Transcript Types of Fossils
Today’s Agenda…3/7 Bellringer: What causes variation among organisms? What will happen to helpful variations? What will happen to harmful variations? (answer all questions) Notes on Fossils & Extinction Homework: Fossils and Extinction Questions Test corrections due by tomorrow! What could have caused the two variations? Mutations Different allele combinations What will happen when it reproduces? Why? The frog that survives will reproduce The offspring will have similar traits to the parents The frog will pass on the helpful trait What will happen to each of the frogs? Why? The frog that blends in with the environment will survive and reproduce The frog that did NOT blend in the environment will not survive (it will be eaten by predators or unable to hide from prey) What will happen to the population of frogs with each variation over time? The population of the frog with the helpful variation will increase. The population of the frog with the harmful variation will decrease. How does this activity show natural selection? Nature “selected” the frog with the camouflage to survive and reproduce One frog was better suited to the environment than the other, so it will survive The frog that is adapted to the environment will survive One frog is a better fit for the environment so it will survive How does natural selection lead to evolution? Evolution is a gradual change in a species over time. The species of frogs will change over time to include mostly frogs that are well suited to that environment. The other frog may evolve in an environment it is better suited to Looking Into the Past Fossils & Extinction Study Pack #5 Today’s Targets… I understand what fossils and the fossil record are. I can describe the usefulness of the fossil record. I understand that fossils provide evidence of biological change. Fossils Fossils are traces of past organisms preserved in Earth’s crust Can be actual structures or just imprints of structures Fossils are normally found in sedimentary rock Layers of sand, silt, clay or mud are compacted and cemented together with fossils inside Types of Fossils Page 344 Figure 9 Cast fossils Minerals fill in cracks to create a cast Example: Animal tracks become filled in Fossils in amber Sticky material from trees harden and trap insects Imprint An Fossils organism leaves an imprint on sediment that later hardens to become rock Types of Fossils Mineralized fossils Minerals replace wood or bone Petrified wood Frozen fossils Determining a Fossil’s Age Relative Dating Younger rock layers are on top of older rock layers Provides an estimate of a fossil’s age Fossils found in lower layers of sedimentary rock are older than those found in upper layers Page 345 Determining a Fossil’s Age Determining a Fossil’s Age Radiometric More or absolute dating accurate Use the amount of radioactive elements in the rock where the fossil is found to determine its age The Fossil Record The fossil record provides us with clues that organisms have changed over time Organisms have gone from simple to more complex It is incomplete Evidence of evolution The Fossil Record Fossils What tell us: organisms in the past looked like & whether they are similar to those today How organisms changed over time The roles the organisms played within communities and food chains How Earth’s climate has changed over time How Earth’s surface has changed over time Extinction Most of the organisms that have ever existed are extinct today Once a species is extinct, it can never come back to life Extinction causes – competition, predation, climate changes, natural disaster Human activity – habitat destruction, overhunting Natural Review In your own words, what is a fossil? In what kind of rock are fossils found? Why aren’t fossils found in igneous rocks? Why aren’t fossils found in metamorphic rocks? What are the different types of fossils? What parts of an organism are preserved as fossils? Review Which provides a more exact age of a fossil: relative or absolute dating? Which fossil is the oldest? Which fossil is the youngest? Review Does the fossil record show all organisms that lived in the past? Are most of the species of organisms in the fossil record still alive today? According to the fossil record, how have organisms changed over time? What clues does the fossil record provide? Review What causes extinction? What is probably the greatest cause of extinction today?