Genetics and Evolution Review Bio 120

1. How do biologists define evolution?

2. What is a population?

3. What islands were important to Charles Darwin's thinking on evolution?

4. Biogeography is how living things are distributed around the world. How was Darwin surprised by the the biogeography he observed on his trip around the world?

5. While fossils support the theory of evolution, we can't rely on the fossil record ever being complete. Why?

6. How does the existence of fossils support the theory of evolution?

7. How did LaMarck explain inheritance?

8. What was the hypothesis of catastrophism?

9. While the theory of evolution does not indicate humans came from chimps, it does indicate a _________________________ between chimps and humans.

10. Upon what observations did Darwin base his theory of evolution by natural selection?

11. What must occur for a new species to evolve?

12. What isolating mechanisms help maintain a species as a distinct group?

13. Describe how allopatric speciation could happen.

14. What is usually involved in sympatric speciation?

15. How is stabilizing selection different from directional selection?

16. Is their a plan to evolution?

17. What mechanisms of evolution can lead to less genetic diversity in a population?

18. What is a gene pool?

19. Who was Alfred Wallace and why is he an important figure in the history of the theory of evolution?

20. What is the source of all new genes in a population?

21. What mechanism of evolution keeps separate populations from being isolated?

Genetics

1. How is a phenotype different from a genotype?

2. How is the law of segregation different from the law of independent assortment?

3. What is an allele?

4. If a pair of alleles are the same we call this genotype _____, and if the alleles are different the genotype is called _____.

5. PKU is a recessive disorder. If "dad" has PKU , and "mom" is homozygous dominant, what is the chance a child will have PKU?

6. In four o'clock flowers, the petal color is either red, pink, or white. How do you think flower color is inherited and why?

7. Hemophilia is an X-linked disorder. If mom carries the gene, and dad is normal, what is the chance the couple's daughter will be a carrier? What is the chance the daughter will have hemophilia?

What is the chance their son will have hemophilia?

8. Mom has O blood, and Dad has AB. They have a child with B blood. Is this possible?

9. There are three alleles present in the population for blood type. This is called _____________

10. A gene that is only expressed if it is in the homozygous condition must be a ______ gene.

I1. In a certain species of flower there are two petal colors, blue or red. If two blue flowered plants are crossed, the offspring are always blue. If two red plants are crossed, sometimes only red flowering plants are produced, while other times both red and blue flowering plants are produced. If a red plant and blue plant are crossed, sometimes the offspring are all red, while other times both red and blue offspring are produced. Which color is dominant?

New Discovery in Seal Evolution

photo by Alex Tirabasso/Canadian Museum of Natural History

A newly describe fossil from the arctic sheds new light on seal evolution. The fossilized remains of Pujilla darwini indicate the animal walked on land,and had webbed feet, but not flippers. The early seal is estimated to be 23 million years old, and is the oldest fossil found yet of seal ancestors.

The species name honors Charles Darwin who predicted that marine mammals would be found to have evolved from land animals. It also appears that this early seal ancestor lived in fresh water, which is something Darwin had also predicted.


Read more about this discovery here

Happy Birthday Mr. Darwin

What concepts did Darwin develop, and why were they so revolutionary?

Species can change- Living things are not fixed, but can change over many generations.

Common Descent—All life on Earth shares a common ancestry. Yes, even humans.
Drawing from one of Darwin's notebooks

Gradualism--The change of a species takes a long time.
Marine Iguana, Isabela Island, Galapagos

Land Iguana, North Seymour Island, Galapagos.
The land iguana and marine iguana evolved from a common ancestor, probably an iguana from the mainland of South America.

Natural selection
Certain randomly acquired traits are helpful.

Individuals with helpful traits survive longer, have more offspring, so over time these traits increase in a
population.

Nature selects which traits are beneficial, and which are not.

Small ground finch, San Cristobal Island, Galapagos

Medium ground finch, San Cristobal Island, Galapagos.

The main difference between "Darwin's finches" is the size and shape of their bills. What advantage would their be to an individual with a beak like the one found on the medium ground finch? What about the the bill found on the small ground finch?

Others prior to Darwin had suggested species may have changed over time, and were not fixed. However, Darwin was the the first to suggest a logical mechanism (natural selection) though which these changes occurred.

Darwin Day Special: Evolution of Lice

Pubic louse (Pthirus pubis)

Biologists wonder about all kinds of things. Dr. Robert Weiss for example wondered why humans are parasitized by two different species of lice, head lice (Pediculus humanus) and pubic lice (Pthirus pubis commonly called crabs). What would have caused this separation of lice into two species, both of which occupy different habitats on the body? After all our ancestors were hairy all over so why specialize in different areas of the body?

Head louse (Pediculus humanus)



It turns out Dr. Weiss discovered pubic lice that infect humans evolved from lice found on gorillas (Pthirus gorillae). The two species of lice diverged about 3.3 million years ago according to David Reed from the University of Florida, however humans and gorillas diverged earlier, about 7 million years ago. Dr. Reed's work also demonstrated that human head lice probably came from our hominid ancestors. Dr. Weiss hypothesizes that later our human ancestors caught the pubic lice ancestor from the gorillas while hunting and butchering them. This close contact would have allowed the gorilla lice to jump onto our ancestors, burrow in and start feeding!

