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BIOL 200 > Final Exam > Flashcards

Final Exam Flashcards

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1
Q

What is the fundamental division of life and how is it organized in humans?

A
  • Life is cellular.
  • In humans, life is organized into 30 trillion cells, each containing genetic material inside a nucleus.
  • This genetic material is organized into chromosomes.
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2
Q

What are chromosomes and how many do humans have?

A

Chromosomes are packages of genetic material made of DNA.
Humans are diploid and have 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes (XX or XY).

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3
Q

What is the significance of human chromosome #2?

A

It is the result of a fusion of two ancestral chromosomes found in chimps. This fusion event occurred 0.75–4.5 million years ago and contributed to the genetic isolation of humans from other great apes.

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4
Q

What is DNA and how is genetic information stored in it?

A

DNA (deoxyribonucleic acid) is a double helix made of nucleotides: A pairs with T, G pairs with C.

The sequence of these bases stores genetic information, and the strands are complementary.

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5
Q

What are the three steps in the flow of genetic information in a cell?

A
  1. Replication – DNA is copied before cell division.
  2. Transcription – DNA is transcribed into messenger RNA.
  3. Translation – mRNA is translated into a protein with the help of transfer RNA.
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6
Q

What portion of the human genome codes for proteins?

A

Only about 2% of the human genome codes for proteins (exons). The remaining 98% is non-coding DNA, some of which regulates gene expression.

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7
Q

Define gene, allele, genotype, and phenotype.

A

Gene = a DNA sequence that codes for a protein. An allele is a variant of a gene.

Genotype = the combination of alleles an individual has (AA, Aa, aa).

Phenotype = the observable trait (e.g., eye color).

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8
Q

What are autosomal recessive and autosomal dominant diseases?

A

Recessive: Requires two copies of the mutated gene (e.g., aa) — Tay-Sachs, albinism.

Dominant: One copy of the mutated gene causes disease (e.g., Aa) — Huntington’s disease.

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9
Q

What is phenylketonuria (PKU) and how is it treated?

A

PKU is an autosomal recessive disorder that prevents metabolism of phenylalanine. It causes intellectual disabilities if untreated. Treatment involves a diet low in phenylalanine (essential amino acid).

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10
Q

What are polygenic traits and give an example?

A

Traits controlled by multiple genes.

E.g. Human height is influenced by at least 423 genes and shows a continuous bell-shaped distribution.

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11
Q

What is epigenetics?

A

Epigenetics refers to chemical modifications (e.g., DNA methylation) that alter gene expression without changing the DNA sequence. These changes can be caused by environment, diet, trauma, etc.

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12
Q

How do mutations create genetic variation?

A

Mutations can occur in both coding and non-coding regions. On average, each person has ~60 new mutations. Some mutations are harmful, neutral, or beneficial.

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13
Q

What is Down’s syndrome and how is it detected?

A

A chromosomal disorder caused by trisomy 21. Detected by amniocentesis (weeks 15–20 of pregnancy). Risk increases with maternal age.

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14
Q

What traits make humans unique?

A

Bipedalism, language, large brain, precision grip, consciousness, agriculture, cultural evolution, super-cooperation, and non-reproductive sex.

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15
Q

What is meant by humans as “super-cooperators”?

A

Humans form complex social bonds, remember hundreds of individuals, and work in groups — more sophisticated than any other social species.

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16
Q

What makes human language unique?

A

Human language is open-ended with infinite possibilities.

Animal communication is typically closed and limited.

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17
Q

What is the role of culture in human evolution?

A

Culture allows non-genetic transmission of behaviors and knowledge (e.g., language, tools, customs). It interacts with genes to shape phenotypes.

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18
Q

What is the key contribution of Darwin and Wallace?

A

They proposed natural selection as the mechanism for evolution: differential reproductive success leads to evolution over generations.

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19
Q

What is the structure of a Darwinian argument?

A
  1. Variation in a trait exists.
  2. Some variation is heritable.
  3. Some traits lead to higher reproductive success.
  4. Those individuals leave more offspring.
  5. Over time, the advantageous trait becomes more common.
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20
Q

What is “tree thinking” in evolutionary biology?

A

Understanding evolutionary relationships based on the recency of a common ancestor, not similarity in appearance. Evolution is a bush, not a ladder.

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21
Q

Did humans evolve from chimpanzees?

