Transcript Evolutionary Theory Basic Concepts

ORIGIN OF SPECIES: THE WORK
OF CHARLES DARWIN
James A. Van Slyke
CHARLES DARWIN (1809-1882)
Born the Fourth of Five children (two
sons) in Shrewsbury, England; same
day as Lincoln
 Grew up in family of doctors
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Dr. Robert Darwin (Father)
 Dr. Erasmus Darwin (Grandfather; early
theories about evolution)
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Well-known as a traveler and scientist
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Later became ill and was unable to travel
Married Emma Wedgwood; had 10
children
ON THE ORIGIN OF SPECIES (1859)
Worked on the book for 8 years
 The term “evolution” not used in book
 Gained acceptance in biological science
 Would still take many years to demonstrate the
process empirically
 The theory was in place, but many of the causal
factors were still missing
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ON THE ORIGIN OF SPECIES
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General observations of nature
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Great variety of pigeon types
Distinguishing features; Interesting characteristics
 Yet, all have a common origin in the rock pigeon of India
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Breeding champions
Characteristics can be changed through breeding
 Good dog = best breeding from other good dogs
 Current example – Racing Horses
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Subtle changes occur, both good and bad, as a
species proceeds through time
ON THE ORIGIN OF SPECIES
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General Observations of Nature
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All organisms compete in the struggle for existence
Either as prey or predators
 Competition for resources (water, food, space)
 Competition for mates and survival of offspring
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Struggle is not necessarily direct one on one
competition or violence
Complex interplay between many factors
 Interdependent relationship between species
 Clover
fertilization from bumble bees
 Field mice are predators
Cats are predators of
field mice
 Once disturbance in the chain can affect all species
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NATURAL SELECTION
Certain species traits enable organisms to
survive and reproduce
 Other traits may decrease survival in some
populations
 Variance in species traits will foster survival for
some some and extinction for others
 Dependent upon the species trait and the
environment of expression
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i.e. gills work great in water; not so great in the
desert
SEXUAL SELECTION
Certain traits may increase or decrease
reproduction rather than survival
 Male competition for female mates
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Can be violent; brutal (two stags fighting)
Females may choose based on different forms of
display
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Bird songs; special feathers or colors
DIVERSIFICATION
Different species will occupy different roles or
ecological niches in an environment
 A type of division of labor
 Different species will adapt to different food
sources, survival mechanisms, etc.
 This will diversify the types of species present in
any particular ecological system
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VARIATION
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Natural selection works on small differences in
traits
Instincts
 Physical characteristics
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Natural selection narrows the variation in
character traits
 Very slow process
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“slow and gradual accumulation of numerous, slight,
yet profitable, variations