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Introduction to evolution and mechanisms of evolution
Terms in this set (43)
all the changes that have transformed life on earth from its earliest beginnings to the diversity that characterizes it today
-the earth is young and unchanging.
-organisms are products of special creation.
-species do not change and there is no extinction.
(1707-1778) Founder of taxonomy, the branch of biology concerned with naming and classifying organisms. Developed two part system of naming organisms.
(1769-1832) theory of catastrophism. Extinction occurs and was due to a catastrophic event that destroyed many species living in that area at that time.
(1726-1797) - Geologist. Theory of gradualism. Profound geological changes took place through the cumulative effect of slow but continuous processes
Geologist. Theory of uniformitarianism. Determined that the earth is very old, and persistent (i.e. no cataclysmic events). processes can cause great change. Published "Principles of Geology" in 1830.
Wrote "Essay on the Principle of Population" in 1798. Human suffering is due to population's tendency to grow faster than food supply.
Jean-Baptiste de Lamarck
Published the first plausible theory of evolution in 1809. Tried to explain the fossil record and the diversity of life.
1. Concept of use and disuse. Parts of an individual used extensively became larger and stronger; parts that were not used, deteriorated.
2. Acquired characteristics are inherited.
Alfred Russel Wallace
Independently developed his own ideas of evolution by natural selection.
1859 - Published his "Origin of Species"
1. Descent with modification. All living things are related in some way; some are more
related than others.
2. Natural selection and adaptation.
Individuals that "fit" the environment have a higher probability of reproducing, (i.e. greater "Reproductive Success").
Some of the "fit" characteristics are heritable and passed to the offspring.
• 14 different species of closely related birds
• Originally one species fragmented into several populations and were geographically
isolated (islands) in different environments.
• Eventually, these different populations diverged and became separate species.
• Example: beak size was an adaptation to the food available on a particular island.
Darwin's main tenets
1. All species have the potential for exponential growth.
2. Exponential growth leads to a "struggle for existence."
3. Organisms within a species vary in their abilities to survive and reproduce.
4. Those individuals most fit are naturally selected by their environment as the
parents of the next generation. This results in gradual change over generations.
• Sources: mutation, recombination (meiosis and crossing-over) and random fertilization.
• This variation is random, i.e., without preference to positive or negative effects.
• At least some component of the observed variation must be heritable.
All life forms are descended from pre-existing life forms (descent with modification).
Natural selection is the mechanism that drives evolution.
Acts on an individual's phenotype and not directly on genes or genotypes.
The effect of selection is to maintain or alter the frequency of alleles in a population.
The evolutionary process has no long-term goal or distant ideal target.
• In the natural world, the criterion for selection is short-term survival or reproduction.
• Cumulative natural selection is blind to the future.
• What in hindsight may appear to have been an achieved goal is nothing more than an
incidental consequence of cumulative selection after many generations.
• Phenotype is the unit of selection
• Genotype is the unit of inheritance
• Population of a species is the unit of evolution
o The change in genetic composition of a population over time.
o Populations evolve, NOT individuals!
Describes the geographical distribution of species. Organisms spread
over a certain region, then populations evolve in response to the new environment.
Homologous structures are due to common descent.
• Anatomical similarities indicate common descent
• Analogous structures may have similar form and/or function, but arise from
different origins in the process of convergent evolution.
Similar embryonic development indicates relatedness.
Similarities in DNA and protein sequence indicate relatedness. The genetic code is common to all living things.
A chronicle of pre-existing life forms reveals evolutionary transitions.
Organisms are categorized based on relatedness. Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
a change in the genetic makeup of a population over time
a localized group of individuals belonging to the same species
groups of populations that have the potential to interbreed
- all alleles at all loci in all individuals within a population
the frequency of a specific allele within the gene pool of a population
in a non-evolving population, the frequencies of alleles in a population's gene pool remains constant from one generation to the next.
The math equivalent of a Punnet square is the equation:
p2 + 2pq + q2 = 1
Factors that maintain genetic equilibrium:
1. no genetic drift - large population size
2. no gene flow - immigration or emigration
3. no mutation
4. random mating
5. no selection - all genotypes reproduce equally
the change in the gene pool of a population over a succession of generations.
Factors that disrupt genetic equilibrium and can cause microevolution:
1. genetic drift
2. gene flow
4. nonrandom mating
5. natural selection
changes in gene pool of a small population due to chance
1. bottleneck effect - population reduced drastically by a disaster; the
gene pool of the survivors is not usually representative of the original
2. founder effect - a few individuals colonize an isolated habitat; the
smaller gene pool may not be representative of the original large population
migration of individuals into or out of a population
a change in one allele; one per 105-106 gametes
1. has a small effect on allele frequency in a large population unless genetic drift or natural selection causes an increase
2. only original source of genetic variation
inbreeding; mate with neighbors that tend to be closely
differential reproductive success; likely to be adaptive, but
adaptation is limited to the variability present in the population
Genetic Basis of Variation
variation is raw material for natural selection
A. Mutation - point mutation or chromosome changes
Most have no effect or a negative effect.
Sometimes, a new allele may give the individual increased fitness when the environment changes.
B. Recombination-unique combinations of different alleles Crossing over during meiosis
Pairing of gametes to form a zygote
Modes of Natural Selection
A. Stabilizing selection - intermediate phenotypes favored
B. Directional selection - favors relatively rare individuals
C. Disruptive or diversifying selection - individuals on both extremes are favored
• A heritable trait that improves the reproductive success of an individual and makes an organism more "fit" for life in its local environment.
• Examples of these traits include structures, physiology, behavior, etc.
• Not all evolution is adaptive
• Chance events can affect the evolution of a population.
• Genetic Drift (bottleneck effect and founder effect), Gene Flow and Mutation can result in
allele frequency changes independent of adaptation.
• These events can cause non-adaptive or even maladaptive changes with regard to a
population's "fitness" to its environment.
Natural selection 2
Nonrandom reproduction (differential reproductive success) alone has the ability to shape and mold populations to their local environments.
• Selection can only edit variations that exist in the population.
• New alleles do NOT arise in response to the needs of the organism.
• New alleles are rare and arise randomly.
• Natural Selection + Random Variation = Evolution
• The mechanism of evolution which explains how populations evolve and the emergence of
THIS SET IS OFTEN IN FOLDERS WITH...
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