ANT 111 Study Guide Exam 1
1. Introduction to Anthropology
What is Anthropology?
The scientific study of humans, past and present, viewed holistically and comparatively.
Focuses on biological (human evolution, variation, and primatology), cultural (human societies, customs, and beliefs), linguistic (language and its role in culture), and archaeological (past human societies through material remains) aspects of human life.
Four Subfields of Anthropology
Subfield
Focus
Example
Cultural Anthropology
Human societies, customs, and beliefs, often through ethnographic fieldwork.
Studying kinship systems and marriage traditions in different cultures to understand social organization.
Biological Anthropology
Human biology, evolution, variation, and adaptability across time and space, including primatology and forensic anthropology.
Analyzing skeletal remains from an archaeological site to understand ancient diets, disease patterns, and genetic relationships.
Linguistic Anthropology
Language and its role in human communication, social life, and cultural context.
Investigating how language shapes social identity among indigenous groups or how conversational patterns reflect cultural values.
Archaeology
Past human societies through the excavation and analysis of material culture (artifacts, ecofacts, features).
Excavating stratified middens to learn about early human technology, foodways, and settlement patterns from discarded tools and refuse.
2. Biological Foundations: Cells & DNA
A. Cells: The Building Blocks of Life
Somatic Cells: Make up body tissues (e.g., skin, muscle, bone). These are diploid (contain two sets of chromosomes, one from each parent) and divide through mitosis, producing genetically identical daughter cells. Do not pass genetic changes (somatic mutations) to offspring.
Gametes: Reproductive cells (sperm and egg cells in animals). These are haploid (contain one set of chromosomes) and are formed through meiosis, a cell division process that produces genetically unique cells. Only changes in gametes (germline mutations) are inherited by offspring.
B. DNA Structure and Function
Double Helix: The iconic twisted ladder shape of DNA proposed by Watson and Crick.
Sugar-Phosphate Backbone: Forms the invariant sides or 'rails' of the ladder, providing structural support.
Nitrogenous Bases (A, T, G, C): Form the 'rungs' of the ladder. They pair specifically: Adenine (A) always pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds. This complementary pairing is crucial for replication and protein synthesis.
Genes: Specific segments of DNA located at a particular locus on a chromosome. Each gene contains the instructions (code) for synthesizing specific proteins, which in turn determine traits or regulate biological processes. These proteins are the functional units that express genetic information.
C. DNA Replication
The biological process of producing two identical replicas of DNA from one original DNA molecule. This occurs before every cell division (mitosis and meiosis) to ensure each new cell receives a complete set of genetic instructions.
Steps:
Enzymes, primarily DNA helicase, unwind and unzip the double helix by breaking the hydrogen bonds between complementary base pairs, creating a replication fork.
New, free-floating nucleotides in the nucleus pair with the exposed single-stranded bases on each original strand, guided by the enzyme DNA polymerase following the A-T, G-C rule.
Two identical DNA molecules are formed, each consisting of one original (parental) strand and one newly synthesized strand (semiconservative replication).
D. Protein Synthesis
The process by which genetic information encoded in DNA is translated into functional proteins. This is often referred to as the Central Dogma of Molecular Biology.
Transcription: The first step, where the genetic information from a gene segment on DNA is copied into a messenger RNA (mRNA) molecule. This occurs in the nucleus.
Translation: The second step, where the mRNA sequence is used as a template to build a specific sequence of amino acids, forming a protein. This occurs at ribosomes in the cytoplasm, assisted by transfer RNA (tRNA) molecules that carry specific amino acids.
Codons: Three-base sequences (triplets) found in mRNA that specify a particular amino acid or signal the start/stop of protein synthesis. Each codon corresponds to one of 20 standard amino acids.
Example: The mRNA codon AUG serves as the start codon and codes for the amino acid methionine. Other codons like UAA, UAG, and UGA are stop codons.
