Compare and contrast gradualism (uniformitarianism) and catastrophism
explanations of the history of earth.
- Catastrophism -> The hypothesis by Georges Cuvier that each
boundary between strata corresponded in time to a catastrophe that
had destroyed many of the species living there.
-> A view of Earth's history that attributes profound change to
the cumulative product of slow, but continuous processes.
- Uniformitarianism -> Charles Lyell's idea that geographic
processes have no changes throughout history.\
• How does descent with modification explain the adaptations of
organisms as well as the unity and diversity of life?
- -decent with modification simply means that organisms share
many characteristics, each coming from a common ancestor, the
diverse modifications come from each animal living in different
environments. They accumulated these modifications over
• How are natural selection and artificial selection different?
- Artificial Selection -> Modification of a species by human
intervention so that certain desirable traits are represented in
- Natural Selection -> The process
in nature by which, according to Darwin's theory of evolution, only
the organisms best adapted to their environment tend to survive and
submit their genetic characteristics in increasing numbers to
• What are Darwin's four observations/inferences about nature?
- Observation 1 - members of a population vary in inherited
- Observation 2- all species can produce more offspring
than their environment can support, and many survive to
- Inference 1 - individuals whose inherited traits
give them a higher probability of surviving and reproducing in a
given environment tend to leave more offspring.
- Inference 2
- the unequal ability of individuals to survive and reproduce will
lead to the accumulation of favorable traits in the population over
• Summarize the main ideas of natural selection. What role do
individuals versus populations have in this process?
- Natural selection is a process in which individuals with
favorable inherited traits are more likely to survive and
• List two direct observations of evolutionary change and explain.
- Two examples provide evidence for natural selection: natural
selection in response to introduced plant species, and the evolution
of drug-resistant bacteria
• What are homologous structures?
- Homologous structures are anatomical resemblances that
represent variations on a structural theme present in a common
• Explain the four types of data that are used to document
- The fossil record
- Direct observations
• List and explain four sources of genetic variation.
- gene duplication
- Crossing over
• Why is genetic variation important?
- Variation in heritable traits is a prerequisite for
• List the five conditions for Hardy-Weinberg equilibrium and explain
why populations are rarely in Hardy-Weinberg equilibrium.
- No mutations
- Random mating
- No natural
- Extremely large population size
- No gene
• What does the Hardy-Weinberg equation test?
- Tests whether a population is evolving or not.
Hardy-Weinberg equation describes the genetic makeup we expect for a
population that is NOT evolving at a particular locus
• Describe three ways that allele frequencies can be altered in a population.
- Natural selection
- Natural selection results in alleles
being passed to the next generation in proportions that differ
from those in the present generation.
- Genetic drift (bottleneck and founder effects) including the
four key points
- The process in which chance events cause
allelic frequencies to fluctuate unpredictably from one
generation to the next
The bottleneck effect is a sudden reduction in
population size due to a change in the environment
The founder effect occurs when a few
individuals become isolated from a larger population
- Explain gene flow
- The transfer of alleles into
or out of a population due to the movement of fertile
individuals or their gametes
• How does natural selection lead to adaptive evolution?
- Natural selection consistently selects for traits that will
allow members of a population to best adapt to their environment,
while gene flow and genetic drift can possibly decrease the
• Explain the role of directional, disruptive, stabilizing, and
sexual selection in natural selection.
- Directional selection favors individuals at one extreme end of
the phenotypic range
- Disruptive selection favors
individuals at both extremes of the phenotypic range
Stabilizing selection favors intermediate variants and acts against
- Sexual selection is natural selection
- It can result in sexual dimorphism, marked
differences between the sexes in secondary sexual
Intrasexual selection is direct competition
among individuals of one sex (often males) for mates of the
Intersexual selection, often called mate
choice, occurs when individuals of one sex (usually females) are
choosy in selecting their mates
• What are the four different species concept approaches to defining
The biological species concept states that a
species is a group of populations whose members have the potential
to interbreed in nature and produce viable, fertile offspring; they
do not breed successfully with members of other populations
The morphological species concept defines a species
by structural features
The ecological species concept views a species in
terms of its ecological niche
- Whether two can survive in
each other’s environment.
The phylogenetic species concept defines a species
as the smallest group of individuals on a phylogenetic tree
• Know the prezygotic and postzygotic reproductive barriers that
contribute to reproductive isolation.
