1.6 Evidence For Evolution

The Big Five Extinctions

• Ordovician (445 Million Years Ago)

  • Die Off: 85%

  • Causes: Rapid Cooling, Falling Seas

• Devonian (360 Million Years Ago)

  • Die Off: 70%

  • Causes: Asteroid Impacts, Rapid Cooling

• Permian (250 Million Years Ago)

  • Die Off: 95%

  • Causes: Volcanic Activity, Atmospheric Change, Rapid Global Warming

• Triassic (200 Million Years Ago)

  • Die Off: 76%

  • Causes: Atmospheric Change, Rapid Global Warming

• Cretaceous (K-T) (65 Million Years Ago)

  • Die Off: 80%

  • Causes: Asteroid Impacts, Volcanic Activity, Falling Sea Levels

Cretaceous-Tertiary Extinction: K-T

• Chicxulub Crater

  • Iridium layer found at K-T boundary (~65 MYA) indicates asteroid impact

  • Iridium more common in asteroids than Earth rocks

  • Chicxulub crater is 120 miles in diameter, 8-10 miles deep, confirming impact site.

Mass Extinctions - Last 500 Million Years

• Major extinctions: Ordovician, Devonian, Permian, Triassic, Cretaceous.

• Timeline indicates sporadic occurrences of mass extinctions.

Why Adaptive Radiations After Mass Extinctions?

• Mass extinctions create unoccupied niches, allowing surviving species to thrive and diversify.

• Increased competition among species (e.g., mammals) drives adaptation and niche specialization.

Evidence for Evolution

• Types of Evidence:

  • Fossil Evidence

  • Anatomical Evidence

  • Molecular Evidence (DNA)

Discussion Points

• How would you prove evolution to a skeptic?

• Types of evidence to use.

Conceptual Diagram: Evidence of Evolution

• Main Components:

  • Natural Selection

  • Fossils

  • Anatomical Evidence

  • Molecular Evidence

Fossils of > 250,000 Species

• Includes ancient fossils from various periods:

  • 1.8 billion year-old fossils

  • 2.3 billion year-old fossils

  • Examples include: Bacterium, Tiktaalik, Trilobite, Stromatolite, Archaeopteryx, Charniodiscus, Homo sapiens.

In the News

• Recent finding of a one-billion-year-old fossil could represent the oldest multicellular animal, shedding light on the evolution of complex life forms.

Anatomical Developmental Patterns: Vertebrate Embryos

• Comparable morphologies evident in fish, reptiles, birds, and mammals during early development stages.

Comparative Anatomy

• Homologous Structures vs. Analogous Structures:

  • Structures that share a common ancestry (homologous) and those that do not (analogous).

Molecular Commonalities Among Cells

• Essential molecules:

  • ATP: Energy molecule

  • DNA: Information storage

  • L-amino acids: Building blocks of proteins.

Molecular Biochemistry: Amino Acid Sequences of Proteins

• Differences in proteins correlate with the time since organisms last shared a common ancestor.

• Phylogenetic trees based on molecular data align with other evolutionary criteria.

In-Class Question on Mass Extinctions

• Examines multiple-choice questions focusing on the role of mass extinctions in evolution.

Order Primates

• Timeline: Evolved 80-75 MYA

• Include Lemurs, Lorises, Tarsiers, Monkeys, and Apes.

• Most modern primates have arboreal adaptations.

Major Primate Traits

• Traits and Advantages:

  1. Grasping Hand - for tool use and mobility.

  2. Binocular Vision - enhances depth perception.

  3. Large Brain - supports complex social interactions.

  4. Parental Care and Sociality - improves survival rates.

Adaptive Advantages of Grasping Hands

• Provides enhanced gripping and tool-using abilities for survival and resource gathering.

Adaptive Advantages of Binocular Vision

• Crucial for navigating tree canopies and assessing distances.

Adaptive Advantages of Large Brain

• Facilitates advanced sensory processing, learning, and social behavior.

Adaptive Advantages of Parental Care & Sociality

• Promotes offspring survival and enhanced cooperation within groups.

Ancestor & Evolution of Primates (85-30 Million Years Ago)

1. Earliest common ancestor (85 MYA)

2. Early primate evolution (80-75 MYA)

3. Dinosaur extinction (65 MYA)

4. Adaptive radiation of primates (65-45 MYA)

After Extinction of Dinosaurs

• Adaptive radiation of primates in the aftermath of dinosaurs' extinction, leading to diverse primate species.

Early Primates (30 Million Years Ago)

• Example: Aegyptopithecus zeuxis - reveals traits leading to Old World Monkeys, discovered in Egypt.

Family Tree of Human Evolution

• Chronological order of key species: Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis.

Hypotheses of Human Evolution

• Multiregional hypothesis vs. Out of Africa hypothesis: contrasting theories about human origins and migrations.

Timeline of Human Evolution: A Resource

• Key human ancestors listed with fluctuating climate changes impacting evolution.

Australopithecus Afarensis - Lucy

• Discovered in Ethiopia, noted for bipedal traits and anatomical differences from modern humans.

Homo Habilis - Handy Man

• Tools associated with Homo habilis, showcasing early technological advancements.

Homo Erectus - The Upright Man

• Significant evolutionary marker with advanced tool usage.

Homo Neanderthalensis

• Comparative features with modern humans—evidence of significant cognitive and social abilities.

Humans & Neanderthals: Genetic Comparison

• Analysis of mitochondrial DNA reveals evolutionary pathways and interbreeding events.

Human Evolution: Putting it All Together

• Emphasizes ongoing research and discoveries impacting our understanding of human evolution.

Reminders

• Exam is next session—review all materials thoroughly for preparation.

Human Evolution: Ongoing Research

• Highlight the latest findings in human evolution and genetics, predicting future pathways.