ORIGIN OF SPECIES: THE WORK OF CHARLES DARWINJames 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 Dr. Robert Darwin (Father) Dr. Erasmus Darwin (Grandfather; early

theories about evolution) Well-known as a traveler and scientist

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

ON THE ORIGIN OF SPECIES

General observations of nature Great variety of pigeon types

Distinguishing features; Interesting characteristics Yet, all have a common origin in the rock pigeon of India

Breeding champions Characteristics can be changed through breeding Good dog = best breeding from other good dogs Current example – Racing Horses

Subtle changes occur, both good and bad, as a species proceeds through time

ON THE ORIGIN OF SPECIES

General Observations of Nature 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

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

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 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 Can be violent; brutal (two stags fighting)

Females may choose based on different forms of display 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

VARIATION

Natural selection works on small differences in traits Instincts Physical characteristics

Natural selection narrows the variation in character traits

Very slow process “slow and gradual accumulation of numerous,

slight, yet profitable, variations