- Prezygotic barriers block fertilization from occurring by
- Impeding different species from attempting to mate
- Preventing the successful completion of mating
Hindering fertilization if mating is successful
Habitat isolation: Two species encounter
each other rarely, or not at all, because they occupy
different habitats, even though not isolated by physical
Temporal isolation: Species that breed at
different times of the day, different seasons, or different
years cannot mix their gametes
Behavioral isolation: Courtship rituals and
other behaviors unique to a species are effective barriers
Mechanical isolation: Morphological
differences can prevent successful completion of mating
Gametic Isolation: Sperm of one species may
not be able to fertilize eggs of another species
- Postzygotic barriers prevent the hybrid zygote from
developing into a viable, fertile adult
Reduced hybrid viability: Genes of the
different parent species may interact and impair the
hybrid ’s development or survival in its
- Reduced hybrid
Reduced hybrid fertility: Even if
hybrids are vigorous, they may be sterile
- Hybrid breakdown
Hybrid breakdown: Some
first-generation hybrids are fertile, but when they mate
with each other or with either parent species, offspring
of the next generation are feeble or sterile
• Explain how allopatric and sympatric speciation occur.
- In allopatric speciation, gene flow is
interrupted or reduced when a population is divided into
geographically isolated subpopulations
- For example, the
flightless cormorant of the Galápagos likely originated from a
flying species on the mainland
speciation occurs in populations that live in the same geographic
area. Occurs if gene flow is reduced through polyploidy, sexual
selection, and habitat differentiation
• Explain the time course of speciation in terms of the fossil record
and rate of speciation.
Fossil records don’t show gradual changes between species they just
show a rapid change
• Differentiate between macroevolution and microevolution.
- Macroevolutionary changes over large time scales
- Formation of a new species
- microevolution -changes within a species; not the creation of a
- Examples: resistant bacteria to antibiotics and
insects resistant to pesticides.
• Understand what information can be found in the fossil record.
- Old layers in the fossil record would be associated with older
- The fossil record reveals changes in the history of
life on Earth
- The fossil record shows changes in kinds of
organisms on Earth over time
- The fossil record is biased in
favor of species that
- Existed for a long time
Were abundant and widespread
- Had hard parts
- Fossil record only shows sudden change not gradual
change in species.
- The fossil record is biased in favor
of species that
- Existed for a long time
abundant and widespread
- Had hard parts
• Explain how radiometric dating is performed.
- The "absolute" ages of fossils can be determined by
- radioactive “parent” isotope decays to a
“daughter” isotope at a constant rate
• Know the hypothesis for the origin of eukaryotes through serial endosymbiosis.
- The endosymbiont theory proposes that mitochondria and
plastids (chloroplasts and related organelles) were formerly small
prokaryotes living within larger host cells
• Understand how continental drift could explain the distribution and
diversity of life on earth.
- Continental drift has many effects on living organisms
- A continent’s climate can change as it moves north or
- Separation of land masses can lead to allopatric
• What is the role of Hox genes in animal development?
- homeotic genes that determine where basic features are located,
providing positional information in an animal embryo. Changes to
these genes result in significant morphological changes. For example
two hox genes prevent limb formation in snakes.
• How can hierarchical classification and phylogeny be linked together?
- Phylogeny is the evolutionary history of a species or group of
- Systematists depict evolutionary
relationships in branching phylogenetic trees
• Know how to "read" a phylogenetic tree.
- Phylogenetic trees show patterns of descent, not phenotypic
- Phylogenetic trees do not indicate when species
evolved or how much change occurred in a lineage.
- It should
not be assumed that a taxon evolved from the taxon next to it.
- Shared ancestral
- Shared derived characteristics
• Explain how phylogenies are determined.
- morphological and molecular data. To infer phylogenies,
- information about morphologies, genes,
- biochemistry of living organisms.
• Understand the difference between analogy (convergent evolution)
and homology (shared ancestry).
- Homology is similarity as a result of shared ancestry
- Analogy is similarity due to convergent evolution.
• What is a shared derived character?
- A shared derived character is an evolutionary novelty unique to
a particular clade. In comparison with its ancestor, an organism has
both shared and different characteristics.
• How are maximum parsimony and maximum likelihood different?
- Maximum parsimony assumes that the tree that requires the
fewest evolutionary events (appearances of shared derived
characters) is the most likely
- The principle of maximum
likelihood states that, given certain rules about how DNA changes
over time, a tree can be found that reflects the most likely
sequence of evolutionary events
- Parsimony is the fewest
turns But since there’s construction the route is slower -so maximum
• What are molecular clocks and how can they be used?
- A molecular clock uses constant rates of evolution in some
genes to estimate the absolute time of evolutionary change
- similar genes or segments of DNA occur in different species and
appear to have a reliable mutation rates, they can be used as a