Theory of Evolution
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Transcript of Theory of Evolution
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Theory of Evolution
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Intro
• Today we are going to start a unit on evolution• It is important to note that everything that we will be
discussing today in the classroom will be based in biology and scientific principles
• In order to be respectful to all people’s beliefs and ideas
• I would also ask you to stick to the principals of biology
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What is Evolution
• Has anyone ever heard about evolution before?
• What is the idea of evolution?
• Where have you heard the term evolution before?
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What is Evolution
• Evolution is the change over time of inherited traits in a population
• It is a hotly debated topic
• It is a relatively simple definition, however it has many different aspects to it
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History of Evolution• Many years ago there were
different ideas of how the organisms on planet earth came to be
• People believed that organisms always the way that they currently saw them
• They did not have the ability to observe populations, see interactions between species or see other ecosystems
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History of Evolution• Since people were so used
to the fact that the world did not change, many people were skeptical of the new ideas of evolution
• Many of the scientists that believed the world was slowly changing were ridiculed, mocked and/or punished
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Jean Baptiste Lamarck
• Jean Baptiste Lamarck was the first biologist to propose the idea that populations of organisms change over time
• His ideas were considered radical for the time that they were introduced
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Jean Baptiste Lamarck
• Lamarck had the idea that most organisms passed on their traits based on use and disuse
• He believed that organisms changed over time based on their use and disuse of certain characteristics
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Jean Baptiste Lamarck• A good example of this
would be a giraffe• Lamarck would believe that
a giraffe originally started out as a short necked animal
• Over time the giraffe stretched its neck to get food
• Over time the giraffe grew a longer neck and passed it on to its offspring
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Disproving Lamarck• While Lamarck had the
right ideas that organisms change, he did not have the right method of change
• Just by using or not using a trait does not ensure it will be passed on to the next generation
• A runt in a litter of puppies would demonstrate this
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Disproving Lamarck
• Just because an organism really wants a trait and may use it does not ensure the trait will be passed on
• You can think about several things in your own life that may apply
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Darwin
• However a few years later in the 1830’s a young biologist set sail on a voyage on the HMS Beagle
• Charles Darwin’s voyage was one of the most important events in biology
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Darwin• He sailed around the
world for five years making observations where ever he went
• One place that had particular impact on him was the Galapagos Islands
• It was there that he started to form the first ideas of evolution
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Darwin
• http://www.joost.com/36ziwbw/#/?noScroll=true&video_info=36ziwbw
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Natural Selection
• Darwin found on his journey that certain animals were better suited for their environments than other animals
• Darwin found that some of these animals were better suited to survival than others
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Natural Selection• Darwin believed that
certain animals were better suited to survival and that helped them live and have offspring
• Those animals that lived and had offspring would be the ones that you see in the world
• This idea was called natural selection
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Natural Selection
• Natural selection can only happen when one organism has an increased chance to spread its genes
• The probability that an organism will pass on its genes to the next generation is referred to as fitness
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Natural Selection
• An organism that has an increase in fitness have a larger chance of passing on their genes
• An organism that has a decrease in fitness has a smaller chance of passing on their genes
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Overproduction
• There are also several other things that Darwin noticed during his travels that helped form his opinion of natural selection
• One of the things he noticed was the number of offspring that were produced
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Overproduction
• Most animals can produce more offspring than can survive to maturity
• This means that some of the offspring will die when they are young
• The offspring that will die are ones that will not be passing their genes on in the gene pool
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Overproduction
• The idea that some offspring do not survive to maturity and cannot contribute their combination of genes is called overproduction
• Examples of this would be wild octopus
• More octopus are produced each year than can survive
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Genetic Variation
• Darwin also noticed that within a population there are a difference in traits
• The difference in traits creates a full range of traits within a species
• This is easy to observe in any population
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Genetic Variation
• The range of traits within a population helps determine how natural selection proceeds
• Natural selection tends to select for certain traits and have certain other traits die out
• The range in traits is called genetic variation
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Genetic Variation• The range in traits allows
for a species to survive if some traits are not variable
• If deer with large antlers are hunted and killed easier, there will be deer that have small antlers that would survive
• If there were no variation among deer, none would survive
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Adaptation
• Some of the variations help an organism survive in an environment
• These variations tend to become more frequent in a population
• The more frequent that trait is in a population, the better chance that population will survive
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Adaptation• A trait that makes an
individual more likely to survive in an environment is called an adaptation
• Something like thick fur in a cold environment is a successful adaptation
• Something like thick fur in a warm environment is not a successful adaptation
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Adaptation
• Remember an adaptation is a something that is passed down from the parents
• Adaptations are not something that is spontaneous or planned by the organism