Chapter 19-Human Evolution

It is inherited by all children from both their mothers and their fathers.

Humans have DNA in the nuclei and in the mitochondria of our cells. How is nuclear DNA inherited?

small brains, opposable big toe, and light skin

If human ancestors had been able to obtain more food (calories and nutrients) with an arboreal lifestyle in highly shaded environments, what trait(s) would have been retained?

identify Africa as the place of origin of all modern humans

"Finding" mitochondrial Eve was an important step in tracing human evolution because it helped us _____.

low sperm count, spina bifida, and anencephaly

A folate deficiency can cause _____.

whether or not the person is related to the "mitochondrial Eve" or the last common female ancestor

A person's skin tone is NOT caused by _____.

Africans

According to the "Out of Africa" hypothesis of human origins and migration, which group of people shows the highest level of genetic diversity?

high-; protects folate from degradation

As hypothesized by Jablonski and Chaplin, darker skin is advantageous in _____ UVB environments because darker skin _____.

an opposable big toe and the ability to live in trees

Australopithecus africanus lacked _____.

mitochondrial; a single female in Africa

Based on _____ DNA, all humans today can trace their ancestry to _____.

99.9%

Based on regions of the human genome, each person's DNA is _____ identical.

Hominids were covered in thick hair and had light skin. Hominids lost some of their body hair and gained more swear glands. Hominids evolved dark and hairless skin.

Hominids evolved under natural selection pressures, which selected for certain traits that conferred an advantage to individuals. Consider the following list of traits. Choose the answer that correctly orders the evolutionary pattern of hominid traits.

They increase, because melanin production is stimulated by UVB exposure.

In response to sunlight (UVB exposure), what happens to melanin levels in the skin?

the levels of UVB light

In the course of human evolution, which environmental factor likely influenced whether populations have mostly light-skinned individuals or mostly dark-skinned individuals?

around the equator

Let's pretend that UVB exposure occurs at the highest levels at the poles, and at the lowest levels at the equator. In this alternate planet Earth, where would you expect to find fair-skinned humans?

The hair of chimpanzees protects their light skin from UVB light.

Our closest primate relatives, chimpanzees, have light-colored skin yet live in tropical (high-UVB) environments. How would the Jablonski−Chaplin hypothesis explain this observation?

the epidermis

Melanocytes, which produce melanin, are located in _____.

mothers; sons and daughters

Mitochondrial DNA is passed from _____ to _____.

Mutations

Mitochondrial DNA variation occurs due to _____.

a big brain

Of the traits that are associated with being human, which of these evolved most recently?

Australopithecus africanus

On the evolutionary tree of humans, which lineage is the oldest?

because fossil evidence shows that modern humans and present-day apes evolved from a common ancestor

On the evolutionary tree of humans, why are humans and apes grouped together?

The weaker the UV light, the darker the skin, because people with light skin are more vulnerable to folate destruction than darker-skinned people.

Research into the evolution of skin color has resulted in a complete hypothesis that explains why skin color varies geographically. Which description is NOT a result of this research?

a greater risk of folate deficiency

Researchers have studied human genetic relatedness and the distribution of certain traits to infer patterns of human migration. Their studies show that humans who migrated northward from Africa had descendants with _____.

genetic diversity decreased as early humans migrated away from Africa and founded new populations

Scientists have found that _____.

Sperm do not contribute their mitochondria to the zygote.

Scientists have studied patterns of mitochondrial DNA to determine where humans first evolved and how they spread. Humans inherit their mitochondrial genes only from their mothers. Why aren't a father's mitochondrial genes passed to his offspring?

One of the earliest hominids, Ardipithecus ramidus, lived 54 million years ago.

Scientists rely on evidence from the fossil record to determine how and when events in human evolution occurred. Which of these major milestones in human evolution is NOT correctly dated?

All humans alive today are related to a single female ancestor.

Scientists used mitochondrial DNA to investigate patterns of human evolution. Which description is a result of this research?

2.6

Simple tool use in humans began approximately _____ million years ago.

were from a geographical area closer to the equator

The darker the skin of a person, the more likely that some of that person's ancestors _____.

the ability to walk upright preceded the evolution of a larger brain

The fossil remains of Ardipithecus ramidus showed that _____.

70,000

The human migration, which led to modern-day Asians, Australians, and Europeans, began approximately _____ years ago.

160,000-180,000

The oldest known fossils of modern humans are approximately _____ years old.

NO

Vitiligo is a disease in which melanocytes are destroyed, causing loss of pigmentation. If a dark-skinned person develops vitiligo, and therefore lighter skin, would his or her race change?

mothers

We all inherit mitochondrial DNA from our _____.

-Mitochondrial DNA mutates at a fairly regular rate. -Individuals with nearly identical mtDNA sequences are more closely related. -Mutations from mothers are passed to offspring without recombination with paternal mtDNA.

What are characteristics of mitochondrial DNA that made it a suitable choice for studying human evolutionary patterns?

A dark-skinned person would have more alleles to produce melanin.

What can you infer about the skin-color alleles of a light-skinned person and of a dark-skinned person?

>99%

What percentage of DNA sequences do all humans share?

Africa

Where did the earliest humans evolve?

"Out of Africa" hypothesis

Which hypothesis about the origin of humans is the most accepted today?

upright walking, then tool use, then fire use, then advanced communication

Which list best represents the order in which human ancestors acquired skills and traits?

human, chimpanzee, Homo melanin, Homo erectus

Which of these groups contains a species that is NOT a hominid?

All of these are found in the fossil record and have been used by scientists to understand human evolution.

Which of these is NOT something found in the fossil record that has been used by scientists to understand human evolutionary patterns?

great apes, humans, orangutans gorillas

Which of these is a hominid?

Homo sapiens

Which of these is the only surviving lineage in the evolutionary history of humans?

folate supplementation and a sunscreen lotion

Which of these would help a fair-skinned person who is living in a high UVB environment?

Ardipithecus ramidus

Which remains are the oldest hominid fossils discovered so far?

In a high-UV-light environment, skin color is more likely to be lighter.

Which statement is NOT a correct description of the relationship between UV light in the environment and how it affects humans?

Scientists constructed an evolutionary tree based on paternal mtDNA to trace human ancestry back to a single female.

Which statement is NOT a way scientists used mitochondrial DNA to determine where humans first evolved and how they spread?

because of the tremendous amount of evolutionary change over 6 million years

Why do living humans look and behave so differently from chimps?

Sperm heads do not contain mitochondria.

Why don't fathers pass on mitochondrial DNA?

1. This occurred because humans underwent natural selection, which resulted in traits that conferred advantages to humans becoming fixed in populations. 2. This occurred because alleles that are harmful in one environmental context may be beneficial in another. 3. This occurred because skin coloration results in different advantages depending on the levels of sun in the region. 4. This occurred because humans are found in areas that range from high-UV-light environments to low-UV-light environments.

Why is there so much variation in human skin coloration?