Biology: Darwin, Wallace, and Lamarck

• Bionotes cover the 3rd quarter of biology

Charles Darwin (1809–1882)

• Darwin is known for his contribution to the theory of evolution.
• In 1859, he published "On the Origin of Species" and proposed the theory of natural selection.
• Darwin's work formed the basis for modern evolutionary biology.

Alfred Russel Wallace (1823-1913)

• Wallace independently came up with the concept of natural selection around the same time as Darwin.
• His studies of the flora and fauna of the Malay Archipelago led him to suggest species evolve due to environmental pressures.
• Wallace's work supported the theory of evolution.
• Darwin and Wallace are jointly credited with the formulation of natural selection.

Jean-Baptiste Lamarck (1744–1829)

• Lamarck is known for his early theory of evolution known as Lamarckism.
• He suggested organisms evolve over time, passing on traits acquired during their lifetime to their offspring.
• Example: Giraffe necks became longer because ancestral giraffes stretched them to reach higher foliage.

Ernst Mayr (1904–2005)

• Mayr was a leading evolutionary biologist.
• He is known for his work on speciation (the formation of new species).
• He defined the biological species concept, stating that species are groups of organisms that can interbreed and produce fertile offspring.

Theodosius Dobzhansky (1900–1975)

• Dobzhansky was a central figure in the Modern Synthesis.
• His work in population genetics showed how genetic variation in populations is essential for evolution.
• "Nothing in biology makes sense except in the light of evolution" highlights the need to understand evolution in biology.

Richard Dawkins (1941–present)

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

Thomas Malthus (1766-1834)

• Malthus was an English economist and demographer whose ideas on population growth influenced Darwin's theory of natural selection.
• His work, "An Essay on the Principle of Population" (1798), discussed the relationship between population growth and resources.
• Malthus believed that limited resources lead to competition among individuals.
• Population growth outstripping resources results in a "struggle for existence" where only a few survive.

Evidences of Evolution

• Fossils are the preserved remains or traces of past organisms.
• The fossil record provides a chronological history of life, showing how species have evolved.

Fossil Evidence

• Fossils are the preserved remains or traces of organisms from the past.
• The fossil record provides a chronological history of life on Earth, showing how species have changed over time.

Crucial Evidence

• Transitional Fossils: Show intermediate stages between different groups, providing evidence of gradual change.
• Archaeopteryx is a fossil with dinosaur and bird characteristics, showing the transition between reptiles and birds.
• Gradual Change Over Time: Fossils in older layers show a gradual change in species.
• The whale evolution fossil record shows changes from land-dwelling, hoofed mammals (e.g., Ambulocetus) to aquatic whales (e.g., Balaenoptera).
• Extinction and New Species: The fossil record indicates the extinction of many species.
• New species appear over time, aligning with natural selection where better-suited species survive.

Comparative Anatomy

• The study of similarities and differences in the anatomy of different species.

Crucial Evidence

• Homologous Structures: Anatomical features that are similar in structure due to shared ancestry, even if they perform different functions.
  • Example: Forelimbs in humans, whales, bats, and cats have different functions but similar bone structures.
• Vestigial Structures: Body parts that have lost their original function through evolution.
  • Examples: Human appendix, pelvic bones in whales, and wings of flightless birds.
• Analogous Structures: Similar structures that have arisen from convergent evolution
  • Different species develop similar traits independently due to similar environmental pressures.
  • Examples of flight structures: wings of bats, birds and insects.

Embryology

• Embryology is the study of the development of embryos from fertilization to birth.
• Embryos of all vertebrates have tail and pharyngeal slits.

Crucial Evidence

• Similarity in Early Development: Early embryos of many vertebrates look similar, suggesting a common ancestry.
• Example: Human embryos have pharyngeal arches (gill slits in fish) during early development.

Genetics and Molecular Biology

• The study of genes, DNA, and proteins to understand the genetic makeup of organisms.
• DNA helps determine recent common ancestors and trace lineage and divergence.

Crucial Evidence

DNA Sequencing

• The more closely related two species are, the more similar their DNA sequences are.
• Humans and chimpanzees share around 98-99% of their DNA, indicating recent common ancestors.

