Intro to Evolution Evolution simply means change over time. many things evolve, including languages, and your view of the world. Intro to Evolution This unit is meant to introduce you to: the development of current evolutionary theory and subtopics processes which influence the change of species over time This unit is not meant to: tell you what you have to believe Intro to Evolution This unit is a spectacular view into what science truly is: we are constantly learning new things on our own and from others making mistakes and learning from them making revisions based on new data improving on techniques that work or don’t work at all. taking data and attempting to determine its meaning figuring out the “how” of things Unit 5 – Lecture 1 Evolutionary Timeline The evolutionary timeline is divided into sections of time called eras – which are then divided into smaller units of time called periods. units of time are determined through use of radiometric dating methods, fossil/rock identification, and geographic strata [rock layers]. evolutionists estimate the age of the earth to be approximately 4.5 billion years old Evol. Timeline – cont’d Hadean: 3.8-4.5 billion years ago think “Hades” very hot very little free oxygen, lots of CO2 lots of N2 [nitrogen] gas lots of water vapor Evol. Timeline – cont’d Precambrian [anything from hadean to cambrian…] cyanobacteria and other prokaryotes sponges & cnidarians [jellyfish/ anemone] Evol. Timeline – cont’d Paleozoic [542 mya – 251 mya] six periods – need to know: Cambrian [1st of six] sudden occurrence - “explosion” of life [Cambrian Explosion] seen in fossil record worms, sea stars, trilobites, fish, reptiles… other chordates and hard-bodied organisms Evol. Timeline – cont’d Mesozoic [251 mya – 65 mya] three periods : Triassic – small mammals Jurassic – dinosaurs Cretaceous – flowering plants Evol. Timeline – cont’d Cenozoic: 65.5 million years ago - present lots of mammals Continental Drift Continental Drift Theory states that continents have moved throughout history continents are still moving approx 6cm a year Plate Techtonics explains HOW continents move Continental Drift – cont’d Continental Movement: Pangaea – central land mass Laurasia [northern continents] & Gondwana [southern continents] end of Mesozoic = modern continents [Triassic] Discuss What is the difference between Continental Drift and Plate Tectonics? Fossils Fossil – evidence of an organism which lived long ago paleontologist – scientist who studies ancient life most fossils are found in sedimentary rock Fossils – cont’d Types of Fossils: trace fossils – animal markings [footprint, trail, burrow] Fossils – cont’d Types of Fossils: casts– mineralization of a space left by a decayed organism [most fossils you think of] molds– empty space in rock from a decayed org. Fossils – cont’d Types of Fossils: imprints – made typically by thin objects that have been pressed into an area Fossils – cont’d Types of Fossils: carbonized – high temps & pressures expel gaseous elements leaving only carbon Fossils – cont’d Types of Fossils: petrified – entire organism is replaced by mineral matter. Fossils – cont’d Types of Fossils: ice- or amber- preserved fossils [True-Form Fossils] Fossils – cont’d Types of Fossils: permineralization – pores are filled with mineral matter without getting rid of organic [carbon] material Fossils – cont’d Types of Fossils: coprolite – fossilized dino poop Discuss Name and describe 5 types of fossils. Fossils – cont’d What do we know about this fossilized organism? Fossils – cont’d Fossils CAN Tell Us…[sometimes] what an organism looked like what kinds of food it probably ate exceptions…like the panda – has very sharp teeth for eating rough bamboo what type of area it may have lived in / climate geography of the area it lived in Fossils – cont’d Fossils CAN’T Tell Us… what colors an organism was almost anything about behavior science does attempt some basic conclusions about organisms based on how they are found nests [nurturing], found traditionally in large groups [may have been a pack organism], etc. what it sounded like we can make comparisons and guess at times based on structure similarities Discuss Discuss with a partner certain things that we can and can’t learn from fossils. Dating Methods Relative Dating – dating new samples based off of comparison to previously dated materials uses circular reasoning: dating rocks by their fossils dating fossils by the rock in which they are found Dating Methods – cont’d Relative Dating [cont’d] geologic layers as in the record are not actually found in their stated order anywhere on earth; they are approximated based on comparison of fossils and other rock these things can lead to misinterpretation Dating Methods – cont’d Radiometric Dating – examining the chemical “half- life” of a substance in the sample to determine its approximate age Dating Methods – cont’d Radiometric Dating [cont’d] half-life – the amount of time it takes for half of a substance to change [decay] into another substance based on isotopes isotope – atoms of an element with a different number of neutrons than is typical the measured isotopes are radioactive and slowly become non-reactive [this is what is measured] Dating Methods – cont’d Radiometric Dating [cont’d] ex: Carbon-14 dating, Potassium-Argon dating, Discuss What is the difference between relative dating and radiometric dating? Dating Methods – cont’d Problems with Radiometric Dating must know original amount of substance present to calculate time must assume constant decay must know no outside influence occurred [like water, extra heat or pressure, other substances which react] Dating Methods – cont’d Problems with Radiometric Dating can’t date rocks which have been in water, but many fossils are formed in sedimentary rock in this case, rock ages are dated by the fossils found in them that have been previously identified recent samples showing millions of years Mt. St. Helens – dated 10 yrs after eruption; showed almost 3 million years date samples showing negative age Discuss What are potential problems in relative dating and in radiometric dating? Science! There are ways that ALL techniques can be refined and improved – that’s the job of science – to keep learning more and going farther with research and doing many trials [when possible] to get to the most accurate data possible. To Know. Homework Complete the Stego/Horse worksheet you received.