Day 15 March 8th Chapter 8

8/2/2019 Day 15 March 8th Chapter 8

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Day 15 March 8 th Chapter 8

Last TIME to retake the exam is by 4pmon Friday. But I have to give you the

password before we walk out of heretoday, because Im gone tomorrow.


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Does evolution lead to the perfectorganism?

1. Yes, organisms survive because they are thebest.

2. Yes, organisms that are perfect can survive

3. No, there is no such thing as a perfectorganism.

4. No, the only thing perfect on this planet isme.


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8.13 Natural selection does not lead toperfect organisms.


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Why doesnt natural selection leadto the production

of perfect organisms?


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Factors that Prevent Populations fromProgressing Inevitably toward Perfection

1. Environments change quickly.

2. Variation is needed as the raw material of selection.

3. There may be multiple different alleles for atrait, each causing an individual to have thesame fitness.


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8.14 Artificial selection is just aspecial case of natural selection.

Apple growers - green, yellow, red, tart, sweet, large, and small.


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8.15 Natural selection can change thetraits seen in a population in several ways.


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Directional Selection

Individuals with one extreme from the range of variation in the population have higher fitness.

The result of such selectionis not surprising: between

1920 and 1945, average milkproduction increased byabout 50% in the United

States. Farmers only let thecows with lots of milk breed


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Turkeys on poultry farms have such largebreast muscles that they cant get close

enough to each other to mate.

How can such a trait evolve?


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So, could this happen in nature?


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Could turkeys with breasts so largethat they cannot mate, occur

naturally?

1. Yes

2. No


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How is medical technology undoingthe work of natural selection in optimizing

the number of babieswith normal birth weights?


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Stabilizing Selection

Individuals with intermediate phenotypes are most fit.


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22 lbs mom was diabetic

Born preemie at 22 weeksWeighed less than 10 oz.


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Should we save every baby born?

1. Yes, we should try to save every baby human or animal.

2. Yes, we should save every human, but not tryto save animal babies

3. No, We should only let the strongest animalsand humans the healthy ones survive.


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Disruptive SelectionIndividuals with extreme phenotypes experience the

highest fitness, and those with intermediatephenotypes have the lowest.


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Based on our discussion so far, what do

you think? Are humans still evolving?

1. Yes2. No3. Unsure


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8.16 Natural selection can cause theevolution of complex traits andbehaviors.

Look at the betta fish!


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1954, William Thompson trained a group of rats to run through a maze for a food reward


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How can a wing evolve if 1% of a wingdoesnt help an organism fly or glide at

all?


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Often, structuresappear because theyserve some otherpurpose.

Functional Shifts


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Biggest wings hottest regions?


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It is indeed remarkable that this theory [evolution] has been progressively accepted by researchers,following a series of discoveries in various fields of knowledge.

The convergence, neither sought nor fabricated, of the results of work that was conducted independently is in itself a significant argument in favor of this theory.

Pope John Paul II, 1996


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Five primary lines of evidence:

1. The fossil record

2. Biogeography

3. Comparative anatomy and embryology

4. Molecular biology

5. Laboratory and field experiments


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8.17 The fossil record

documents the process of natural selection.

Although it has been central to much documentation of theoccurrence of evolution, it is a very incomplete record


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In Darwinstime, it wasassumedthat thedeeperdown in theearth a

fossil wasfound, theolder it was.RelativeDating


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Happened in North America 55 million years ago

Many branches, not just a straight line


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First found innorthern Canadaand estimated at375 million yearsold, Tiktaalik

fossils appear torepresent atransitional phasebetween fish and

land animals.


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8- 18. Geographic patterns of species distributions reflect their evolutionaryhistories.


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History Matters

Who arrived first?

Are numerous different habitats available?

In Hawaii, it appears that a finch-like descendant of the

honeycreepers arrived 4-5 million years ago and rapidlyevolved into a large number of diverse species.The same process has occurred and continues to occur inall locales, not just on islands.


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Day 15 March 8th Chapter 8