Unit 7 - Natural Selection

Evolution

The process by which species change over time through genetic variation and natural selection.

Speciation

The formation of new species when populations become reproductively isolated and evolve independently.

Charles Darwin

The scientist who proposed the theory of natural selection to explain how evolution occurs.

Natural Selection

A process where individuals with favorable traits survive and reproduce more, passing those traits on.

Domestication

The process by which humans breed wild organisms for traits useful to them.

Artificial Selection

When humans select and breed individuals with desired traits, not by nature.

Population Genetics

The study of genetic variation within populations and how it changes over time.

Sexual Selection

A form of natural selection based on an organism’s ability to attract a mate.

Mutation

A random change in DNA that can introduce new traits into a population.

Genetic Drift

A random change in allele frequencies, especially in small populations.

Founder Effect

Genetic drift that happens when a few individuals start a new population with limited genetic variation.

Bottleneck Effect

A sharp reduction in a population's size due to a sudden event (like a disaster).

Gene Flow

Movement of genes between populations through migration, increasing genetic diversity.

Hardy-Weinberg Equilibrium

A condition where allele frequencies in a population remain constant if no evolution occurs.

Fossil Records

Preserved remains or traces of organisms that show how life has changed over time.

Relative Dating

Determining the age of a fossil by comparing its placement with that of fossils in other layers.

Absolute Dating

A method that determines the exact age of a fossil using radioactive decay.

Homologous Structures

Body parts that are similar in structure but may have different functions, showing common ancestry.

Analogous Structures

Body parts with similar functions but different structures, showing convergent evolution.

Vestigial Structures

Body parts that have lost their original function through evolution.

Embryology

The study of embryos, where similar development patterns suggest common ancestry.

Phylogenetic Trees

Diagrams that show evolutionary relationships based on traits and genetic data.

Cladograms

Simplified evolutionary trees showing shared characteristics among species.

Species

A group of organisms that can interbreed and produce fertile offspring.

Prezygotic Barriers

Reproductive barriers that prevent fertilization from occurring between species.

Geographical Isolation

When populations are separated by physical barriers, leading to speciation.

Habitat Isolation

When species live in different habitats and don’t meet to reproduce.

Behavioral Isolation

When different mating behaviors prevent interbreeding between species.

Temporal Isolation

When species reproduce at different times or seasons.

Mechanical Isolation

When reproductive structures are incompatible between species.

Gametic Isolation

When sperm and egg cannot fuse, even if mating occurs.

Postzygotic Barriers

Barriers that occur after fertilization, preventing viable or fertile offspring.

Reduced Hybrid Viability

The hybrid doesn’t survive or develop properly.

Reduced Hybrid Fertility

The hybrid is born healthy but cannot reproduce.

Hybrid Breakdown

The hybrid is fertile, but its offspring are weak or infertile.

Allopatric Speciation

Speciation caused by physical separation of populations.

Sympatric Speciation

Speciation that happens without physical barriers, often due to mutations or behavioral changes.

Gradualism

Evolution occurs slowly and steadily over long periods of time.

Punctuated Equilibrium

Evolution occurs in rapid bursts with long periods of stability in between.

Divergent Evolution

Two related species evolve different traits due to different environments.

Convergent Evolution

Unrelated species evolve similar traits due to similar environments.

Parallel Evolution

Two related species evolve similarly after being separated.

Coevolution

Two species evolve in response to changes in each other.

Adaptive Radiation

One species evolves into many different forms to fill different ecological niches.

Extinction

The complete disappearance of a species from Earth.

Mass Extinction

A widespread and rapid decrease in biodiversity where many species die off at once.

Oparin-Haldane Hypothesis

The idea that life began in a “primordial soup” of organic molecules formed under early Earth conditions.

Miller-Urey Experiment

An experiment that simulated early Earth and produced organic molecules, supporting the origin of life theories.

RNA World Hypothesis

The theory that RNA was the first genetic material and enzyme before DNA and proteins evolved.

Francesco Redi’s Experiment

Disproved spontaneous generation by showing that maggots only appear on meat when flies lay eggs on it.