Evolution Notes

Charles Darwin

• English naturalist and author of "On the Origin of Species" (1809-1882).

• Introduced evolution by natural selection.

• Naturalism: belief that all organisms and events arose from natural processes.

• Darwinian Evolution: Descent with modification by natural selection.

Modern Evolution

• Theory of Evolution includes population genetics, natural selection, and genetic variation (mutations).

• Natural Selection: Organisms with traits suited to their environment pass on favorable traits.

Classification and Taxonomy

• Biologists classify organisms using a logical system.

• Taxonomy: Classifies organisms and assigns universally accepted names.

• Carolus Linnaeus (1707-1778): Classification based on structural similarity.

  • Placed organisms into groups and assigned scientific names.

• Binomial nomenclature: Two-part scientific name (genus and species).

Binomial Nomenclature Rules

• Scientific name: genus (capitalized) and species (not capitalized).

• All scientific names are in Latin, italicized or underlined.

• Organisms in the same species can mate and produce fertile offspring.

Phylogeny and Phylogenetic Trees

• Modern taxonomy considers an organism's phylogeny (evolutionary history).

• Phylogenetic trees show evolutionary relationships.

• Branch points indicate the most recent common ancestor.

Large-Scale Processes Influencing Life

• Continental Drift: Continents move over time, impacting habitats and climates.

• Mass Extinctions: Large numbers of species become extinct.

• Adaptive Radiations: Organisms form new species to fill vacant ecological niches.

Population Genetics

• Population: Group of same species in same area.

• Population size changes based on births, deaths, immigration, and emigration.

• Growth Rate: Amount of population size change over time.

Population Growth Dynamics

• Exponential Growth: Rapid growth with abundant resources and no predators.

• Logistic Growth: Growth slows as resources become limited, approaching carrying capacity.

• Carrying Capacity: Number of individuals an environment can support.

Genetic Variance and Speciation

• Genetic variance: Diversity of genes and traits within a population.

• Higher genetic variance increases ability to adapt.

• Speciation: Splitting of one lineage into two or more distinct groups.

Genetic Drift and Gene Flow

• Genetic Drift: Random change in gene frequency within a population.

• Gene Flow: Change in gene pool through migration.

Origin of Life and Biogenesis

• Biogenesis: All living things come from pre-existing living things.

• Francesco Redi: Disproved spontaneous generation (abiogenesis) with experiments on maggots.

• Louis Pasteur: Further disproved spontaneous generation.

Abiotic Synthesis of Organic Molecules

• Scientists hypothesize simple cells formed via abiotic synthesis.

• Stages include: abiotic synthesis of monomers, formation of macromolecules, packaging into protobionts, origin of self-replicating molecules.

Oparin Hypothesis

• Proposed early Earth atmosphere contained ammonia, hydrogen gas, water vapor, and hydrocarbons.

• These gases formed organic compounds like amino acids in water bodies.

Miller-Urey Experiment

• Tested Oparin's hypothesis, producing organic compounds (amino acids) from gases and electric sparks.

• Demonstrated abiotic synthesis of organic molecules is possible.

Formation of Cell-Like Structures

• Microspheres: Spherical; protein molecules organized as a membrane.

• Coacervates: Droplets composed of different molecules including amino acids and sugars.

First Life-Forms and Protobionts

• Protobionts: Collections of molecules surrounded by a membrane-like structure.

• Exhibit reproduction and metabolism; precursors to prokaryotic cells.

RNA as First Genetic Material

• First genetic material likely RNA due to its variety of shapes and catalytic abilities (ribozymes).

• Ribozymes: RNA molecules that act as enzymes and can replicate themselves.

Early Cellular Development

• RNA molecules replicated and responded to natural selection within protobionts.

First Single-Celled Organisms

• Early cells were anaerobic prokaryotes.

• Autotrophs evolved, including chemosynthetic organisms.

Rise of Photosynthesis

• Photosynthetic cells used carbon dioxide and sunlight to produce organic compounds.

• Damaging byproduct was oxygen, which led to cellular respiration.

Formation of Ozone Layer

• Oxygen in atmosphere formed ozone layer, protecting Earth from UV radiation.

Rise of Eukaryotes

• Eukaryotic cells emerged with DNA organized into chromosomes and membrane-bound organelles.

Endosymbiosis Theory

• Small aerobic prokaryote lived inside larger anaerobic prokaryote.

• Aerobic prokaryote became mitochondria.

• Photosynthetic cyanobacteria became chloroplasts.

Evidences Supporting Endosymbiotic Theory

• Chloroplasts and mitochondria:

  • replicate independently.

  • contain own DNA (circular).

  • have own ribosomes (similar to prokaryotes).

  • have inner membranes containing enzymes found in prokaryotic plasma membranes.

Multicellular Eukaryotes

• Single-celled eukaryotes gave rise to multicellular forms.

• Fossil evidence dates back 565 million years.

Morphology and Homologous Structures

• Morphology: Classification based on structures possessed by the organism.

• Homologous structures: Same structure, different functions derived from common ancestor.

Analogous and Vestigial Structures

• Analogous structures: Similar in function but not in structure; not from common ancestor.

• Vestigial structures: Reduced in size or function from previous ancestor.

Cladistics

• Method using shared derived characters to establish evolutionary relationships.

• Derived character: Evolved only within groups under consideration.

Cladograms

• Diagram showing evolutionary relationships among organisms.

Cellular and Biochemical Similarities

• Similar cell structures serve as evidence of common ancestry.

• Similar chemical compounds found within cells show relationships.

Genetic and Embryological Similarities

• Similarities in number and type of chromosomes.

• Embryological development provides evidence of phylogenetic relationships.

Fossil Evidence and Limitations

• Fossils show similarities between organisms today and those now extinct.

• Fossil record: incomplete record. It's biased toward species that existed a long time, were abundant, and had hard shells or skeletons.

Earth's Age and Radioactive Dating

• Earth is estimated to be over 4.5 billion years old.

• Rocks and sediments are dated through radioactive dating using isotopes.

Radioactive Isotopes and Half-Life

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Radioactive isotopes undergo radioactive decay with a specific half-life.

• Half-life: Time for half of an isotope sample to decay.

Carbon-14 Dating

• Living things take in carbon-12 and carbon-14 constantly.

• When dead, carbon uptake stops, and carbon-14 decays.

• Limited to organic remains less than 75,000 years old.

Dating Older Rocks and Fossils

• Use isotopes with longer half-lives (Potassium-40, Uranium-238).

• Date rock layers by measuring radioactive isotopes.

• Assign relative age to fossils found in those layers.