General Biology and Evolutionary Principles

Comprehensive vocabulary flashcards covering basic biological concepts, Darwinian evolution, population genetics, speciation mechanisms, and macroevolutionary history.

Biology

The scientific study of life.

Cell

The smallest, most basic and fundamental unit of life.

Organism

Any individual form of life.

Unicellular Organism

A form of life consisting of a single cell, usually visible only under a microscope.

Multicellular Organism

A form of life consisting of multiple cells.

Emergent Properties

Properties that emerge upon combining smaller parts, creating a whole that is greater than the sum of its individual parts.

Natural Selection

The process by which the natural environment selects for individuals in a population with heritable traits that confer higher fitness.

Taxonomy

The branch of science concerned with naming, identifying, and classifying organisms.

Autotrophs

Organisms that acquire energy by producing their own food.

Heterotrophs

Organisms that acquire energy by consuming other living organisms.

Scientific Method

A systematic procedure used to answer questions, test ideas, and gain scientific knowledge.

Hypothesis

A proposed and testable explanation for an observation.

Theory

A broad, testable explanation of many observations that is supported by a large body of evidence.

Independent Variable

The variable in an experiment that is intentionally manipulated by the researcher.

Dependent Variable

The variable in an experiment that is measured to determine if it is affected by the independent variable.

Negative Control

A control group in an experiment where no response is expected, used to prevent false positives.

Positive Control

A control group in an experiment where a response is expected, used to prevent false negatives.

Scala Naturae

Aristotle's view that life-forms are fixed and can be arranged on a ladder of increasing complexity.

Paleontology

The study of fossils, largely developed by French scientist Georges Cuvier.

Strata

Superimposed layers of sedimentary rock formed from compressed mud and sand over time.

Uniformitarianism

The principle incorporated by Charles Lyell stating that mechanisms of change are constant over time, operating today as in the past.

Inheritance of Acquired Characteristics

Jean-Baptiste de Lamarck's incorrect principle stating that an organism could pass modifications gained during its lifetime to its offspring.

Adaptation

An inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.

Artificial Selection

The selective breeding of domesticated plants and animals by humans to encourage desirable traits.

Homology

Similarity in anatomical or molecular characteristics resulting from shared common ancestry.

Homologous Structures

Anatomical features in different species that share an underlying theme inherited from a common ancestor, even if adapted for different functions.

Vestigial Structures

Remnants of features that served an important function in an organism's ancestors but have minimal or no function in the current organism.

Convergent Evolution

The independent evolution of similar features in distantly related lineages that adapt to similar environments.

Analogous Features

Characteristics that share similar functions across different species but do not share a common evolutionary origin.

Biogeography

The scientific study of the geographic distributions of species.

Endemic

Referring to species of plants or animals that are found exclusively in one particular geographic location.

Microevolution

Evolutionary change on its smallest scale, defined as a change in allele frequencies in a population over generations.

Gene Pool

The aggregate of all copies of every type of allele at every locus in all members of a population.

Hardy-Weinberg Equilibrium

The state of a non-evolving population where allele and genotype frequencies remain constant across generations under Mendelian inheritance.

Genetic Drift

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

Founder Effect

Genetic drift that occurs when a few individuals become isolated from a larger population and establish a new population with a different gene pool.

Bottleneck Effect

Genetic drift that occurs when a severe drop in population size drastically reduces genetic variation by chance.

Gene Flow

The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.

Relative Fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.

Directional Selection

Natural selection that favors individuals at one extreme of a phenotypic range, shifting the population curve in that direction.

Disruptive Selection

Natural selection that favors individuals at both extremes of a phenotypic range over intermediate phenotypes.

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

Sexual Dimorphism

Differences between secondary sex characteristics of males and females of the same species.

Heterozygote Advantage

A situation in which individuals who are heterozygous at a particular locus have greater fitness than both types of homozygotes.

Frequency-Dependent Selection

A form of balancing selection in which the fitness of a phenotype depends on how common it is in the population.

Speciation

The evolutionary process by which one species splits into two or more species.

Macroevolution

Broad pattern of evolutionary change above the species level, including the emergence of major new groups of organisms.

Biological Species Concept

The definition of a species as a group of populations whose members can interbreed in nature to produce viable, fertile offspring.

Reproductive Isolation

The existence of biological factors or barriers that impede members of two species from interbreeding and producing viable, fertile offspring.

Prezygotic Barriers

Reproductive barriers that prevent fertilization by impeding mating, preventing completed mating, or hindering egg fertilization.

Postzygotic Barriers

Reproductive barriers that operate after a hybrid zygote forms, preventing it from developing into a viable, fertile adult.

Morphological Species Concept

A definition of species based on body shape and other structural features.

Ecological Species Concept

A definition of species in terms of its ecological niche and interactions with its environment.

Phylogenetic Species Concept

A definition of species as the smallest group of individuals that share a common ancestor on an evolutionary tree.

Allopatric Speciation

The formation of new species in populations that are geographically isolated from one another.

Sympatric Speciation

The formation of new species in populations that live in the same geographic area.

Polyploidy

A chromosomal condition resulting from cell division errors that yield extra sets of chromosomes.

Autopolyploid

An individual that has more than two chromosome sets derived from a single species.

Allopolyploid

A fertile polyploid individual formed when two different species interbreed and produce offspring whose chromosome number subsequently doubles.

Hybrid Zone

A geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry.

Reinforcement

The natural selection process that strengthens prezygotic barriers to reproduction, reducing the formation of unfit hybrids.

Punctuated Equilibria

A model describing periods of apparent evolutionary stasis in the fossil record punctuated by sudden change during speciation.

Protocells

Abiotically produced droplets with membranes that maintain an internal chemical environment distinct from their surroundings.

Ribozymes

RNA molecules that function as enzyme-like catalysts.

Radiometric Dating

A method for determining the absolute age of rocks and fossils based on the characteristic decay rate of radioactive isotopes.

Half-Life

The time required for $50\%$ of a radioactive parent isotope to decay into its daughter isotope.

Stromatolites

Layered rocks that form when prokaryotes bind thin films of sediment together.

Endosymbiont Theory

The theory that mitochondria and plastids originated as small prokaryotes engulfed by host cells, eventually evolving a symbiotic relationship.

Serial Endosymbiosis

A sequence of endosymbiotic events in which ancestral mitochondria evolved before plastids in the eukaryotic lineage.

Cambrian Explosion

A period in geologic history ($535\text{--}525$ million years ago) when many present-day animal phyla suddenly appeared in the fossil record.

Plate Tectonics

The theory that Earth's continents are part of great crustal plates floating on the mantle that move over time via continental drift.

Pangaea

The supercontinent formed about $250$ million years ago when all of Earth's landmasses drifted together.

Mass Extinction

An event in which large numbers of species become extinct worldwide due to disruptive environmental changes.

Adaptive Radiation

A period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill vacant ecological roles.

Heterochrony

An evolutionary change in the rate or timing of developmental events relative to an ancestral species.

Paedomorphosis

An evolutionary condition in which the sexually mature adult stage of a species retains juvenile features of its ancestors.

Homeotic Genes

Master regulatory genes that control the spatial organization and placement of body parts during development.

Exaptation

A structure that evolved in one context and later became co-opted for a different evolutionary function.