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Biology > Chapter 24 - Human Evolution > Flashcards

Chapter 24 - Human Evolution Flashcards

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AP® Biology flashcards Biology 101 flashcards
0
Q

True or False: Prosimians are thought to represent the same lineage as the one that gave rise to humans.

A

FALSE. Prosimians are separate from the one that gave rise to humans.

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1
Q

What does comparative anatomy/comparison of morphologies show in terms of human lineage?

A

All primates (400 species) share general features such as nails, eyes on the front of the face, some that have opposable thumbs, etc.

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2
Q

What group do humans belong to?

A

The monophyletic great ape group

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3
Q

What is the closest relative to humans?

A

Chimpanzees

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4
Q

How did DNA analysis link humans and chimpanzees together?

A

Firstly, morphological analysis first established that chimpanzees are closely related to humans.
They then denatured DNA strands, comparing the temperature of DNA denaturation for chimpanzee-human and human-human DNA molecules. The temperature was approximately1 degree of difference.

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5
Q

Why, if chimpanzees and humans are so genetically similar, are they so morphologically different?

A

One cause could be differences in gene regulation, which could have major morphological and physiological consequences.

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6
Q

When did humans and chimpanzees split?

A

about 5-7 million years ago

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7
Q

True or False: For the first several years of human evolution, all the fossils from the human lineage are found in Africa.

A

TRUE

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8
Q

What is missing from the fossil record?

A

Whether or not certain species can interbreed.

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9
Q

What is the taxon for the members of all the different species in the lineage leading to humans?

A

hominins

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10
Q

Describe the history and features of “Ardipithecus ramidus”

A

“Ardi”

  • bipedal but still arborial
  • 4.4 million years old
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11
Q

Describe the history and features of “Australopithecus afarensis”

A

“Lucy”

  • fully bipedal
  • 3.2 million years old
  • short stature, small brain
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12
Q

True or False: All hominins have a common ancestor, and all these lineages lead to modern humans.

A

FALSE: hominins branched off, and ultimately went extinct except for humans.

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13
Q

What is the first hominid that left Africa?

A

Homo ergaster/Homo erectus around 2 million years ago.

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14
Q

Describe the history and features of “Homo Neanderthalensis”

A

Existed 30,000 to 600,000 years ago

-flatter heads, thicker brains

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15
Q

What is the multi regional hypothesis?

A

A hypothesis of human origin that implied that different Homo ergaster populations throughout the Old World evolved in parallel with limited gene flow between them to each produce h. sapiens.

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16
Q

What is the out-of-Africa hypothesis?

A

A hypothesis developed in 1987 that overturned the multi regional hypothesis. It posits that modern humans arose much more recently from Homo heidelbergensis in Africa 200,000 years ago.

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17
Q

How was the out-of-Africa hypothesis supported?

A

Rebecca Cann analyzed DNA sequences of a segment of mitochondrial DNA from people from various areas around the world.
Cann calibrated the phylogenetic tree and supported the fact that the deepest roots of the tree were from Africa. Additionally, the tree itself is shallow, and so calibrated the tree to date back to the most common human ancestor as being 200,000 years ago.

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18
Q

What is Mitochondrial DNA and why is it useful?

A

a small circle of DNA found in every mitochondrion. Mitochondria are much more abundant than typical cells and are easier to extract.
Furthermore, mtDNA are easier to inherit because they are inherited from the maternal egg. There is no opportunity therefore for genetic recombination between mtDNA molecules, so the only differences are in mutation.

19
Q

True or False: The out-of-Africa theory was further support by reconstructing the human phylogeny using the Y chromosome DNA sequences

A

TRUE

20
Q

What is Cro-Magnon?

A

The first population of homo sapiens to arrive in Europe.

22
Q

What is the controversy surround Neanderthals?

A

That studies from mtDNA show that there was no genetic input/interbreeding between Neanderthals and modern humans, but whole-genome studies suggests there was. Could be that genetic drift bred the mtDNA from Neanderthals. This is all speculative.

23
Q

When did humans and chimps split?

A

5-7 million years ago

24
Q

Where did events that produced language occur?

A

Africa

25
Q

What was one of the first changes in human lineage and what evidence do we have?

A

The shift to bipedalism. We have evidence from Lucy, 3.2 mya and Ardi, 4.4 mya (partially bipedal)
A telling trace fossil is also evidence, found in Tanzania, which are dated 3.5 myo

26
Q

Why did hominids become bipedal?

