Exhibit #1: Adaptation A process that enables organisms to become better suited to their environments Better suited individuals were better able to reproduce and pass their genes on to their young (example Black and Peppered Moths) 1848 Pre Industrial Revolution - Light bark trees 1898 Post Industrial Revolution -Dark bark trees -Trees stained by pollution 1034 peppered moths 245 peppered moths 376 Black moths 976 black moths A change in the environment led to a change in the number of each variety of moth The dark moths became better adapted to their environment and therefore survived better
Exhibit #2: The Age of the Earth The planet Earth is more than 4 billion years old James Hutton (1788) Proposed that rocks, mountains and valleys had been changed gradually by rain, heat and cold, the activity of volcanoes and other natural forces Charles Lyell (1830) Agreed with Hutton and suggested that the land is constantly moving and shifting. Forces beneath the Earth s surface twist and bend some rock layers, bury others, and even push up some parts of the sea floor into mountain ranges. The Earth has changed over the long period of its existence
Using radioactive dating, scientists have determined that the Earth is about 4.5 billion years old. Scientists have divided this time into large units called Eras Eras are divided into Periods Periods are divided further into Epochs Note that these periods do not have standard lengths
Exhibit #3: Fossils Preserved remains of ancient organisms found in rock, sediment and stone Many fossils found by geologists in the 1800 s did not resemble any currently living creatures The Geological Time Scale: Called the clock in the rocks Scientists noticed that certain layers of rock appeared in the same vertical order wherever they were found Lower layers were formed first and were older than upper layers Assuming that the ground has not been disturbed, scientists could determine the approximate dates of the fossils
Relative Dating: a technique used by scientists to determine the age of fossils relative to other fossils in different layers of rock Limited because geologists (rock scientists) did not know how long it took for each layer to form. Radioactive Dating: Rock contains radioactive elements that decay over time The traces of radioactive isotopes present in a sample allow geologists to determine the approximate age of the sample. Geologists use a unit called the half life to determine the age of the sample A half life is the time it takes for ½ of the atoms of a radioactive element to decay.
Carbon 14 Dating: A useful form of radioactive dating that is used to measure the age of material that was once alive (like bones) Carbon 14 is present in the atmosphere and is absorbed by living bodies. After an organism dies it can no longer absorb carbon 14 and it decays into nitrogen - 14. By comparing the amount of Carbon 14 and Nitrogen 14, scientists can determine the age of a sample Not accurate for samples more than 60000 years old
2 Problems with Fossil Evidence: 1. Fossils left behind represent some of the organisms from the past BUT only those in areas with sedimentary rock formation 2. Not all organisms are preserved well as fossils
The Fossil Record: Scientists that study fossils are called Paleontologists The fossil record represents the preserved collective history of the Earth s organisms Incomplete Not all organisms are preserved as fossils Applies only to areas with sedimentary rock Shows that change followed change on Earth
Exhibit #4: Evidence of Change in Living Organisms Similarities in Early Development: Embryos are organisms in early stages of development Many embryos are similar in appearance during the early stages of development. Why? Similarities in Body Structure: Basic morphology (body shape) appears to be similar in a variety of different species
Analogous Structures: Structures that are similar in appearance and function BUT have different origins and usually different internal structures (ex) bird wings and insect wings Homologous Structures: Dissimilar parts of different organisms that developed from the same ancestral body part (ex) Arms (human) and fins (fish)
Vestigial Structures Structures that no longer serve a useful purpose or function in an organism Result of an evolutionary change?
Exhibit 5: DNA Comparison Comparison of DNA or RNA gives an indication of how closely related two organisms are and how recently they split from the same evolutionary path Can also compare protein: (See example on sheet that Mr. Lloyd will give you!)