Evolution, Fossils, and Key Figures in Biology

Definition of evolution in biology

Evolution is the change in allele frequencies in a population over generations.

Origin of Species publication

Published by Charles Darwin in 1859.

Definition of a scientific theory

a well-supported explanation of natural phenomena based on evidence and testable hypotheses.

Why evolution is a good theory

Because it is supported by massive evidence, makes testable predictions, and explains biological diversity.

Why evolution is both a fact and a theory

It is a fact because populations change over time; it is a theory because the mechanisms explaining how evolution happens form a scientific theory.

Microevolution vs macroevolution

Microevolution is changes within populations over time; macroevolution is large-scale evolutionary change such as speciation and extinction.

Five processes that cause evolution

Mutation, natural selection, genetic drift, gene flow, nonrandom mating.

Big ideas in Origin of Species

Descent with modification and natural selection.

Number of cetacean species

About 90 cetacean species exist including dolphins, porpoises, and whales.

Why cetacean evolution was a problem for Darwin

Lack of transitional fossils at the time made it hard to show how land animals evolved into fully aquatic whales.

How we know cetaceans are mammals

They have hair (embryonically), mammary glands, warm-bloodedness, lungs, and three middle ear bones.

Definition of transitional form

A fossil showing intermediate traits between ancestral and derived groups.

Why transitional forms matter

They show gradual evolutionary change and support macroevolution.

Darwin's response to missing whale transitional fossils

He predicted they eventually would be found; later fossils proved him correct.

Artiodactyl definition

Even-toed hoofed mammals like deer, pigs, hippos.

Evidence cetaceans evolved from artiodactyls

Shared DNA, ankle bone (astragalus) shape, and fossil intermediates linking whales to hippos.

Astragalus

Ankle bone diagnostic of artiodactyls.

Involucrum

A thickened inner ear bone unique to cetaceans.

Convergent evolution example in cetaceans

Streamlined body shape similar to fish.

Adaptation example in cetaceans

Blubber for insulation in water.

Vestigial structure example in cetaceans

Reduced hind limb bones.

Homology example in cetaceans

Forelimb bones homologous to other mammals.

Capt. Fitzroy

19th-century British naval captain of the HMS Beagle.

Charles Darwin

19th-century English naturalist who proposed evolution by natural selection.

Erasmus Darwin

18th-century naturalist who proposed early evolutionary ideas.

Buffon

18th-century French naturalist who suggested species change over time.

Wallace

19th-century naturalist who independently conceived natural selection.

Lyell

19th-century geologist who developed uniformitarianism.

Hooker

19th-century botanist and Darwin's supporter.

Lamarck

French biologist who proposed inheritance of acquired characteristics.

Von Baer

19th-century embryologist who described developmental patterns.

Paley

18th-19th century theologian known for watchmaker analogy.

Mary Anning

19th-century fossil collector who discovered marine reptiles.

Cuvier

French scientist who established extinction.

Archbishop Ussher

Calculated Earth's age as 6000 years.

Hutton

Geologist who proposed deep time.

Lord Kelvin

Estimated Earth was much younger due to cooling models.

Owen

Anatomist who coined "Dinosauria."

Malthus

Wrote about population growth, inspiring natural selection.

Artificial vs natural selection

Artificial selection is human-controlled breeding; natural selection occurs through environmental pressures.

Uniformitarianism

Idea that geological processes operated in the past the same as today.

Scientific advances after Darwin

Genetics, Mendelian inheritance, fossils, radiometric dating, DNA discovery.

Geology's importance to Darwin

Showed Earth was old enough for evolution.

Darwin's geological contributions

Coral reef theory, fossils, uplift and subsidence.

The Weald example

Used to show erosion over long timescales.

Extinction proof

Cuvier demonstrated that species go extinct.

Relative vs absolute dating

Relative orders layers; absolute dating gives numerical ages.

Three rock types

Igneous forms from cooling melt; sedimentary forms from deposition; metamorphic forms from heat/pressure. Fossils found mostly in sedimentary rock.

Definition of a fossil

Any preserved remains or traces of past life.

Why fossil record is incomplete

Most organisms don't fossilize.

Why fossil record is biased

Favors hard parts, large populations, shallow marine species.

Why study fossils

Gives direct evidence of life's history.

Steno's laws

Basic principles of stratigraphy like superposition and horizontality.

Role of fossils in stratigraphy

Used to correlate rock layers.

Trilobite fossils meaning

Rock containing trilobites must be Paleozoic.

Protons neutrons electrons

Protons and neutrons have mass; electrons do not.

Atomic number

Number of protons.

Atomic weight

Protons + neutrons.

Isotope

Atoms of same element with different neutron numbers.

Radioactive isotope

Unstable isotope that decays over time.

Half-life

Time for half the atoms to decay.

Radiometric dating

Used on igneous rocks for absolute ages.

Radiocarbon dating

Measures decay of carbon-14 in organic material younger than ~50,000 years.

Age of Earth

4.54 billion years.

Earliest fossils (controversial)

About 3.8-4.1 billion years.

Oldest definitive fossils

Stromatolites from ~3.5 billion years.

Great Oxidation Event

2.4 billion years ago when oxygen rose.

Oldest eukaryotes

~1.6-2.1 billion years old.

Oldest animals

~600 million years old.

Oldest multicellular fossils

~1.2 billion years old.

Cambrian Explosion

~540 million years ago.

Invasion of land

Plants ~470 mya; animals ~420 mya; fungi ~440 mya.

End-Permian extinction

252 mya.

End-Cretaceous extinction

66 mya.

Oldest apes

~25 mya.

Age of Homo sapiens

~300,000 years.

Carboniferous forests significance

Produced coal and oxygen rise.

Cenozoic grasslands significance

Drove evolution of grazers.

Three domains

Archaea, Bacteria, Eukarya; bacteria likely first.

Three multicellular kingdoms

Plants, animals, fungi.

Four eons

Hadean, Archean, Proterozoic, Phanerozoic.

Why few early fossils

Early life was microscopic and lacked hard parts.

Miller-Urey experiment

Simulated early Earth and formed amino acids.

Is life monophyletic?

Yes, all life descends from common ancestor.

Could new life evolve today?

Probably not because existing organisms would consume it.

Great Oxidation Event meaning

Oxygen rise due to cyanobacteria; anaerobes dominated before it.

Purpose of phylogenies

Show evolutionary relationships and test hypotheses.

Parts of phylogeny

Tips are species; nodes are ancestors; branches show change; root shows common origin.

Rooted vs unrooted trees

Rooted shows time direction.

Unrooted tree of life

Major groups: Bacteria, Archaea, Eukarya.

Monophyletic group

Ancestor + all descendants.

Paraphyletic group

Ancestor but not all descendants.

Polyphyletic group

Group lacking common ancestor.

Bifurcation

A node splitting into two branches.

Polytomy

More than two branches from a node.

Reticulation

Hybridization or HGT in trees.

Most recent common ancestor

Closest shared ancestor of two taxa.

Linnaean binomial

Two-part species name.

Linnaean classification hierarchy

Domain to species (8 ranks).

Relation to phylogeny

Classification reflects evolutionary relationships.