Evolution_2_2025 LMS
Page 1: Introduction to Evolution
Evolution Overview
Discusses evidence supporting evolution, including the fossil record and living species.
Page 2: Learning Objectives
Understand evidence for evolution, encompassing:
Fossil Record
Comparative Anatomy
Homologous and Analogous Traits
Vestigial and Atavistic Structures
Comparative Embryology
Common Ancestry
Convergent Evolution
Phylogenetic Constraint
Adaptive Radiation
Geographic Distribution
Domestication
Page 3: Principles of Science
Nature of Science:
Guided by natural law.
Explanations must reference natural law.
Must be testable.
Conclusions are tentative.
Must be falsifiable.
Scientific Method:
Hypothetico-Deductive Method:
Formulate hypotheses from observations, derive predictions, and validate through evidence to potentially reject hypothesis.
Page 4: Evidence for Evolution – The Fossil Record
Cited by Cleveland P. Hickman, Jr.
Page 5: Stratigraphy
Stratography Principles:
Fossils in deeper rock layers are older than those above; this establishes the chronological age of fossils.
Page 6: The Order of the Fossil Record
If species were created independently, the fossil record would show no order.
Fossil Record Insights:
A dated sequence of morphological changes provides evidence for common ancestry.
Page 7: Evolutionary Trends
Trends in Organisms:
Directional changes in organism features and diversity, including:
Increased size of molars in horses.
Loss of toes in equine evolution.
Increased species diversity.
Evolutionary Concepts:
Perpetual Change
Common Ancestry
Anagenesis: evolution within a lineage.
Page 8: Intermediate Forms
Example: Archaeopteryx:
Bone impressions confirm it as a bird, though original feathers are disintegrated.
Cladogenesis:
Represents the division of a single lineage into distinct lineages.
Page 9: Evolutionary Stability
Lingula:
Marine organism unchanged for approximately 400 million years.
Horseshoe Crab:
Morphologically unchanged for about 250 million years.
Page 10: Evolutionary Failure
Dinosaurs' Extinction:
Following the Cretaceous, birds and mammals dominated land vertebrates.
Page 11: Evidence for Evolution
Key Evidence Indicators:
Perpetual Change
Common Ancestry
Intermediate Forms
Cladogenesis and Anagenesis
Evidence of Evolutionary Failure and Stability.
Page 12: Living Species as Evidence for Evolution
SPL: Focus on contemporary species and their evolutionary connections.
Page 13: Comparative Anatomy
Definition: Study of anatomical similarities and differences among species.
Common Ancestry:
Features shared due to descent from a common ancestor.
Page 14: Vertebrate Forelimb Homologies
Despite functional differences (e.g., flight, swimming), all vertebrate forelimbs share a common anatomical pattern.
Quote by T. H. Huxley: "Unity of plan, diversity of execution."
Homology Definition: Same organ across different organisms under various forms and functions.
Page 15: Phylogenetic Constraint
Evolution constrained by ancestry; certain inherited traits limit potential variations for adaptations.
Page 16: Comparative Embryology
Homologies: Indicates common ancestry.
Developmental Stages:
All terrestrial animals exhibit non-functional gill slits in embryos.
Vertebrate embryos show a primitive tail.
Page 17: Vestigial Features
Structures with reduced functions indicating evolutionary history:
Whales: Hip structures from terrestrial ancestors.
Snakes: Remnants of hindlimbs from lizard ancestors; forelimbs absent.
Human Appendix: Vestigial structure reduced from cecum.
Page 18: Atavistic Features
Reappearance of ancestral traits in modern species, e.g., horses occasionally born with extra toes.
Reflects underlying ancestral developmental patterns.
Page 19: Analogous Features
Features that evolve independently under similar environmental pressures, showcasing convergent evolution.
Page 20: Convergent Evolution
Similar features evolve in separate lineages due to similar lifestyles; these features are termed analogous.
Page 21: Homology vs. Analogy
Homology: Similar bone structure in vertebrate forelimbs indicates a common ancestor.
Analogy: Bat, bird, and butterfly wings function similarly but evolved independently.
Page 22: Homologies and Analogies
Homologies: Inherited traits reflecting common ancestry.
Analogies: Traits sharing function but developed independently due to convergent evolution.
Page 23: Homoplasy
Definition: Structures appearing similar but may or may not be homologous or analogous.
Page 24: Summary of Similarities
Homology: Shared ancestry reflecting common structures.
Analogy: Similar forms due to common function in similar habitats.
Homoplasy: Unrelated structures that appear similar.
Page 25: Comparative Matrix
Summary of relationships:
Homology: Common ancestry leads to shared structures.
Analogy: Similar function; different ancestry leads to similar forms.
Homoplasy: Structures appear alike but do not imply any commonality.
Page 26: Adaptive Radiation
Evolution of diverse species from a common ancestor, exemplified by Galapagos finches.
Page 27: Divergent and Convergent Evolution
Divergent Evolution: Speaks to how species differ after splitting from a common ancestor.
Convergent Evolution: Accentuated by independent evolution of similar traits.
Page 28: Artificial Selection and Natural Selection
Darwin's Observation: Domestic species illustrate principles of natural selection.
Variation in populations correlates with natural selection.
Descent with modification noted.
Artificial Selection: A tool providing evidence for natural selection mechanisms.
Page 29: Canine Domestication
Many dog breeds descended from wolves, illustrating artificial selection processes dating back approximately 15,000 years ago.
Page 30: Summary of Evolutionary Principles
FACT: Evidence derived from fossil records and living species.
COURSE of Evolution: Descent with modification; gradualism vs. punctuated equilibrium; mosaic evolution.
Mechanism of Evolution:
Natural Selection
Mutation
Gene Flow
Random Genetic Drift - key evolutionary forces.