Evolution Unit Test Study Guide
Be familiar with the following terms and concepts and cite examples from the text.
Evolution- the process of change over time
Charles Darwin and his contribution to science- developed a scientific theory of biological evolution that explains how
modern organisms evolved over long periods of time through descent from common ancestors
Summary of Darwin’s Key observations (i.e. specific organisms):
Collected 68 species of beetles from Brazilian rainforest
Observed flightless ground dwelling birds in South America and in Australia
Collected finches in Galapagos Islands
Noticed that rabbits were missing from grasslands of Africa and South America
3 patterns of diversity Darwin observed (cite examples)
1. species vary globally - rhea of South America VS ostrich of Australia
2. species vary locally – tortoise shells differ from island to island in the Galapagos
3. species vary over time – extinct glyptodont is similar to the armadillo
Summary of Darwin’s Theory of Evolution by Means of Natural Selection
The process by which organisms with variations most suited to their local environment survive and leave more offspring.
The environment influences fitness of the organism.
Know the following people and their contribution to Darwin’s theory
Lamarck (include what was wrong with his theory)- suggested that organisms could change during their lifetimes
by selectively using or not using various parts of their bodies. He also suggested that individuals could pass these
acquired traits on to their offspring, enabling species to change over time.
All organisms have an inborn urge to become more complex and perfect
Organisms do not have an inborn urge to become more perfect, evolution does not mean that a species becomes
“better”, evolution does not progress in a predetermined direction, traits acquired by individuals during their lifetime
cannot be passed on to offspring
Alfred Russell Wallace- wrote an essay on evolution with ideas similar to Darwin’s, prompted Darwin to write
his book, “On the Origin of Species”
Hutton-concludes that our Earth is more than a few thousand years old, and that the processes that changed the
Earth in the past are the same processes that operate in the present
Lyell- concludes that the laws of nature are constant over time, “uniformitarianism”, therefore is would take
more than a few thousand years to carve out a valley like the grand canyon
Malthus- if human population grew unchecked, there wouldn’t be enough living space and food to support that
population
Artificial Selection- nature provides the variations, and humans select those they find useful through breeding practices
Natural selection- the process by which organisms with variations most suited for their local environment survive and
leave more offspring
Under what 3 conditions does natural selection occur?
1. more individuals are born than can survive ( the struggle for existence )
2. there is natural heritable variation ( variation and adaptation)
3. there is variable fitness between individuals ( survival of the fittest )
How does it affect a species?
From generation to generation, populations continue to change as they become better adapted, or as their
environment changes
Fitness- how well an organism can survive and reproduce in its environment
Principle of common descent- all species - living and extinct - are descended from ancient common ancestors
Describe the difference between natural selection on single gene traits vs. polygenic traits
Single gene traits will have two distinct phenotypes, polygenic traits result in a range of phenotypes
Types of selection (for polygenic traits):
Directional- when individuals at one end of the curve have higher fitness than other individuals, the range of
phenotypes shifts because some individuals are more successful at surviving and reproducing than others, increase in
average beak size of Galapagos finches is an example
Stabilizing- when individuals near the center of the curve have higher fitness than individuals at either end,
mass of human infants at birth is an example
Disruptive- when individuals at either end of the curve have higher fitness than the middle, birds with large or
small beaks might have an advantage
Gene pool- consists of all the genes, including all the different alleles for each gene, that are present in a population
Genetic drift- over time, a series of chance occurrences can cause an allele to become more or less common in a
population
Founder effect- occurs when a small subgroup of a population migrates into an established population
Bottle neck effect- a change in allele frequency following a dramatic reduction in the size of a population, this can
sharply reduce a populations genetic diversity
Allele frequency- the number of times that an allele occurs in a gene pool
Genetic equilibrium- a population where the allele frequency stays the same
Hardy-Weinberg principal- the allele frequencies in a population remain constant unless one or more factors cause
those frequencies to change
Equation (must understand each variable):
P + q = 1.0
p = frequency of dominant gene in a population
P2 + 2pq + q2 = 1.0
q = frequency of recessive gene in population
p2 = frequency of homozygous dominant individuals in a population
2pq = frequency of heterozygous individuals in a population
q2 = frequency of homozygous recessive individuals in a population
5 conditions that can Maintain genetic equilibrium
1. the population must be large
2. there can be no mutations
3. there must be random mating
4. there can be no movement into or out of the population
5. no natural selection takes place
Describe the following sources of evidence for evolution:
