Biological Anthropology Exam #1

What is Essentialism (Plato)?

Species have fixed “essences” that do not change.

What is the Great Chain of Being (Aristotle)?

Hierarchical ordering of life forms from simple to complex, with humans at the top.

What is the Fixity of Species?

Belief that species were created by God and remained unchanged (Medieval Europe).

What was the Young Earth Hypothesis?

Calculated Earth to be ~6,000 years old (Archbishop Ussher, 1650; created 4004 BCE).

Who proposed the heliocentric solar system?

Copernicus & Galileo. the planets revolve around the sun

Who advocated empirical observation and rational inquiry?

Francis Bacon & René Descartes.

Who introduced the concept of “species”?

John Ray (reproductively isolated groups).

Who developed binomial nomenclature?

Carl Linnaeus developed the binomial nomenclature system in the 1750s. His system established the convention of using a two-part, Latinized name (genus and species) for each organism, which provided a standardized method for classifying and naming all species.

Who suggested species could change due to environment?

Comte de Buffon.

Who had early ideas of common ancestry and gradual change?

Erasmus Darwin.

Who proposed inheritance of acquired characteristics?

Jean-Baptiste Lamarck.

Who established natural selection as a mechanism of evolution?

Charles Darwin.

What key influences shaped Darwin’s theory?

Lyell’s Uniformitarianism and Malthus’ Essay on Population.

Who co-discovered natural selection with Darwin?

Alfred Russel Wallace.

What is the Modern Synthesis?

Combines natural selection + Mendelian genetics + population biology

Who argued for Uniformitarianism? What is Uniformitarianism?

Charles Lyell, states that the Earth's present geological processes are the key to understanding its past and that these processes occur gradually and consistently over vast periods

What are the principles of Natural Selection?

Overproduction, variation, heritability, differential reproduction.

Difference between prokaryotes and eukaryotes?

Prokaryotes lack a nucleus; eukaryotes have a nucleus and organelles. Prokaryotic cells, such as bacteria and archaea, have their genetic material (DNA) located freely in the cytoplasm, not within a membrane-bound nucleus. In contrast, eukaryotic cells, found in plants, animals, fungi, and protists, contain a well-defined nucleus that encloses the DNA and also possess other specialized, membrane-bound internal structures called organelles.

What organelle produces energy and has maternal DNA?

Mitochondria

What organelle makes proteins?

Ribosomes

Who discovered DNA’s structure?

Watson & Crick, with Rosalind Franklin’s X-ray crystallography.

What are DNA base pairs?

A–T, C–G.

How many chromosomes do humans have?

46 (23 pairs).

Difference between mitosis and meiosis?

Mitosis produces two genetically identical diploid (2n) somatic cells for growth and repair, while meiosis produces four genetically unique haploid (n) gametes for sexual reproduction by reducing chromosome number and increasing genetic diversity through crossing over.

What is crossing over?

Crossing over is the physical exchange of segments of genetic material between homologous chromosomes during meiosis. This process occurs in prophase I and results in recombinant chromosomes that have new combinations of genes, leading to increased genetic diversity in the gametes (egg and sperm) and, subsequently, in the offspring. 

What is the central dogma?

The Central Dogma of molecular biology is the principle that genetic information flows in one direction, from DNA to RNA to protein, a process that can be summarized as DNA → RNA → Protein. It describes how a cell uses the instructions in DNA to create functional proteins, with the key steps being transcription (DNA to RNA) and translation (RNA to protein).

What is a codon?

A codon is a sequence of three consecutive nucleotides in a strand of DNA or RNA that acts as a unit of genomic information. Each codon corresponds to a specific amino acid or provides a signal for the cell to either start or stop protein synthesis. The entire set of codons and their corresponding amino acids forms the genetic code. 

Example of point mutation?

Sickle cell anemia is a classic example of a point mutation, where a single change in the DNA sequence of the beta-globin gene results in the substitution of glutamic acid with valine at the sixth position, leading to the formation of abnormal hemoglobin that causes red blood cells to sickle shape under low oxygen conditions. 

Who discovered inheritance patterns with pea plants?

Gregor Mendel

Mendel’s Laws?

1. The Law of Segregation

• What it means:

  Each individual has two alleles (versions of a gene) for a trait. During the formation of sex cells (gametes), these two alleles separate from each other. 

• Result:

  Each gamete receives only one allele for that trait. Offspring receive one allele for each trait from each parent. 

• Example:

  If a pea plant has alleles for tallness (T) and shortness (t), its gametes will either carry a T or a t allele. 

2. The Law of Independent Assortment

• What it means: Genes for different traits are inherited independently of one another. 

• Result: The allele inherited for one trait does not influence the allele inherited for another trait. 

• Example: A pea plant's height (tall or short) does not affect the shape of its seeds (round or wrinkled). The inheritance of seed shape is independent of the inheritance of plant height. 

