How the Earth formed About 4.5 billion years ago From a cloud of gas and dust (nebula) that also formed the Sun and other planets and comets and asteroids… “chunks” stuck together, which attracted more chunks, which stuck and attracted more chunks…

How the Earth formed Kept getting hit with meteors (bombardment), volcanic eruptions Atmosphere not like today ammonia (NH3), hydrogen sulfide gas (H2S), water vapor and methane (CH4), carbon dioxide (CO2)

Miller and Urey (1950’s) Proposed that these simple atmospheric molecules at high temperatures (e.g. lightning) could form amino acids Comets/meteorites also have traces of amino acids

First living things About 3.5 billion years ago Simple, one celled, autotrophic prokaryotes Chemosynthesis: use chemicals to make energy Some species still around today, at bottom of ocean by volcano vents (Archaea) Cyanobacteria Took CO2 out of atmosphere and release O2. Responsible for our atmosphere today Eventually one may have been swallowed by another and survived inside to make eukaryotes (endosymbiosis)

Spontaneous generation Stated that nonliving things could turn into living things (mice from wheat/cloth) Remember that in the 17th century (and earlier) not everyone was educated Biogenesis: living things can only come from living things…what we believe now

Hutton People believed Earth about 6000 years old (biblical account) James Hutton: noticed rock layers in mountains were bent/folded, but were flat when formed So forces inside the Earth must have done that, but it would take longer than 6000 years Deep-time…things happened much farther back in time than we thought

Lyell Said that the processes going on today, geologically, were going on back then, too Called Uniformitarianism Was a competing theory (Cuvier) called catastrophism where big geological events happened and species became extinct

Jean Baptiste Lamarck Believed in spontaneous generation, and that simple things could become more complex in their life time Organisms change over life-time (acquired traits) Pass that on to children Inheritance of acquired characteristics

Jean Baptiste Lamarck

Charles Darwin And Alfred Russel Wallace (Darwin published book first) Noticed differences between finch (bird) species as traveled by ship around the world (HMS Beagle, Galpagos Islands) Descent with modification Traits passed on to children over time

Charles Darwin

Comparing Lamarck and Darwin

4 Parts of the Theory Struggle for existence: nature produces more offspring than can survive at one time. Competition for resources (food, water, space, etc.). Variation/Adaptation: genetic differences in a population. (adaptations) Survival of the Fittest: Creatures with best adaptations survive. Natural selection: ones that survive reproduce more like themselves Note: nature (environment) “picks” what’s best…different from us picking (artificial selection…breeding)

4 Parts of the Theory

Scientific Theories Hypothesis: a working idea, educated guess, can change drastically with new evidence, not considered fact by scientific community Law: describes what happens, often short or mathematical (F=ma) lots of evidence to back it up, rarely changes, but could, considered fact by scientific community Theory: explains how or why something happens, often long and detailed, lots of evidence to back it up, often changes in small details, but could, considered fact by scientific community

Proof for Evolution So over time, what a species looks like can change Transitional species Fossils of species in between modern and older set up a series where can see changes

Transitional species

Proof for Evolution Rocks form in flat layers Older ones at bottom Fossils in rocks similar closer together Farther apart fossils are, more different

Proof for Evolution Embryology: Creatures look very similar when young From common ancestor

Proof for Evolution Anatomy: Homologous structures look alike inside and out (common ancestor, e.g. human arms, dog legs, bird wings) Analagous structures look the same outside, but inside very different (evolved separately, e.g. bird wings, insect wings) Vestigial structures seem to serve no function, but “left over” from ancestor (e.g. appendix, tail bone)

Structures Homlogous Analogous

Structures Vestigial Humans: Muscles that move ears Appendix Tonsils Body hair Tail bone Wisdom teeth

Proof for Evolution Biogeography: Organisms far apart look similar Organisms close together have slight differences

Proof for Evolution Molecules/genetics: DNA and RNA sequences are incredibly similar between similar creatures Many genes similar between organisms