Download Unit 5 Answers - Iowa State University

Exam 5 Review: Evolution
and Speciation
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Andre
BIOL 211
Dr. Debinski, Dr. Heath
November 6
Explain the differences between the theories explaining evolution over time.
Greeks:
Great Chain of Being –
organized based on
complexity
Typological Thinking –
all animals are specific
unchanging types
Lamarck:
Inheritance of Acquired
Characteristics
Darwin:
Theory of Evolution by Natural
Selection –
Pattern – evolution
Process – descent with
modification
Evolution acts on populations
Natural selection acts on
individuals
Explain the following evidences for evolution.
Fossils:
-
Radioactive Decay Data: shows absolute ages of extinct animals – disproves
typological thinking
-
Transitional Features: traits that are the intermediate between the ancestral
species and the modern species
-
Law of Succession: fossil species are similar to the living species in the same
area
Vestigial Traits: non-functional traits in an organism, but similar or functional in another
related organism
Homology:
Genetic Homology: similarity in DNA
Structural Homology: homology occurring at the adult stages (similar structure)
Developmental Homology: homology occurs during the developmental stages
(embryonic development)
Internal Consistency: data and research from independent sources to support a theory
What are Darwin’s Four Postulates? How does modern science interpret them?
1. Individuals vary in their traits
2. Variations are heritable, then passed on to offspring
3. More offspring are produced than can survive
4. Certain heritable traits are better for survival and reproduction
1. Heritable Variation (1 + 2)
2. Leads to different reproductive success (3 + 4)
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Compare the terms.
Adaptation vs Acclimatization – adaptation is the heritable trait that increases fitness in a
specific environment; acclimatization the genotype is staying the same, the phenotype is
changing to the environment
Polygeny vs Pleiotropy – polygenic traits are affected by multiple genes; pleiotropic traits are
when a single allele is affecting multiple traits
Pleiotropic traits are a genetic constraint on evolution
Explain how the Theory of Evolution by Natural Selection is testable.
1. Drug resistant tuberculosis
2. Beak size and body size changes in Galapagos finches
Mutations occur because the organism needs to adapt and solve a problem. Mutations occur at
random
T or False
Evolution is progressive, continually producing better and more complex organisms.
T or False
There is no such thing as a “higher” or “lower” organism because each organism tends to be well
adapted to their environment.
True or F
Define the following terms:
The Modern Synthesis: era where scientists research proves evolution (Darwin’s theory)
Gene Pool: genotypes and their frequencies in a population
What is the Hardy-Weinberg Principle?
p+q=1
p2 + 2pq + q2 = 1
p = dominant allele frequency
q = recessive allele frequency
p2 = homozygous dominant genotype
2pq = heterozygous genotype
q2 = homozygous recessive genotype
What is inbreeding depression and what does Heterozygote Advantage have to do with it?
Inbreeding Depression – decline in fitness in a population because of increases in the
homozygous individuals
Heterozygote Advantage – advantage towards heterozygote individual’s fitness
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu
What are the four mechanisms that change allele frequencies in populations? How is this related
to the Hardy-Weinberg Principle?
Natural Selection
Genetic Drift
Gene Flow
Mutation
Hardy-Weinberg CANNOT have any of the previous occurring because evolution would be
happening in the population. Hardy-Weinberg also requires random mating
Explain the four patterns of natural selection.
Directional Selection: favoring one side/direction of characteristics
Stabilizing Selection: favors the average, does not favor the extremes
Disruptive Selection: favors the extremes
Balancing Selection: all variations of the trait are equally favored
What is genetic drift?
Random change in the allele frequencies. Easily acts on small populations
-
Founder effect – a small new group starts a new population in a new area, resulting
in changes to the allele frequencies
-
Bottleneck effect – large amount of original population is killed off, resulting in
changes to the allele frequencies
What is gene flow?
Movement of alleles between populations
What is mutation?
Random change in a gene (most are deleterious, some are beneficial)
Speciation…
Explain how these changes result in speciation.
1. Genetic Isolation – gene flow is interrupted between populations
2. Genetic Divergence – characteristics change enough to prevent interbreeding between
the said populations
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu
There are 3 main approaches to identify a species. Explain each and provide examples.
Biological Species Concept (BSC):
Two species are different because they can’t interbreed or produce viable/fertile offspring
Prezygotic isolation – before fertilization; based on habitat, behavior, mechanical
differences
Postzygotic isolation - after fertilization; offspring don’t survive or can’t reproduce
Low hybrid zygote viability – doesn’t make it past the egg/developmental stage
Low hybrid adult viability – lives, but it has a shortened life/weaker
Hybrid infertility – lives, but completely infertile
Morphospecies Concept (MSC):
Different in size and shape and other physical features
Disadvantages:
Polymorphic Species – can be split into 2+ species
Cryptic species – different in non-morphological/physical traits
Phylogenetic Species Concept (PSC):
Species are defined as the smallest monophyletic groups based on their evolutionary history
Disadvantage: subspecies
How is allopatric speciation different from sympatric speciation?
Allopatric: different areas
-
Dispersal: group of organisms leaves a pop, moves to a new area and colonizes to
form a new population
-
Vicariance: physical barrier splitting a population
Sympatric: same area
-
External events: Disruptive selection based on ecological niches
-
Internal events: Chromosome mutation – polyploid speciation
o Autopolyploid – offspring of a parent that self-fertilizes
o Allopolyploid – parents that are different species
When isolated populations come into contact, interbreeding can occur. Other outcomes include:
-
Reinforcement: selection occurring for traits that isolate populations
-
Hybrid Zones: the geographic area where 2 populations can interbreed and
commonly have hybrid offspring
1060 Hixson-Lied Student Success Center  515-294-6624  [email protected]  http://www.si.iastate.edu