A

No. Humans and chimps share a common ancestor; they are evolutionary cousins, not ancestors and descendants.

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22
Q

What is a major misconception about evolution?

A

That evolution is progressive and leads to “better” species. Evolution adapts populations to their environments — not toward a hierarchy.

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23
Q

How do humans rank species, and why is it problematic?

A

We rank based on relatedness, intelligence, pain perception, cuteness, and usefulness.

However, evolutionary theory does not support any species ranking.

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24
Q

What does Stephen Jay Gould say about evolution?

A

He criticized the idea of evolution as progress and described it as a bush of life shaped by extinction, not a linear ladder of improvement.

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25
What is the ethical implication of the Tree of Life?
It promotes a humble view — humans are one of many species. Our dominance doesn't imply superiority, and ethical decisions should reflect that interconnectedness.
26
What does the concept of race imply biologically?
If races are real: implies significant human variation & discrete groupings. If race is a myth: human variation is continuous and follows a bell curve — no discrete groups.
26
What is a ‘race’ in biology?
An informal taxonomic division below the subspecies, indicating morphological or genetic variation — not ranked and rarely used.
27
What is the “Recently Out of Africa” hypothesis?
Modern humans evolved in Africa ~300,000 years ago and spread globally by 70,000 BP. Archaic humans like Neanderthals and Denisovans went extinct or interbred with them.
28
What did the Human Genome Project (2003) reveal about race?
All humans are >99% genetically identical. Genetic variation is mostly within populations (85.4%) and only ~6% between traditional racial groups.
29
What does "cline" mean in human genetics?
Genetic variation changes gradually over geographical space (a cline), not sharply between races. There are no distinct genetic boundaries.
30
What are the evolutionary reasons for skin color variation?
- Dark skin protects against UV and folate degradation. - Light skin helps synthesize Vitamin D in low-UV areas. - Skin color is a recent adaptation and evolves rapidly.
31
What is the biological definition of sex?
Sex (the noun) refers to gamete size: males produce small sperm, females produce large eggs. Some species lack biological sexes.
32
What is sexual reproduction vs asexual reproduction?
Sexual reproduction involves the mixing of genes between two individuals (usually via sex). Asexual reproduction involves cloning without gene mixing.
33
What is hermaphroditism?
Simultaneous hermaphrodites: have both male and female organs at once. Sequential: - Protandrous: male → female - Protogynous: female → male
34
What are different sex determination systems in animals?
Mammals: XX/XY Birds: ZW/ZZ Reptiles: temperature-dependent Fish: environmental and social cues
35
What is intersex?
Individuals born with biological characteristics that do not fit typical male or female classifications (~1–2% of population). Includes chromosomal, hormonal, or anatomical differences.
36
How is sex determined in humans?
Chromosomally: XX = female, XY = male SRY gene on Y chromosome triggers testes development → testosterone → male phenotype Absence = female development
37
What determines gender identity biologically?
Likely fixed at birth and confirmed at puberty. Involves genes and hormone exposure during critical development periods.
38
What was learned from the David Reimer case?
Attempting to assign a gender different from biological sex failed, indicating gender identity is strongly biologically rooted and not learned.
39
What is 5-alpha-reductase deficiency?
A rare condition in XY individuals resulting in low testosterone. They appear female at birth but develop male traits at puberty. Illustrates hormonal effects on gender identity.
40
What is Complete Androgen Insensitivity Syndrome (CAIS)?
XY individuals with nonfunctional androgen receptors → develop as phenotypic females but are genetically male.
41
Is sexual orientation fixed at birth?
Most evidence suggests yes. Twin studies, hormone exposure, and epigenetic factors all play roles. No evidence that postnatal environment changes orientation.
42
What is the “birth order effect” in male sexual orientation?
The more older brothers a male has, the higher the likelihood of being gay. May be due to maternal immune responses affecting brain development.
43
Is there a “gay gene”?
No single gene has been definitively linked to homosexuality. Likely polygenic + hormone/environment interaction.
44
What is the “greater male variability” hypothesis?
The idea that males show more variation in traits like intelligence, leading to more men at both extremes. This is debated and strongly influenced by culture.
45
What do studies say about sex differences in math ability?
