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Evolution & natural Selection
Yellow = DO NOT WRITE!
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The Origin Of Life We are not completely sure how life exactly came to be. The most widely accepted theory is that a right combination of different organic molecule reacted to form the first prokaryotic cell about 4 billion years ago. Knowledge of past life comes from fossils, ice-core drilling, chemical analysis, and DNA analysis.
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What is natural selection?
A term coined by Charles Darwin. Natural Selection describes the survival and reproduction of organisms with particular traits.
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What is evolution? Charles Darwin proposed that because nature will “choose” or “select” the organism with the characteristics that best suit their environment, the characteristics of the species over time will also change. This is called Evolution.
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Charles Darwin & his finches
Charles Darwin went to the Galapagos islands and noticed there were a lot finches (small species of bird) that looked exactly the same except for one key difference. Beak shapes/sizes. He figured out that long ago there must have been a common ancestor to all those finches, that ancestor split off in different directions on the tree of life due to natural selection and evolution. Finches with large beaks were seed eaters. Finches with small beaks were insect eaters.
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What is adaptation? ADAPT OR DIE
An inherited trait that increases an organisms chance of survival and reproduction in a certain environment is an adaptation. Examples: Deer with fur that is a little bit thicker compared to other deer with thinner fur may survive a very cold winter. The deer with the thicker fur survived and we are able to reproduce. Their offspring also had thicker fur and so nature selected the thicker furred deer to survive. A lion with sharper claws may be able to kill and devour its prey quicker and more efficiently than a lion with duller claws. That lion with sharper claws goes on to reproduce. Its offspring has sharper claws as well. The duller clawed lion dies out. ADAPT OR DIE
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Coevolution When organisms evolve adaptations to other organisms in their environment we call this coevolution. (Think the symbiotic relationships from the previous chapter) These two different species had such a strong relationship that they have evolved together over time. Examples: The Hawaiian honeycreeper and the lobelia flower. Homo Sapiens & Canines
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Natural selection usually takes hundreds, thousands, and even millions of years to occur. Humans have sped up that process by choosing the traits we want the most. The selective breeding of organisms by humans for specific characteristics is called artificial selection. Artificial Selection
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Artificial Selection Examples you should know!
Canines & Humans: We chose certain characteristics that we wanted and bred them out. You want a fat dog with a lot of wrinkles? Bam here's a sharpei. You want a strong dog with jaws that will lock? Bam here’s a pit-bull. Now when I say “bam” it’s not instant, what breeders would do is take two dogs with that characteristic and have them mate. Then take their offspring and have them mate. Do this enough over hundreds of years and you get all the different types of dogs that you see today!
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Corn: corn did not start off as the corn you know today
Corn: corn did not start off as the corn you know today. It was once something called maize. (it can still be found today) Maize is a vegetable with different colors all over it. The darker colored kernels were not as sweet. The lighter colored kernels were sweet. So what did we do? We bred and bred and bred the types of maize that had more lighter kernels compared to darker kernels to get the corn that we eat today (sweet yellow corn). We didn’t stop there though we kept breeding larger ears of corn as well so that farmers would get more bang for their buck. Smaller ears of corn would be eaten while the larger ears of corn were bred first. Artificial selection is a type of Genetic Modification. Corn, Dogs, and a lot of your everyday food and items are GMO’s – Genetically Modified Organisms!
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Gmo’s: what is true? Misconceptions: There's been a huge backlash against GMO’s. you may see some of your food packaging saying “GMO free” but in reality everything you eat unless you farm all your own food is a genetically modified organism. If you have a dog or cat, it is also a GMO. The Truth: There have been hundreds of studies that show there is nothing to worry about when it comes to GMO’s. (there’s more to worry about when it comes to our factory farming and the antibiotics and chemicals put into our food but not the actualy evolution of our food. The Bad: we are at a time in history that we can edit the characteristics of anything. Including humans. This brings up morality issues. If we can, SHOULD we? Some believe it’s against nature or it’s against god to do so. What do you think?
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Evidence of Evolution Fossil Evidence: we date fossils by radioactive or carbon dating and by looking at the layers of our earth. The farther down you go the older the fossil is. This also helps explain continental drift. Similarities of organisms characteristics and DNA: Look at a big cat like a tiger and look at a house cat. They look really similar right? They share 96% the same DNA as each other. Humans and Chimpanzees also have quite a few similar characteristics and we share about 98%the same DNA. Similarities in Embryology: The development of the fetus in almost all animals (including humans) acts & looks EXACTLY the same in the first few months!
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Mutations Mutations are a permanent change to a gene in DNA.
Mutations are MOSTLY harmful, sometimes neutral, and RARELY beneficial. Examples: Harmful – A frog having an extra limb may not be able to move as well and avoid predation. Neutral – Humans developing blue eyes. Nothing happened. Beneficial – Hammerheads are a mutation. The skull changed shape randomly and because of this shape their eyes can see much more around it and their mouth can catch prey under the sand.
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Biological Resistance
Biological Resistance is the natural or genetic ability of an organism to avoid or repel attack by biotic agents (pathogens, pests, parasites) or to withstand the effects of abiotic agents (chemicals, pesticides, salt, heavy metals). Example: There is a reason why when you get antibiotics you need to finish them! If you don’t use all of the antibiotic not all of the pathogen will die. Which means I could become resistant to that antibiotic, replicate and become impossible to kill!
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