Weiss et al. Apes, lice and prehistory. Journal of Biology, 2009; 8 (2): 20 DOI: 10.1186/jbiol114

Darwin Day Special: More from Sir David Attenborough

This is a clip from the trailer of the new series, and a bit of a preview in which Sir David talks about one of the most compelling parts of Darwin's theory-that is that we, as humans, are not separate from the natural world, but part of it.

Darwin Day Special: from Dinos to Turkeys

Darwin Day Special: National Geographic's new show "Morphed"

National Geographic is broadcasting a series of shows this week as part of a new series called "Morphed" You can visit the website here, and watch short video segments about whale evolution, the evolution from dinosaur to birds, and bear evolution.

I watched the video clips, and did cringe a bit when in the one about the transition ancestors of whales underwent from land animals to marine animals, the narrator talks about a paleontologist "going after the biggest fish in the sea." Whales, after all are mammals like you and me, not fish.



There is a great deal of information on the website including a short preview of a program on Darwin's notebooks that includes a re-enactment of Darwin in Patagonia.

The series starts broadcasting tomorrow.

Darwin Day Special: OK so flies evolve... but what about people

In my last post I wrote about work that demonstrates the evolution of fruit flies over a period of a couple of hundred years. This kind of research shows us we can look around at the living world and see evidence that evolution is happening around us, but what about us? Are there things in our bodies that hint at our evolutionary past?

Why do we have parts in our bodies that don't function? Why do we have things like goose bumps, which don't do anything for us? Structures present in an organism, but not functional (even though these structures may function in other organisms) are called vestigial structures.

What is responsible for the construction of vestigial structures during development? Sequences of DNA.
Where does DNA come from? Our ancestors......

For a list of vestigial structures found in humans click here.

Darwin Day Special: Flies that live on apples providing more clues to formation of new species

Biologists from Notre Dame, Michiagan State and the University of Florida have just published an article in which they describe how the introduction of apple trees to the US 400 years ago has affected the evolution of a type of fruit fly AND the parasitic wasp that feeds on the maggots of the fly.

Prior to the presence of apple trees in the US, these flies Rhagoletis pomonella found mates, and laid eggs on the fruit of the hawthorn tree. In the 1800's some of these flies began going to apples to mate and lay their eggs instead. These flies have now become genetically different from the flies that still visit the hawthorn fruit.

This is an example of how new species can form. Over time mutations, natural selection and other mechanisms of evolution affect the two fly population in different ways, until they are so genetically different they become species.


What is really interesting to me is how fast this happens, and that the same kind of speciation is also happening to the parasitic wasps that feed on the maggots of the flies. This is an example of co-evolution. Co-evolution happens when the evolution of one species affects the evolution of another.

So you see, it is not necessary to go off to some exotic place to study evolution. The process of evolution is happening all around us. Articles like this make me wonder what kind of evolution could be going on right here at the college?


Forbes et al. Sequential Sympatric Speciation Across Trophic Levels. Science, 6 February 2009: 776-779 DOI: 10.1126/science.1166981

Darwin Day Special: Discovery of new transitional fossil of whales announced

Boy oh boy, give me a little free time and look at all the posts I can publish! I'll leave the news about the giant fossil snake, Titanaboa cerrejonensis, for you to find on your own by the way.

Philip Gingerich and colleagues have just published an article describing fossils of whale ancestors they discovered in Pakistan. They found two adults, one male and one female, and as they uncovered the fossil of the female whale they discovered a fetus inside. These early whale ancestors still had legs, and most likely gave birth on land.

The fetus had teeth and was facing head first toward the birth canal which is why the researchers believe the animals gave birth on land. As you can imagine, heading into the water head first to take one’s first gulp of air would be disastrous for the baby. Modern whales are born tail first.

The well formed teeth suggest the young were very precocious, and ready to feed soon after birth.

The name of this 45 million year old ancestral whale fossil is Maiacetus inuus. You can read the article by Gingerich and colleagues here as well as see photos and drawings of the fossils.

Darwin Day Special: 635 Million year old Steroids

Scientists at the University of California at Riverside working with scientists at MIT have have discovered massive amounts of steroids in sediments that are 635 million years old. These steroids were made by sponges, and are the earliest evidence of animal life discovered to date!

You can read more about this discovery here

David Attenborough and the Tree of Life

Another preview about the Tree of Life. This is a wonderful representation of the Tree of Life on Earth. It is a beautiful presentation, even if it does seem to leave out plants. Algae at least get a brief mention. Take a look!

David Attenborough's new program: Darwin and the Tree of Life--

My favorite natural historian, Sir David Attenborough has developed a new program about Darwin and evolution. I am not sure when it will be broadcast, but I imagine it will be ready by the 200th anniversary of Darwin's birth which is Feb. 12.
Take a look at this short interview of Sir David for a preview of the coming show.

Evolution Quesitons

1. How do biologists define evolution?

2. What is a population?

3. What islands were important to Charles Darwin's thinking on evolution?

4. Biogeography is how living things are distributed around the world. How was Darwin surprised by the the biogeography he observed on his trip around the world?

5. While fossils support the theory of evolution, we can't rely on the fossil record ever being complete. Why?

6. How does the existence of fossils support the theory of evolution?

7. How did LaMarck explain inheritance?

8. What was the hypothesis of catastrophism?

9. While the theory of evolution does not indicate humans came from chimps, it does indicate a _________________________ between chimps and humans.

10. Upon what observations did Darwin base his theory of evolution by natural selection?