E. Mutations
Heritable changes in the DNA sequence. Mutations are the ultimate source of all new genetic variation and can be spontaneous (e.g., replication errors) or induced (e.g., by radiation).
Point Mutation: A change in a single nucleotide base pair within a DNA sequence.
Example: GCACAA → GCACCA (a substitution where A is replaced by C). These can lead to: silent mutations (no change in amino acid), missense mutations (change to a different amino acid), or nonsense mutations (change to a stop codon, prematurely terminating protein synthesis).
Frameshift Mutation: An insertion or deletion of nucleotides that are not in multiples of three. This shifts the 'reading frame' of the mRNA codons downstream from the mutation, drastically altering the amino acid sequence and usually leading to a non-functional protein.
Chromosomal Mutations: Large-scale changes affecting entire chromosomes or significant portions of them. These include deletions (loss of a segment), duplications (repetition of a segment), inversions (reversal of a segment), and translocations (movement of a segment to a different chromosome).
3. Mendelian Genetics
A. Gregor Mendel’s Experiments
An Austrian monk who conducted groundbreaking studies on inheritance using garden pea plants (Pisum sativum) with clearly defined, dichotomous traits (e.g., tall vs. short height, smooth vs. wrinkled seeds, green vs. yellow pods).
Key Findings:
Traits are inherited as discrete units (which we now call genes), rather than blending.
He proposed the concepts of dominant traits (e.g., tallness, denoted by 'T'), which mask the expression of recessive traits (e.g., shortness, denoted by 't') when both are present.
His experiments demonstrated a predictable 3:1 phenotypic ratio in the F2 generation after crossing two heterozygous parents (e.g., 3 tall plants: 1 short plant). This led to his two fundamental laws:
Law of Segregation: During gamete formation, the two alleles for a heritable character separate (segregate) from each other so that each gamete carries only one allele.
Law of Independent Assortment: Alleles for different genes (e.g., seed color and seed shape) assort independently of each other during gamete formation, meaning the inheritance of one trait does not influence the inheritance of another.
B. Genotype vs. Phenotype
Term
Definition
Example
Genotype
The specific genetic makeup or allele combination of an individual for a particular trait. It describes the internally coded, heritable information.
For pea plant height, possible genotypes are: TT (homozygous dominant), Tt (heterozygous), tt (homozygous recessive).
Phenotype
The observable physical or biochemical characteristics of an organism, resulting from the interaction of its genotype with the environment. It's the expressed trait.
For pea plant height, the phenotypes are: Tall plant (resulting from TT or Tt genotypes) or Short plant (resulting from tt genotype).
C. Punnett Squares
A diagrammatic tool used to predict the possible genotypes and phenotypes of offspring resulting from a genetic cross. It illustrates the combinations of alleles that can be passed from parents to offspring.
Example: Cross between Tt \times Tt (two heterozygous tall plants):
T t
--------
T | TT | Tt
--------
t | Tt | tt
- **Possible offspring genotypes**: **25\%** **TT** (homozygous tall), **50\%** **Tt** (heterozygous tall), **25\%** **tt** (homozygous short).
- **Possible offspring phenotypes**: **75\%** Tall plants, **25\%** Short plants (giving the characteristic 3:1 phenotypic ratio).
D. Inheritance Patterns
Pattern
Description
Example
Dominant/Recessive
One allele (dominant) completely masks the expression of another allele (recessive) in a heterozygote. The recessive trait only appears when two copies of the recessive allele are present.
In pea plants, Tall (T) is dominant over short (t). Huntington's disease in humans follows an autosomal dominant pattern.
Codominance
Both alleles in a heterozygote are fully and separately expressed, resulting in a phenotype that shows characteristics of both alleles simultaneously.
Human AB blood type, where both I^A and I^B alleles are expressed, producing both A and B antigens on red blood cells.
Incomplete Dominance
Neither allele is completely dominant over the other, resulting in a blended or intermediate phenotype in the heterozygote.
