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Understanding Evolution

• Evolution through natural selection is a mechanism for species' change over time.
• Ancient Greeks had mixed ideas regarding evolution, with Plato viewing species as static.
• Buffon (18th century) suggested species evolved with geography influencing species differences.
• Hutton (18th century) proposed gradual geological changes over long periods, contrasting the catastrophic events theory.
• Lyell (19th century) expanded on Hutton's ideas and influenced Darwin by suggesting Earth was much older.
• Lamarck (early 19th century) suggested evolution via inheritance of acquired traits, later disproven but still influential.
• Darwin and Wallace independently discovered natural selection in the mid-19th century.
• During Darwin's voyage (1831-1836, H.M.S. Beagle), species worldwide were observed , especially in the Galapagos Islands.
• Finches were noted to have beak shapes suited to their food sources.
• Species adapt over time based on environmental pressures.
• Wallace's Expeditions led to similar conclusions about species adaptation.
• Species with beneficial traits survive and reproduce more successfully, known as "Survival of the fittest".
• Over time, this process leads to evolutionary changes in a population.
• Three main principles of natural selection:
• Inheritance: traits are passed from parents to offspring
• Overproduction and Competition: more offspring than resources, leading to competition
• Variation and Differential Survival: offspring vary; with beneficial traits surviving and reproducing more.
• Natural selection is the only known mechanism for adaptive evolution.

Processes and Patterns of Evolution

• Variation is required for natural selection and differences must have a genetic basis.
• Environmental factors do not lead to evolutionary change.
• Mutation refers to changes in DNA that create new genetic variations (alleles).
• Adaptations are heritable traits that help an organism survive and reproduce.
• Beneficial traits can change depending on the environment.
• Divergent evolution is when two species evolve in different directions from a common ancestor.
• Convergent evolution is when similar traits evolve independently in species that do not share a recent common ancestor.

Evidence of Evolution

• The fossil record shows gradual changes over time.
• Homologous structures show same basic structure, different function, and a shared ancestor.
• Vestigial structures have no apparent function and are leftover from ancestors.
• Analogous structures perform similar functions, but have different evolutionary origins.
• Embryology shows relatedness between organisms by examining development.
• Convergent evolution in form: similar environments lead to similar traits due to selection pressures.
• The geographic distribution of organisms aligns with evolutionary history and tectonic plate movement.
• DNA's universality proves a common ancestor for all organisms.
• Similarities in DNA sequences reflect evolutionary relationships.
• Gene duplication allows for evolution of new protein functions by modifying one gene copy while the other remains functional.

Speciation

• Species is a group of individual organisms that interbreed and produce fertile, viable offspring.
• Members of the same species share external and internal characteristics from their DNA.
• A hybrid is a cross between two species.
• Speciation means the formation of two species from one original species.
• Allopatric speciation involves geographic separation of populations from a parent species and subsequent evolution, with "allo" meaning "other" and "-patric" meaning "homeland".
• Sympatric speciation involves speciation within a parent species remaining in one location, where "sym-" means "same" and "-patric" means "homeland"; new species form in the same habitat without physical separation.
• Biologists think of speciation events as one ancestral species splitting into two descendant species.
• Dispersal occurs when a few members of a species move to a new geographical area.
• Vicariance is when a natural situation arises that physically divides organisms.
• Adaptive radiation is when a single species evolves into multiple new species due to adaptation to different environments.
• Polyploidy (extra chromosome sets) is a key mechanism in plants.
• Autopolyploid: extra chromosome sets from the same species.
• Allopolyploid: chromosome sets from two different species.
• Polyploidy leads to reproductive isolation

Reproductive Isolation

• Genetic and phenotypic divergence between populations can prevent mating or result in nonviable/sterile offspring.
• Prezygotic barriers prevent mating or fertilization from occurring.
• Temporal isolation means species reproduce at different times.
• Habitat isolation means populations live in different habitats.
• Behavioral isolation signifies differences in mating behaviors.
• Gametic Isolation means incompatibility of gametes.
• Mechanical Isolation means differences in reproductive structures.
• Postzygotic barriers affect offspring without fertilization.
• Hybrid inviability means hybrids don't survive past embryonic stages.
• Hybrid sterility means hybrids are born but cannot reproduce.
• Hybrid zones are areas where two closely related species continue to interact and produce hybrids.

Chapter 19 Terms

• Adaptive evolution is the increase of frequency of beneficial alleles and decrease in deleterious alleles due to selection.
• Allele frequency (gene frequency) is the rate at which a specific allele appears within a population.
• Assortative mating occurs when individuals tend to mate with those who are phenotypically similar to themselves.
• The bottleneck effect is the magnification of genetic drift as a result of natural catastrophes.
• Cline
• Directional Selection
• Diversifying Selection
• Evolutionary Fitness

Additional Notes from lecture - dated 2/12/2025

• Pangea split into Laurasia and Gondwana during the Triassic and Jurassic periods of the Mesozoic.

