What is uniformitarianism? • It is the principle of James Hutton. It states that Earth processes occurring today are similar to those that occurred in the past. • His saying was, “The present is the key to the past.” • Prior to Hutton it was thought that the Earth was only thousands of years old. Now we believe it to be 4.5 billion years old.
What are fossils? • They are the remains, imprints, or traces of organisms. • WHY ARE THEY IMPORTANT? They provide evidence to when, where and how an organism lived. They give us clues to the Earth’s past and how it has changed! http://www.brainpop.com/science/earthshistory/geologictime/
What conditions are needed for fossil formation? Protection - The dead organism must be protected from the elements (animals, insects, bacteria, weather, etc.). Needs to be buried quickly by sediments, ice, sap, etc. Hard parts - Most fossils are hard parts of an organism such as bones, teeth and shells.
Types of Fossils 1) Molds- hollow impression of a dead organism in rock after it gets removed
Types of Fossils 2) Casts- sediments fill the mold, leaving a copy of the once living organism
Types of Fossils 3) Trace- an impression left in a rock made by a living thing during its daily activities.
Types of Fossils 4) Petrification – plant or animal tissue replaced by minerals
Types of Fossils 5) Original remains– an entire plant or animal encased and preserved in ice, sap, or another material or just a part of an organism like a tooth or a bone http://fossils
What are index fossils? • Index fossils • They are remains of species that were abundant and wide spread, but only existed on earth for a relatively short time.
How are index fossils used to determine ages of rock? • Geologists can estimate ages of rock layers based on index fossils they contain because they knew when the specific species existed. The fossil evidence can be used to determine if the same rock layers were formed in different places at the same time (correlating rock layers). Example: Trilobite
How can fossils be used to determine environments long ago? 1. Fossils found in particular areas show what the climate was like long ago. Example: tropical plant fossils found in the eastern U.S. 2. Fossils found in particular areas show if an area was covered by an ocean. Example: crinoid fossils found in North America, which is found today in the ocean.
Target 3: What are relative ages? • It is the age of a rock layer in comparison to other things. • It doesn’t tell you the exact age of the rock layer, but it shows that it is older or younger than the material around it. Ex. Granite inclusion – younger than the rock it is included or stuck in. • If a fossil in a top layer is older than one in a bottom layer one can hypothesize the layers have been turned upside down from mountain building
What is the principle of superposition? It states that if rocks layers are undisturbed, the oldest layers are at the bottom.
What can cause disturbances in rock layers and • REFER TO THE OTHER POWERPOINT
What are unconformities? They are gaps in rock layers that are missing. They are caused by erosion or as a result of rock deposits not forming
Target 4: What are absolute Ages? • It is the age in actual years of a rock or other material. Radioactive decay is used to determine the age.
What is radioactive decay? • Radioactive decay is the process of an isotope (parent) breaking down into a more stable isotope (daughter). • In order for this to occur neutrons will break down into protons and electrons. The protons remain while the electrons leave the atom as beta particles. • Also isotopes can give off 2 protons and 2 neutrons which are called alpha particles. • Both processes result in the formation of new elements known as daughter products.
What is half-life? The parent isotope undergoes radioactive decay to form a daughter product. The half-life of an isotope is the time it takes for half of the isotopes to decay into the daughter products. Example: Carbon dating - Carbon -14 has a half-life of 5,730 years. So it will take 5,730 years for half of the carbon-14 to change into nitrogen-14. Now only half of the original carbon-14 remains. In another 5,730 years half of the remaining carbon-14 will change to nitrogen-14
Target 5. What is geological time Scale? • It is the division of Earth’s history based on fossil records. http://www.brainpop.com/science/earthshistory/geologictime/
What are the four major divisions of the Geological time scale? • Eons – longest division of time based on the appearance of many profoundly different fossils (Precambrian – single celled organisms and Phanerozoic – emergence of multi-celled organisms) • Eras – divisions of time based on major changes of the fossil record due to a mass extinction. A mass extinction occurs when over 90% of the Earth’s species go extinct. (mass extinction at end of Mesozoic Era – death of dinosaurs) • Periods – division of time characterized by the extinctions of many species. • Epochs – shortest division of time based upon subtle changes in climate, soil, vegetation leading to a minor change in the fossil record. (currently we are changing epochs due to human activity)
Target 6: Evolution • What is a species? • A species is a group of organisms that normally reproduces only with other members of their group. • Examples: dogs, lions, cheetahs, king cobras, etc.
What is evolution? • Evolution is a process by which species change over time, usually becoming more complex. • This idea was first posed by Greek philosophers. • Fossil records support the idea of evolution. • Until Darwin no one was able to state “how” species evolve.
4. Evolution is when organisms change over time. So, modern organisms descended from ancient ones
7. Evolution is a Theory – Just like Gravity! • Evolution is a well supported explanation of phenomena that have occurred in the natural world • A theory in science is a well tested hypothesis, not just a guess
What is natural selection? • Charles Darwin came up with a way to explain “how” species evolve through the theory of natural selection • Natural selection is a process causing heritable traits that are helpful for survival and reproduction to become more common in a population, and harmful traits to become more rare. This occurs because individuals with advantageous traits are more likely to reproduce, so that more individuals in the next generation inherit these traits. (short neck vs. long neck giraffes)
10. Natural Selection • The traits that help an organism survive in a particular environment are “selected” in natural selection
11. Natural Selection and Species Fitness • Overtime, natural selection results in changes in the inherited characteristics of a population. • These changes increase a species fitness (survival rate)
Asexual Reproduction • Asexual Reproduction is the process by which a single organism produces a new organism identical to itself. An asexually reproducing organism does not require a partner to produce offspring. • Examples: • Budding – grow off of an existing organism • Regeneration – fragments grow into a new organism • Fission – bacteria and other single celled organisms just copy their DNA and split into 2 cells
mitosis • Asexual reproduction • Function is to copy genetic material to make a new cell • Why? Multi-celled organisms -Body cells die so it is imperative to make new cells. Chromsomomes must be duplicated • Single-celled organisms reproduce to make a new organism (cloning of dna – exact copy) • Example: copy a cookbook to give to a friend
Pros and Cons of Asexual Pros • Mass reproduction • Offspring retains beneficial qualities from parent • Reliable- not many steps • No need to find a mate Cons • There is little genetic diversity so if the environment changes, the species may find it difficult to adapt to the new conditions
Sexual Reproduction • Sexual Reproduction is the process by which a new organism develops from joining of male and female sex cells. An organism that reproduces sexually requires a partner, with the offspring sharing characteristics from each parent
Pros and cons of sexual Pros • Offspring is a unique organism. This gives the organisms a better chance to adapt to a changing environment due to having a unique set of DNA Cons • Needs 2 organisms • Not fast occurring