biology chap 24

Question 1

Analyzing DNA sequences in different populations provided us with what new information?

Answer 1

that the chimpanzees are more closely related to humans than gorillas are

Question 2

Charles Darwin noted that the human lineage probably arose out of Africa. Which of the following was most likely the reason behind his hypothesis?

Answer 2

Gorillas and chimpanzees, which are the primates most closely related to humans, only live in Africa.

Question 3

The first DNA comparison studies between humans and chimpanzees relied on which of the following?

Answer 3

The more complementary two strands of DNA are, the higher the melting point.

Question 4

Many researchers hypothesize that modern humans have derived from the Homo ergaster populations that spread around the world starting about 2 million years ago. This hypothesis is known as the:

Answer 4

multiregional hypothesis

Question 5

There is a phenomenon called parental leakage, in which a small amount of the mitochondrial DNA from the father is found in the offspring. If parental leakage is assumed to occur in most matings, how would it change our interpretation of studies of mitochondrial DNA in human ancestors and in groups of different modern humans?

Answer 5

If it is truly a small amount, then those deviations shouldn’t influence the conclusions generated from the study

Question 6

There is some debate about whether Homo floresiensis is a separate species or an aberrant form of Homo sapiens. Regardless, what we do know is that H. floresiensis were only found on an Indonesian island and adults were only 3 feet tall. What could explain this distinct phenotype?

Answer 6

The smaller body size was necessary for an island, as food is often limited.

Question 7

When Rebecca Cann decided to research on the evolution of humans, she chose to study mitochondrial DNA. Which of the following explains why she chose this type of DNA?

Answer 7

because mitochondrial DNA is more abundant and therefore easier to extract

Question 8

Which of the following hypotheses is the most current and accepted one with regard to modern human origins?

Answer 8

the out-of-Africa hypothesis

Question 9

You are working in a lab and come across a gene, Gene X, that you think might explain some of the differences seen between chimpanzees and humans. Which of the following results would support your hypothesis?

Answer 9

if Gene X was active in humans, juvenile chimpanzees and inactive in adult chimpanzees

Question 10

Which of the following hominin lineages is correct?

Answer 10

Homo ergaster → Homo heidelbergensis → Homo sapiens

Question 11

Which of the following statements about great apes is correct?

Answer 11

Bonobos are more closely related to humans than to orangutans

Question 12

Which of the following explains how chimpanzees and humans can be so different with such similar genomes?

Answer 12

The genetic differences could have occurred in genes responsible for development.

Question 13

Cann’s studies involving mitochondrial DNA showed that the two deepest branches of the human family tree are African. Which of the following observations explains this statement?

Answer 13

that all humans evolved in Africa and only later migrated to other places

Question 14

Imagine that one of your friends has just learned about the multiregional hypothesis, and she is astonished that humans evolved independently (on different continents). What evidence would you provide your friend that contradicts the multiregional hypothesis?

Answer 14

Caan’s research using mitochondrial DNA demonstrated that humans originated in Africa, and subsequently migrated to other continents.

Question 15

Which of the following, if true, would force us to reevaluate the findings that Cann discovered with regard to the human family tree?

Answer 15

if human fossils were discovered in Asia that had DNA completely different from the DNA found in early Homo sapiens in Africa

Question 16

There are seemingly conflicting studies that have taken a look at whether Neanderthals interbred with human ancestors. One study of mitochondrial DNA suggests that the two groups did not interbreed. Another study, of the whole genome, suggests that they did. Which of the following could explain these results?

Answer 16

Mitochondrial DNA is passed on the maternal side, so if Neanderthal females did not interbreed with our ancestors, Neanderthal mitochondrial DNA would never have entered the modern human gene pool.

Question 17

A young student is trying to figure out the order in which certain traits evolved in humans. Which of the arrangements below is most likely correct?

Answer 17

bipedalism → opposable thumbs → human jaw → language

Question 18

What does it mean to say that humans are neotenous?

Answer 18

that humans in their adult state resemble juvenile chimpanzees

Question 19

What does it mean when it is said that the tree of human evolution is shallow?

Answer 19

that all humans, no matter how distantly related they are, share a recent common ancestor

Question 20

Phenotypic differences between humans and chimpanzees may be better explained by the time during development when genes are turned on in humans and chimpanzees, than by genetic differences themselves.

Answer 20

true

Question 21

There is a phenomenon called parental leakage, in which a small amount of the mitochondrial DNA from the father is found in the offspring. If parental leakage is assumed to have occurred throughout human history, how does it change our interpretation of Matthias Krings and Svante Päabo’s studies of mitochondrial DNA in specimens of Neanderthals and modern humans?

Answer 21

If the paternal mitochondrial DNA did show up in the offspring alongside maternal mitochondrial DNA, these would have immediately indicated that the two groups interbred.