General Biology I Unit 4

Microevolution

The change in allele frequencies within a population over generations.

Speciation

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

Macroevolution

Large-scale evolutionary change above the species level, affecting major taxonomic groups.

Radiometric dating

A method for determining the age of objects using the known, steady decay rates of radioactive isotopes.

Radiocarbon dating

A radiometric dating method using carbon-14 with a 5730-year half-life; used for organic remains up to ~60,000 years old.

Electron spin resonance dating

“Trapped-electron” dating used to determine ages of materials like tooth enamel; effective up to 5 million years.

Potassium-Argon dating

A radiometric technique using the decay of K-40 to Ar-40 to date volcanic rock up to billions of years old.

Stromatolites

Living mounds of mineralized cyanobacterial biofilms; the oldest known fossils (~3.5 billion years old).

Protocell

A membrane-bound collection of organic molecules thought to be the precursor to true cells.

Ribozymes

RNA molecules capable of catalyzing chemical reactions, including self-replication.

Miller-Urey experiment

An experiment simulating early Earth conditions that produced organic molecules, including amino acids.

Plate tectonics

The theory that Earth’s crust is divided into plates that float and move due to convection in the mantle.

Continental drift

The gradual movement of Earth's continents over geological time.

Mass extinction

A rapid and widespread loss of biodiversity marking transitions between major geological eras.

Adaptive radiation

Rapid diversification in which a single ancestor gives rise to many new species, often after ecological opportunities arise.

Biological species concept

Defines species as groups whose members interbreed in nature and produce fertile offspring; relies on reproductive isolation.

Reproductive isolation

Physical, biological, or behavioral barriers preventing species from interbreeding.

Allopatric speciation

Speciation that occurs when populations are geographically separated.

Sympatric speciation

Speciation that occurs in populations living in the same area due to ecological or genetic factors.

Polyploidy

Condition of having more than two sets of chromosomes; often causes instantaneous plant speciation.

Hybrid

Offspring resulting from the mating of individuals from two different species.

Hybrid vigor

When hybrids show superior traits (e.g., increased fitness) compared to parent species.

Habitat isolation

A pre-zygotic barrier where species occupy different habitats and rarely encounter one another.

Temporal isolation

A pre-zygotic barrier where species breed at different times (season, day, or year).

Behavioral isolation

A pre-zygotic barrier where differences in courtship behaviors prevent mating.

Mechanical isolation

A pre-zygotic barrier where morphological differences prevent mating or fertilization.

Gametic isolation

A pre-zygotic barrier where gametes (egg & sperm) cannot fuse due to molecular incompatibility.

Reduced hybrid viability

A post-zygotic barrier where hybrids fail to develop properly or die early.

Reduced hybrid fertility

A post-zygotic barrier where hybrids survive but are sterile (e.g., mule).

Hybrid breakdown

A post-zygotic barrier where first-generation hybrids are fertile but their offspring are weak or sterile.

Fossil record

The chronological collection of life’s remains showing historical changes in species over time.

Biogeography

The study of the geographic distribution of species.

Homology

Similarity in structure due to shared ancestry.

Homologous structures

Structures with similar internal anatomy but different functions due to shared ancestry (divergent evolution).

Analogous structures

Structures with similar function but different ancestry; result of convergent evolution.

Convergent evolution

Independent evolution of similar traits in unrelated organisms due to similar environmental pressures.

Artificial selection

Selective breeding by humans to increase desirable traits in organisms.

Population

A group of individuals of the same species living in a specific geographic area.

Gene pool

All alleles present in a population.

Genetic variation

Differences in DNA sequences between individuals of a population.

Hardy-Weinberg equilibrium

A state where allele frequencies remain constant if no mutation, migration, drift, non-random mating, or selection occurs.

Mutation

A change in DNA sequence; the ultimate source of new genetic variation.

Genetic drift

Random changes in allele frequency, strongest in small populations.

Founder effect

When a few individuals start a new population with allele frequencies different from the original.

Bottleneck effect

When a population undergoes a drastic reduction in size, altering allele frequencies.

Gene flow

Movement of individuals (and their alleles) between populations.

Natural selection

Process where better-adapted individuals survive and reproduce, increasing advantageous alleles.

Evolutionary fitness

An individual’s ability to contribute viable, fertile offspring to the next generation.

Relative fitness

Fitness measured relative to others in the population.

Sexual selection

A type of natural selection based on traits that increase mating success.

Sexual dimorphism

Differences in appearance between males and females of the same species.

Intrasexual selection

Competition between individuals of the same sex (usually males) for mates.

Intersexual selection

Mate choice, often where females select males based on traits or displays.

Directional selection

Selection that favors one extreme phenotype.

Disruptive selection

Selection that favors both phenotypic extremes and acts against intermediates.

Stabilizing selection

Selection that favors intermediate phenotypes and reduces extremes.

Theory of evolution

The concept that species change over time and modern species descend from ancestral ones.

Adaptation

A heritable trait that increases survival and/or reproduction in a specific environment.

Phylogeny

Evolutionary relationships among organisms

Taxonomy

Biological classification

Shared derived character

Distinguishing feature of a group that is not shared by previous ancestors

Claude

Group of organisms composed of common ancestor and all descendants

Vertebral column

Support structure, also protects nerve cord

Vertebrates

Organisms with a skull and vertebral column

Chondrichthyans

Cartilaginous fish; sharks and rays with derived character of jaws and paired appendages

Ray-finned fish

Greatest number of species of any vertebrate; derived character of internal bony skeleton, lungs/lung derivative

Lobe-finned fish

Bony; derived character of loved appendages (precursor to limbs)

Tetrapod

“Four feet;” jawed vertebrates that have limbs and feet that can support their weight on land

Convergent evolution

Unrelated species develop similar traits due to similar environmental pressures

Divergent evolution

Closely related species develop different traits as they adopt to different environments

Analogous structures

Similar function, different origin

Homologous structures

Shared origin, different function

Amphibians

Organisms that have legs with digits; first vertebrates to colonize land

The Sixth Mass Extinction

Climate change, deforestation, overharvesting

Reptiles

Organisms with an amniotic egg; capable of completing life cycles without “attachment” to water

Ectothermic

Absorb external heat rather than generating most of their own

Mammals

Organisms with hair and mammary glands producing milk

Monotremes

Oldest lineage of mammals; lay eggs

Marsupials

Nurse in external pouch after short pregnancy

Placental mammals

Placenta provides nutrients from mother

Apes

Species with larger brains relative to body size compared to monkeys and other primates

Hominins

Group including modern humans and extinct human ancestors

Homo erectus

First hominins to migrate out of Africa; first humans to use fire

Homo neanderthalensis

Last common ancestor with humans 400,000 years ago. Interbred with Homo sapiens: non-Africans roughly 2% Neanderthal DNA

Homo sapiens

Originated in Africa, migrated all over the world. Highest levels of brain cognition and adaptability; sophisticated use of tools and fire.