Genetic Mutations

• Mutations accumulate in the genome over time.
• Mutations are passed down through generations.
• Comparing genetic sequences of different species traces how mutations have accumulated and diverged.

Species Distribution

• The study of the geographic distribution of species.

Crucial Evidence

• Species Distribution: 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

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

Divergent Evolution

• Related species evolve different traits and adapt to different environments, leading to the development of distinct species.
• Occurs when two or more species with a common ancestor evolve in different ways due to different selective pressures.
• Example: Wolves and dogs

Convergent Evolution

• Organisms from different evolutionary backgrounds evolve similar traits or behaviors because they adapt to similar environments or ecological niches.
• Example: Worms and snakes have developed legless bodies to move efficiently through their environments

Taxonomy

• Taxonomy is the branch of biology that deals with the classification, naming, and identification of living organisms.
• Taxonomy organizes biological diversity into hierarchical categories based on shared characteristics.

Key Concepts in Taxonomy

Hierarchy of Classification

• Organisms are classified into a hierarchy of categories (taxa).
• Hierarchy starts from the broadest to most exclusive groups and becoming more exclusive at each level
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Mnemonic: "Dear King Philip Came Over For Good Soup"

Binomial Nomenclature

• Developed by Carl Linnaeus.
• Binomial nomenclature is a two-part system.
• Each species is given a scientific name consisting of:
  • Genus name (capitalized)
  • Species name (lowercase)
• Example(s):
  • Homo sapiens (humans)
  • Panthera leo (lion).
• Scientific names are universally used and consistency in identifying species, regardless of language.

Taxonomic Classification Criteria

• Organisms are classified based on shared characteristics.
• Shared characteristics include
  • Morphology (structure)
  • Genetics
  • Evolutionary relationships (phylogeny).
• Genetic data is used in classification to use DNA sequencing to determine closely related species.

Phylogenetic Tree

• A phylogenetic tree (cladogram) shows the evolutionary relationships,among species based on common ancestry.
• It traces how species are related through branching points that represent common ancestors.
• DNA or protein sequences are used in systematics.

Modern Taxonomy

• Cladistics groups species based on common ancestry and not only shared traits.
• Molecular phylogenetics transforms taxonomy by providing methods to determine evolutionary relationships by analyzing DNA, RNA, or protein sequences.

Domains of Life

• In recent times, the concept of domains was added to the classification hierarchy.
• Three domains of life:
  • Bacteria: Single-celled, prokaryotic organisms without a nucleus.
  • Archaea: Single-celled, prokaryotic organisms that differ from bacteria in genetic and biochemical characteristics.
  • Eukarya: Eukaryotic cells that have a nucleus and organelles (includes plants, animals, fungi, and protists).

Evolutionary Relationships and Cladistics

• Cladistics groups organisms based on shared evolutionary history, using the concept of a clade.
• A clade is a group of organisms that includes a common ancestor and all its descendants.
• Cladograms are used to represent evolutionary relationships and branching patterns.

Cladistic Analysis, Parsimony

• Parsimony is the principle to choose the simplest explanation with the fewest evolutionary changes needed.

Species Concept

• A species is the most specific level of classification.
• It refers to a group of organisms that can interbreed and produce fertile offspring.

Allopatric Speciation

• Allopatric speciation happens when a population is geographically isolated into separate groups preventing them to have gene flow with each other.
• Isolated populations may evolve into species because of different selective pressures.

Sympatric Speciation

• Sympatric Speciation happens when a new species evolves from the parent species within the geographic area without geographic barriers
• It is cause by Changes in behavior, ecology, or chromosomal changes.

Carl Linnaeus

• Developed binomial nomenclature and a hierarchical system for classifying organisms.

Ernst Mayr

• Contributed to the biological species concept and the understanding of speciation.

Charles Darwin

• Revolutionized taxonomy with his theory of evolution.

Summary Of Rules In Writing The Scientific Name

• Genus is capitalized, species is lowercase.
• Italicize the entirety of the scientific name.
• Abbreviate is acceptable, but only after the first time the full name is stated.
• 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.