A

Functional changes, like gathering from trees or looking for predators or long distance travel. Freed up hominids’ hands.
Could carry material over long distances, manipulate food, use tools

27
Q

What anatomical changes characterized the development of bipedalism in hominids?

A
  • Reposition of foramen magnum from back of skull to over vertebral column
  • Flat spin to s-shaped spine directly over pelvis
  • Wide stance shorter legs to basin-like pelvis with longer legs, with legs directly under body
  • Narrowing of food with more developed heel and larger big toe
28
Q

If chimps and humans have extraordinarily similar genes, why are their physical characteristics so different?

A

-Changes in regulation of genes responsible for human neoteny

29
Q

What is neoteny? What is an example as it applies to humans and chimps?

A

The long-term evolutionary process in which the timing of development is altered to that a sexually mature organism still retains the physical characteristics of the juvenile form
An example is that the juvenile chimp looks much more like an adult human than an adult chimp does.

30
Q

What supports human neoteny?

A
  • large heads
  • lack of hair
  • position of foramen magnum at base of skull
  • mentality of questioning and playfulness
31
Q

What has allowed for humans’ success?

A

Large brain size for our bodies.

32
Q

What factors promoted the evolution of the large human brain?

A

All speculation:

  • Tool use: manual dexterity, nervous system development
  • Social Living: coordination and organization
  • Language
33
Q

What information can fossils give us about the mental power of an organism?

A

We can measure the volume of a fossil’s cranium - but take care to acknowledge that size is not the only factor in intelligence - rewiring an important factor

34
Q

What is the significance of the FOXP2 gene?

A

It is an evolutionary-conserved gene that encodes transcription factors that play important roles in development. Humans with mutations here have problems with speech/language

  • Other animals with impairment in FOXP2 also have communication problems
  • Humans have 2 extra amino acids here than chimps
  • Neanderthals have shown to possess the modern human version of FOXP2 - differences arose before split with them 600,000 ya
35
Q

How genetically varied are humans?

A

Genetic variation is actually quite low - we are about .1% different between individuals

36
Q

Why are humans so phenotypically different?

A

0.1% is actually a lot of difference since our genome is so large. This means each person differs by 3 million bp (mostly in noncoding DNA), which can influence coding proteins and influence the phenotype. Recombination during meiosis also affects it.

37
Q

How do we know how different human populations arose?

A

By analyzing different populations’ mtDNA and Y chromosomes

38
Q

When and where did Homo Sapiens arise?

A

Africa, about 60,000 years ago to the Middle East, and 50,000 years ago to Asia/Australia, and 15,000 years ago to North America

39
Q

How does the movement of human populations impact human evolution?

A

Human migration out of Africa beginning 60,000 ya is very recent, so there is little time for populations to undergo changes

40
Q

Which populations today are more varied genetically? African population or non-African populations?

A

African population - the individuals that comprise current non-Africans were a small group that left Africa - therefore genetic drift occurred.

41
Q

True or False: Different groups that are phenotypically different are also proportionally genetically different.

A

False.

  • 85% of total amount of genetic variation occurs WITHIN a population
  • 8% of genetic variation occurs within races between nationalities (ex: in Caucasians)
  • 7% occurs BETWEEN races
42
Q

True or False: There is a distinct racial pattern in base-pair mutations

A

False: an African is as likely to have a particular base-pair mutation in a gene as a European.

43
Q

What are the differences we see in genetic variation between groups due to? What is an example of this?

A

Likely due to selection -

  • Ex: people with dark skin tend to live in high levels of solar radiation, people with light skin don’t - this is likely due to selection since heavily pigmented skin limits UV radiation
  • Ex: hot climates favored tall bodies like the Masai, whereas cold areas favored stockier bodies like the inuit. - but keep in mind this is simplistic
44
Q

What is the likely explanation for visual differences in facial features, etc. between races?

A

Likely sexual selection - operates solely on characteristics that can readily be seen

45
Q

What human genes are under selection for resistance to malaria?

A
  • Homozygote SS are disadvantaged because they have severe sickle cell but total protection from malaria
  • Heterozygote SA are preferred because they have mild protection against malaria and no sickle cell
  • Homozygote AA are at disadvantage b/c no protection from malaria
  • S ALLELE IS ONLY BENEFICIAL IN THE PRESENCE OF MALARIA - natural selection response to regional disease
  • G6PD is a gene involved in glucose metabolism - heteros can have severe anemia, but have resistance to malaria which offsets favism - mainly a feature of populations affected by malaria

Biology (9 decks)

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