Human Evolution - Ch. 58 - Natural Selection in Modern Humans Flashcards
What are four examples of natural selection in modern humans?
Skin colour, malaria resistance, lactase persistence, and menopause
Did humans evolve from chimpanzees?
No. Chimpanzees (and bonobos) are the group of modern species that we share the most recent common ancestor with.
Have humans stopped evolving?
No. Some examples of natural selection that cause human evolution include: malarial resistance, skin colour, menopause, and lactase persistence
What is wrong with the statement: “The human mind is too complex to have evolved”
- Complexity is hard to define.
2. This ‘complexity’ has evolved across many different groups over time.
What is the fitness tradeoff for having darker skin vs. fairer skin?
Darker skin offers better UV protection (so against mutations that lead to cancer, and against folate breakdown)
Lighter skin offers better vitamin D absorption
Define natural selection in 2 steps.
(1. ) Heritable phenotypic variation among individuals in a population
(2. ) leads to differential survival and reproductive success among individuals in the population
What is the name of pigment that determines skin colour? What produces that pigment?
melanin; melanocytes
Is folate an essential or non-essential vitamin?
essential
Is vitamin D an essential or non-essential vitamin?
non-essential
What can folate deficiency result in?
lower reproductive success, or infertility
What makes a nutrient essential?
the human body must gain the nutrient by diet, i.e., it cannot synthesize the nutrient
What species cause malaria in humans?
5 species of Plasmodium
What are two forms of Hemoglobin (Hb)? Which one is the common form, and which is mutant?
Hemoglobin A (HbA) and Hemoglobin S (HbS). HbA is common, HbS is the mutant form
A human with the deadly sickle-cell disease has what two alleles?
Homozygous HbS HbS
A human with resistance to malaria has what two alleles?
Heterozygous HbA HbS
(In regions where malaria is endemic)
When the HbS allele is rare, natural selection selects (for/against) heterozygous individuals.
When the HbS allele is increasingly common, natural selection selects (for/against) heterozygous individuals.
When the HbS allele is rare, natural selection selects FOR heterozygous individuals.
When the HbS allele is increasingly common, natural selection selects AGAINST heterozygous individuals.
What term is described by: “the ability of an individual to contribute viable offspring to the next generation, compared to others within its population”
biological fitness
What is “menopause”?
The time in which human females stop menstruating, permanently, or the longevity of an organism long past its reproductive age
What are the 3 hypotheses under the Theory for the Origin of Human Menopause?
lifespan artifact hypothesis, grandmother hypothesis, and mating behaviour hypothesis
What does the lifespan artifact hypothesis suggest? What is its problem?
The lifespan artifact hypothesis suggests that menopause evolved due to increased longevity in humans (because of tools, cooking, medicine, etc.).
Problem: why did male fertility become extended with longevity?
What does the grandmother hypothesis suggest?
What is its problem?
The grandmother hypothesis suggests that a mother contributes care to her children’s offspring, thus increasing the number of her grandchildren who survive to reproductive maturity.
Problem: how many children must be produced by a woman’s offspring to replace each missed opportunity for the woman to produce another child of her own? (how to overcome steep selection gradient?)
What does the mating behaviour hypothesis suggest?
What is its problem?
The mating behaviour hypothesis suggests that menopause evolved due to a change in mating behaviour—involving only young adult females and adult males. [Could be male preference (nonadaptive) or intergenerational female competition (sexual selection).]
Problem: The computer simulations suggested that tens or even hundreds of thousands of years would have been required for female-specific late-onset fertility-diminishing mutations to have accumulated and ultimately produce a menopause phenotype. We may not have had an extended lifespan for that long of a time period to accumulate such mutations.
Lactose is a disaccharide made up of what two monosaccharides?
glucose and galactose
What is milk?
The primary food source for young mammals: a nutrient-rich liquid containing proteins, lipids, carbs, vitamins, and minerals. It is produced by mammary glands
