I. I.History of Evolutionary Thought A. A.Before Darwin Concept of evolution predates Darwin by >2000 years (not widely accepted) Fossils known long before

I. History of Evolutionary Thought

A. Before Darwin• Concept of evolution predates Darwin by >2000 years

(not widely accepted)• Fossils known long before Darwin and recognized as

remains of organisms

1. Aristotle (384-322 B.C.)• Organisms could be arranged on a natural scale of

increasing complexity (scala naturae)• Species fixed and unchanging

2. Carolus Linnaeus (1707-1778)• Swedish physician who founded taxonomy• Believed in natural theology (study nature to understand the

Creator)• Developed binomial nomenclature and modern classification

hierarchy• Did not intend system to reflect evolutionary relationships


A. Before Darwin3. James Hutton (1726-1797)

• Gradualism

4. Jean Baptiste de Lamarck (1744-1829)• Old earth, adaptation (natural change w/o divine

guidance), evolution

5. Thomas Malthus (1766-1834)• Population increase Competition for survival

6. Georges Cuvier (1769-1832)• Paleontology, extinction, catastrophism

7. Charles Lyell (1797-1875)• Uniformitarianism

Fig. 22.2


B. Charles Darwin (1809-1882)• Went to University of Edinburgh at 16 to study

medicine• Transferred to Cambridge University; changed

major to theology• Became protégé of botanist

• Initial observations for theory of evolution made on 5-year cruise to prepare navigation charts for British Navy; naturalist aboard HMS Beagle

• 1831-1836

Fig. 22.5


B. Charles Darwin (1809-1882)1. Crucial information for development of theory

a. Similarities & differences among species in Galapagos Islands vs. South America• Suggested divergence from common ancestor

b. Principles of Geology (1830) by Lyell• Contradicted idea of static, young earth

c. Artificial selection• Selective breeding in dogs, cattle, wild mustard

Fig. 22.9


B. Charles Darwin (1809-1882)1. Crucial information for development of theory

a. Similarities & differences among species in Galapagos Islands vs. South America• Suggested divergence from common ancestor

b. Principles of Geology (1830) by Lyell• Gradualism contradicted idea of static, young

earth

c. Artificial selection• Selective breeding in dogs, cattle, wild mustard

d. Writings of Malthus on population growth• Suggested that not all offspring can survive when

resources are limited


B. Charles Darwin (1809-1882)2. Major components of evolutionary theory

a. Descent with Modification• Recognized that groups in Linnaeus’ classification

hierarchy could reflect patterns of descent from common ancestors

b. Natural Selection• Mechanism by which populations adapted to local

conditions• Developed from five major observations and three

inferences (according to Ernst Mayr)


B. Charles Darwin (1809-1882)3. Observations

a. Overproduction – Not all offspring survive to reproduce

b. Stability – Populations tend to remain stable in size

c. Limited Resources

d. Within-Species Variation – Not all individuals identical

e. Heritability – Traits passed from parent to offspring

4. Inferencesa. Competition – Leads to limited survivorship

b. Differential Fitness – Best adapted individuals most likely to survive

c. Gradual Change – Favorable traits accumulate over generations

II. Evidence for Evolutionary Theory

A. Natural Selection• Has been tested experimentally

Fig. 22.13


A. Natural Selection• Has been tested experimentally

• Soapberry bugs• Drug resistance


B. Homologies1. Anatomical

• Homologous features derived from same structure in ancestor

• Homoplastic features arose from same functional need (convergent evolution)

• Some important clues to ancestry come from vestigial structures• Ex: Hindlimb bones in whales and some large

snakes

Fig. 22.15


2. Embryological• Features in early development often conserved

throughout a taxon• Ex: Gill pouches and tail in mammals, just like fishes,

amphibians, reptiles, birds

3. Molecular• Divergent traits based on divergent genes and

proteins• Some proteins and parts of proteins diverge more than

others (some regions conserved)

Fig. 22.16

Documents

I. I.History of Evolutionary Thought A. A.Before Darwin Concept of evolution predates Darwin by >2000 years (not widely accepted) Fossils known long before