EVOLUTIONARY PROCESSES AND PATTERNS • Theories of species creations and diversity prior to evolutionary theory • Theory of Special Creation – Species are unchanged through time and are independent of one another – All species were created independently by “…the Trinity on the October 26th 4004 B.C. at 9:00 in the morning” Archbishop James Ussher 1664.
EVOLUTIONARY PROCESSES AND PATTERNS. Theories of species creations and diversity prior to evolutionary theory Theory of Special Creation Species are unchanged through time and are independent of one another - PowerPoint PPT Presentation
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EVOLUTIONARY PROCESSES AND PATTERNS
• Theories of species creations and diversity prior to evolutionary theory
• Theory of Special Creation– Species are unchanged
through time and are independent of one another
– All species were created independently by “…the Trinity on the October 26th 4004 B.C. at 9:00 in the morning” Archbishop James Ussher 1664.
EVOLUTIONARY PROCESSES AND PATTERNS
• Theories of species creations and diversity prior to evolutionary theory
• Theory of Spontaneous Generation– New organisms (species) may
suddenly appear wherever conditions are suitable
– Some new life-forms arise spontaneously from streams, soils, rotting meat, and other nonliving materials; not all life arises directly from living organisms
EVOLUTIONARY PROCESSES AND PATTERNS
• Theories of species creations and diversity prior to evolutionary theory
• Prior to Darwin and Wallace - Lamarck– New simple life forms arise by
spontaneous generation and change over time into more complex life forms
– Individuals change in response to their environment and the changes are passed to the next generation.
EVOLUTIONARY PROCESSES AND PATTERNS
• Theories of Evolution• Darwin and Wallace
– Species are related to one another, and they change over time, thus species existing today have descended, with modifications, from other preexisting species.
– Natural selection acts on individuals; individuals with certain favorable characteristics will produce more offspring.
Evolution
• What is evolution?
• Microevolution: survival through the inheritance of favorable characteristics – mutations – selection
• Macroevolution: progression of biodiversity through geological time – speciation – extinction
Evolution• How does it occur?
Evolution
• Species – group of potentially interbreeding natural populations capable of producing viable offspring
• Speciation (through reproductive isolation) – division of populations
(allopatric speciation) – barriers to reproduction
– Increasing resemblance of organs or organisms serving the same function (analogous) • insect wings vs. bird
wings (mimicry) • spurges vs. cacti • aloes vs. agaves • via Convergence
Darwinian Selection
• All natural selection results in evolution, but not all evolution is the product of natural selection.
• What is evolution?
• What is natural selection?
• What is an adaptation?
Darwinian Selection• All natural selection results in evolution, but not all evolution is
the product of natural selection.• What is evolution?
– Evolution is the change in allele frequencies (or traits) over time.
Darwinian Selection
• All natural selection results in evolution, but not all evolution is the product of natural selection.
• What is evolution?– Evolution is the change in allele frequencies (or traits)
over time.
• What is natural selection?
–
• What is an adaptation?
Darwinian Selection
• All natural selection results in evolution, but not all evolution is the product of natural selection.
• What is evolution?– Evolution is the change in allele frequencies (or
traits) over time.
• What is natural selection?– .
• What is an adaptation?
Darwinian Selection
•Sum it all up
Insects, spiders, nectar
Tools use to get insects
Leaves and fruit
Ticks off of iguanas etc.
Seeds
Darwinian Selection
Is there variation about a trait?
Darwinian Selection
Is the variation heritable and not the result of maternal effects?
Darwinian Selection
Is there an excess of individualsso that only some animals liveto reproduce?
Are resources limited?
Darwinian Selection
Is reproduction nonrandom?
The drought of 1977 eliminated seed set by most of the plants producing small soft seeds. Tribulus cistoides seeds are large and hard and became the dominant food item. Only large birds with deep beaks could defend resources and access the resources
Darwinian Selection
Is reproduction nonrandom?
Darwinian Selection
Did evolution occur?
The El Niño of 1983 produced 1359 mm of rain and lavish seed set by the small soft seeded plants. Birds with shallow beaks harvest these seeds more efficiently and thus reproduced better than birds with deep beaks, undoing the selection shown here. Fluctuating environmental conditions maintain both phenotypes.
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Directional Selection
• Phenotype at one extreme of population distribution has selective advantage.
• Leave more offspring• Mean for trait shifts
which way?
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Stabilizing Selection
• Intermediate phenotypes have selective advantage.
• What happens to the distribution for the trait?
Types of Selection
• Directional Selection
• Stabilizing Selection
• Disruptive selection
Disruptive Selection
• Intermediate phenotypes selected against
Darwinian Selection
• At what level does natural selection work?– Genes– Individual– Group– Population– Species
Darwinian Selection
• .
Darwinian Selection
Darwinian Selection
Darwinian Selection
Darwinian Selection
Darwinian Selection
Darwinian Selection
Darwinian Selection
Darwinian Selection
• The consequences of natural selection are expressed at the population level.– Natural selection, like all forms of evolution
results in a change in allele frequencies (or frequencies of a trait).
Genetic drift
• Genetic drift results in a gradual loss of genetic diversity
• Over time an individual locus and gene frequency will drift until one allele becomes fixed