No significant differences in average performance, but slightly more males at the highest performance levels. Gender gaps narrow in more equal societies.
46
What is congenital adrenal hyperplasia (CAH)?
A genetic condition causing excess androgens. Girls with CAH show more "male-typical" play behaviors, supporting a hormonal basis for some sex differences.
47
How significant are behavioral differences between sexes?
Empathy: Women ~1 SD higher Aggression/Spatial Tasks: Men ~0.5 SD higher Toy Preferences: 2 SD Most other differences are small or shaped by culture.
48
What is the main conclusion about gender differences from neuroscience?
“The brain is no more gendered than the liver.” Small average differences, large individual overlap. Brain plasticity and environment matter.
49
What did Darwin think about gender?
Though a progressive in some ways, Darwin held sexist beliefs typical of his time, believing women to be intellectually inferior due to inheritance patterns.
50
Why is it important to study sex differences in health?
Biological sex leads to real differences in disease risk, immune function, and treatment outcomes. Historically, medical research overlooked these differences, leading to male-biased data and poorer outcomes for women.
51
Who is the 'stronger sex' biologically?
Although men have more muscle mass and upper body strength, women live longer and survive better at every age. Women also have stronger immune responses and are more resistant to most major diseases.
52
What are X-linked disorders and why are they more common in men?
Men have only one X chromosome, so any mutation (e.g., in color blindness, hemophilia, DMD) is expressed. Women must inherit two copies of the mutation to be affected.
53
Why were women excluded from many clinical trials before the 1990s?
Concerns about pregnancy, hormone fluctuation, and cost led to male-only studies. This bias resulted in poor understanding of female-specific symptoms and drug reactions.
54
What is the grandmother hypothesis?
Post-menopausal longevity in women evolved to support their children and grandchildren, increasing survival and fitness of kin — supported by data in humans and orcas.
55
Do biological races exist?
No. There are no discrete genetic boundaries among human populations. Race is a social construct, not a biological one.
56
What are the real drivers of racial health disparities?
Social determinants: poverty, access to care, diet, environmental exposure, and racism — not genetics.
57
What is the case of sickle cell disease and why is it misunderstood?
Sickle cell is often wrongly labeled a "Black disease" but is an adaptation to malaria. It occurs in populations from malaria-endemic regions across Africa, the Middle East, and southern Europe.
58
How has racial bias affected pain treatment?
Studies show Black patients are systematically undertreated for pain due to false beliefs about biological differences (e.g., thicker skin, higher pain tolerance).
59
What does “race-conscious” medicine advocate for?
Focusing on social and structural factors — not race itself — to improve care for historically marginalized groups.
60
What were the major shifts in human diet through history?
Hunter-gathering (2.5 MYA) Cooking food (1.8 MYA–400k YA) Agriculture (12,000 YA) Domesticated animals (10,000 YA) Processed foods (modern era)
61
How did cooking change human evolution?
Cooking made food more digestible, saving energy and time. It enabled larger brains and shorter guts — humans became reliant on cooked food.
62
What is the evidence for pre-agricultural plant use?
Fossilized starch granules on tools and teeth show humans ate grains and tubers at least 100,000 years ago, well before farming.
63
What dietary changes did agriculture bring?
Pros: More reliable food supply, population growth Cons: Narrower diet, shorter stature, more cavities, iron deficiency, and infectious diseases from domesticated animals.
64
How did lactase persistence evolve?
Normally, humans lose the ability to digest milk after childhood. A mutation kept lactase active in adults — it spread rapidly in dairy cultures (e.g., Europe, Africa, South Asia).
65
Why do humans have such a “needy” diet compared to other animals?
Due to our evolutionary past, mutations have made us reliant on external sources for vitamins (e.g., C, D, B12), amino acids, and minerals like iron.
66
Why don’t we make vitamin C like other mammals?
A mutation inactivated the gene for vitamin C synthesis. Natural selection didn’t eliminate it because early diets were rich in fruit. Today, this makes deficiency (scurvy) more likely without dietary intake.
67
What is the evolutionary explanation for the obesity crisis?
Mismatch between past (boom-bust food availability) and present (constant access to calorie-dense foods). We evolved to binge and store fat, which now leads to chronic disease.
68
What are better indicators of health than BMI?
Waist circumference and body fat percentage. BMI is flawed — doesn’t account for muscle, sex, or ethnicity.
69
