Evolution and Speciation (Topic A4.1.1-4.1.7)

Page 1: Evolution as Change

• Definition of Evolution: Change in heritable characteristics of a population over time.

Page 2: Evolution of Whales

• Odontoceti (Toothed Whales): Key species in the evolutionary lineage of modern whales.

• Transition Timeline: Various species and their ages:

  • Pakicetus inachus: 47 million years ago

  • Ambulocetus natans: 47-41 million years ago

  • Malacetus inuus: 41 million years ago

  • Rodhocetus kasrani: 4130 years ago

  • Dorudon atrox: 4034 years ago

  • Basilosaurus cetoides: 10 million years ago

  • Orcinus orca: 11 million years ago

Page 3: Fundamental Definition of Evolution

• Evolution fundamentally describes the change over time.

Page 4: Change in Organisms

• In organisms, evolution refers to heritable changes in populations, not individuals.

Page 5: Importance of Genetic Change

• Biological Evolution: Continuous change must be at the genetic level; changes that are non-genetic are not considered evolutionary.

Page 6: Historical Perspective on Evolution

• Adaptation: Organisms appear to fit their environment well. Example: Fennec fox adaptations for desert survival.

• Theories: Contrast between Darwinian evolution and Lamarckism.

Page 7: Charles Darwin vs. Jean-Baptiste Lamarck

• Darwinian Evolution: Recognized as correct by modern science; bases on natural selection.

• Contrasting Theories: Lamarck's ideas proposed that traits acquired during a lifetime could be passed on.

Page 8: Lamarckism Explained

• Proposed by Lamarck: Traits can be acquired and inherited (e.g., giraffes stretching necks).

• Pre-darwinian acceptance of this theory.

Page 9: Darwinian Natural Selection

• Mechanism of Natural Selection:

  • Variation within species.

  • Beneficial traits enhance survival and reproductive success.

  • Less adapted individuals are less likely to reproduce.

Page 10: Lamarck's Giraffe Explanation

• Lamarck's view: Giraffes stretch necks to reach food, leading to longer necks in offspring.

Page 11: Darwin's Giraffe Explanation

• Darwin’s view: Some giraffes are born with longer necks due to natural variation.

• Advantage of longer necks leads to increased reproductive success over time.

Page 12: Definition of Theory in Science

• Scientific Theory: Represents the highest level of understanding; it explains phenomena and is repeatedly tested.

Page 13: Distinction of Laws and Theories

• Scientific Laws: Describe what happens; theories explain how and why.

Page 14: Quote on Evolution

• Theodosius Dobzhansky: "Nothing in biology makes sense except in the light of evolution."

Page 15: Limitations of Proving Evolution

• The theory cannot be formally proven due to varying universal scenarios. Requires ongoing scientific validation.

Page 16: Evolution vs. Gravity

• Richard Dawkins Quote: Comparison of evolution with gravity to illustrate widespread acceptance despite being "just a theory".

Page 17: Human Lineage

• Human ancestors include: Australopithecus afarensis, Homo erectus, Homo neanderthalensis, Homo habilis, Homo sapiens.

Page 18: Evidence from Fossils

• Fossil Evidence: Provides insight into evolution and Earth's age (4.5 billion years).

Page 19: Defining Fossils

• Fossils: Evidence of past life; includes remains, impressions, carbon residues, and other imprints.

Page 20: Fossil Record Significance

• Fossils provide evidence for time and evolutionary history; aquatic organisms fossilize more readily than land organisms.

Page 21: Evolutionary Trends from Fossils

• Fossils allow paleontologists to track evolutionary changes and identify intermediate species.

Page 22: Age of Earth

• Approximate age: 4.5 billion years. Previous beliefs suggested a much younger Earth, insufficient for Darwinian evolution.

Page 23: Relative Dating of Fossils

• Relative Dating: Technique to assess the age of fossils compared to others without specific ages.

Page 24: Radioactive Dating

• Radioactive Dating: Measures decay of radioactive elements. Key isotopes: Uranium-238, Potassium-40, Carbon-14.

Page 25: Carbon-14 Dating

• Used for dating much younger samples (up to 50,000 years); important for archaeological findings.

• Sample Calculation: Example of determining the age based on Carbon-14 to Nitrogen-14 ratio.

Page 26: Determining Fossil Age

• Example Analysis: Calculating the age of a bone sample using the C-14 decay formula.

Page 27: Half-life Calculation Example

• C-14 Half-life: 5770 years; illustrates how to derive age from sample ratios over half-lives.

Page 28: Common Ancestry Evidence

• DNA Evidence: Technological advancements in sequencing DNA provide deeper insights into evolutionary relationships.

Page 29: Importance of DNA Sequencing

• DNA sequencing alters the perception of evolutionary ancestry, allowing for better classification beyond physical traits.

Page 30: Tools for Evolutionary Analysis

• Genome sequencing and tools like Clustal Omega help uncover species' evolutionary history and relationships.

Page 31: Cladograms

• Diagrams based on DNA sequence similarities illustrate evolutionary relationships.

Page 32: Genetic Similarities

• DNA comparison reveals common ancestry and levels of relatedness among species.

Page 33: Sequencing 2.3 Million Species

• Collation of DNA sequences enhances understanding of species divergence from a common ancestor.

Page 34: Universal Genetic Code

• All organisms utilize DNA similarly, providing a basis for comparison of amino acids and sequences.

