Evolution

Evidence of evolution

Fossils

Fossils show a timeline of life, with changes and transitional forms linking ancient and modern species.

Comparative Anatomy

Homologous Structures Body parts with similar structures but different functions suggest a common ancestor.

Analogous Structures Similar functions but different structures show adaptation through convergent evolution.

Vestigial Structures
Useless or reduced organs are remnants of functional parts in ancestors.

Embryology

Early embryos of different vertebrates look alike, hinting at shared ancestry.

Biochemistry

(Molecular Biology) DNA and protein comparisons show how closely related organisms are on a genetic level.

Biogeography

Species distribution across the globe supports the idea of common origins and adaptation to environments.

Artificial Selection

Humans select traits in organisms (like crops or pets), showing how selection can shape species over time.

Darwin's Hypothesis

Species that reached remote islands by air or water evolved into new species due to isolation and adaptation.

Natural Selection

Process where organisms with traits that help them survive are more likely to live longer and have more offspring.

Darwin’s Finches: Different beak shapes adapted to different food sources; reduces competition.

Animal

Camouflage (e.g., insects, Potoo): Blending in increases survival.

Anteaters: Evolved longer tongues to access food in tunnels.

Cheetahs: Faster cheetahs catch prey more efficiently and reproduce more.

Adaptation: A trait that helps an organism survive or reproduce better in a certain environment.

Cobra: Defense mechanism.

Venus Fly Trap: Adaptation to low-nutrient environments.

Angler Fish: Bioluminescent lure helps catch prey in deep sea.

Walking Stick: Camouflage → predator avoidance.

Fossils in Africa: Predicted human origins based on living apes

Directional Selection:Favors one extreme version of a trait.

Stabilizing Selection: Favors the average trait, not the extremes.

Disruptive Selection: Favors both extreme traits, not the average.

Variation

Genetic Variation: Caused by differences in DNA (mutations, meiosis, sexual reproduction)

Environmental Variation:
Caused by surroundings (climate, diet, experiences)

Genetic Variation

Mutations: Random changes in DNA

Creates new gene combinations during reproduction

Sexual Reproduction: Mixing of genes from two parents

Microevolution

Genetic Drift

Gene Flow

Natural Selection: Individuals with favorable traits are more likely to survive and reproduce.

Stabilizing Selection

Directional Selection

Disruptive Selection

Sexual Selection

Movement of alleles between populations through migration.

Mutations

Non-Random Mating

Mating is not by chance, driven by phenotype or inbreeding.

Random changes in DNA sequence passed through gametes.

Random changes in allele frequencies in small populations.

Speciation

Microevolution – change in gene and allele frequency
(therefore phenotype traits) in a population

Speciation – evolutionary formation of a new species

Allopatric Speciation: Occurs when groups of the same species are separated by a physical barrier.

Sympatric Speciation: Occurs in the same geographic area.

Macroevolution – large evolutionary changes over
time that result in the formation of a new taxonomic
group

Reproductive Isolation: Prevents gene flow between species.

Prezygotic Mechanisms (before fertilization)

Ecological Isolation

Temporal Isolation

Behavioural Isolation

Mechanical Isolation

Gametic Isolation

Postzygotic Mechanisms (after fertilization)

Zygotic Mortality

Hybrid Inviability

Hybrid Infertility

Human Evolution

Primates: Humans belong to the order Primates.

Common Ancestor: Humans share a common ancestor with chimpanzees

Hominins: A group that includes modern humans and all of our extinct relatives that evolved after we split from a common ancestor with chimpanzees.

Australopithecus

Homo habilis

Homo erectus

Homo neanderthalensis

Homo sapiens (Modern Humans)

Fossils: Show gradual changes in skull, teeth, posture, and brain size.

DNA Evidence: Shows close genetic relationship between humans and other primates.

Artifacts & Tools: Tools show progression in intelligence and cultural development.

Carbon Dating: Helps determine age of fossils and tools.

Bipedalism

Larger Brain Size

Use of Tools

Language and Communication

Culture