Chapter 13: How populations evolve
A.Explain what a scientific theory is and how it differs from the colloquial use of “theory”.
A theory is a widely accepted explanatory idea that is broader in scope than a
hypothesis, generates new hypotheses, and is supported by a large body of evidence.
B.Explain why the concept of evolution is regarded as a theory of great significance
C.Describe how fossils provide strong evidence for the theory of evolution.
The fossil record shows a constant change in species and the fact that many
species have become extinct and is therefore strong evidence for evolution.
D.Describe how homologies and molecular biology provide strong evidence for the
theory of evolution.
The function of homologous structures differs, so if they had been uniquely
engineered, it would have been expected that their basic designs would be very
different, so the logical explanation is that they are variations on an anatomical structure
of an ancestral organism that over millions of year has become adapted to different
functions. Homologies therefore provide strong evidence for the theory of evolution, as
does molecular biology, as all living things share to process of going from DNA to
proteins to amino acids.
E.Explain how artificial selection influenced Darwin’s development of the idea of natural
selection.
Because Darwin thought that species formed gradually over long periods of time,
he knew that he wouldn’t be able to study the evolution of new species by direct
observation. However, insights into how incremental change occurs could be seen in
examples of artificial selection.
F.Explain why individuals cannot evolve.
Populations, not individuals, evolve because natural selection occurs through
interactions between individual organisms and the environment.
G.Describe the five conditions required for the Hardy-Weinberg equilibrium.
1. Very large population (the smaller the population, the more likely that allele
frequencies will fluctuate by chance from one generation to the next)
2. No gene flow between populations (when individuals move into or out of
populations, they add or remove alleles, altering the gene pool)
3. No mutations (mutations modify the gene pool)
4. Random mating (if individuals mate preferentially genotype frequencies
change)
5. No natural selection (the unequal survival and reproductive success of
individuals can alter allele frequencies)
H.Use the Hardy-Weinberg equation to determine genotype and allele frequencies in a
population.
I.Discuss the key components of natural selection.
The key components are variation and heritability. There must be a variety of
characteristics that are inherent to a given species or organism, and some of them must
be able to be passed on to the next generation.
J.Describe how natural selection, genetic drift, and gene flow cause microevolution.
Natural selection: the environment favors advantageous characteristics, and
those are the alleles that are passed on to the next generation
Genetic drift: Chance events can cause allele frequencies to fluctuate
unpredictably from one generation to the next. The smaller the population, the more
impact genetic drift is likely to have.
Gene flow: A population may gain or lose alleles when fertile individuals move
into or out of a population or when gametes are transferred between populations.
K.Describe the ways that natural selection alters populations.-see J
L.Explain why natural selection cannot lead to perfect organisms.
1. Selection can act only on existing variations. It favors only the fittest variants
from the phonotypes that are available, which may not be the ideal traits. New,
advantageous traits do not rise on demand.
2. Evolution is limited by historical constraints. Evolution doesn’t scrap ancestral
anatomy and build each new complex structure from scratch. Rather, it co-opts existing
structures and adapts them to new situations.
3. Adaptations are often compromises.
4. Chance, natural selection, and the environment interact. Chance events such
as wind don’t necessarily transport the individuals that are best suited to the new
environment. In small populations, genetic drift can result in the loss of beneficial
alleles. Also, the environment may change unpredictably from year to year.
Chapter 14: The origin of species
A.Distinguish between microevolution and speciation
Microevolution is changing in allele frequency, and is the mini steps that lead to
speciation, which is a change in a population over a long period of time.
B.Describe several ways to define species.