When a true-breeding red flower (RR) is crossed with a true-breeding white flower (WW), the offspring (RW) have pink flowers.
4. Beyond Mendel: Complex Traits
A. Polygenic Traits
Traits that are controlled by multiple genes at different loci, each contributing a small, additive effect to the phenotype. These traits typically vary along a continuum rather than in discrete categories.
Show continuous variation (a range of phenotypes rather than distinct categories), often represented by a bell curve in a population.
Examples: Human height, skin color, hair color, eye color, intelligence, and predisposition to many common diseases like heart disease or diabetes.
B. Environmental Influence
The environment plays a significant role in modifying the expression of genes, demonstrating that phenotype is a result of both genotype and environmental factors.
Phenotypic Plasticity: The ability of one genotype to produce different phenotypes when exposed to different environmental conditions, allowing organisms to adapt to varying circumstances.
Example: Himalayan rabbits have a gene for fur pigment that is only active at lower temperatures. They develop dark fur in cold body areas (like ear tips, nose, paws) but white fur in warmer areas, demonstrating how temperature influences gene expression.
Other examples: Nutrition influencing height potential, sunlight affecting skin pigmentation, or exercise influencing muscle mass.
C. Heritability
A statistical measure that estimates the proportion of phenotypic variation in a population that is due to genetic variation, rather than environmental influences. It is specific to a population and environment.
Height: Estimated to be \sim60-80\% heritable, meaning a large portion of individual differences in height within a population can be attributed to genetic factors, but environmental factors like nutrition still play a role.
IQ: Estimated to be \sim30-75\% heritable, indicating a substantial genetic component, but the environment (e.g., education, nutrition, social stimulation) plays an equally significant, if not more, role in cognitive development.
Important note: Heritability is a population-level statistic and does not refer to the proportion of a trait that is genetic in an individual. A high heritability does not mean the trait is unchangeable by the environment.
5. Evolutionary Mechanisms
A. Forces of Evolution
Force
Description
Example
Mutation
Random, spontaneous changes in the DNA sequence. Mutations are the ultimate source of all new genetic variation (new alleles) in a population, providing the raw material for other evolutionary forces to act upon.
The sickle cell mutation (a single point mutation in the beta-globin gene) arose independently multiple times and provides resistance to malaria in heterozygotes.
Gene Flow
The movement of alleles between populations through migration and subsequent interbreeding of individuals. It tends to reduce genetic differences between populations and can introduce new alleles into a population.
When individuals from one population (e.g., a city) migrate and interbreed with individuals from another population (e.g., a rural village), new alleles are introduced into the recipient gene pool, increasing genetic diversity.
Genetic Drift
Random fluctuations in allele frequencies from one generation to the next, particularly pronounced in small populations. It can lead to the loss of alleles or the fixation of others, purely by chance.
Founder effect in Amish populations: A small group of German founders carried a rare allele for Ellis-van Creveld syndrome (a form of dwarfism) at a higher frequency than the general population. Due to their reproductive isolation, this allele increased in frequency within the Amish community.
Bottleneck effect: A drastic reduction in population size (e.g., due to a natural disaster) can lead to a random subset of alleles surviving, reducing genetic diversity.
Natural Selection
The differential survival and reproduction of individuals based on their phenotypic traits. Traits that enhance an individual's fitness (survival and reproductive success) in a given environment tend to become more common in subsequent generations.
Lactase persistence in dairy-farming populations: Individuals with a genetic mutation allowing them to digest lactose into adulthood had a nutritional advantage in cultures relying on fresh milk, leading to the increased frequency of this trait over generations.
B. Types of Natural Selection
Type
Description
Example
Directional Selection
Favors one extreme phenotype over the average or other extreme within a population. It leads to a shift in the population's phenotypic average over time.
Giraffes with longer necks were favored in environments where food sources were higher up, leading to an increase in average neck length in the population over time.
Stabilizing Selection
Favors intermediate or average phenotypes and selects against extreme variations. This reduces phenotypic variation and maintains the status quo in a population that is well-adapted to its environment.
