Biology Semester 2 Study Guide: Abiogenesis and Evolution

Vocabulary flashcards based on lecture notes covering the origins of life (abiogenesis), Darwinian evolution, mechanisms of natural selection, evidence of evolution, and primate/hominin development.

Abiogenesis

The scientific study of how life first arose from non-living (inorganic) matter through natural chemical and physical processes on early Earth.

Spontaneous generation

An old, incorrect belief that living organisms could arise spontaneously from non-living material, which was disproved by Louis Pasteur's swan-neck flask experiment.

Oparin-Haldane hypothesis

The proposal that early Earth had a reducing atmosphere ($NH_3$, $CH_4$, $H_2$, $H_2O$) where simple inorganic molecules combined into organic molecules in a nutrient-rich "primordial soup."

Miller-Urey experiment (1953)

A study that simulated early Earth conditions (lightning and primordial gases) and resulted in the spontaneous formation of amino acids, proving organic molecules can arise from inorganic chemicals.

RNA World hypothesis

The hypothesis that RNA was the first self-replicating molecule because it can both store information and catalyze reactions.

Ribozymes

RNA molecules that act as enzymes (catalysts), supporting the idea that RNA could perform the jobs of both genes and proteins.

Coacervates

Droplets of organic molecules that form spontaneously in water with a membrane-like boundary; proposed by Oparin and Haldane as possible "proto-cells."

Panspermia

The hypothesis that life, or its chemical building blocks, arrived on Earth from space via meteorites.

LUCA (Last Universal Common Ancestor)

The hypothetical single organism from which all life descends, likely possessing DNA, ribosomes, and basic metabolism.

Uniformitarianism

The geological principle, supported by Lyell and Hutton, that Earth is extremely old and has undergone slow, gradual changes over time.

Biogeography

The study of the geographic distribution of species; Darwin used this to suggest populations evolved in isolation on islands.

Selective / Artificial Breeding

The process where humans select which organisms reproduce based on desired traits, used by Darwin as evidence that selection can shape populations.

MVIDA

The fundamental principles of natural selection: Mutation, Variation, Inheritance, Differential survival/reproduction, and Adaptation.

Fitness

An organism's ability to survive and reproduce in its specific environment.

Selection pressure

Any environmental factor, such as predators, disease, or food availability, that affects an organism's survival and reproduction.

Stabilizing Selection

A type of natural selection that favors the average phenotype and eliminates extremes, keeping the population similar (e.g., human birth weight).

Directional Selection

Natural selection that favors one extreme phenotype, causing the population trait to shift over time (e.g., antibiotic resistance).

Disruptive Selection

Natural selection that favors both extremes and eliminates the average, which can lead to two distinct groups (e.g., bird beak sizes).

Sexual Selection

A form of selection where traits improve mating success even if they may reduce overall survival (e.g., a peacock's tail).

Homologous Structures

Structures that share the same underlying anatomy but have different functions, providing evidence of common ancestry and divergent evolution.

Analogous structures

Structures with the same function but different underlying anatomy that evolved independently through convergent evolution (e.g., bird vs. insect wings).

Vestigial Structures

Reduced or non-functional structures that were functional in ancestors, such as the human coccyx or whale hind limb bones.

Molecular clock

A technique that uses the rate of accumulated DNA mutations to estimate the time when two species diverged.

Speciation

The process by which a population splits into two or more isolated populations that eventually become distinct species that can no longer interbreed.

Allopatric speciation

A form of speciation that occurs when geographic isolation separates a population.

Punctuated Equilibrium

The theory that evolution occurs in rapid bursts separated by long periods of little change (stasis), explaining gaps in the fossil record.

Genetic Drift

Random changes in allele frequency due to chance rather than selection; its effects are stronger in small populations.

Bottleneck Effect

A dramatic reduction in population size leading to a loss of genetic diversity, where survivors represent only a fraction of the original gene pool.

Gene Flow

The movement of alleles between populations through migration, which increases variation in the receiving population and reduces differences between populations.

Bipedal

Walking upright on two legs, a key human adaptation that frees hands for tool use and allows for long-distance running.

Melanin

A skin pigment that acts as an adaptation to UV radiation; levels vary with latitude to prevent DNA damage or allow vitamin D synthesis.