Page 35: Mutation Accumulation

• Over time, mutations lead to genetic variation, which helps understand evolutionary divergence.

Page 36: DNA Comparison Scope

• More genetic differences correlate with longer times since divergence among species; fewer suggest closer relationships.

Page 37: Comparing Molecular Sequences

• Use of non-coding DNA, gene sequences, amino acid sequences tailored based on species relationship distance.

Page 38: Appropriate Context for Comparison

• Amino Acid Usage: Best for distantly related species.

• Base Sequences: Preferred for closely related organisms.

Page 39: Example of Selective Breeding

• Selective Breeding: Manipulation by humans to enhance desired traits in dogs, representing an evolutionary process.

Page 40: Artificial Selection Process

• Traits become common through selective breeding, not limited to animals as it applies to plants too.

Page 41: Brassica Example

• Plants like Brassica have been bred for different foods via artificial selection to modify various attributes.

Page 42: Domesticated Fox Experiment

• Dmitry Belyaev's experiment on foxes showcases rapid evolution through selective breeding for tameness.

Page 43: Domesticated Fox Results

• The domestication project resulted in friendly foxes showing dog-like behaviors, continuing research under Lyudmila Trut.

Page 44: Evolutionary Speed Examples

• Evolutionary changes can happen quickly as seen with dogs, plants, and foxes through human intervention.

Page 45: Early Dog Domestication

• Dogs domesticated around 15,000 years ago; reasons for domestication remain speculative, but include hunting and protection.

Page 46: Breeding for Specific Traits

• Different dog breeds arose for specific purposes: hunting, herding, racing, and toy sizes highlight artificial selection's efficacy.

Page 47: Rapid Evolution Evidence

• Showcases how selective breeding leads to observable evolutionary changes across species.

Page 48: Homologous Structures Evidence

• Homologous Structures: Anatomically similar features across different species indicating shared ancestry.

Page 49: Speciation Defined

• Speciation: Diverging evolutionary process leading to distinct species from a common ancestor.

Page 50: Common Adaptations

• Consideration of whether species share evolutionary ancestry despite physical similarities.

Page 51: Pentadactyl Limb Example

• Classical example of homologous structures; evidence of common ancestry through similarity in limb structure.

Page 52: Function of the Pentadactyl Limb

• Despite similar underlying bone structures, limbs have evolved for varied functions based on the species’ habitat and behaviors.

Page 53: Bone Structures in the Pentadactyl Limb

• Includes humerus, radius, ulna, carpals, metacarpals, and phalanges seen across species (humans, cats, horses, bats, dolphins).

Page 54: Analogous Structures Defined

• Analogous Structures: Similar function but different evolutionary origins; e.g., wings of birds vs. wings of insects.

Page 55: Evolutionary Product of Analogous Structures

• Analogous traits arise through convergent evolution due to adaptation to similar environments without recent common ancestors.

Page 56: Example of Convergent Evolution

• Dolphins and sharks share similar traits (e.g., fins) despite not having common ancestors exemplifying convergent evolution.

Page 57: Vestigial Structures Definition

• Vestigial Structures: Functionless remnants of organs from ancestors showing evolutionary divergence.

Page 58: Vestigial Structures Examples

• Goosebumps, wisdom teeth as examples of vestigial structures in modern organisms.

Page 59: Speciation Explained

• Definition: Separate species arise when populations can no longer interbreed and produce viable offspring.

Page 60: Models of Speciation Overview

• Two models:

  • Gradualism: Slow, continuous evolution.

  • Punctuated Equilibrium: Rapid changes followed by stability.

Page 61: Gradualism Explained

• Evolution happens gradually over long periods; changes may not be evident in short timeframes.

Page 62: Example of Gradualism

• Horse evolution illustrates gradualism with numerous intermediates in the fossil record.

Page 63: Distinction of Speciation and Gradualism

• Speciation occurs when populations diverge and cannot reproduce after significant changes over time.

Page 64: Punctuated Equilibrium Defined

• Punctuated Equilibrium: Characterized by sudden evolution followed by stasis in change.

Page 65: Example of Punctuated Equilibrium

• Kingfisher birds in Papua New Guinea rapidly evolving during geographic shifts in habitats.

Page 66: Reproductive Isolation Defined

• Reproductive Isolation: Barriers preventing interbreeding, preserving distinct gene pools between populations.

Page 67: Divergence Over Time

• Geographic separation increases divergence over time, leading to speciation.

Page 68: Differential Selection Defined

• Selection by environmental pressures favors certain traits, leading to evolutionary changes in populations.

Page 69: Chimpanzee and Bonobo Divergence

• Example of divergence due to differential selection influenced by geographic barriers like the Congo River.

Page 70: Adaptations in Bonobos vs. Chimpanzees

• Bonobos adapted for forests; physical differences reflect distinct survival strategies in their environments.

Page 71: Bonobo Behavior Insights

• Unique traits (helpfulness, non-violent behavior) observed in bonobos provide insights into evolution and social structures.

Page 72: Evolutionary Relationship Clarity

• While closely related to humans, bonobos are more closely related to chimpanzees than to humans, highlighting evolution paths.

Page 73: Guiding Questions on Evolution

• Consider the evidence supporting evolution and how various structures reflect commonality and diversity in species.

Page 74: References

• Various sources cited for further reading and verification on evolutionary topics.