Human birth weight: Babies born with an average weight (around \sim7 lbs) have higher survival rates than those born significantly smaller or larger, leading to the preservation of intermediate birth weights.
Disruptive Selection
Favors individuals at both extremes of the phenotypic range over intermediate phenotypes. This can lead to the divergence of phenotypes within a population and may be a step towards speciation.
Finch beak sizes: In an environment with two distinct food sources—small seeds and large, hard seeds—finches with large beaks (for crushing hard seeds) and finches with small beaks (for manipulating small seeds) are favored, while finches with medium beaks are at a disadvantage.
C. Speciation
The evolutionary process by which new biological species arise from existing species. It involves the splitting of a single evolutionary lineage into two or more distinct species that can no longer interbreed.
Allopatric Speciation: Occurs when populations are geographically isolated (e.g., by a mountain range, river, or ocean). This physical barrier prevents gene flow, allowing independent evolutionary paths to diverge due to mutation, genetic drift, and local natural selection, eventually leading to reproductive isolation.
Example: Darwin’s finches on different Galápagos Islands. Each island presented unique environmental pressures, leading to distinct beak sizes and shapes adapted to local food sources, eventually resulting in multiple distinct species unable to interbreed.
Sympatric Speciation: Occurs when new species arise within the same geographic area as the parent species, without physical isolation. This can happen through polyploidy (common in plants), sexual selection, or habitat differentiation.
6. Human Adaptation and Variation
A. Biological Adaptations
Adaptation
Description
Example
Bergmann’s Rule
Within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. This is because larger bodies have a smaller surface area-to-volume ratio, which helps conserve heat.
Polar bears (large body mass, small surface area) are adapted to arctic cold, while desert foxes (smaller body mass, larger surface area) are adapted to dissipating heat in warm climates.
Allen’s Rule
Individuals in colder climates tend to have shorter limbs (or appendages like ears, tails, and bills) than individuals in warmer climates. Shorter limbs reduce the surface area exposed to cold, minimizing heat loss.
Inuit populations often exhibit relatively shorter limbs and stockier builds, which are adaptations that help conserve body heat in cold arctic environments compared to populations in warmer equatorial regions.
Sickle Cell Trait
Individuals who are heterozygous for the sickle cell allele (AS genotype) have a protective advantage against severe forms of malaria, which is a significant selective pressure in tropical regions. While homozygous individuals (SS) suffer from sickle cell anemia, the heterozygote advantage maintains the allele in the population.
Common in sub-Saharan Africa, parts of the Middle East, and India—regions where malaria is or was endemic. The sickle cell allele provides a clear example of balanced polymorphism in these populations.
B. Lactase Persistence
The continued ability to digest lactose (the sugar in milk) into adulthood, beyond the typical weaning period of infancy. Most adult mammals lose the ability to produce lactase enzyme after weaning.
Evolutionary Advantage: The ability to digest fresh milk as an adult offered a significant nutritional advantage in populations that began dairy farming approximately 9,000 to 10,000 years ago. Access to a readily available, high-calorie, and nutrient-rich food source favored individuals with the lactase persistence allele, leading to its rapid spread in these populations.
This is a prime example of gene-culture co-evolution, where a cultural practice (dairy farming) drove a genetic change (lactase persistence) in human populations.
C. Balanced Polymorphism
A situation where two or more alleles for a specific gene are maintained in a population at relatively stable frequencies over generations, often because heterozygotes have a higher fitness than either homozygote (known as heterozygote advantage).
Example: The sickle cell trait (heterozygous AS genotype) in malaria-prone regions. While homozygous normal individuals (AA) are susceptible to malaria and homozygous sickled individuals (SS) suffer from sickle cell anemia, the AS heterozygotes are resistant to malaria and do not suffer from severe anemia, thus having the highest fitness. This maintains both the normal and sickle cell alleles in the population.
