Evolution Theorists: Darwin, Wallace, and Lamarck

• Study notes generated from the text provided

Charles Darwin (1809–1882)

• Darwin is a famous scientist linked to evolution theory.
• In 1859, he proposed natural selection in On the Origin of Species.
• Darwin's research set the stage for modern evolutionary biology.

Alfred Russel Wallace (1823–1913)

• Wallace also conceived natural selection around the same time as Darwin.
• Wallace studied the flora and fauna of the Malay Archipelago.
• Wallace proposed that species evolve responding to environmental pressures.
• Wallace's work significantly supported evolution theory.
• Wallace's contributions aided Darwin's thinking, both credited for natural selection.

Jean-Baptiste Lamarck (1744–1829)

• Lamarck is known for his early theory of evolution, called Lamarckism.
• Lamarck proposed organisms change over time and pass acquired traits to offspring.
• Lamarck suggested giraffes' necks lengthened as ancestors stretched to reach higher foliage.

Ernst Mayr (1904–2005)

• Mayr was a leading 20th-century evolutionary biologist.
• Mayr is best known for his work on speciation and the biological species concept.
• Mayr defined species as groups of organisms that can interbreed and produce fertile offspring.

Theodosius Dobzhansky (1900–1975)

• Dobzhansky was a key figure in the Modern Synthesis.
• Dobzhansky's work in population genetics showed genetic variation is essential for evolution.
• Dobzhansky famously stated, "Nothing in biology makes sense except in the light of evolution."

Richard Dawkins (1941–present)

• Dawkins is a contemporary evolutionary biologist, author of The Selfish Gene (1976).
• Dawkins popularized the gene-centered view of evolution.
• Dawkins argues natural selection acts at the gene level, not the individual or species.

THOMAS MALTUS (1766-1834)

• Malthus was an English economist and demographer.
• Malthus’s ideas on population growth influenced Charles Darwin's theory of natural selection.
• Malthus’s best known work, An Essay on the Principle of Population (1798), connects population growth and resources.
• Malthus believed limited resources cause competition.
• Malthus believed population growth outstripping resources leads to a "struggle for existence".

Fossil Evidence

• Fossils: Preserved remains or traces of past organisms.
• The fossil record provides a chronological history of life on Earth.
• The fossil record shows how species have changed over time.

Crucial Fossil Evidence

Transitional Fossils

• These fossils show intermediary stages between different organism groups.
• Transitional fossils provide evidence of gradual change.
• Archaeopteryx, a fossil with both dinosaur and bird traits, shows a transition.

Gradual Change Over Time

• Fossils in progressively older layers show gradual species changes.
• The evolution of whales shows a sequence of changes from land-dwelling mammals (Ambulocetus) to aquatic whales (Balaenoptera).

Extinction and New Species

• The fossil record shows extinction of species and emergence of new ones.
• Fossil records fit natural selection, where some species are better suited to survive.

Comparative Anatomy

• Comparative Anatomy: The study of similarities and differences in anatomy of different species.

Crucial Comparative Anatomy Evidence

Homologous Structures

• Homologous Structures: Anatomical features with similar structure from shared ancestry, but different functions.
• The forelimbs of humans, whales, bats, and cats have similar bone structures but different functions.

Vestigial Structures

• Vestigial Structures: Body parts that lost their original function through evolution.
• Examples: human appendix, whale pelvic bones, ostrich wings.

Analogous Structures

• Analogous Structures: Similar structures from convergent evolution, where different species develop similar traits.
• Wings of bats, birds, and insects serve for flight but evolved separately

Embryology

• Embryology: The study of embryo development from fertilization to birth.
• Embryos of all vertebrates have tails and pharyngeal slits.

Crucial Embryology Evidence

Similarity in Early Development

• Early vertebrate embryos (fish, birds, humans) look remarkably similar, suggesting common ancestry.
• Human embryos, like other vertebrates, have pharyngeal arches (gill slits in fish) during early stages.

Genetics and Molecular Biology

• Genetics and Molecular Biology: The study of genes, DNA, and proteins to understand organisms' genetic makeup.
• DNA helps determine how recently species shared common ancestors and helps trace lineage and divergence.

Crucial Genetics and Molecular Biology Evidence

DNA Sequencing

• The more closely related species are, the more similar their DNA sequences
• Humans and chimpanzees share about 98-99% of their DNA, supporting a recent common ancestor.

Genetic Mutations

• Over time, mutations accumulate in the genome, passed down through generations.
• Comparing genetic sequences of different species traces mutation accumulation and divergence, supporting descent with modification.

