Mutations, Evolution, and Hardy-Weinberg: Key Concepts for Biology (32-36)

Mutation

A change in the DNA sequence.

Spontaneous Mutation

Mutations that occur due to mistakes in DNA replication or proofreading errors.

Induced Mutation

Mutations that occur due to external factors such as UV radiation, chemicals, x-rays, or viruses.

Somatic Mutations

Mutations that happen in body cells and are not passed to offspring; can cause cancer.

Germline Mutations

Mutations that happen in egg or sperm and are passed to offspring, creating new alleles.

Alleles

New versions of genes created by changes in DNA.

Example of Mutation

Rock pocket mouse Mc1r gene mutation leading to dark fur.

Random Mutations

Mutations that do not occur because an organism 'needs' them.

Neutral Mutation

A mutation that has no fitness effect.

Deleterious Mutation

A mutation that is harmful.

Beneficial Mutation

A rare mutation that increases fitness.

Point Mutations

Substitutions in DNA that can be silent, missense, or nonsense.

Silent Mutation

A point mutation that causes no amino acid change and has no effect on phenotype.

Missense Mutation

A point mutation that changes one amino acid and can be good, bad, or neutral.

Nonsense Mutation

A point mutation that changes a codon to a STOP codon, resulting in a short, usually nonfunctional protein.

Frameshift Mutations

Mutations caused by insertion or deletion of 1-2 nucleotides that shift the reading frame and almost always destroy function.

Less Harmful Insertion/Deletion

Inserting or deleting 3 nucleotides is less harmful because it doesn't shift the reading frame.

Genetic Variation Source

Mutations are the ultimate source of genetic variation because they create new alleles for natural selection to act on.

Acclimation

Individual changes temporarily in response to the environment that are not genetic and not inherited.

Adaptation

An inherited trait that increases fitness; also the population-level process of becoming better suited to the environment.

Fitness

How well an organism reproduces compared to others.

Evolution

Change in allele frequencies in a population over generations.

Scientific Theory

A well-supported explanation backed by extensive evidence.

Lamarck

A scientist who thought acquired traits could be inherited, which is incorrect, but he suggested species change.

Darwin

A scientist who observed variation in the Galápagos and developed the theory of natural selection.

Natural Selection

The process where individuals with beneficial traits survive and reproduce more due to competition.

Wallace

A scientist who independently discovered natural selection and helped push Darwin to publish.

Fossil Record

Evidence that shows extinct species, transitional forms, and the order of species appearance/disappearance.

Biogeography

The study of species distribution that follows continental movement and shows related species living near each other.

Anatomical Homologies

Same structure, different function (human arm, whale flipper).

Developmental Homologies

Embryos look similar (gill slits, tails).

Molecular Homologies

DNA similarities across species.

Vestigial Traits

Traits with reduced or no function now (goosebumps, python hind limb bones, blind salamander eyes).

Stabilizing Selection

Favors the middle (Example: robins laying 4 eggs).

Directional Selection

Favors one extreme (Example: Peppered moths shifting from light → dark during Industrial Revolution).

Diversifying Selection

Favors both extremes (Example: Gray + Himalayan rabbits blend in; white rabbits don't).

Sexual Selection

Selection for traits to increase mating success.

Sexual Dimorphism

Males and females look different (ornaments, colors, size).

Trade-offs in Evolution

Bright colors attract mates and predators.

History in Evolution

Evolution can only modify existing traits.

Genetic Limits

Sometimes no variation exists.

Environment Changes

What's good now may not be later.

Hardy-Weinberg Principle

Predicts what happens to allele frequencies if NO evolution occurs.

Conditions for No Evolution

1. Very large population 2. Random mating 3. No mutation 4. No migration (gene flow) 5. No natural selection.

Natural Selection (Mechanism)

Alleles that improve fitness increase in frequency.

Genetic Drift

Random changes; strongest in small populations.

Bottleneck Effect

Population reduced suddenly → loss of diversity.

Founder Effect

Few individuals start new population → limited alleles.

Non-Random Mating

Mating preferences change genotype frequencies.

Gene Flow

Movement of alleles between populations; increases genetic diversity in receiving population.

Microevolution

Small changes in allele frequencies (one generation to next).

Macroevolution

Large-scale patterns over long times (new groups, extinction).