7. Human Life History and Senescence
A. Life History Stages
Infancy/Childhood: Characterized by rapid growth, brain development, prolonged dependency on parents for care and provisioning, and a relatively long juvenile period facilitating learning and cultural transmission. Weaning typically occurs during infancy.
Adolescence: A unique human stage marked by a significant pubertal growth spurt and the development of secondary sexual characteristics, leading to reproductive maturity. This phase allows for further learning and social integration before full adult responsibilities.
Adulthood: Typically the period of peak reproductive years, parenting, and resource acquisition. Adults contribute significantly to the group's survival and reproduction.
Senescence: The biological process of aging, characterized by a gradual decline in physiological function, an increase in disease susceptibility, and a decline in fertility (eventually leading to menopause in human females).
B. Grandmother Hypothesis
A well-supported hypothesis suggesting that the extended post-reproductive lifespan of human females (menopause) evolved because older women (grandmothers) contribute significantly to the fitness of their offspring by helping to raise grandchildren. This increases the survival and reproductive success of their children's offspring.
Evidence: Grandmothers can provide food, childcare, share accumulated knowledge, and offer support, allowing their daughters to have more children or space births more closely, thereby increasing the number of surviving descendants.
8. Scientific Method in Anthropology
A. Steps of the Scientific Method
Observation: Identifying a phenomenon or asking a specific, testable question based on observations of the natural world. (e.g., "Why do some human populations maintain the ability to digest lactose into adulthood while others do not?").
Hypothesis: Proposing a tentative, testable explanation for the observed phenomenon. A good hypothesis is falsifiable. (e.g., "Dairy farming practices exerted selective pressure favoring lactase persistence alleles in human populations.").
Experiment/Data Collection: Designing and conducting a study to test the hypothesis, gathering empirical data through systematic observation, controlled experiments, or comparative studies. (e.g., Compare the frequency of lactase persistence alleles in populations with a long history of dairy farming versus those without, while controlling for confounding variables).
Analysis: Interpreting the collected data using statistical and analytical methods to identify patterns, relationships, and trends.
Conclusion: Formulating a conclusion that states whether the data support or reject the hypothesis. This step often leads to new questions and further research.
B. Evolutionary Theory
A unifying framework in biology that explains the diversity of life on Earth. It posits that all species are descended from common ancestors and have diversified over time through a process primarily driven by natural selection.
Charles Darwin: Jointly with Alfred Russel Wallace, proposed the mechanism of natural selection as the primary driver of evolutionary change in his monumental work On the Origin of Species by Means of Natural Selection (1859).
Key Points of Natural Selection:
Variation: Individuals within a population exhibit heritable variations in their traits.
Inheritance: These variations can be passed from parents to offspring.
Overproduction: Organisms produce more offspring than can survive to reproduce, leading to a struggle for existence.
Differential Survival and Reproduction (Fitness): Individuals with traits that are better suited to their environment (adaptive traits) are more likely to survive, reproduce, and pass on those advantageous traits to the next generation, making them more common over time. This leads to adaptation.
9. Critical Thinking Questions
Genetics:
How would you use a Punnett square to predict the offspring of two heterozygous parents (Aa × Aa) and what are the expected genotypic and phenotypic ratios?
What is the precise difference between a homozygous individual (e.g., AA or aa) and a heterozygous individual (e.g., Aa), particularly in terms of allele composition and expression?
Evolution:
How does genetic drift fundamentally differ from natural selection in terms of the underlying mechanisms driving changes in allele frequencies and the role of adaptation?
Why is the sickle cell allele maintained in populations where malaria is common, even though its homozygous form can cause a severe genetic disease (sickle cell anemia)? Explain the concept of heterozygote advantage.
Human Variation:
How do Bergmann’s Rule and Allen’s Rule scientifically explain observed differences in body size and shape among human populations living in different climatic zones, relating to thermoregulation?
