Big Idea 1 Review: The process of evolution explains the diversity and
unity of life.
Connecting evolutionary changes in a population over time to change(s) in the environment by
describing 2–3 examples
peppered moth, sickle cell anemia, DDT resistance in insects, introduction of nonnative species,
introduction of predator, cataclysmic event
The sickle-cell allele causes mutations in hemoglobin but also confers malaria resistance
It exemplifies the heterozygote advantage
Describing a limited set of given conserved features and core processes shared within and between
domains of life
DNA as the genetic material, a shared genetic code, common metabolic pathways (photosynthesis and
CR, ETC’s), number of limbs, etc as evidence of common ancestry.
Explaining how a phylogenetic representation reflects ancestral differences and similarities
In addition to fossils, phylogenetic history can be inferred from morphological and molecular similarities
in living organisms
Organisms with very similar morphologies or similar DNA sequences are likely to be more closely related
than organisms with vastly different structures or sequences
In constructing a phylogeny, systematists need to distinguish whether a similarity is the result of
homology or analogy
Homology is similarity due to shared ancestry
Analogy is similarity due to convergent evolution
Describing how given data support the concept of a common ancestry within and between phylogenetic
domains and for all life.
Analyzing data related to questions of speciation and extinction throughout Earth’s history.
Analysis may include (1) identifying patterns of speciation and/or extinction, (2 determining rates of
speciation and/or extinction, and (3) connecting changes in gene frequency to speciation.
Justifying the selection of data that address questions related to reproductive isolation and speciation
pre- and post-zygotic and allopatric and sympatric isolation
Describing a model that represents evolution within a population and providing evidence to support the
description
evolution due to genetic variation, such as antibiotic resistance, structure, or process, such as the brain,
immune system, or linkage of a given population to common ancestors, through genetic, physiological,
and morphological data
Evaluating scientific hypotheses about the origin of life on Earth
organic “soup” model, solid surface, and predicting how a hypothesis would be revised in light of new
evidence
“RNA World” hypothesis, new ideas about reducing atmosphere
Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or
membrane-like structure
Experiments demonstrate that protobionts could have formed spontaneously from abiotically produced
organic compounds
For example, small membrane-bounded droplets called liposomes can form when lipids or other organic
molecules are added to water
The “RNA World” and the Dawn of Natural Selection
The first genetic material was probably RNA, not DNA
RNA molecules called ribozymes have been found to catalyze many different reactions, including:
Self-splicing
Making complementary copies of short stretches of their own sequence or other short pieces of RNA
Early protobionts with self-replicating, catalytic RNA would have been more effective at using resources
and would have increased in number through natural selection
Describing several sources of evidence from multiple scientific disciplines that support biological
evolution
Fossil records, morphological features, DNA and/or protein sequences, radioactive dating, distribution,
or extant and extinct species
The absolute ages of fossils can be determined by radiometric dating
The magnetism of rocks can provide dating information
Magnetic reversals of the magnetic poles leave their record on rocks throughout the world
The Permian extinction killed about 96% of marine animal species and 8 out of 27 orders of insects
It may have been caused by volcanic eruptions
The Cretaceous extinction doomed many marine and terrestrial organisms, notably the dinosaurs
It may have been caused by a large meteor impact
Mass extinctions provided life with unparalleled opportunities for adaptive radiations into newly
vacated ecological niches
The First Prokaryotes
Prokaryotes were Earth’s sole inhabitants from 3.5 to about 2 billion years ago
Photosynthesis and the Oxygen Revolution
The earliest types of photosynthesis did not produce oxygen
Oxygenic photosynthesis probably evolved about 3.5 billion years ago in cyanobacteria
The First Eukaryotes
The oldest fossils of eukaryotic cells date back 2.1 billion years
Endosymbiotic Origin of Mitochondria and Plastids
The theory of endosymbiosis proposes that mitochondria and plastids were formerly small prokaryotes
living within larger host cells
The prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell as
undigested prey or internal parasites
In the process of becoming more interdependent, the host and endosymbionts would have become a
single organism
Key evidence supporting an endosymbiotic origin of mitochondria and plastids:
Similarities in inner membrane structures and functions
Both have their own circular DNA
The Earliest Multicellular Eukaryotes
Molecular clocks date the common ancestor of multicellular eukaryotes to 1.5 billion years
The oldest known fossils of eukaryotes are of relatively small algae that lived about 1.2 billion years ago
The “Cambrian Explosion”
Most of the major phyla of animals appear in the fossil record of the first 20 million years of the
Cambrian period
Two animal phyla, Cnidaria and Porifera, are somewhat older, dating from the late Proterozoic
Molecular evidence suggests that many animal phyla originated and began to diverge much earlier,
between 1 billion and 700 million years ago
Colonization of Land by Plants, Fungi, and Animals
Plants, fungi, and animals colonized land about 500 million years ago
Symbiotic relationships between plants and fungi are common today and date from this time
Applying mathematical models (e.g., Hardy-Weinberg formula) to convert a data set from a table of
numbers reflecting a change in the genetic makeup of a population over time and explaining the
cause(s) and effect(s) of this change, such as natural selection, genetic drift, changes in population size,
migration, mutations, and nonrandom mating.
Hardy-Weinberg
Their formulas are used to establish allele frequencies at genetic equilibrium (no evolution is occurring)
The following conditions must all be fulfilled
The population is very, very large
There is no migration of individuals
No mutations
Mating is completely random
All members survive and reproduce successfully
The formulas
Allele frequency: fraction of that particular allele in the population
The sum of all the allele frequencies = 1
p = frequency of the dominant allele
q = frequency of the recessive allele
p+q=1
To figure the frequency of each genotype use: p2 + 2pq + q2 = 1
Microevolution
Change in relative allele frequency over time; if allele frequency changes evolution occurs
Causes of microevolution
Genetic drift: change in a small gene pool due to chance
Bottleneck event: population size is drastically reduced, leaving only the alleles of the survivors in the
gene pool
Founder effect: the small group starting a new colony contribute only their alleles to the new population
Gene flow: gain or loss of alleles through immigration or emigration
Non-random mating: organisms tend to mate with neighbors although they are capable of mating with
any member of their species anywhere on earth