BIO 151: Unit 1 (Bell curve, Macroevolution & Microevolution)

Practice flashcards covering concepts of selective pressure, macroevolution, microevolution, and species classification.

Stabilizing Selection

Selection that favors the average phenotype; extremes are selected against, leading to reduced variation and a population that stabilizes around the mean. Ex. Human baby weight (~7 lbs optimal).

Directional Selection

Selection that favors one extreme phenotype, causing the trait distribution to move in one consistent direction. Ex. Peppered moths camouflaging with darkened trees during the Industrial Revolution.

Disruptive Selection

Selection that favors both extreme phenotypes over the average, increasing variation and potentially leading to speciation. Ex. Cuttlefish mating strategies where large males fight and small males mimic females.

Divergent Evolution

The process where species diverge from a common ancestor, accumulating enough differences over time to form distinct lineages. Ex. Primates diverging into different modern apes.

Macroevolution

Large-scale changes in evolution that result in the creation of new species (speciation), representing microevolution accumulated over many generations.

Biological Species Concept

The most common definition of a species, referring to a group of organisms that can interbreed and produce viable, fertile offspring. Ex. Horses and donkeys are separate species because their hybrid, the mule, is infertile.

Binomial Nomenclature

A scientific naming system for species, typically consisting of two parts (Genus capitalized, species lowercase) and italicized, used to ensure universal accuracy. Ex. Homo sapiens.

Microevolution

Small genetic changes within a single species over time, specifically a change in the genetic variance (allele frequency) in a population. Ex. A moth population shifting from mostly black to mostly white.

Hardy-Weinberg Principle of Equilibrium

A principle stating that allele and genotype frequencies in a population will remain stable from one generation to the next unless evolutionary forces (such as gene flow, natural selection, mutation, small population size, or non-random mating) are acting upon them.

Classifying Species

“Dear King Philip Came Over For Green Spaghetti”

Domain: Eukarya (cells with nuclei)

Kingdom: Animalia (animals)

Phylum: Chordata (backbone)

Class: Mammalia (mammals)

Order: Primates

Family: Hominidae (great apes/humans)

Genus: Homo

Species: sapiens