Chapter 10: Natural selection

Evolution

A change in a population over time.

Natural selection

A process that occurs in terms of individuals but is defined in terms of populations.

Charles Darwin

A scientist whose work greatly contributed to our understanding of evolution.

Offspring competition

The competition among offspring for limited resources.

Variability

The existence of differences among organisms in a population.

Fitness

The measure of evolutionary success based on reproductive success.

Favorable traits

Traits that increase the likelihood of survival and reproduction.

Heritability

The likelihood of passing traits to subsequent generations.

Biotic factors

Living factors that can influence evolutionary fitness.

Abiotic factors

Non-living factors that can influence evolutionary fitness.

Paleontology

The study of fossils to reveal the various organisms and major lines of evolution.

Fossil Dating

The process of determining the age of a fossil by analyzing the age of the rocks where it was found, the rate of decay of isotopes, or geographical data.

Biogeography

The study of the distribution of flora and fauna in the environment, which has revealed related species in widely separated regions of the world.

Embryology

The study of the development of an organism, which has revealed that all vertebrates show fish-like features called gill slits.

Morphological Homologies

The study of the anatomy of various animals, which has revealed that some animals have similar structures that serve different functions. Homologous structures point to a common ancestor, while analogous structures evolved independently.

Molecular Biology

The study of biological molecules, which has provided the most compelling proof of evolution through the similarity at the molecular level.

Continuing Evolution

The ongoing process of evolution, which can be observed through small changes in DNA and changes in the fossil record over time.

Phylogenetic trees

Charts used to study relationships between organisms, built using data from the fossil record or molecular record.

Genetic variability

Differences in people, the foundation of evolution, allows for natural selection to occur.

Causes of evolution

Natural selection requires genetic variation and environmental pressure, biotic and abiotic factors can affect the direction of evolution.

Divergent evolution

When populations become reproductively isolated from each other due to different variation and environmental pressures, they could each change in different ways and no longer be able to mate.

Convergent evolution

The process by which two unrelated and dissimilar species come to have similar traits, often because they have been exposed to similar selective pressures.

Speciation

The process by which populations become different species, can occur through allopatric or sympatric speciation.

Pre-zygotic barriers

Prevent fertilization between individuals of different species.

Post-zygotic barriers

Related to the inability of a hybrid organism to produce offspring.

Directional selection

Occurs when natural selection favors one extreme of a trait, leading to a shift in the population towards that extreme.

Artificial selection

A type of selection where humans directly affect variation in other species.

RNA-world hypothesis

The hypothesis that the original life-forms were simply molecules of RNA.

Primitive Atmosphere

The atmosphere of Earth in its early stages, which contained mostly inorganic molecules and was rich in gases like methane, ammonia, hydrogen, and water.