4 Fossil RecordWhat is a fossil? -The preserved remains of a once-living organism.How do fossils help scientists?1. Tells us what organisms lived long ago2. Shows how the Earth’s surface has changed.3. Help us understand what past environments may have been like.
5 How do we get fossils? Fossils are formed in SEDIMENTARY ROCK. If an organism dies and is buried by sediment rock, it’s bones are protected from rotting.Over time, more sediment layers build on top of the remains. Minerals replace all or part of the organism’s body. The preserved remains may later become exposed by erosion or the Earth’s movement.
6 How do we know the age of fossils? You have to DATE them!
7 Which fossil came first? Relative DatingAge of fossils RELATIVE toother rocks or fossils.2. Radioactive datingACTUAL age of fossils using the half life of radioactive isotopes
8 How does Relative Dating work? Rock layers form in order of age – the oldest layers on the bottom and the youngest on the top.Scientists use index fossils to compare the ages of fossils.Index fossil: a species easily recognizable, existed for a short period of time, and wide geographic range.*** Does NOT give age in years***ABCDE
9 How does Relative Dating work? Looking at this mountain, where would you expect to find the oldest fossils?BCDE
10 Which is older B or D?Index FossilsFound FossilsSAME AGE
11 How Does Radioactive Dating Work? Throughout an organism’s life, it takes in Carbon-14. Once the organism dies it no longer takes in Carbon-14. The C-14 present in the plant or animal begins to decay at a certain rate called half-life. Half-life: the length of time required for half the radioactive atoms in an organism to decay.Carbon-14 half life: 5,730 years
12 What do you notice about the percent of original C-14 remaining? Decay of Carbon-14Years from Present5,73011,46017,19022,92028,65034,38040,11045,84051,570Percent of Original C14 Remaining1005025220.127.116.11.560.780.390.20What do you notice about the percent of original C-14 remaining?
13 What are the scientific explanations for data showing periods of stasis and sudden appearance in the fossil record?The fossil record suggests that evolution has proceeded at different rates for different organisms at different times.
14 GradualismThe idea that evolution involves a slow, steady change in a particular line of descent.
15 Showing very little change over time Example: Horseshoe crabs STASISShowing very little change over time Example: Horseshoe crabs
16 Punctuated equilibrium Definition-Stable periods interrupted by rapid changesRapid Evolution may occur because:A) small pop becomes isolated from the large populationB)small group migrates to a new environment--FINCHES
18 Geographical Distribution Similar animals living in different locations are the product of different lines of evolutionary descent.
19 3rd type of Evidence Homologies 3 types of HomologiesAnatomicalMolecularDevelopmental (embryology)
20 Homologous Structures Homologous Structure: structures that have different mature forms but develop from the same embryonic tissues.Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from common ancestors.
21 Homologous Structures Not all homologous structures serve important functions. Vestigial organs: Organs in animals that are reduced in size to where they are just traces of homologous organs in other species.
22 Which structures are analogous? Homologous? Analogous StructuresAnalogous Structure: the similarity of structure between two species that are not closely related.Which structures are analogous? Homologous?Answer:Analogous- Bird to Insect, Bat to InsectHomologous- bird and bat wings
23 How do Analogous Structures Occur? Convergent Evolution: Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Natural Selection may result in body structures and even whole organisms that look very similar without having the same common ancestor.
24 EmbryologyPigCowRabbitHumanComparative Embryology: the comparison of early stages of development Pharyngeal (throat) pouches in embryotic stages shows one sign that vertebrates evolved from a common ancestor.
25 Molecular BiologyMolecular Biology studies amino acid sequences of similar proteins in different species to discover the molecular history of evolution and common ancestor.
26 Molecular BiologyMolecular Biology is the BEST WAY to determine how closely species are related to one another.Which two species are most closely related based on these nucleotide sequences?Species 1ATGTAGCTGSpecies 2ATCTGACTCSpecies 3AGGTACCAGSpecies 4AGGCGGCAG