Species Distribution

• Species Distribution: The study of the geographic distribution of species.
• The distribution of species across continents supports evolution.
• Marsupials are mainly in Australia, while placental mammals dominate other continents.
• Marsupials evolved in isolation after Australia separated from other landmasses.

Adaptive Radiation

• Adaptive Radiation: Species evolve to fill different ecological niches in different geographic areas.
• Darwin's finches on the Galápagos Islands evolved into different species with varied beaks adapted to different food sources.

Divergent Evolution

• Divergent Evolution: Related species evolve different traits adapting to different environments.
• Divergent Evolution occurs when species sharing a common ancestor evolve differently due to selective pressures.

Convergent Evolution

• Convergent Evolution: Organisms from different backgrounds evolve similar traits adapting to similar environments.
• Worms and snakes developed legless bodies for efficient movement, but from different lineages.

Taxonomy

• Taxonomy: Biology branch classifying, naming, and identifying living organisms.
• Taxonomy organizes biological diversity into hierarchical categories.

Hierarchy of Classification

• Organisms are classified into a hierarchy of categories (taxa).
• Classification starts broad and becomes more specific.

Hierarchy levels

• Domain (e.g., Archaea, Bacteria, Eukarya).
• Kingdom (e.g., Animalia, Plantae, Fungi).
• Phylum (e.g., Chordata, Arthropoda).
• Class (e.g., Mammalia, Insecta).
• Order (e.g., Carnivora, Lepidoptera).
• Family (e.g., Felidae, Canidae).
• Genus (e.g., Panthera, Homo).
• Species (e.g., Panthera leo [lion], Homo sapiens [humans]).

Mnemonic

• "Dear King Philip Came Over For Good Soup" helps remember the order of Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Binomial Nomenclature

• Binomial Nomenclature: A two-part system of naming species developed by Carl Linnaeus.
• Each species gets a scientific name consisting of a capitalized Genus name and a lowercase species name.
• Example: Homo sapiens (humans), Panthera leo (lion).
• Scientific names are universally used, ensuring clarity and consistency.

Taxonomic Classification Criteria

• Organisms are classified based on shared characteristics, including morphology (structure), genetics, and phylogeny (evolutionary relationships).
• Modern taxonomy uses genetic data.

Phylogenetic Tree

• Phylogenetic Tree: A diagram showing evolutionary relationships among species based on common ancestry.
• It traces species relationships through branching points representing common ancestors.
• DNA or protein sequences are used in systematics.

Modern Taxonomy

• Modern taxonomy uses cladistics, grouping species based on common ancestry.
• Molecular phylogenetics analyzes DNA, RNA, or protein sequences, improving methods to determine relationships.

Domains of Life

• Domains are the highest level of classification.
• The three domains of life: Bacteria, Archaea, and Eukarya

Bacteria

• Bacteria: Single-celled, prokaryotic organisms without a nucleus.

Archaea

• Archaea: Single-celled, prokaryotic organisms differing from bacteria genetically and biochemically.

Eukarya

• Eukarya: Organisms with eukaryotic cells, including plants, animals, fungi, and protists.

Evolutionary Relationships and Cladistics

• Cladistics groups organisms by shared evolutionary history using clades. is a group including a common ancestor and all descendants.
• A cladogram represents evolutionary relationships.

Cladistic analysis, parsimony

• Cladistic analysis, parsimony refers to choosing the simplest explanation with the fewest evolutionary changes.

Species Concept

• Species: A group of organisms that can interbreed and produce fertile offspring.

Allopatric Speciation

• Allopatric Speciation: Geographic isolation prevents gene flow, leading to different species over time due to selective pressures, genetic drift, and mutations.

Sympatric Speciation

• Sympatric Speciation: A new species evolves within the same geographic area.
• Reproductive isolation occurs without geographic barriers, due to behavior, ecology, or chromosomal changes.

Carl Linnaeus

• Carl Linnaeus developed binomial nomenclature and a hierarchical system for classifying organisms and is known as the father of modern taxonomy

Ernst Mayr

• Ernst Mayr contributed to the biological species concept and the understanding of speciation

Charles Darwin

• Charles Darwin revolutionized taxonomy showing that species are related through common ancestry and can change over time

Summary of Rules in Writing the Scientific Name

• Genus is capitalized, species is lowercase
• Italicize (or underline if handwritten) the whole scientific name
• Abbreviate the genus after the first mention
• Use no punctuation between genus and species
• Include species authority (scientist who named the species) if necessary
• Subspecies names are written after the species name without italics