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Transcript
Name:
Date:
Subject:
Natural Selection
Objectives
Objective 1: ASWBAT describe Darwin’s Theory of Natural Selection.
Objective 2: ASWBAT describe the four steps of natural selection and identify what step of
natural selection is being described in a scenario.
On a scale of 1 – 3 how well you can do on this objective now.
(1 – Not at all
2 – I know it a little bit
3 – I know it very well)
Highlight your choice.
Objective: 1
Objective: 2
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Key Vocabulary Words
On a scale of 1 – 3 how well you know the vocabulary words below.
(1 – Not at all 2 – I know it a little bit 3– I know it very well)
Evolution
Offspring
Genetic Variation
Reproduction
Mutation
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Pre-quiz
Do your best to answer the following questions.
1. What is the theory of evolution?
Answer:
2. What is a mutation?
Answer:
3. How are mutation connected to evolution?
Answer:
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Natural Selection
For many years scientists suspected that life changes over time, but they did not
understand how it worked. Charles Darwin was the first person to offer the mechanism
that is still accepted as true today. He called his theory of how evolution worked natural
selection. Natural selection is the theory that species compete in the environment and
the ones with the best traits survive to pass those traits to their offspring. It is also
sometimes called “survival of the fittest”. Nature “Selects” who survives and who doesn’t.
Natural selection is very complicated process, but it can be simplified into 4 steps.
1. Over production of offspring.
2. Genetic Variation.
3. Struggle to survive.
4. Successful reproduction.
1. Over Production of Offspring
One strategy that most living things use to survive is to create as many offspring as they
possibly can. In fact they produce more offspring then could possibly survive. The more
offspring they produce the more likely that the species will survive.
Why do you think that not
all of the offspring can
survive?
Lots of offspring!
2. Genetic Variation
Of all the offspring that are produced by a species no two are exactly alike. All of them are
little bit different genetically. This variety is due to sexual reproduction and mutations.
Sexual reproduction creates offspring they are a random mix of their parent’s genes that
causes all of the offspring to be slightly different from them. Mutations are random
changes in genes that create new version of genes that change the traits of a species. Both
of these factors cause a significant amount variation with in a population of a species.
Genetic Variation
3. Struggle to Survive
Some people don’t realize it but nature is a cruel world. The truth is that nature doesn’t
care who survives and who doesn’t. Of all the offspring that are born in a year very few
survive to be an adult. Because all of the offspring are slightly different traits some have
advantages over the others that make them more likely to survive. Only the ones with the
best traits survive and the rest simply don’t. This is why natural selection is also called
“survival of the fittest”. Only the fittest or the ones with the best traits survive.
Not the fittest!
Video: Babies Struggle to Survive
4. Successful reproduction
One of the ultimate goals in the natural world is to survive long enough to pass on your
genes to the next generation. The organisms with the best traits are able to survive and
pass those traits that made them successful to their offspring. They are the “fittest”. When
the survivors reproduce the process of natural selection begins all over again.
Inherited successful traits
Video: Natural Selection https://www.youtube.com/watch?v=0SCjhI86grU
1. What is natural selection?
Answer:
2. Why is natural selection sometimes called “survival of the fittest”?
Answer:
3. Name and describe each of the four steps to natural selection.
Name
Description
Step 1.
Step 2.
Step 3.
Step 4.
For the following questions identify which step of natural selection is being
described.
4. A goose needs to fly thousands of miles to reach food during the winter.
Answer:
5. A jellyfish lays thousands of eggs.
Answer:
6. A blue whale successfully reaches the birthing waters and gives birth to a healthy baby
whale.
Answer:
7. All of the baby wolves are a little different in size.
Answer:
Examples of Natural Selection
Antibiotic Resistance in Bacteria
Video: Antibiotic Resistance https://www.youtube.com/watch?v=zjR6L38yReE
Audio: Bacterial Competition In Lab Shows Evolution Never Stops
http://www.npr.org/blogs/health/2013/11/15/245168252/bacterial-competition-inlab-shows-evolution-never-stops
Video: Penicillin
Action! – Let’s see how bacteria evolve to be antibiotic resistant.
Audio: Antibiotic Resistance
http://www.npr.org/templates/story/story.php?storyId=1142191
Peppered Moth
At the beginning of the nineteenth century, most moths in the UK were an off-white color,
highly adapted to hiding from predators, such as birds, by resting on pale, mottled grey
tree trunks. But the Industrial Revolution polluted the environment, raining soot down on
the countryside. As a result, white moths became highly visible on the now blackened tree
trunks. Black moths, on the other hand, such as the peppered moth (which had previously
been quite rare), suddenly had a competitive advantage. They were well camouflaged on
black tree trunks, and their numbers grew exponentially. By the early twentieth century,
they were the dominant moth form in polluted areas of the UK.
The above story is considered the classic example of "evolution in action." It shows how an
environmental change can give one form of a species a selective advantage, leading to its
dominance. Its validity rests upon experiments conducted by researcher H.B.D. Kettlewell
during the 1950s, which demonstrated that white moths do have an advantage over dark
moths on pale trees, and a disadvantage on dark trees, and vice versa.
Before Pollution
After Pollution
Pocket Mouse Evolution
Video: Pocket Mouse Evolution https://www.youtube.com/watch?v=wrTXvrKBlbc
Action! – Lets have a natural selection relay race.
Quiz
Directions: Answer the following questions to see if you met the objectives.
1. What is the theory of natural selection?
Answer:
2. Why is natural selection sometimes called survival of the fittest?
Answer:
3. Name and describe each of the four steps to natural selection.
Name
Description
Step 1.
Step 2.
Step 3.
Step 4.
For the following questions identify which step of natural selection is being
described.
4. A gazelles runs from predators in order to avoid being eaten.
Answer:
5. A female spider lays thousands of eggs.
Answer:
6. All of the beetle offspring are slightly different in size and color.
Answer:
7. The strongest bear survives to be an adult and produces offspring.
Answer: