different DNA sequences)
e. Gene pool
All the genes in a population
16. Genetic variation creates biodiversity (the differences in all living things). Explain how the
following things provide the biodiversity that evolution can then act upon.
 Mutations!!
Mutations are a change in a gene that results in a different protein (and therefore a different
phenotype). This is how all new traits come about. If this new trait is beneficial then that
individual will survive longer and reproduce more than the rest of the population, and the
population will evolve to have this trait.
 Type of mutations
o Point Mutations (base substitution)
o Reading frameshift (insertion or deletion)

Sexual Reproduction (Use the terms crossing over, segregation, and random fertilization)
1) Crossing Over – DNA of nonsister chromatids exchange during prophase 1 (so every
chromosome is different)
2) Independent Assortment – Homologous chromosome pairs line up independently of each
other during metaphase I (so each sperm / egg receives a different set of chromosomes)
3) Random fertilization – every sperm/egg is different and it is random as to which sperm
fertilizes an egg to create a zygote
17. Which type of mutations matter in evolution: mutations in somatic cells or mutations in gametes.
Why?
Gametes – Evolution is in a population over many generations (no 1 person has ever
evolved). So, a mutation in a gamete would be passed to the next generation. Because that
individual had a mutation in their first cell, every single cell in their body would show the
mutation and it could continue to be passed on. Mutations to somatic cells would only affect
that 1 area and could not be passed on to offspring (so would not matter in evolution).
18. The factors listed in question 16 all detail how genetic variation can be created. The phenotypic frequencies
in a population can then be shuffled once these variations have been created. Explain how each of the
following aspects of evolution affect the phenotypic frequencies in population.
a. Gene flow
Immigration or emigration of alleles into/out of a population
b. Genetic drift
Changes in a gene pool due to chance (has greater effect on smaller populations)
i. Bottleneck effect (how does this create genetic drift)
Decrease in population size after catastrophe may leave only certain alleles available
ii. Founder effect (how does this create genetic drift)
When a few individuals colonize a new area (same reasoning as bottleneck)
19. Hardy-Weinberg equilibrium allows us to study if a population’s gene pool is changing from
generation to generation. There are 5 rules that must be followed for a population to stay in
equilibrium (or in other words, if you break any of these rules then the population will evolve.
Once again, these would be the 5 things that would cause evolution.) List the 5 rules of HardyWeinberg and explain why breaking each of them would cause evolution to occur.
a. Very large population (so no genetic drift)
i. Bottleneck effect
ii. Founder effect
b. No gene flow between populations (so no introduction of new alleles)
c. No mutations (so no introduction of new alleles)
d. Random mating (so 1 phenotype cannot reproduce at a greater rate than others)
e. No natural selection (so 1 phenotype does not survive longer than others)
20. If a population is in Hardy-Weinberg equilibrium, what happens to the frequencies of the alleles
and the genotypes present in the population change generation and generation?
Allele frequencies and genotype frequencies remain constant (because population is in
equilibrium)
21. What is the equation for allele frequencies in Hardy-Weinberg equilibrium? Note: This is for the
ALLELES, not for the actual organisms themselves.
p+q=1
p= frequency of dominant allele
q = frequency of recessive allele
22. What is the equation for the genotype frequencies in Hardy-Weinberg equilibrium? Note: This is
the equation for the actual organisms.
p2 + 2pq + q2 = 100% = 1.0
p2 = frequency of homozygous dominant individuals
2pq = frequency of heterozygous individuals
q2 = frequency of homozygous individuals
23. A population of snakes is in Hardy-Weinberg equilibrium. A dominant allele for skin color makes
the snake black while the recessive allele makes them albino. A sample of 100 snakes was taken
from a population. Of the 100 snakes captured, 75 of them were black and 25 were white. What
percentage of the 100 snakes would be expected to be heterozygous? (Hint: Steps to do this
problem. 1. Find the percentage of the recessive allele (q) from the number of homozygous
recessive (q2), 2. Find the percentage of the dominant allele (p) by plugging calculate
number of heterozygotes by plugging the allele frequencies into the proper location in the
genotype frequency equation.)
1) 25 / 100 = white which means they are homozygous recessive
^^ q2 = 0.25
Take square root of q2 to find q. Square root of 0.25 is 0.5. So q = 0.5
2) p + q = 1
p + 0.5 = 1
p = 0.5
3) p2 + 2pq + q2 = 1
(0.5)2 + 2(0.5)(0.5) + (0.5)2 = 1
0.25 + 0.5 + 0.25 = 1
p2 (homozygous dominant) = 25%
2pq (heterozygous) = 50%
q2 (homozygous recessive) = 25%
24. What is sexual dimorphism?
Di = 2 and morph = shape
This means males and females look differently
Like peacocks, humans, deer
25. What is coevolution?
2 species having a symbiotic relationship and evolving together
26. We have most discussed phenotype (physical) changes in organisms over time due to differing levels of
fitness. Behaviors can also evolve over time as well. Define the difference in the following type of
behaviors:
a. Innate behavior –
A behavior you are born with. It is so important to an organism’s fitness that if they didn’t do it, they
would survive/reproduce.
b. Learned behavior A behavior learned during one’s lifetime.