What specific types of evidence (e.g., demographic, historical) support the Grandmother Hypothesis as an evolutionary explanation for post-menopausal longevity in human females?
Adaptation:
How does lactase persistence in human populations serve as a compelling example of gene-culture co-evolution, illustrating how cultural practices can exert selective pressure on the human genome?
Why is phenotypic plasticity considered an important adaptive mechanism for human survival, especially in environments that are variable or unpredictable?
10. Practice Problems
A. Punnett Square Practice
Cross a heterozygous tall (Tt) pea plant with a homozygous short (tt) pea plant. Draw the Punnett square and list all possible genotypes and phenotypes of the offspring, along with their respective probabilities.
B. Natural Selection Scenario
In a population of moths, dark-colored moths are more common in polluted industrial areas, while light-colored moths are more common in clean, unpolluted areas. Explain this phenomenon using the principles of natural selection, discussing how environmental changes influence survival and reproduction.
C. Heritability Calculation
If the heritability of height in a particular human population is estimated to be 80%, what does this statistic precisely tell you about the relative roles of genetics versus environment in determining height within that population? Does it mean 80% of an individual's height is due to genes?
11. Key Terms to Master
Term
Definition
Allele
A variant form of a gene, occupying a specific locus on a chromosome. For example, for the gene determining pea plant height, T (tall) and t (short) are alleles.
Locus
The specific physical location or position of a gene or other DNA sequence on a chromosome. Plural: loci.
Mitosis
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth and repair. It produces diploid, genetically identical somatic cells.
Meiosis
A type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores. It produces haploid, genetically unique gametes (sperm/egg).
Heritability
The proportion of observed phenotypic variation in a population that is attributable to genetic variation among individuals, ranging from 0 (all environmental) to 1 (all genetic).
Founder Effect
A special type of genetic drift that occurs when a new population is established by a very small number of individuals from a larger population. This new population's gene pool may have a reduced genetic diversity and a different allele frequency from the original population, purely by chance.
Balanced Polymorphism
A situation where natural selection maintains stable frequencies of two or more alleles in a population, often because heterozygotes have a higher fitness than either homozygote (heterozygote advantage).
12. Visual Aids
A. Punnett Square Example
T t
--------
T | TT | Tt
--------
t | Tt | tt
This Punnett square represents a cross between two heterozygous parents (Tt \times Tt). The possible offspring genotypes are: 25% TT, 50% Tt, and 25% tt. Phenotypically, this results in 75% Tall and 25% Short offspring.
B. Natural Selection in Action
Example: The classic case of Peppered Moths (Biston betularia) in industrial England.
Before pollution: Light-colored moths were camouflaged on lichen-covered tree trunks, making them less visible to bird predators. Dark-colored moths were rare and easily spotted.
During industrial pollution: Soot from factories darkened tree trunks, killing lichens. Now, the dark-colored moths were camouflaged, and the light-colored moths were easily seen. This led to a rapid increase in the frequency of dark moths and a decrease in light moths, demonstrating directional selection.
After pollution control: With environmental regulations, lichens returned and tree trunks lightened, reversing the selective pressure and leading to an increase in light-colored moths again.
13. Exam Tips
Understand concepts: Don’t just memorize terms—strive for a deep understanding of how and why biological processes and evolutionary mechanisms work the way they do.
Practice Punnett squares: Regularly draw them for various crosses involving different inheritance patterns (e.g., dominant/recessive, codominance) to master predicting offspring genotypes and phenotypes.
Relate to real life: Connect abstract concepts (like lactase persistence, sickle cell trait, or Bergmann's/Allen's rules) to tangible examples in human evolution and variation. Ask yourself why these adaptations occurred.
Review lecture slides: Pay special attention to bolded terms, key definitions, and specific examples discussed by your instructor, as these often highlight crucial points.
This comprehensive guide covers everything you need for your exam, from basic genetics to complex evolutionary concepts. Use it to test your understanding, practice problems, and connect ideas across topics. Good luck!