O RIGIN OF S PECIES : T HE W ORK OF C HARLES D ARWIN James A. Van Slyke

C HARLES D ARWIN ( ) 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

O N THE O RIGIN OF S PECIES (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

O N THE O RIGIN OF S PECIES 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

O N THE O RIGIN OF S PECIES 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

N ATURAL S ELECTION 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

S EXUAL S ELECTION 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

D IVERSIFICATION 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

V ARIATION 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