Theory of Evolution: Adaptability and Diversity

• Evidence supporting the theory of Evolution

Overview

• Early evolutionary views, defining evolution, and navigating science and religion are highlighted.
• Differentiating scientific "facts" from "theories" is explored.
• Key focus includes the evidence supporting evolution.

Accounting for Adaptability and Diversity

• Understanding how life forms adapt to environments and the diversity of life forms is discussed.
• Th. Dobzhansky's perspective: "Nothing in biology makes sense except in the light of evolution" (1973).

Early Seeds of Evolutionary Thinking

• Discussions include the classical view, and contributions from Buffon in 1770, Erasmus Darwin in 1770, and Lamarck in 1810.

The Classical View

• Living organisms are seen as constant and unchanging.
• The root of this idea is traced back to the Greeks, with Aristotle noting the difficulty in classifying some bizarre life forms like sponges.

Challenges to the Classical View

• Global explorations from the 1500s show diversities of life forms
• Some appeared related to European forms and others with no resemblance.

World distribution of organisms

• Marsupial mammals were generally rare, but all Australian mammals were marsupials
• Cactus plants are common in North and South American deserts but absent in Australian and Asian deserts.
• If all species were created at the same time in the same place, a question arises about why so many are restricted to particular parts of the world.

Buffon (1770s)

• If species spread from a single point of creation, they'd be stopped by mountains or seas, suggesting the creation of species is spread out.
• Species might not have been created in perfect condition; pigs' lateral toes don't reach the ground, suggesting species modify over time.

Erasmus Darwin (1770s)

• Erasmus Darwin was inspired by domesticated animal diversity from selective breeding.
• Proposed that all organisms share a common ancestor, an idea later used by his grandson, Charles Darwin.

Jean Baptiste de Lamarck (1809)

• Life was created long ago in a simple state, and then gradually improved.
• A specific mechanism proposed stated this change occurs through the inheritance of acquired characteristics.
• Species change over time, and the environment is a factor in this change.

What is Evolution?

• As defined by Charles Darwin, it is descent with modification.
• Darwin was not the first to suggest that evolution occurs, but he was the first to suggest a plausible mechanism and present a strong case that evolution occurs.

Descent with modification

• All organisms can be traced back through a series of common ancestors.
• Descent with modification allows for tests of Evolution.
• Renovating a house and finding vestiges of the original house is an applicable analogy.

Scientific Theories and Facts

• Gravity is presented as a scientific fact.
• Key point: all experiments testing gravity have consistently demonstrated its occurrence.

Science vs. Religion

• Science and religion are not incompatible because they are designed for different tasks.
• Religion serves as a belief system that generates shared values and culture.
• Science is a specific tool for asking questions and rigorously testing them.
• Scientists of different faiths all use the same approaches for asking and testing questions.

Testing in Science

• The key science aspect: making predictions and testing them
• In science, belief is burdened by the need for repeatable tests to support the stated assertion.
• The approach must put fundamental ideas on trial and try to prove them wrong.

Evolution as a Scientific Fact

• Variety signs should be detectable if evolution has occurred.
• Signatures of shared ancestry are key.
• It is an undefeated champ for over 150 years of aggressive testing because each time it undergoes a test, evidence is shown.
• Each new genome sequenced can be used as a test for evolution.

Evidence for Descent with Modification

• Includes biogeography, functional morphology, paleontology, comparative embryology, animal and plant breeding, and molecular evidence.

The Voyage of the HMS Beagle (1831-36)

• Charles Darwin traveled the world on the HMS Beagle from 1831-1836

Armadillos and Glyptodonts

• Both living armadillos and extinct fossil glyptodonts are found in the same locations in South America.
• Darwin proposed the armadillo evolved from the glyptodon or a close relative, rather than separate creation.

Galapagos Islands species variation

• Darwin observed slightly different finch species on each island
• He noted all displayed similarities to a mainland South American species.

Evidence from Functional Morphology

• Vestigial organs in humans include muscles for moving ears and a tailbone
• Vestigial toes in the horse
• Vestigial limbs in whales and snakes

Homologous Structures

• Similar blueprints can be seen in different organisms
• Structures of many organisms were put together with the same pieces.
• Whale's fin, bat's wing, and human hands have similar bones

Fossil Evidence

• Fossils show progression from simple to more complex forms over time.
• Multiple examples of transitional forms exist.
• Direct evidence for descent with modification can be shown

Comparative Embryology

• Early in the field of embryology , embryos of different vertebrates were observed to be similar

Comparative Embryology

• Early in the development of species, similar stages can be seen
• It is expected of species who descended from a common ancestor, as developmental pattern can be seen to play out in embryogenesis

Laws of Development

• Haeckel created the phrase: "Ontogeny recapitulates phylogeny" and it states that during development, the embryo seems to pass through stages of more primitive adult organisms
• von Baer's law: Structures present early in development are widely distrusted among animals and it is the later features tend to distinguish species

Evidence from Animal Breeding

• Darwin was very impressed by how domesticated animals had been changed by artificial selection.Breeds of dogs, cattle, pigeons are example

Recent Evidence

• Explosion of data confirms and expands Darwin's observations
• Recent data: Molecular Data, Protein Sequencing, DNA sequencing, whole genome sequencing

Molecular Evidence of Shared Ancestry

• A bat's biochemistry is much closer to that of a whale, rather than a bird and evolution predicts this.
• DNA sequences can be used to determine how closely related species are.

Genomic Evidence

• Most of DNA is non-coding and contains signatures of inactivated genes.
• Many shared genes are shown between widely divergent species.
• Common metabolic enzymes in vertebrate eyes that are present in bacteria are shown to be have duplicated and diverged.

Shared Errors: Pseudogenes

• Defective copies of genes no longer work but contain early stop codons.
• Humans and chimps share pseudogenes with same errors in the same location
• Are copied from the same page and came from a common ancestor

Summary: Why Evolution?

• Explains strange observations of biogeography, functional morphology, embryology, and molecular biology
• Explains "fossils", rocks, vestigial traits, and genomic data.
• Stood the test of time under continual testing for well over 100 years and exhibits testable predictions.