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Transcript of 2.1 Section Objectives – page 35 Identify natural selection as a mechanism for evolution....
![Page 1: 2.1 Section Objectives – page 35 Identify natural selection as a mechanism for evolution. Today’s Objective: Can be found in the book: Pg. 393 - 399.](https://reader036.fdocuments.us/reader036/viewer/2022062713/56649cdb5503460f949a4f5c/html5/thumbnails/1.jpg)
• Identify natural selection as a mechanism for evolution.
Today’s Objective:
Can be found in the book: Pg. 393 - 399
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Darwin and Natural Selection• Charles Darwin (1809- 1882)
He was an English scientist and it took him years to develop his theory of evolution.
• He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey.
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• As the ship’s naturalist, Darwin studied and collected biological and fossil specimens at every port along the route.
• The specimens were quite diverse, and he became curious about possible relationships among species.
Darwin and Natural Selection
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• Breeding organisms with specific traits in order to produce offspring with ideal traits is
called artificial selection.
(Intentional breeding for certain traits)
A Goldendoodle
(Golden retriever/ Poodle)
Mendel and the pea plants
Who have we studied that
bred organisms through artificial
selection?
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• Darwin observed that in nature, the traits of individuals vary in populations.
• Variations are then inherited.
• Darwin hypothesized that there was a force in nature that picked which traits are better for survival in a species.
Darwin and Natural Selection
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• On the Galápagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere.
• These observations led Darwin to consider the possibility that species can change over time.
Darwin and Natural Selection
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• He realized that individuals struggle to compete in changing environmental conditions.
• What do individuals compete for?
• Only some individuals survive the competition and live to produce offspring.
Darwin and Natural Selection
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• Natural selection is the idea that organisms with favorable variations survive, reproduce, and pass their variations to the next generation.
• Organisms without these variations are less likely to survive and reproduce.
Darwin and Natural Selection
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• Darwin proposed the idea of natural selection to explain how species change over time.
1.In nature, organisms produce more offspring than can survive.
Darwin and Natural Selection
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2. In any population, individuals have variations.
• Fish, for example, may differ in color, size, and speed.
Darwin and Natural Selection
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3. Individuals with certain useful variations, such as speed, survive in their environment, passing those variations to the next generation.
• Whereas slower individuals would not survive to reproduce.
Darwin and Natural Selection
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4. Over time, offspring with FAVORABLE variations make up most of the population.
• The allele for the unfavorable variation may cease to exist.
Darwin and Natural Selection
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Why do you think more and more bad bacteria (like the kind that cause sinus infections) are becoming
resistant to anti-biotics?
How do you think natural selection will affect this species
of moth? (both the same species, just
have variations)
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Question 1What is the difference between artificial and natural selection?
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Natural Selection:
Nature’s way of making sure the best traits live on….
“Survival of the fittest”
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• Recall that an adaptation is any variation that aids an organism’s chances of survival in its environment.
• Examples are:
Thorns on plants
Special colorings for an organism
Enhanced night vision
ADAPTATIONS
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• The ancestors of today’s common mole-rats looked
similar to this….
• Learning about adaptations in mole-rats can help you understand how natural selection has affected them.
ADAPTATIONS
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• Some ancestral rats may have avoided predators better than others because of variations such as the
size of teeth and claws.
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• Ancestral rats that survived passed their variations to offspring.
• The structural adaptations of common mole rats include large teeth and long claws.
• These body parts enable them to dig tunnels and defend against predators.
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• Over time, natural selection produced modern mole-rats.
• Their blindness may have evolved because vision had no survival advantage for them.
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Then Now
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• Some other structural adaptations are subtle.
• Mimicry is a structural adaptation that enables one species to resemble another species.
ADAPTATIONS
• In one form of mimicry, a harmless species has adaptations that result in a physical resemblance to a harmful species.
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• Another subtle adaptation is camouflage, an adaptation that enables species to blend with their surroundings.
• Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.
ADAPTATIONS