EVOLUTION

Agenda

• “E” experiment

• “U” experiment

• Squirrels

-Food web

-Natural selection

• Weekly reminders

• Q&A

For this seminar, you will simulate an example of natural selection with the words you use. When your instructor announces "START," you should have a chat about the weather in your area. The only hitch is that you may not use the letter 'e' in anything that you type. Any words that contain the letter 'e' will be ignored. You and your classmates will talk about the weather in your area for five minutes total, after which your instructor will announce "STOP," and you will be allowed to use the letter 'e' again.

“E” Experiment

How is th_ w_ath_r?

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Reflect on your conversation and discuss the following topics with your classmates:

1) In your new, 'e'-free environment, what adaptations to language did you and your classmates make?

2) What things were more difficult to talk about, and why?

A “u” free environment

Image credits Microsoft Clip Art

A “u” free environment

3) If you were to live in a 'u'-free environment, what other letters might struggle and die out?

Possible endangered “u” things…U-turn, Ugly duckling, Ulna and ulcerative colitis, underwear, unemployed, unhappy, uncles, or under water, undertow, understory, upstairs, upright, upside down cake, or upset, Utah, USA, and Uranus, uranium, Universe, unicorn, uniform, unicycle, unzip Umbrellas and umpires Utensils and utopia, Urgent and urchin, Ukuleles, Use us, Union, united, utility, unit, udder, ultra, unable, ultimate…

Muted, bugle, bug, dug, jug, mug, pug, rug, you, menu, thou, ecru, thru or through, bandeau, beau, caribou, fondue, Haiku tableau, snafu, tiramisu, tofu, trousseau, tutu, bureau, plateau, bayou, luminosity.

Squirrels and the food web

Image credit: Microsoft Clip Art

Squirrels and natural selection

4) Think about this experiment as a way to show how changes in environment force creatures (like you) to adapt and change. Now, think about squirrels. What might happen to them if all the oak trees (and therefore acorns) died out?

What adaptations might they have to make to adjust to the acorn-free world?

How might these changes affect their body structures?

After 50,000 years of living in an acorn- free world, how might squirrels look?

Why does this kind of evolutionary change take so long?

Mutations and natural selection Science explains that all living things share common ancestors, and over time, natural selection gives rise to variations and changes. A human example of natural selection is the ability to digest lactose. Lactose is the main sugar in milk composed of a glucose molecule linked to a galactose molecule. The human digestive system has not always been able to digest lactose. It took a genetic mutation (natural selection) to enable humans to digest lactose.   Not everyone has this mutation. Most northern Europeans, whose ancestors domesticated cattle, have the mutation and can digest lactose. Descendants of cultures who did not raise cattle for milk (most Asians and many Africans) do not have the mutation and cannot digest lactose. In the U.S. up to 15% of European descendants, 75-80% of Africans and Latinos, 75-100% of American Indians and Asians are lactose intolerant. 

Another example… Anyone whose family has been touched by hereditary disease has probably asked: If natural selection is supposed to get rid of harmful genetic traits, why are there so many hereditary diseases in the first place?

Scientists have long known that sickle cell anemia, which causes blood cells to deform, protects against malaria (a fatal parasite that eats hemoglobin). There is a high frequency of the sickle cell genes in malaria endemic regions. Scientists believe this to be due to the advantage against fatal malaria.   The sickle cell gene is found widely throughout Africa and in countries with African immigrant populations (e.g., the Caribbean, UK, and US), in some Mediterranean countries (e.g., Greece), the Middle East, and parts of India. In my opinion, sickle-cell anemia is an unfortunate by-product of evolutionary adaptation. When people inherit one copy of the sickle-cell gene, they acquire a beneficial resistance to malaria that has ensured the gene's survival. When people inherit two copies of the sickle-cell gene, the result is a deadly disease. 

Geographic Isolation In response to a predator, the tiny brown anolis lizards on several Caribbean and Bahamian islands underwent natural selection twice: first for long legs, then for short legs.   A hurricane flooded the islands and swept away the brown anolis lizard’s natural predator, the larger, ground-dwelling curly-tailed lizard (Leiocephalus carinatus). Researchers then reintroduced the curly-tailed lizard. After six months, researchers observed that the surviving brown anolis lizards had longer legs than those on islands without curly-tailed lizards.  After a year, the researchers observed that the process of natural selection had reversed. The surviving brown anolis lizards now had shorter legs than those on islands without curly-tailed lizards. So, what happened? 

Further ExplanationWhen the brown anolis lizard lives without predators, it stays mostly on the ground, where long legs make for fast moves. In the first six months, the brown anolis lizard stayed on the ground, dodging the curly-tailed lizards.

However, after a year of running from the curly-tailed lizards, the brown anolis lizards learned to climb up into trees and bushes, where shorter legs make for better agility.

So, do you think natural selection is a long-term process, a short-term process, both, or neither? Why?

  

Fish The Antarctic ice fish species of today has no red blood cells (hemoglobin). Red blood cells thicken blood, making it difficult to pump in extreme cold. The Antarctic ice fish species has developed other circulatory features (think fish antifreeze) instead. This fish’s blood, rather than being red, is colorless and nearly transparent. Scientists, however, discovered that the gene for hemoglobin remains in the fish’s DNA. Natural selection leaves its signature in DNA. This tells us the Antarctic ice fish evolved from red-blooded ancestors in warmer waters.

Class, what do you think will happen to this fish species if the water temperature rises in the Antarctic?  

Questions?

Image credit: Microsoft Clip Art