chapter 15 darwin’s theory of evolution. before darwin? “natural theology” began to explain...
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CHAPTER 15 DARWIN’S THEORY
OF EVOLUTION
Before Darwin?
“Natural Theology”
Began to explain the origins of fossils
1. Use and disuse of parts
2. Inheritance of “acquired characteristics”
Mechanism for evolution adaptations:
“Stretching” Problem?
Jean Baptiste Lamarck (1809)
“change linked to physical changes in environment”
CHARLESDARWIN
-Father of Modern Evolutionary Theory
-21 years old:“naturalist”
HMS BEAGLE
1831-1836
5 year Mapping expedition
“Collect specimens”
GALAPAGOSISLANDS
Support a great biodiversity
Giant Tortoise Marine Iguana
Sally Light Foot Crab
Blue Footed Booby
Finch
Penguin
While on the Beagle, Darwin read Charles Lyell’s Principles of Geology??
Life?
Earth has “changed” slowly over a “long period of time”
Endemic, but resemble species on SA mainland
“Volcanic”
Colonized from mainland Diversified on different islands
13 types of FinchesBeak adaptations to food available
In 1844, he wrote a long essay on the origin of species and natural selection
Reluctant to publish
Continued to compile evidence to support his theory (22 years).
In June 1858, Alfred Russell Wallace sent
Darwin a manuscript containing
a theory of natural selection essentially
identical to Darwin’s.
“Darwinism”
November 24, 1859
Within a decade: “Science = Biological diversity due to evolution”Avalanche of Evidence
Darwin envisioned the diversity of life as evolving by
1. A gradual accumulation of minute changes
2. Through the actions of natural selection
3. Operating over vast spans of time.= Darwinism
The Darwinian view of life has two main features.
(1) The diverse forms of life have arisen by descent with modification from ancestral species.
(2) The mechanism of modification has been natural selection working over enormous tracts of time.
1. “Descent with modification”
Common Ancestor
= all present day organisms are related through descent from unknown ancestors in the past
Common Ancestor
“Dead Ends”
About 99% of all species thathave ever lived are extinct
Descendents accumulated diverse modifications/ adaptations that fit them to specific ways of life/ habits
Essay on human population by Thomas Malthus in 1798.
Suffering - disease, famine, homelessness, war
Population > food supply/ resources =
“Struggle for Existence”
“Competition” for?
Food, Space, Predation, Mates
2. The theory of Natural Selection
Unique mechanism of evolution
“Adaptation”
“Individuals that have physical or behavioral traits that bettersuit their environment are more likely to survive/reproduce”
Driven by?
Artificial Selection
Selecting individuals with the desired traits as breeding stock.
Natural selectionNature?
Nature selects for the “strong” phenotype
Less FavorableVariations =EXTINCT
Struggle for Existence
Genetic Variation
Adaptation
Evolution
Population
Natural Selection
Gene Pool
Speciation
Competition
Reproductive Isolation
Mutations
EVOLUTION KEY TERMS
Evolution
EXAMPLES OF NATURAL SELECTION?
MUTATIONS!!!!
Alexander Flemming 1952
Physiological Adaptation = changes in metabolic processes Penicillin
Resistant Bacteria
Evolution of drug resistance in HIV
3TC affects viral enzymes “reverse transcriptase”
Evolution of insecticide resistance in insect populations
Initial?
Gene Frequency?
What helps?
Enzymes
Not Creating!!
Mimicry = copy the appearance of another species
Palatable Unpalatable
Camouflage = blend in with surroundings
Cephalopod
Frogfish
Homology?
Similarity in characteristics resultingfrom common ancestry
Homologous StructuresSame structure but different function (modified)
ANATOMICAL HOMOLOGIES:
Anatomical imperfections
Back and knee problems
Boa and Python Families
Whales and Dolphins
Vestigial Organs
Why reduced in use?
Mole-Rat
Continues to be inherited
Embryological Homologies
Molecular Homologies
“Genetic Code”
BiogeographySpecies of close local are more closely related than similar species (way of life) elsewhere
ANALOGOUS STRUCTURE
Same Function =Different Structure
Sugar glider marsupial mammal (Australia)
Flying squirrel eutherians/placental mammal (North America)
Adapted to same way of life, but different ancestors.
= Kangaroo
Convergent Evolution= distantly related organisms evolve similar traits
Steam-line bodies
Occupy similar environment
Divergent Evolution= species once similar become more and more distinct
Small extremitiesRetain heat
Large extremitiesLose heat
“ADAPTIVE RADIATION”
END
EVOLUTIONOF
SPECIES
Species = look alike, interbreed, produce fertile offspring
Speciation = evolution of a new species
“Transitional Forms”
Geographic Isolation• = a physical barrier separates a
population into groups
Prevent Interbreeding
Tree frogs in Amazon Basin
Deforestation
Gene Pool Changes
KaibabAbert
Grand Canyon
Reproductive Isolation
= past interbreeding organisms are preventedfrom producing fertile offspring
Mating Behavior
ZebroidsSterile
Gene Pool Closed
Major episodes that shaped life as a phylogenetic tree
Fossil Record?
“Tetrapods”Fins Limbs
Lobed-Fin FishesGills and Lungs (underdeveloped)
Fleshy Lateral Fins
Coelacanth
Amphibian Reptile
Tim
e --
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“Genetic Variation”
“Competition”
WOLF (like) WHALE
“Limited Resources”
“Struggle for Existence”
“Differential reproduction”
“Gene Frequency”
“Survival of the Fittest”“Adaptation”
“Natural Selection”
Transitional/ Intermediate forms
?
“Just a theory”?
“There is grandeur in this view of life;with its several powers having been originallybreathed by the Creator into a few forms orinto one; and that, whilst this planet has gonecycling on according to the fixed law of gravity,from so simple a beginning endless forms most wonderful and most beautiful have been,and are being evolved.”