What nutrients are most concerning for vegetarians or vegans?
Vitamin B12, iron, and complete amino acids. These can be supplemented or obtained from diverse plant sources (e.g., quinoa, chickpeas, fortified foods).
70
Why is reducing meat consumption important for the planet?
Meat (especially beef and lamb) produces high GHG emissions, uses more land and water, and creates inefficient energy transfer (90% loss per trophic level).
71
What does “eating lower on the food chain” mean?
Eating more plants and fewer animals. This reduces environmental impact and supports global food sustainability.
72
How does food contribute to climate change?
Food systems contribute 25% of global greenhouse gas emissions — roughly equivalent to transportation. Meat is a major contributor, especially due to methane from ruminants.
73
What is the sustainable diet of the future likely to include?
Less red meat More local and seasonal food Increased reliance on legumes, grains, and vegetables Possibly lab-grown meat or insect protein
74
Does evolution create perfect organisms? Why or why not?
No. Evolution is constrained by existing anatomy and variation. It makes the “best available” solutions, not optimal ones — as seen in imperfect structures like the human eye, spine, and laryngeal nerve.
75
What is the significance of the human eye in evolutionary anatomy?
Though highly complex, the retina is wired backward — photoreceptors face away from incoming light, leading to a blind spot and vulnerability to detachment. Cephalopods (e.g., octopus) have better eye design.
76
What is the recurrent laryngeal nerve and why is it inefficient?
It loops from the brain under the aorta to the larynx — a detour inherited from fish ancestors. In giraffes, the nerve is ~15 feet long!
77
What are some examples of vestigial organs in humans?
Appendix: debated function, possible immune role Coccyx (tailbone): remnant of ancestral tails Wisdom teeth: now often impacted or removed Goosebumps: once used to raise body hair for warmth or intimidation
78
What major anatomical adaptations are associated with bipedalism?
Spine curvature for balance Pelvis reshaped to support organs Femur angles inward Larger knees, glutes, Achilles tendon Arched feet for spring
79
Who was Lucy, and why is she significant?
Australopithecus afarensis (3.2 MYA), walked upright before brain enlargement. Evidence that bipedalism preceded other key human traits.
80
What problems are caused by our upright posture?
Lower back pain (40% lifetime incidence) Slipped/herniated discs ACL injuries (esp. in women) Achilles tendon rupture Painful childbirth due to narrow pelvis and big baby heads
81
What is the obstetrical dilemma hypothesis?
Suggests a trade-off between a pelvis narrow enough for walking and wide enough to birth large-brained infants, leading to difficult human labor.
82
How does human brain size compare to other mammals?
It is 7x larger than expected for our body size. While Neanderthals had slightly larger brains, our brain is more efficient (higher EQ).
83
How does the human brain grow?
Grows faster in utero and continues maturing longer than any other primate. Allows 2x as many neurons, especially in the neocortex.
84
What are some cognitive features of the brain?
Pattern detection Memory storage > recall Makes predictions to compensate for delays (e.g., in vision) Subject to bias (confirmation bias, false memories) Teen brains are more impulsive (evolutionary advantage?)
85
Why is memory not fully reliable?
Susceptible to false memories Influenced by suggestion Changes over time (e.g., 9/11 eyewitness accounts) Designed more for survival than accuracy
86
What are the three lines of defense in the immune system?
Physical barriers – skin, mucous membranes Innate immunity – immediate, nonspecific (macrophages, neutrophils) Adaptive immunity – slower, specific (B/T cells, antibodies, memory cells)
87
What’s the difference between active and passive immunity?
Active: from infection or vaccination (long-lasting) Passive: from mother (placenta, breast milk) — temporary
88
What causes autoimmune disorders?
Immune system mistakenly attacks self-cells. Includes diseases like rheumatoid arthritis, MS, Crohn’s disease. Affects ~7.5% of Americans, mostly women.
89
What is the difference between an epidemic and a pandemic?
Epidemic: local/regional outbreak Pandemic: global outbreak (e.g., COVID-19, Spanish Flu)
90
What were the deadliest pandemics in history?
Black Death (1346–53): up to 200 million Spanish Flu (1918–20): 17–100 million HIV/AIDS: 40.1 million & counting COVID-19: ~7 million as of 2023
91
How do vaccines work and why are they important?
Introduce harmless antigens → stimulate adaptive immune response. mRNA vaccines saved 14–20 million lives globally during COVID-19.
92
What lessons did COVID-19 teach us?
Vaccines and masks work Science needs good communication Social inequality affected outcomes Pandemics are more likely in the future due to dense populations, climate change, habitat encroachment
93

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