UNIT 7 Natural Selection & Evolution essentials FULL STUDY GUIDE

Honors 8th Grade BIOLOGY I

Selective Breeding

Humans selecting organisms with desirable traits to be parents of the next generation.

Artificial Selection

Another term for selective breeding in which humans choose traits.

Trait

A heritable characteristic passed from parent to offspring.

Adaptation

An inherited trait that increases an organism’s chance of survival or reproduction.

Natural Selection

Process where individuals with advantageous traits survive and reproduce more.

Genetic Variation

Differences in DNA among individuals in a population.

Population

A group of the same species living and reproducing in the same area.

Biological Fitness

An organism’s ability to survive and reproduce relative to others.

Selective Pressure

Environmental factor that favors or eliminates certain traits.

Gene Pool

All alleles present in a population.

Gene Flow

Movement of alleles into or out of a population through migration.

Genetic Drift

Random changes in allele frequencies, strongest in small populations. CHANCE EVENT!

Bottleneck Effect

Genetic drift caused by a drastic reduction in population size.

Founder Effect

Genetic drift when a small group starts a new population with limited variation.

Speciation

Formation of new species over time. Species are split into 2 or more.

Allopatric Speciation

Speciation caused by geographic isolation.

Sympatric Speciation

Speciation caused by reproductive isolation.

Prezygotic Barrier (before zygote)

A reproductive barrier that prevents mating or fertilization.

Postzygotic Barrier (after zygote)

A reproductive barrier occurring after fertilization that prevents hybrid survival or reproduction.

Hybridization

Crossing dissimilar individuals to combine desirable traits.

Hybrid Vigor

Increased strength or hardiness in hybrid offspring. ex. Mules are stronger than horses and donkeys

Adaptive Radiation

Evolution of many species from one ancestor to fill different niches.

Polyploidy

Condition of having more than two sets of chromosomes, common in plants.

Punctuated Equilibrium

Evolutionary pattern of long stability interrupted by rapid change.

Genetic Engineering

Direct manipulation of DNA to produce desired traits.

Transgenic Organism

Organism containing foreign DNA from another species.

Recombinant DNA

DNA formed by combining genetic material from different sources.

Theory of Evolution

Scientific explanation that species change over time through natural processes.

Camouflage

Adaptation allowing organisms to blend into their environment.

Mimicry

Adaptation where one organism resembles, acts, and sounds like another for protection.

Variation

Differences among individuals in a population.

Selection

Process where the best‑adapted individuals survive and reproduce.

Descent with Modification

Gradual change in populations over generations. coined by CHARLES DARWIN

Hardy-Weinberg Equilibrium

Model describing allele and genotype frequencies in a non-evolving population.

Assumptions of Hardy-Weinberg Equilibrium

No selection, No mutation, No migration, Large population, Random mating

p

Frequency of the dominant allele in a population. (noun)

q

Frequency of the recessive allele in a population. (noun)

p²

Frequency of the homozygous dominant genotype. (noun)

2pq

Frequency of the heterozygous genotype. (noun)

q²

Frequency of the homozygous recessive genotype. (noun)

Comparative Anatomy

Study of similarities and differences in body structures of different species. (noun)

Homologous Structures

Structures with the same origin but different functions, indicating common ancestry. (noun)

Vestigial Structures

Structures that no longer serve their original function but remain from ancestors. (noun)

Fossils

Preserved remains or traces of ancient organisms. (noun)

Transitional Forms

Fossils showing intermediate traits between ancestral and modern species. (noun)

Embryology

Study of early developmental stages of organisms. (noun)

Biochemical Evidence

Comparison of DNA and amino acid sequences to determine evolutionary relationships. (noun)

Cladogram

Diagram showing evolutionary relationships among organisms. (noun)

Analogous Structures

Structures with similar functions but different origins, showing convergent evolution. (noun)

Convergent Evolution

Evolution of similar traits in unrelated species due to similar environments. (noun)

Directional Selection

Natural selection that favors one extreme phenotype, causing the population’s traits to shift in one direction. (noun)

Stabilizing Selection

Natural selection that favors the intermediate phenotype and selects against both extremes. (noun)

Disruptive Selection

Natural selection that favors both extreme phenotypes and selects against the intermediate phenotype. (noun)

Sexual Selection

Natural selection based on traits that increase an organism’s ability to attract mates. (noun)