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What Darwin Never Knew
Biol: Evol Biodiv & Ecol Lab (BIOL 412)
University of New Hampshire
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Chapter 31: Animal Diversity In-class Activity What Darwin Never Knew youtube/watch?v=kNPbjtej1Hk
As you watch NOVA’s What Darwin Never Knew, answer the following questions.
Charles Darwin was born 200 years ago, and it has been 150 years since he published the work that has become the bedrock of our understanding of how diverse life on Earth evolved.
Darwin felt that his work was incomplete. What was the question that was still unanswered? How did evolution take place?
Darwin was offered a position on the British Navy Ship, the HMS Beagle, whose mission was to survey the waters around South America.
Name three things that the 26-year-old Darwin collected: a. plants b. animals c. rocks
The turtles that Darwin encountered while visiting the Galapagos Islands differed from others that he had seen in what way? The tortoises on the islands weighed up to 600 pounds, and they allowed Darwin to ride on their backs.
Darwin also encountered 13 different species of finches. Finches on each island differed in what way? The beaks of the finches all differed in size and shape depending on which island they lived.
Which feature in the following creatures suggested that they descended from different organisms: a. Snake embryos: small bumps, the beginning formation of legs b. Whale embryos: teeth as embryos, but not in adults c. Human embryos: tiny slits in the neck, similar to gills
There seemed to be an explanation for the vast diversity of animals. Beginning with a common ancestor, over time, across generations, species could change dramatically. Some might add new
body features, others might lose them. This is a process Darwin called Descent With Modification
Darwin showed that nature was a battlefield, and that everything was in competition. The pattern that Darwin saw was that the creatures that survived were those best adapted to the specific environments in which they lived.
Darwin realized that variation must be the starting point for change in nature. Such a tiny variation might make the difference between life and death.
What significant evidence of evolution is apparent in the phenotype of the pocket mouse? The fur of the pocket mouse matches the color of the tan rocks, helping it camouflage in its environment. However, in the areas where the ground is dark from old lava, the mouse is easily spotted by predators. The mice living in the dark rock areas now have darker fur to better match their environment.
What is the molecular cause of this phenotypic change? Mutation
The DNA molecule is one of the real secrets of life. It is a perfect system for storing the vast amounts of information necessary for building all kinds of creatures. (34:05)
Mutation generates variation, differences between individuals. Mutations can happen as our DNA copies itself when our cells divide, and our bodies develop. (37:10)
Describe one of the examples of evolution in action (Colobus monkey or Antarctic fish) Because of a mutation, Colobus monkeys can see the difference between nutritious red leaves from the tough green ones.
When the final answer (of how many genes humans have) came in 2003, it was a shocker: 23,000 genes, the same number as a chicken, less than an ear of corn.
The embryo is where the action is. What fascinates modern biologists is that all these different animals don’t just look the same, they are using virtually the same set of key genes to build their bodies.
HOX genes give orders that cascade through a developing embryo, activating entire networks of switches and genes that make the parts of the body. They are absolutely critical to the shape and form of a developing creature.
Oftentimes, the origin of whole new structures in evolution don’t involve the origin of new genes or whole new genetic recipes. Old genes can be reconfigured to make marvelously wonderful new things.
How identical is the DNA between humans and chimps? 99%
One percent may not sound like much, but it’s still some 30 million of DNA’s chemical letters: A’s, T’s, C’s, and G’s.
The human brain is vast – 3 times bigger than a chimp’s and is structured differently.
A mutation in our jaw muscle allows the human skull to keep expanding into adulthood, creating a bigger space for our brain.
How many different mutations are responsible for microcephaly? 21
We now know that DNA works in many different ways, through genes that make the stuff of our bodies, through switches that turn those genes on and off, and through sequences of DNA’s chemicals that throw those switches.
Conclusion: 35. Describe/explain two important things Darwin learned from his journey on the Beagle. Darwin learned that the finches on the Galapagos Islands had different beak shapes and sizes depending on which island they lived on and what food source was available to them. Darwin also came to the conclusion that nature was all about competition, and the animals that survived were best adapted to their environment.
- Describe/Explain two improvements that scientists have made to Darwin’s original ideas? Scientists have now concluded that it’s not about what genes you have, but how you use them that creates diversity in the animal kingdom. In addition, switches are the reason why some genes aren’t present in virtually the same organisms. Switches turn on and off genes allowing for changes in organisms.
What Darwin Never Knew
Course: Biol: Evol Biodiv & Ecol Lab (BIOL 412)
University: University of New Hampshire
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