Big Five Mass Extinctions

• End Ordovician (444 Mya), 86% of species, 57% of genera, and 27% of families went extinct due to changes in temperature, climate, and atmospheric gases.
• Late Devonian (360 Mya), 75% of species, 35% of genera, and 19% of families went extinct due to rapid growth and diversificationof plants.
• End Permian (250 Mya), 96% of species, 56% of genera, and 57% of families went extinct due to global warming.
• End Triassic, 80% of species, 47% of genera, and 23% of families went extinct due to underwater volcanic activity.
• End Cretaceous, 76% of species, 40% of genera, and 17% of families went extinct after the earth was hit by an asteroid, in which limited the oxygen left to breath.
• The 6th mass extinction is driven by human actions today.
• Acid rain.
• Volcanoes in North America.
• Earthquakes have been initiated recently from the Appalachians, sitting on a fault line.
• San Andreas Fault in California exists.

Figures in Evolution History

• Aristotle (300 BC) was the father of the scientific method and created the Scala Naturae, the great chain of being.
• Carl Linnaeus (1700s) developed a taxonomic classification system.
• George Cuvier (1800s) studied extinction based on fossils.
• Jean-Baptiste Lamarck (1800s) proposed evolution through gradual improvement.
• Charles Lyell (1830) theorized about the supercontinent Pangea in Principles of Geology.
• Charles Darwin (1830s-50s) described "descent with modification"/evolution by natural selection (On the Origin of Species, 1859).
• Alfred Russell Wallace (1858) proposed evolution by natural selection.
• Modern Synthesis (1918-1942) combined evolution by natural selection & Gregor Mendel's work on genetics.
• Modular evolution exists from the 1990s-Present.

Types of Evolution

• Microevolution is a change in gene frequency within a population over a short period.
• Macroevolution is a major evolutionary change over long periods of time.
• Hardy-Weinberg Principle:

Evidence of evolution comes from:

• Fossil Record
• Biogeography, Plate Tectonics, Continental Drift
• Comparative Morphology
• Morphological divergence, which is change from the body from a common ancestor.
• Homologous structures (homologies) are body parts that appear different in different lineages but are similar in some aspect and suggests a common ancestor. Modified to a different size, shape, or function in different lineages.
• Morphological Convergence is the independent evolution of similar body parts in different lineages.
• Analogous Structures (Analogies) are body parts that look alike in different lineages but did not evolve in a common ancestor.
• Comparative Development:
• Similar patterns of embryonic development reflect shared ancestry.
• Master genes that control embryonic development patterns have changed very little or not at all over evolutionary time, and master genes with similar sequence and function in different lineages suggest those lineages are related. Molecular Genetics:
• Consistencies in genetic codes are used to understand LUCA (Last Universal Common Ancestor).
• Biological Evolution is a change in heritable traits in a population over generations.
• Look at convergence by looking at fossil records, embryo development, molecular comparative (looking at genes), homologies, comparative morphology, macro vs micro evolution
• Micro is gene-frequency changing in a population,
• Macro is species changing over time when looking at all the species.

Traits

• Innate traits are what you are born with
• Acquired traits are what you obtain over time.

Genetics

• Mendel is the father of genetics that worked with pea plants.
• Phenotype is a phonetic term for a visible characteristic (short hair, brown eyes, etc)
• Genotype a genetic term relating to what type of genetic material you have (Heterozygous vs Homozygous)
  • Heterozygous genes are different (hetero- means different or other) while Homozygous genes are the same (homo-means the same). Refers to genetic makeup of the DNA.
• DNA contains ATCG bases to our code
• Each base is attached to a sugar and a phosphate.
• we read them in 3's (a triple code).
• A gene is a section of DNA that codes for something, for example: a type of color of a flower.
• Allele: you get 2 alleles, one from mom and dad. Can be dominant or recessive
• Mendel called them factors, not alleles.
• Biological Evolution:
• Individuals do not evolve, populations do evolve.
• Common descent: all species are related and gradually change over time/generations.

Requirements for Evolution

• Genetic Variation/Mutation:
• Genetic variation increases populations chance of survival from selective forces.
• Phenotypes change based on gene expression.
• Mutations may vary between different cultures.
• Sexual Reproduction
• Increases genetic variability.
• Sexual Reproduction of closely related individuals can lead to increased mutations. Genome- mapping out where every gene is in our body. -Natural Selection: Adaptive Evolution Variation, Competition, Adaptations, Selection , Gene Flow and Genetic Drift.
• Survival of the fittest does not mean strongest or best'
• Genetic bottlenecks are stochastic events that limit genetic variation in a population and result in founding populations that can lead to genetic drift:

Hardy-Weinberg Equilibrium

• All 5 assumptions must be kept in order for Hardy-Weinberg Equilibrium to happen-No Selection, No Mutation, No Migration, Large Population and Random Mating.
• P+q=1 (allele frequencies). P is dominant allele frequency. Q is recessive allele frequency.
• p^2+2pq+q^2=1
• p^2 is homozygous dominant, while 2pq is heterozygous, and q^2 is homozygous recessive.