Evidence for Evolution
History of Evolutionary Thought
- Charles Darwin (1809-1882)
- Initially studied medicine, then theology, before becoming a naturalist.
- Traveled the world on the HMS Beagle.
- Observed species relationships and distributions.
- In 1859, presented the first concrete evidence and mechanism for evolution in "On the Origin of Species."
Darwin's Journey on HMS Beagle
- The journey included stops at various locations around the world, including:
- Azores
- Canary Islands
- Cape Verde Islands
- Bahia
- Rio de Janeiro
- Montevideo
- Falkland Islands
- Tierra del Fuego
- St. Helena
- Ascension
- Mauritius
- King George Sound
- Hobart
- Sydney
- New Zealand
- Tahiti
- Cocos Islands
- Galapagos Islands
- Callao
- Valparaiso
Evidence Collected by Darwin
- Artificial Selection
- Fossil Records
- Comparative Anatomy
- Comparative Embryology
- Biogeography
- Taxonomy
Artificial Selection
- Breeding for desired traits.
- Examples: hens with more eggs, varieties of dogs, large vegetables.
- Directly contradicts the belief that species do not change.
- Dog Breed example
- Wolf is the ancestor of all modern dog breeds
- Bloodhound
- Dalmatian
- Airedale
- Border Collie
- Pekingese
Vegetables from One Species
- Many vegetables are derived from one species, Brassica oleracea, through artificial selection for different traits.
- Cabbage: Selection for terminal buds.
- Cauliflower: Selection for flower clusters.
- Brussels sprouts: Selection for lateral buds.
- Broccoli: Selection for stems and flowers.
- Kohlrabi: Selection for stem.
- Kale: Selection for leaves.
Fossil Record
- Fossils are evidence of past life forms and are formed in various ways:
- Mineralization
- Trapped in amber/tar
- Footprints in soft soil
- Soft vs. hard tissues
Archaeopteryx
- Archaeopteryx is an example of a fossil record of a species.
Transitional Fossils
- Tiktaalik roseae
- A 375-million-year-old fish.
- Exhibits characteristics of both fish and tetrapods.
Comparative Anatomy
- Similarities in structure of functionally different organisms.
- Example: Bones in Human arm, Dolphin fin, Bat wing, Bird wing
- Humerus
- Radius
- Ulna
- Carpals
- Metacarpals
- Phalanges
Comparative Anatomy: Homologous vs. Analogous Structures
- Homologous Structures
- Different species with similar underlying structure but different function.
- Example: Bones of vertebrate legs, wings, and fins.
- Analogous Structures
- Unrelated species with similar features and function but different underlying structure.
- Example: Insect wings and bird wings.
- Convergent Evolution
- Independent evolution of similar features or functions in unrelated species.
- Example: Eye of cephalopods and vertebrates.
Convergent Evolution: The Eye
- The eye of humans and octopuses are examples of convergent evolution.
- Human eye components:
- Eyelid
- Cornea
- Pupil
- Iris
- Ciliary muscle
- Lens
- Retina
- Optic nerve
- Octopus eye components:
- Optic ganglion
Vestigial Organs
- Nonfunctional, reduced parts.
- Examples: appendix, wisdom teeth, coccyx in humans, vestigial pelvis in whales.
- Common ancestry explains them as unused parts.
- Example: Baleen whales
- Vestigial hip and thigh bones
- Example: Toothed whales, dolphins, and porpoises
- Vestigial pelvis
Comparative Embryology
- Features in embryos that do not show up in adults:
- Pharyngeal pouches
- Tail
- Tubular heart
- Suggests common ancestry.
- Examples: Reptile, Bird, Pig, Human
- All have gill pouches and a tail in the embryo stage
Biogeography
- Study of the distribution of species.
- Distinct species groups on different continents.
- Example: Marsupials in Australia
- Nearctic Species
- Gray fox
- Moose
- Agouti
- Beaver
- Palearctic Species
- Argali
- Brown Bear
- Black Bear
- Snow Leopard
- Chamois
- Aoudad
- Neotropical Species
- Tapir
- Jaguar
- Sloth
- Anteater
- Ethiopian Species
- Zebra
- Lion
- Oriental Species
- Tiger
- Indian Boar
- Indian Elephant
- Australian Species
- Koala
- Thylacine
- Platypus
- Kangaroo
Evidence Collected by Darwin (Recap)
- Artificial Selection
- Fossil Records
- Comparative Anatomy
- Comparative Embryology
- Biogeography
- Protein and DNA Sequence Data
Darwin's Conclusions from Evidence
- Many species have existed before that no longer exist.
- Species show relatedness in the fossil record and other forms of evidence.
- Species have changed over time to their current state.
- All life is related through descent with modification.
Natural Selection
- Darwin proposed natural selection as a mechanism for how these changes arose.
- Capacity for overproduction.
- Yet few survive due to limited resources.
- Individuals vary in traits.
- Those that survive are those whose traits allow them to obtain resources and reproduce successfully.
Darwin's Publications
- 1838-43: Zoology of the Voyage of H.M.S. Beagle
- 1838: Part 1 No. 1 Fossil Mammalia, by Richard Owen (Preface and Geological introduction by Darwin)
- 1838: Part 2 No. 1 Mammalia, by George R. Waterhouse (Geographical introduction and A notice of their habits and ranges by Darwin)
- 1839: Journal and Remarks (The Voyage of the Beagle)
- 1842: The Structure and Distribution of Coral Reefs
- 1844: Geological Observations on the Volcanic Islands visited during the voyage of H.M.S. Beagle
- 1846: Geological Observations on South America
- 1849: Geology from A Manual of scientific enquiry; prepared for the use of Her Majesty's Navy: and adapted for travellers in general., John F.W. Herschel ed.
- 1851: A Monograph of the Sub-class Cirripedia, with Figures of all the Species. The Lepadidae; or, Pedunculated Cirripedes.
- 1851: A Monograph on the Fossil Lepadidae, or, Pedunculated Cirripedes of Great Britain
- 1854: A Monograph of the Sub-class Cirripedia, with Figures of all the Species. The Balanidae (or Sessile Cirripedes); the Verrucidae, etc.
- 1854: A Monograph on the Fossil Balanidæ and Verrucidæ of Great Britain
- 1858: On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection (Extract from an unpublished Work on Species)
- 1859: On the Origin of Species
- 1881: The Formation of Vegetable Mould through the Action of Worms
Darwin's Last Book
- The Formation of Vegetable Mould through the Action of Worms was published 138 years ago (in Oct. 1881).
- Darwin's health was failing, and he wanted to complete this book before he died.
Modern Synthesis
- Darwin did not know how traits were inherited.
- Gregor Mendel's work was published in 1866 but was not noticed until 1900.
- Modern synthesis (neo-Darwinism) recognizes:
- Mutations as the source of variations.
- A change in allele frequency as a measure of evolution.