1. Biogeography- The study of where organisms live now and where they and their ancestors lived in the past.
Patterns in the distribution of living and fossil species tells us how modern organisms evolved from their
ancestors
2. Age of Earth and fossil record- radioactive dating indicates that Earth is about 4.5 billion years old ( universe is
about 13.8 billion years old )
a. Many recently discovered fossils form series that trace the evolution of modern species from extinct
species, the evidence we do have tells an unmistakable story of evolutionary change
Geologic Time Scale- based on both relative and absolute dating, the major divisions are eons, eras and periods
Index fossils- used to find relative age of rock layers and surrounding fossils in those layers
What makes a good index fossil? Easy to recognize, have a wide geographic range, but existed for a
relatively short period of time
Relative dating- determines the relative age of a rock layer or fossil by comparing its placement with that of
fossils in other rock layers
Radiometric dating- uses the number of remaining reactive atoms to calculate the age of a sample
3. Comparative anatomy
Homologous structures- structures that are shared by related species and that have been inherited from a
common ancestor ( organisms that share homologous structures have descended, with modification, from a common
ancestor )
Vestigial structures- body parts that are reduced in size or not used by an organism ( hip bones in a bottlenose
dolphin )
4. Universal genetic code and molecular biology – provide evidence of common descent
4 types of isolation that lead to speciation:
1.
Reproductive isolation - when a population splits into two separate species they no longer interbreed with each
other ( due to behavioral isolation, geographic isolation or temporal isolation )
2. Behavioral isolation - occurs when two populations that are capable of interbreeding develop differences in
courtship rituals or other behaviors, then they do not interbreed ( Eastern and Western meadowlarks use
different mating songs )
3. Geographic isolation - when two populations are separated by geographic barriers like lakes, rivers, or
mountains ( abert’s squirrel and kiabab squirrel of the Grand Canyon )
4. Temporal isolation – When two or more species reproduce at different times ( species of orchids in the rain
forest bloom on different days, therefore they cannot spread pollen to each other )
Rate of Evolution- gradualism vs. punctuated equilibrium
Gradualism says that evolution is a slow and steady process, punctuated equilibrium describes evolution as being
interrupted by brief periods of rapid change ( could be thousands of years )
Macroevolution- describes patterns in anatomy, physiology,phylogeny, ecology and behavior of living and fossil
organisms which have resulted as a result of evolution over long periods of time
Compare/contrast the two patterns of macroevolution:
Adaptive radiation is the process by which a single species or a small group of species evolves over a relatively short time
into several different forms that live in different ways. (after dinosaur extinction, mammals diversified through adaptive
radiation )
Convergent evolution is the process by which unrelated organisms evolve into forms that resemble on another.
(mammals that feed on termites evolved five times in different regions in the world )
Coevolution- when a relationship between two organisms becomes so specific that neither organism can survive
without the other, an evolutionary change in one organism may be followed by a change in the other organism. (flowers
and pollinators )
Scientific names vs. common names
Common names can vary from place to place, scientific names remain the same
Binomial nomenclature (what is it and who is responsible for it?)
Carlos Linnaeus developed the system of binomial nomenclature meaning that each organism is assigned a two-part
scientific name ( Genus and species (specific epithet))
Format used when writing scientific names ( Genus capitalized and specific epithet lowercase, all italicized or
underlined if hand-written)
Systematics - science of naming and grouping organisms by their evolutionary relationships
Taxon (taxa pl.)
-
Refers to a ranking level on the Linnaean system of classification
Linnaean system of classification: Kingdom, phylum, class, order, family, genus, species
Domain- a larger, more inclusive category than a kingdom
What are the 3 domains of living things?
Bacteria, Archaea, Eukarya
Study Figure 18-14
Modern Classification systems
Cladograms are used to show – how species and higher taxa are related to one another by showing how evolutionary
lines, or lineages, evolved and branched off from common ancestors over time
Shared derived characters- a trait that arose in the common ancestor of a particular lineage and was passed along to its
descendents
How do genes function as shared derived characters?
The more similar the DNA sequences of two species, and the more derived characters they share, the more recently
they shared a common ancestor. Therefore, the more closely related in evolutionary terms.
Characteristics of early Earth:
Atmosphere with little or no free oxygen, composed primarily of carbon dioxide, water vapor, nitrogen with lesser
amounts of carbon monoxide, hydrogen sulfide and hydrogen cyanide. Sky would be pinkish-orange, oceans would be
brown with lots of dissolved iron
Miller and Urey- 1953 – used the work of Oparin to create an experiment that mimics the early Earth. After a week the
experiment yielded amino acids. In 1955 Miller repeated experiment and produced cytosine and uracil
Endosymbiotic theory- prokaryotes were the ancestors of eukaryotes. A symbiotic relationship evolved over time
between primitive eukaryotic cells and the prokaryotic cells within them
Order of evolution of traits (up to multicellularity) Prokaryotes, photosynthesis (cooled the earth and added O2 to
atmosphere), aerobic respiration, eukaryotes, sexual reproduction, multicellularity
Describe how sexual reproduction contributes to diversity.
Offspring receive genetic material from two parents. Meiosis and fertilization shuffle and reshuffle genes, generating
lots of genetic diversity
What other mechanism previously discussed leads to diversity (hint: meiosis)?
Crossing over