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Evolution standards

1. 1.A.1: Natural selection is a major mechanism

a. According to Darwins theory of natural selection. Competition for limited
resources result in differential survival. Individuals with more favorable
phenotypes are more likely to survive and produce more offspring, thus
passing traits to subsequent generations.
b. Evolutionary fitness is measured by reproductive generations
c. Genetic variation and mutation paly roles in natural selection. A diverse
gene pool is important for survival of a species in a changing environment
d. Environments can be more or less stable or fluctuating, and this affects
evolutionary rate and direction, different genetic variations can be
selected in each generation.
e. An adaption is a genetic variation that is favored by selection and is
manifested as a trait that provides and advantage to an organism in a
particular environment.
f. In addition to natural selection, chance and random events can influence
the evolutionary process, especially for small populations.
g. Condition for a population or an allele to be in hardy Weinberg equilibrium
are (1) a large population size, (2) absence of migration, (3) no net
mutations, (4) random mating and (5) absences of selection. These
conditions are seldom met.
h. Mathematical approaches are used to calculate the changes in allele
frequency, providing evidence for the occurrence of evolution in a
- Graphical analysis of allele frequencies in a population
2. 1.A.2: Natural selection acts on phenotypic variations in populations.
a. Environments change and act as selective mechanism on populations.
- Flowering time in relation to global climate change
- Peppered moth
b. Phenotypic variations are not directed by the environment but occur
through random changes in the DNA and through new gene combinations.
c. Some phenotypic variations significantly increase or decrease fitness of
the organism and the population.
- Sickle cell anemia
- Peppered moth
- DDT resistance in insects
d. Humans impact variation other species.
- Artificial selection
- Loss of genetic diversity within a crop species
- Overuse of antibiotics
3. A.3: Evolutionary change is also driven by random processes.
a. Genetic drift is a nonselective process occurring in small populations.
b. Reduction of genetic variation within a given population can increase the
differences between populations of the same species.

4. 1.A.4: Biological evolution is supported by scientific evidence from many

disciplines, including mathematics.
a. Scientific evidence of biological evolution uses information from
geographical, geological, physical, chemical and mathematical
b. Molecular, morphological and genetic information of existing and extinct
organisms add to our understanding of evolution.
1. Fossils can be dated by a variety of methods that provide evidence for
evolution. These include the age of the rocks where a fossil is found,
within phylogenetic trees, and the mathematical calculations that take
into account information from chemical properties and/or geographical
2. Morphological homologies represent feature shared by common
ancestry, vestigial structures are remnants of functional structures,
which can be compared to fossils and provide evidence for evolution.
3. Biochemical and genetic similarities, in a particular DNA nucleotide and
protein sequences, provide evidence for evolution and ancestry.
4. Mathematical models and simulations can be used to illustrate and
support evolutionary concepts.
- Graphical analyses of allele frequencies in a population
- Analysis of phylogenetic trees
- Construction of phylogenetic trees based on sequence data

5. 1.B.2: Phylogenetic trees and cladograms and graphical representations of

evolutionary history that can be testes.
a. Phylogenetic trees and cladograms can represent traits that are either
derived or lost due to evolution.
- Number of heart chambers in animals
- Opposable thumbs
- Absence of legs in some sea mammals
b. Phylogenetic trees and cladograms illustrate the speciation that has
occurred, in that relatedness of any two groups on the tree is shown by
how recently two groups on the tree is show by how recently two
groups had a common ancestor.
c. Phylogenetic trees and cladograms can be constructed from
morphological similarities of living or fossil species, and from DNA and
protein sequence similarities, by employing computer programs that
have sophisticated ways of measuring and representing relatedness
among organisms.
d. Phylogenetic trees and cladograms are dynamic, based on the
biological data used, new mathematical and computational ideas, and
current and emerging knowledge.
6. 1.C.1: Speciation and extinction have occurred throughout the Earths history.
a. Speciation rates can vary, especially when adaptive radiation occurs
when new habitats become available.

b. Species extinction rates are rapid at times of ecological stress.

