Darwin and Pre-Darwinian Ideas

Darwin and Pre-Darwinian Ideas

• Darwin is not the originator of the idea of evolution.
• Anaximander (610-546 B.C.) posited that life began in the oceans and humans descended from aquatic creatures.
• Empedocles (494-434 B.C.) proposed that life forms arose randomly, with only the successful ones surviving.
• However, pre-Darwinian ideas regarding the evolution of life forms were not widely accepted.

Plato's Theory

• Plato (427-347 B.C.) theorized that the world consists of two realms: perceived and ideal.
• The perceived world is imperfect and illusory, whereas the ideal world is perfect and real.
• Individuals in the animal kingdom are reflections of an ideal, leading to variations within a species.
• Plato believed in the pre-existence of perfect beings and, therefore, did not believe in evolution

Aristotle's Ladder

• Aristotle (384-322 B.C.) proposed a "scale of nature" where species are ordered from least to most perfect.
• Every organism is created to fulfill a specific role, leaving no vacancies; one implication of this is no evolution

Natural Theology

• Aristotle's "Ladder of Nature" was integrated into Judaeo-Christian culture.
• Species were thought to be deliberately designed for specific roles and hence could not change.
• Al-Jahiz of Iraq discussed gradual change and natural selection in the 9th century.
• In the 1700s, natural theology studied nature to better understand God, linking biology to religion.
• Soame Jenyns (1757) compared the universe to a family where everything has its place.
• The concept of biological evolution was considered a subversive threat to the ruling classes.

Fossils and Catastrophism

• Fossils are mineralized remains or impressions of past organisms preserved in rocks; the study of fossils is paleontology.
• Georges Cuvier (1769-1832) was a French paleontologist who made critical observations about fossils.
• Fossils occur in sedimentary rock layers, with each layer having a distinctive set of fossils
• Older layers contained fossils increasingly different from modern organisms.
• Cuvier recognized that species could become extinct but rejected evolution.
• Catastrophism holds that periodic catastrophes wipe out local organisms, which are then replaced by others, rejecting evolution.

Hutton's Gradualism

• James Hutton (1726-1797) proposed the theory of gradualism.
• Geological features are created by slow, subtle processes over extended time periods.

Key Implications and Theories

• Fossils provided insight that earth must be very old.
• Slow cumulative processes acting over long periods of time can have an major effect.
• Resource scarcity can be a principle that generates conflict, with implications for evolution and natural selection.

Setting the Stage for Evolutionary Thought

• For millennia, scholars from varied backgrounds debated static versus changing forms.
• The discussions included considering the meaning of fossils and species classification.
• How conflict and resource availability affect population change were also debated.

Carolus Linnaeus and Taxonomy

• Each culture had unique names, but the introduction of scientific names changed this.
• Carolus Linnaeus (1707-1778) founded modern taxonomy for naming/classifying living organisms using binomial nomenclature.
• Linnaeus's 7-level hierarchical classification system.
• Linnaeus believed in a static classification system.

Binomial Nomenclature and Taxonomy vs. Phylogeny

• Binomial nomenclature involves assigning two Latin names to a species: a genus and a specific epithet.
• Before the 18th century, scientists used polynomial names for species up to 12 Latin words.
• The first word of the polynomial became the genus, and the second word became the specific epithet.
• Phylogeny depicts the "file-gen" or "tree of life".
• Taxonomy focuses on naming systems.

Linnaean System Evolution

• Linnaeus introduced the system in Systema Naturae (1735) and described all known plants using polynomials.
• Systema Naturae was revised in 1758 to include binomial names for animals.
• Similar species share the same generic name but have different specific names, indicating relatedness based on looks.

Binomial Names and Generic Names

• Specific names often describe a feature of the animal; for instance, Glossophaga longirostris translates to "long snout."
• Specific epithets can honor a scientist or refer to a place.
• Scientific names should always be italicized (or underlined). Capitalize the generic names, but specific names are not.
• The generic name may be abbreviated if first used without possibility of confusion.

Taxonomic Authority

• Taxonomic authority credits the scientist who assigned the name and is stated via their last name.
• The name assigned by Linnaeus is usually abbreviated L or Linn.
• Authority names are capitalized and not italicized.

Subspecies and Unknown taxa

• Subspecies are geographically or morphologically distinct "varieties" represented with a third italicized, but uncapitalized, subspecific name/epithet.
• The lack of interbreeding is the distinction for different species.
• An unknown species is represented by "sp.", multiple species of a genus as "spp."
• Species that look like a species in a genus can be represented by "cf.".

Common Names and Hierarchical Classification

• Common names for species should not be capitalized unless they are proper names or at the beginning of a sentence.
• Traditional hierarchical classification has seven levels and each level is a rank/taxon.

Taxonomic Ranks and Domains

• A group of similar phyla is categorized as a kingdom, with subsequent groupings into class, order, family, genus, and species.
• Animalia ingest organic food.
• Organisms are classified based on their anatomy rather than their function.
• Additional levels can be created using the prefixes "super-", "sub-", and "infra-" to modify the standard taxonomic ranks.
• Domains, based on DNA analysis, add an eighth level to the Linnaean hierarchy, classifying organisms into Archaea, Bacteria, and Eukaryota.