Evolution
Human Evolution
Bipedalism
Larger Brain Size
Use of Tools
Language and Communication
Culture
Carbon Dating: Helps determine age of fossils and tools.
Artifacts & Tools: Tools show progression in intelligence and cultural development.
DNA Evidence: Shows close genetic relationship between humans and other primates.
Fossils: Show gradual changes in skull, teeth, posture, and brain size.
Homo sapiens (Modern Humans)
Homo neanderthalensis
Homo erectus
Homo habilis
Australopithecus
Hominins: A group that includes modern humans and all of our extinct relatives that evolved after we split from a common ancestor with chimpanzees.
Common Ancestor: Humans share a common ancestor with chimpanzees
Primates: Humans belong to the order Primates.
Speciation
Reproductive Isolation: Prevents gene flow between species.
Postzygotic Mechanisms (after fertilization)
Hybrid Infertility
Hybrid Inviability
Zygotic Mortality
Prezygotic Mechanisms (before fertilization)
Gametic Isolation
Mechanical Isolation
Behavioural Isolation
Temporal Isolation
Ecological Isolation
Macroevolution – large evolutionary changes over
time that result in the formation of a new taxonomic
group
Speciation – evolutionary formation of a new species
Sympatric Speciation: Occurs in the same geographic area.
Allopatric Speciation: Occurs when groups of the same species are separated by a physical barrier.
Microevolution – change in gene and allele frequency
(therefore phenotype traits) in a population
Microevolution
Genetic Drift
Random changes in allele frequencies in small populations.
Mutations
Random changes in DNA sequence passed through gametes.
Non-Random Mating
Mating is not by chance, driven by phenotype or inbreeding.
Gene Flow
Movement of alleles between populations through migration.
Natural Selection: Individuals with favorable traits are more likely to survive and reproduce.
Stabilizing Selection
Sexual Selection
Directional Selection
Disruptive Selection
Natural Selection
Variation
Genetic Variation
Sexual Reproduction: Mixing of genes from two parents
Creates new gene combinations during reproduction
Mutations: Random changes in DNA
Genetic Variation: Caused by differences in DNA (mutations, meiosis, sexual reproduction)
Environmental Variation:
Caused by surroundings (climate, diet, experiences)
Directional Selection:Favors one extreme version of a trait.
Disruptive Selection: Favors both extreme traits, not the average.
Stabilizing Selection: Favors the average trait, not the extremes.
Fossils in Africa: Predicted human origins based on living apes
Animal
Adaptation: A trait that helps an organism survive or reproduce better in a certain environment.
Walking Stick: Camouflage → predator avoidance.
Angler Fish: Bioluminescent lure helps catch prey in deep sea.
Venus Fly Trap: Adaptation to low-nutrient environments.
Cobra: Defense mechanism.
Cheetahs: Faster cheetahs catch prey more efficiently and reproduce more.
Anteaters: Evolved longer tongues to access food in tunnels.
Camouflage (e.g., insects, Potoo): Blending in increases survival.
Darwin’s Finches: Different beak shapes adapted to different food sources; reduces competition.
Process where organisms with traits that help them survive are more likely to live longer and have more offspring.
Evidence of evolution
Darwin's Hypothesis
Species that reached remote islands by air or water evolved into new species due to isolation and adaptation.
Artificial Selection
Humans select traits in organisms (like crops or pets), showing how selection can shape species over time.
Biogeography
Species distribution across the globe supports the idea of common origins and adaptation to environments.
Biochemistry
(Molecular Biology) DNA and protein comparisons show how closely related organisms are on a genetic level.
Embryology
Early embryos of different vertebrates look alike, hinting at shared ancestry.
Fossils
Comparative Anatomy
Vestigial Structures
Useless or reduced organs are remnants of functional parts in ancestors.
Analogous Structures Similar functions but different structures show adaptation through convergent evolution.
Homologous Structures Body parts with similar structures but different functions suggest a common ancestor.
Fossils show a timeline of life, with changes and transitional forms linking ancient and modern species.
