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Standard S7L5 Students will examine how organisms have changed because of inherited characteristics that promote the survival of the organism and future generations of offspring. Learning Target I can explain the process of natural selection. Adaptations Over Time Many organisms on the Earth today existed millions of years ago. Do you think they stayed exactly the same or have changed over time? Characteristics within the next generation are sometimes altered. One change over time involves the camel. Let’s look at some of the changes that have occurred in camels. The characteristics of a species are passed from parent to offspring. • Characteristics of a species may evolve or change. • This is simply saying organisms change over time. • This is a theory. A Theory is… an explanation of things or events based on scientific knowledge that is the result of many observations and/or experiments. Species • A species is a group of organisms that share similar characteristics and can produce fertile offspring. • A species is the smallest of the classification system. • There are 34 species of deer. • Related species would be in a genus. • There may be many species within a genus. • Note the next slides to help explain this. Levels of Classification Clues about Changes • • • • Vestigial Structures Homologous Structures Fossil Record Natural Selection Vestigial Structures Features which serve no useful function any longer in the organism. An example of such features is the pelvis bone in the whale or the “wisdom” teeth in humans. Homologous Structures Those which share a common origin, but serve different functions in today’s species. Clues in Fossils • There were fossil clues left behind in the rocks! • This is called the fossil record. The Fossil Record • Fossil remains have been found in rocks of all ages. • Fossils of the simplest organisms are found in the oldest rocks on the bottom of layered rock • Fossils of more complex organisms in the newest rocks, or rock layers stacked on top • The fossil record supports the theory that simple life forms gradually evolved into more complex ones. Rocks and Fossils • Sedimentary rocks are made up of deposits of organic (once living) and other material, laid down over hundreds of thousands of years. • Organisms are buried in between the layers and their remains may eventually be preserved as fossils. History of the Horse • The history of the horse has been preserved in fossil form. • Over 60 million years the horse evolved from a dogsized rainforest-dwelling creature, into an animal adapted to plains-dwelling and standing up to two meters high. Relative Dating • This does not tell the exact age of a fossil It is an approximation or estimation of age. • The estimation is made by looking at the rock layers below and above the layer in which the fossil is found. • The older rocks are usually below the younger rocks. • So, fossils found in lower layers are usually older than those found in upper rocks. Note the Timeline….. Index Fossils • INDEX FOSSILS are unique or found in only certain time periods. • Index fossils are used to date rock layers. Radioactive Dating • This is a more accurate picture of the age of a fossil. • Radioactive elements are used for this. • While organisms are alive, they take in small amounts of radioactive elements. This stops when they die. By comparing the amount of radioactive element in a sample to the amount of element into which it decays, scientists can calculate the age of a fossil. The Dog Fossil evidence shows that all dogs (scientific name: Canis familiaris) have a common ancestor - the wild grey wolf (Canis lupus). Over 14,000 years humans have 'designed' some 400 breeds of domestic dog, artificially selecting the looks and behavior of each breed. • Neither Precise NOR Accurate • This is a random-like pattern, neither precise nor accurate. The darts are not clustered together and are not near the bull’s eye. • Precise, Not Accurate • This is a precise pattern, but not accurate. The darts are clustered together but did not hit the intended mark. • Accurate, Not Precise • Precise and Accurate • This is an accurate • This pattern is both pattern, but not precise and accurate. precise. The darts The darts are tightly are not clustered, but clustered and their their “average” average position is position is the bull’s the center of the bull’s eye. eye. Who realized things evolved? • In 1831, Charles Darwin, a naturalist, sailed on the HMS Beagle from England to the Galapagos Islands off the coast of South America (near Ecquador). Just so you know … • Darwin made his journey on the HMS Beagle during his twenties. • His book was published in his fifties. On his journey he observed 13 species of small birds called finches. He noticed they were all the same except for body size, beak shape, and what they ate. He then made a startling discovery----- the shape of the beak influenced what the finches ate. Many times more offspring are produced than can survive. • Galapagos finches lay eggs every few months. Darwin realized that in several years two parent finches could produce a huge population! • A population is all the individuals of a species that live in the same area at the same time! • Members of a large population compete for food, space, and other resources. • Darwin realized that the finches must have had to compete for food! • Those finches that can best survive are more likely to reproduce and pass on their characteristics to the next generation. • Finches which had beak shapes that allowed them to eat available food survived and were able to pass on their DNA. • After many generations, these groups of finches became separate species with genetic variations of their beaks to the kinds of foods they ate! What did Darwin do with his discoveries? 1. He shared his findings. 2. He wrote a book known as The Origin of Species. Darwin suggested… 1. An organism’s fitness depends on the traits it inherits from its parents. 2. Any inherited trait that increases an organisms’ fitness is called an adaptation. (The beaks were adaptations.) 3. The fittest survive, or those best adapted to their environment. For Example: • Early giraffes may have had short necks and legs. • When their population grew, they competed for food. • As they ate all the ground vegetation, they started competing for low-hanging leaves. • Some were born with mutations that resulted in longer necks and legs. These were more successful at getting food. • These were the survivors that were left to pass on their DNA. Natural selection in brief.. • Natural selection is the natural process where the best-adapted individuals survive, reproduce, and pass on their DNA. • DNA controls the traits of an organism. • Natural selection is also called “survival of the fittest.” Example of Natural Selection in Action • Before the industrial revolution most peppered moths were pale. • This allowed them to be camouflaged against the pale tree trunks. • Moths with the black colored mutation were easily seen and eaten. • The industrial revolution in the 19th century brought airborne pollution. This put soot everywhere. It also allowed the black moths to blend-in better against the darkened tree bark. • Over time, the mutated black peppered moths were naturally selected to survive and pass on their DNA. Which moth is camouflaged? Black Peppered Moths before the Industrial Revolution Black Peppered Moths after the Industrial Revolution Simulation • After completing this section of the notes, you will participate in a simulation. • Who will survive? • http://peppermoths.weebly.com Variations • The theory of natural selection emphasizes differences among individuals of a species. • These differences are called variations. • A variation is an inherited trait that makes an individual different from other members of its species. • Variations result from mutations in an organism’s genes. Variations • Beneficial variations are what allow an organism to adapt to its environment. • Variations that are involved in adaptations can be color, shape, behavior, or chemical makeup. Darwin’s Theory 1. Every species is fertile enough that if all offspring survived there would be too many. Yet, populations remain roughly the same size. 2. Resources are limited and a struggle for survival takes place. 3. In species that reproduce sexually, no two individuals are identical. 4. There are inherited variations. 5. Those that are less suited to the environment will not survive to pass on DNA. 6. Those individuals that do survive pass on their DNA. These occurrences • slowly produced populations adapted to the environment. • created new varieties and new species after many generations. The Speed of Change • There are two major hypotheses on how change takes place. • Gradualism—Organisms evolve through a process of slow and constant change. (Examples: Camel, Horse-many millions of years) • Punctuated Equilibrium—Species change very rapidly. (Example: Bacteria—decades, thousands, or a few millions of years) Those organisms that can’t adapt or change may become extinct. How do we know that extinct organisms have existed or organisms have changed?-----Clues are there. Extinction • Sometimes species die out or become extinct. • There are many endangered species threatened with extinction now. Reasons for Extinction • Increase in the Number of predators • Failure to compete with other species in the same habitat • Natural catastrophes • Impact of New Diseases • Impact of Man • Rapid Climatic or Other Environmental Change Changes Over Time! Evolution – changes of species over time due to adaptation to their environment • https://www.youtube.com/watch?v=wrTXvr KBlbc