Campbell Unit 4: Mechanisms of Evolution

Evolution

The process of descent with modification, where species gradually become different from their ancestors over time.

Fossils

The preserved remains or traces of organisms from the past, providing evidence of past life forms.

Strata

Layers of rock that are arranged in a sequence, with younger layers on top of older layers, providing a record of geological time.

Paleontology

The scientific study of fossils, developed by Georges Cuvier, which helps us understand the history of life on Earth.

Cuvier's hypothesis

Geologic changes occur through slow, continuous actions, implying an older Earth than previously believed.

Lamarck's hypothesis

The idea that species change over time due to acquired traits being passed on to their offspring, which has been largely discredited.

Adaptations

Characteristics that provide advantages for survival in specific environments, allowing organisms to better survive and reproduce.

Natural Selection

Charles Darwin's theory for why adaptations occur, where individuals with advantageous traits are more likely to survive and reproduce.

Artificial Selection

The process in which humans modify other species by selectively breeding individuals with desired traits, leading to significant changes over time.

Observation 1

Members of a population exhibit variation in inherited traits, which can be observed and measured.

Inference 1

Individuals with advantageous traits are more likely to leave more offspring, passing on those traits to future generations.

Observation 2

All species have the potential to produce more offspring than the environment can support, leading to competition for resources.

Inference 2

This competition results in the accumulation of favorable traits over generations, as individuals with those traits are more likely to survive and reproduce.

Speciation

The process of the formation of new species through evolution, where populations become reproductively isolated and diverge from each other.

Direct Observations

Evidence for evolution based on directly observing changes in organisms over time, such as the evolution of soapberry bugs or antibiotic-resistant bacteria.

Homology

Similarity between different species resulting from common ancestry, providing evidence of shared evolutionary history.

Homologous Structures

Structures that are variations on a common structural theme present in a shared ancestor, indicating a common evolutionary origin.

Vestigial Structures

Structures that served a function in an ancestor but are no longer useful in the current organism, providing evidence of evolutionary history.

Evolutionary Tree

A diagram that shows the evolutionary relationships among groups of organisms, illustrating their shared ancestry and divergence over time.

Convergent Evolution

The independent evolution of similar features in different species, often due to similar environmental pressures.

Analogous

When species share similar features due to convergent evolution, but do not share a common evolutionary origin.

Fossil Record

Evidence for evolution based on comparing fossils to modern-day organisms, providing insights into the history and changes in life forms.

Biogeography

The study of the geographic distributions of species, which can provide evidence of evolutionary history and patterns of speciation.

Pangaea

The theoretical supercontinent that existed around 250 million years ago, which later broke apart into the continents we know today.

Mutation

A change in the DNA sequence, which is a source of genetic variation and can lead to the evolution of new traits.

Genetic Variation

Differences among individuals in the composition of their genes or DNA sequences, which contribute to the diversity of traits within a population.

Neutral Variation

Differences in DNA that do not provide a genetic advantage or disadvantage to an organism, but contribute to overall genetic diversity.

Meiosis

The cell division process that produces gametes (sex cells) with genetic variation, contributing to the genetic diversity within a population.

Hardy-Weinberg Equilibrium

A state in which a population is not evolving, with allele and genotype frequencies remaining constant over generations.

Relative Fitness

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals.

Directional Selection

A type of natural selection where conditions favor individuals with one extreme phenotype, causing a shift in the population towards that phenotype.

Disruptive Selection

A type of natural selection where conditions favor individuals with both extreme phenotypes, reducing the variation within a population.

Stabilizing Selection

A type of natural selection where conditions favor individuals with intermediate variants, reducing the variation within a population.

Sexual Selection

A process where individuals with certain traits are more likely to gain mates and reproduce, leading to the evolution of traits related to mating success.

Sexual Dimorphism

The difference in secondary sexual characteristics between males and females of the same species, often resulting from sexual selection.

Balancing Selection

A type of natural selection that preserves genetic variation in a population, maintaining multiple phenotypic forms.

Plate Tectonics

The movement of Earth's crustal plates, causing changes in landmasses and influencing the distribution of species over time.

Mass Extinction

A disruptive change to the global environment that leads to a high rate of extinction across many different species.

Heterochrony

An evolutionary change in the rate or timing of development, leading to differences in the timing of key developmental events.

Homeotic Genes

Genes that determine basic features during development, playing a crucial role in shaping the body plan of organisms.