Transcript There is a Great Diversity of Organisms on Planet Earth……….why?

There is a Great Diversity of Organisms
on Planet Earth……….why?
Fundamental Principles of Evolution (p. 9-11)
Evolution has a large genetic/molecular component:
1.
P=G+E
Phenotype = Genotype + Environment
2. Environmental effects on phenotype are not inherited
3. Heredity is based on particles (genes). They retain identity
and do not blend. They give rise to continuous and
discrete variation.
4. Genes mutate at relatively low rates (new alleles).
Recombination is an important aspect of evolution.
5. Environmental factors can influence mutation rates but do
not yield specific mutations that are seemingly the best for
surviving in a particular environment.
6. Natural selection can alter populations beyond the original range
of variation by restructuring genomes through recombination,
and thus give rise to new phenotypes.
7. Natural populations are genetically variable.
8. Populations of a species in different geographic areas may
differ in genetically based characteristics. Genotypic
frequencies may vary among populations. Often differences
are adaptive, and thus a product of natural selection.
9. Experimental crosses among populations or species show
that most characteristics have a genetic basis, and most have
a complex or polygenic basis. This suggests that evolution may
occur through small steps.
10. Organisms are not necessarily different species if they exhibit
different characteristics. A species is a collection of populations
that interbreed, and is thus characterized by a common gene pool.
(i.e. Biological Species Concept)
11. However, there is a continuum of differences among populations
and even in the degree of reproductive isolation. There are also a
continuum of differences observed among species, or genera, or
higher taxonomic classifications. This provides evidence that an
ancestral species differentiates into two or more different species.
12. Speciation generally occurs through the genetic differentiation
of geographically separated populations. This creates isolation
and prevents gene flow.
Evolution also has a historical component:
13. The fossil record has gaps among quite different organisms.
This reflects the incompleteness of the fossil record. However,
there are gradations or intermediates that fill some gaps. It seems
likely that the evolution of large differences occurs through many
small steps that are fixed over very long time periods.
14. All observations in the fossil record are consistent with
evolutionary principles and there is no need to invoke NonDarwinian mechanisms (orthogenesis, major-mutational origins,
Lamarckian evolution).
In addition to genetics, statistics is important in evolution
Mean - average value from a sample or population.
Standard deviation - average deviation from the sample or
population mean.
Variance - mean value of the squared deviations
from the sample or population mean.
Probability - likelihood of an event. We often want to know
what the probability of obtaining an estimate of a statistic?
(e.g. could our estimate of the mean or variance be obtained
by chance?).
Confidence - how good or precise is our best estimate?