What is codominance?

In biology, codominance is an inheritance pattern where both alleles (versions of a gene) in a heterozygous individual are equally and fully expressed in the phenotype, rather than blending or one masking the other. This results in a characteristic that shows features of both alleles, such as the AB blood type, where both A and B antigens are present on red blood cells, or a flower with distinct red and white spots from codominant alleles for each color. 

What is polygenic inheritance?

Traits influenced by many genes (e.g., height).

What is epigenetics?

Epigenetics is the study of heritable changes in gene expression that occur without altering the underlying DNA sequence. These changes, which are influenced by factors like environment, behavior, and diet, act like molecular "switches" or "tags" that can turn genes on or off, affecting a cell's function and potentially an organism's traits and susceptibility to disease. 

What is microevolution?

Microevolution is the change in allele frequencies within a population over generations, which can be caused by mutation, gene flow, genetic drift (bottleneck and founder effects), and natural or artificial selection. These small-scale evolutionary changes, which are often directly observable over short periods, accumulate to produce larger-scale macroevolutionary changes over vast geological timescales.  

What are the mechanisms of microevolution?

Mutation, gene flow, genetic drift, natural selection

What is the founder effect?

Loss of variation when a new population is founded by a small group.

What is a bottleneck effect?

The bottleneck effect is a phenomenon in which a population's size is dramatically reduced, leading to a significant loss of genetic diversity and potentially altering the genetic makeup of the remaining population.

What is macroevolution?

Macroevolution describes large-scale evolutionary changes occurring above the species level, focusing on major shifts and trends in life's history over long periods. It encompasses phenomena like the origin of new taxonomic groups (such as mammals), mass extinctions, and significant transformations in the evolutionary tree of life.

Evidence for macroevolution?

Fossils, comparative anatomy, molecular & developmental biology.

What is clinal variation?

Clinal variation describes the gradual, continuous change in a species' biological traits across geographic space, driven by environmental transitions such as temperature or altitude

What is Bergmann’s Rule?

Bergmann's rule suggests that, within the same species, individuals in colder climates tend to be larger, while those in warmer climates are smaller, as a way to conserve or dissipate heat, respectively.

What is Allen’s Rule?

The principle holding that in a warm-blooded animal species having distinct geographic populations, the limbs, ears, and other appendages of the animals living in cold climates tend to be shorter than in animals of the same species living in warm climates.

Why dark skin in high UV areas?

Dark skin offers protection in high-UV environments because melanin, a pigment produced by melanocytes, absorbs and scatters damaging UV rays, preventing them from harming DNA and essential nutrients like folate. This adaptation is a result of natural selection, where individuals with more melanin had a survival advantage against severe UV-related damage, such as sunburn and skin cancer, leading to the evolution of darker skin in populations living near the equator. 

Why light skin in low UV areas?

Light skin is an adaptation to low-UV (ultraviolet) environments because it facilitates the production of Vitamin D, a crucial nutrient that requires UV-B rays for synthesis in the skin. In high-UV environments, dark skin protects against harmful UV radiation by blocking its penetration, preserving essential folate, while also allowing sufficient Vitamin D synthesis. Light skin evolved as a trade-off, allowing for necessary Vitamin D production in environments with less sunlight, even though it offers less protection against the damaging effects of UV radiation. 

What is hypoxia?

Hypoxia is a condition in which the body's tissues do not receive enough oxygen. It occurs when there is a decrease in the partial pressure of oxygen in the blood or tissues, which occurs in high altitudes.

Genetic adaptation in Tibetans at high altitudes?

• EPAS1 Gene:This is the most well-known adaptation. A specific variant of EPAS1 allows Tibetans to use oxygen more efficiently at high altitudes, leading to lower hemoglobin levels compared to other populations. 

What is lactase persistence?

Lactase persistence (LP) is defined as the lifelong ability to produce the enzyme lactase, allowing for the digestion of lactose beyond early childhood.

Why does sickle cell trait persist?

Sickle cell trait persists because it provides a significant selective advantage against malaria in regions where the disease is prevalent

What are cultural adaptations?

Cultural adaptation is the process by which people, individuals or groups, adjust their behaviors, beliefs, and practices to better fit the demands of a new environment or the norms of a different culture.

Types of natural selection?

Directional selection shifts a population's average traits toward one extreme. Stabilizing selection favors intermediate traits, reducing variation in the population. Disruptive (or diversifying) selection favors extreme traits at both ends of a spectrum, increasing variation and potentially leading to speciation. 

How does meiosis generate variation?

Meiosis generates genetic variation through two primary mechanisms: crossing over and independent assortment. Crossing over involves the exchange of genetic material between homologous chromosomes, creating new allele combinations. Independent assortment refers to the random orientation and distribution of homologous chromosome pairs during metaphase I, leading to a unique mix of maternal and paternal chromosomes in each resulting gamete.