HBIO-300: Evolution Quiz (09-14, Monday)

Genotype

The genetic makeup of an individual organism.

Phenotype

The observable physical or physiological traits of an individual resulting from the interaction between its genotype and the environment.

Primary functions of DNA

Cellular replication (acting as the unit of inheritance) and protein synthesis (carrying instructions to produce cellular components).

Components of a nucleotide

A phosphate group, a deoxyribose sugar, and a nitrogenous base.

Four nitrogenous bases in DNA

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

Transcription

The process in protein synthesis where a single-stranded RNA molecule is produced from a DNA template in the nucleus.

Splicing

The process where non-coding stretches of RNA (introns) are removed, leaving only coding sequences (exons) to form mRNA.

Translation

The process in protein synthesis where mRNA is read to assemble a chain of amino acids into a protein in the cytoplasm.

Number of chromosomes in a standard human cell

46 chromosomes, arranged in 23 pairs.

Autosomes

Chromosomes in pairs 1 through 22 that determine general body traits and make up the majority of the genome.

Sex chromosomes

The 23rd pair of chromosomes (X and Y) responsible for sex determination; females have XX and males have XY.

Meiosis

A specialized cell division producing 4 genetically non-identical haploid gametes, each containing 23 chromosomes in humans.

Fertilization

The union of a haploid egg and sperm to restore the diploid number of 46 chromosomes in a zygote.

Crossing over

The exchange of genetic material between adjacent non-sister chromatids of homologous chromosomes during Prophase I of meiosis.

Random assortment

The random alignment and reshuffling of maternal and paternal chromosomes along the cell equator during Metaphase I of meiosis.

Mutation

A random, spontaneous change in the structure, arrangement, or quantity of DNA on a chromosome.

Germ cell mutation

A mutation occurring in sex cells (gametes) that can be transmitted to offspring.

Gene flow (Migration)

The transfer of genes/alleles between previously independent populations, reducing genetic differences between them.

Polymorphism

A genetic locus that has two or more alleles present in at least 1% of the population.

Blood group polymorphism

Variation based on distinct surface proteins on red blood cells (e.g., A, B, AB, O).

Short Tandem Repeats (STRs)

Short DNA sequences that are repeated multiple times, where individuals vary in the number of repeats.

Single Nucleotide Polymorphisms (SNPs)

Specific positions in the genome where individuals differ by a single base pair.

Human genetic variance relative to great apes

Humans possess significantly lower total genetic variation and lower genetic differentiation than non-human great apes.

Approximate number of SNPs in humans vs. common chimpanzees

Humans have about 9 million SNPs, whereas common chimpanzees have about 27 million SNPs.

Reason for low human genetic diversity despite a large global population

A recent human population bottleneck (~65,000 to 90,000-50,000 years ago) involving a small African founding group.

Distribution of human genetic variation

Approximately 87% to 94% of human genetic variation is found WITHIN major geographic regions, with only a small fraction existing BETWEEN regions.

Geographic pattern of within-group human STR variation

Within-population genetic diversity continuously decreases with increasing geographic distance from eastern Africa due to serial founder effects.

Relationship between genetic distance and geographic distance in humans

Pairwise genetic distance between human populations increases proportionally with geographic distance, reflecting reduced gene flow.

Phenotypic variation in human skull form

Most skull variation (85-95%) is found within populations, matching neutral genetic expectations and decreasing in diversity with distance from sub-Saharan Africa.

Phenotypic variation in human skin color

Most skin color variation (about 88%) is found BETWEEN geographic groups, deviating from neutral patterns due to strong natural selection/adaptation.

Definition of Ecology

A branch of biology dealing with the relationships of organisms to one another and to their physical surroundings.

Definition of Habitat

The natural environment in which a species lives and thrives.

Definition of Niche

The role or function of a species within an ecosystem.

Definition of Ecosystem

A community of interacting organisms and their physical environment.

Typological approach

An outdated 18th/19th-century scientific framework that viewed species as fixed, idealized types, treating variation as noise or deviation.

Holotype

The single representative specimen used to formally name and describe a new species under zoological nomenclature rules.

Carolus Linnaeus's Systema Naturae (1758)

The foundational text for binomial nomenclature that classified human racial groups into rigid, stereotyped, and hierarchical categories.

Population approach

The modern scientific framework that views groups as collections of unique individuals exhibiting continuous, overlapping variation without discrete boundaries.

Discrete (Qualitative) traits

Traits controlled by one or two genes that fall into clear, non-overlapping categories (e.g., ABO blood type).

Continuous (Quantitative) traits

Polygenic traits controlled by many genes and environmental factors, exhibiting a wide, graded spectrum of variation (e.g., height).

WEIRD population bias

The overrepresentation of Western, Educated, Industrialized, Rich, and Democratic societies, which make up 12% of the global population but over 80% of biomedical research samples.

Historical vs. modern average human body temperature

Established as 98.6°F (37°C) by Wunderlich in 1851, but modern global averages sit closer to 97.9°F (36.6°C).

Key influences on Darwin's formulation of natural selection

Global biodiversity observations on the HMS Beagle, South American fossils, Galápagos finch variations, Malthus's essay on population growth, and plant/animal breeding.

Thomas Malthus's core premise in 'An Essay on the Principle of Population'

Human populations grow exponentially while food production increases linearly, creating a struggle for existence.

Biological Evolution

A change in the allele frequencies or genetic makeup of a population over time.

Unit of evolution

The population (individuals do not evolve; their genotypes remain constant throughout life).

Four main forces of evolution

Mutation, Natural Selection, Genetic Drift, and Gene Flow.

Genetic drift

Random changes in allele frequencies within a population due to chance events, independent of natural selection.

Founder Effect

A form of genetic drift occurring when a small, isolated subset of a population migrates to establish a new population with a restricted gene pool.

Population Bottleneck

A drastic reduction in population size for at least one generation, significantly reducing genetic diversity.

Inbreeding

Non-random mating between biologically related individuals, which increases homozygosity across all loci and can expose deleterious recessive traits.

Sexual selection

A mechanism where differential reproductive success results from competition within one sex for access to mates or mate choice by the opposite sex.

Directional selection

A mode of natural selection that favors an extreme phenotype, causing allele frequencies to shift continuously toward that phenotype over time.

Stabilizing selection

A mode of natural selection that favors intermediate phenotypes and acts against extremes, reducing variance (e.g., human birth weight).

Adaptation

A heritable trait shaped by natural selection that enhances an organism's survival and reproductive fitness in a specific environment.