- Five major extinctions
- Human impact on ecosystems and species extinction rates.
7. 1.C.2: Speciation may occur when two populations become reproductively
isolated from each other.
a. Speciation results in diversity of life forms. Species can be physically
separated by geographic barrier such as an ocean or a mountain
range, or various pre-and post-zygotic mechanisms can maintain
reproductive isolation and prevent gene flow.
b. New species arise from reproductive isolation over time, which can
involve scaled of hundreds of thousands or even millions of years, or
speciation can occur rapidly through mechanisms such as polyploidy in

8. 1.C.3: Populations of organisms continue to evolve.

a. Scientific evidence supports the idea that evolution has occurred in all
b. Scientific evidence supports the idea that evolution continues to occur.
- Chemical resistance
- Emergent diseases
- Observed directional phenotypic change in a population
- A eukaryotic example that describes evolution of a structure or process
such as heart chambers, limbs , the brain and the immune system
9. 1.D.1: There are several hypotheses about the natural origin of life on earth,
each with supporting scientific evidence.
a. Scientific evidence supports the various models.
1. Primitive earth provided inorganic precursors from which organic
molecules could have been synthesized due to the presence of
available free energy and the absence of a significant quantity of
2. In turn, these molecules served as monomers or building blocks for
the formation of more complex molecules, including amino acids
and nucleotides.
3. The joining of these monomers produced the polymers with the
ability to replicate, store and transfer information.
4. These complex reactions sets could have occurred in solution or as
reactions on solid reactive surfaces.
5. The RNA world hypothesis proposes that RNA could have been the
earliest genetic material.
10.1.D.2: Scientific evidence from many different disciplines supported models
of the origin of life.
a. Geological evidence provides support for models of the origin of life on
1. The earth formed approximately 4.6 billion years ago, and the
environment was too hostile for life until 3.9 bya, while the earliest
fossil evidence for life dates to 3.5 bya. Taken together, this

evidence provides a plausible range of dates when the origin of life

could have occurred.
2. Chemical experiments have shown that it is possible to from
complex organic molecules from inorganic molecules in the absence
of life.
Scientific evidence includes molecular building blocks that are common
to all life forms.
Scientific evidence includes a common genetic code.

11.2.A.2: organisms capture and store free energy for use in biological processes
e. Photosynthesis first evolved in prokaryotic organisms; scientific evidence
supports that prokaryotic photosynthesis was responsible for the
production of an oxygenated atmosphere; prokaryotic photosynthesis
pathways were the foundation of eukaryotic photosynthesis.
12.2.B.3: eukaryotic cells maintain internal membranes that partition the cell
into specialized regions.
c. Archaea and bacteria generally lack internal membranes and organelles
and have cell wall.
13.2.D.2: Homeostatic mechanisms reflect both common ancestry and
divergence due to adaptation in different environmental conditions.
a. Continuity of homeostatic mechanisms reflects common ancestry,
while changes my occur in response to different environmental
c. Homeostatic controls systems in species of microbes, plans and
animals support common ancestry.

14.4.C.1: variation in molecular units provides cells with a wider range of

B1. A heterozygote may be more advantageous genotype than a homozygote
under particular conditions, since with two different alleles, the organism has
two forms of proteins that may provide functional resilience in response to
environmental stresses.
15.4.C.2: environmental factor influence the expression of the genotype in an
b. An organisms adaption to the local environment reflects a flexible
response of its genome.
- Darker fur in cooler regions of the body in certain mammal species
- Alterations in timing of flowering due to clime changes

16.4.C.3: the level of variation in a population affect population dynamics.

b. genetic diversity allows individuals in a population to respond differently to
the same changes in environmental conditions.
- Not all animals in a population stampede.
- Not all individuals in a population in a disease outbreak are equally affected;
some may not show symptoms, some may have mild symptoms, or some
may be naturally immune and resistant to disease.
c. Allelic variation within a population can be modeled by the hardy Weinberg