Evolution- Chapters 1-5

Anthropocene Era

A recent period in Earth's history when human activity started to have a significant impact on climate and ecosystems.

antibiotic resistance

The ability of microbes to survive and reproduce in the presence of antibiotics.

anthropogenic evolution

An evolutionary change due to human activity.

artificial selection

The process of human-directed selective breeding aimed at producing a desired set of traits in the selected species.

comparative anatomy

The study of trait structure and function by comparing anatomical structures across species.

descent with modification

The evolutionary process by which species change over time.

evolution

Broadly defined as any instance of change over time. More specifically, in a biological context, it is the process of descent with modification that is responsible for the origin, maintenance, and diversity of life.

extinction

The loss of all individual in a species

fitness

A measure of reproductive success relative to the average reproductive success in a population.

gene expression

The process by which a gene produces a functional product (often a protein).

major transitions in evolution

Fundamental changes and developments in the organization of living things that have occurred over the history of life.

mating systems

The mode or pattern of reproductive pairing in a population. Mating systems include monogamy, polygyny, and polyandry.

mutation

A change to the DNA sequence.

natural selection

The evolutionary process by which beneficial alleles increase in frequency over time in a population because of increased survival and reproductive success of individuals carrying those alleles. Natural selection is the consequence of variation, inheritance, and differential survival.

neutral mutations

Mutations that do not affect fitness, either because they have no effect on phenotype or because the change in phenotype they induce has no fitness consequences.

phenotype

The observable characteristics of an organism.

phylogenetic tree

A visual representation, in the form of a bifurcating tree, of the evolutionary relationship between species, genera, families, and higher taxonomic units.

selective breeding

A process in which humans decide which plants or animals in a population are allowed to breed. See also artificial selection.

Tachycineta bicolor

A tree swallow.

tree of life

A phylogenetic tree that depicts the evolutionary relationships among all living things.

catastrophism

The theory that the geology of the modern world is the result of sudden, catastrophic, large-scale events.

evolutionary synthesis

The collected efforts, primarily in the 1930s and 1940s, of evolutionary biologists, systematists, geneticists, paleontologists, population biologists, population geneticists, and naturalists in shaping modern evolutionary theory to show that a Darwinian view of small-scale and large-scale evolution alike is compatible with the mechanisms of genetic inheritance. Also known as the modern synthesis.

experimental evolution

An experimental approach that examines evolutionary change in real time, often but not always by studying microbial populations in the laboratory.

gradualism

The hypothesis that evolution proceeds primarily by the accumulation of gradual changes.

hypothesis

The hypothesis that evolution proceeds primarily by the accumulation of gradual changes.

inheritance of acquired inheritance

The hypothesis that traits acquired during the lifetime of an organism are passed on to its offspring

methodological naturalism

An approach in which the world is explained solely in terms of natural, rather than supernatural, phenomena and processes.

natural history

The study of organisms in their natural environments.

natural selection

The evolutionary process by which beneficial alleles increase in frequency over time in a population because of increased survival and reproductive success of individuals carrying those alleles. Natural selection is the consequence of variation, inheritance, and differential survival.

population

A group of individuals of the same species that are found within a defined area and, if they are a sexual species, interbreed with one another.

saltationism

The hypothesis that evolutionary change occurs primarily as a result of large-scale changes.

spontaneous generation

The now-disproved hypothesis that complex life-forms can arise, de novo, from inorganic matter.

struggle for existence

Darwin's idea that organisms are continually in competition for resources.

systematics

Darwin's idea that organisms are continually in competition for resources.

transformational process

A process of change in which the properties of a group change because every member of that group changes.

uniformitarianism

Charles Lyell's theory that the same geological processes that we observe today have operated over vast stretches of time and explain the geology of the past and the present.

variational process

A process of change in which the properties of an ensemble change, not because the individual elements change, but because of some sorting process. In evolutionary biology, the sorting process is natural selection.

adaptation

A trait that increases an organism's fitness and which is the result of the process of natural selection for its current primary function.

antagonistic pleiotropy

A phenomenon in which a single gene has multiple phenotypic consequences with opposing effects on fitness. See also pleiotropic genes.

coevolution

The process in which evolutionary changes to traits in species 1 drive changes to traits in species 2, which feed back to affect traits in species 1, and so on, back and forth, over evolutionary time.

differential reproductive success

The difference in the expected number of surviving offspring that can be attributed to having one particular genotype or phenotype instead of another. This is one component of natural selection.

evolutionary arms race

A form of coevolution in which the species involved each evolve countermeasures to the adaptations of the others; most often associated with host–pathogen and predator–prey coevolution.

exaptation

A trait that currently serves one function today but which evolved from a trait that served a different function in the past.

gene duplication

A new duplicate copy of a gene that is produced by mutation, or the process of producing such a copy.

gene sharing

When a protein has more than one function and is expressed in more than one part of the body.

inheritance

Transmission down across generations.

life history strategy

The way that an organism invests time and resources into survivorship and reproduction over its lifetime.

marker gene

A neutral gene with readily observable phenotypic consequences that can be used to track different experimental lines.

norm of reaction

A curve that represents the phenotype expressed by a given genotype as a function of environmental conditions.

pleiotropic genes

Genes that affect more than a single trait.

trade-off

A situation in which constraints prevent simultaneously optimizing two different characters or two different aspects of a character.

variation

In evolutionary biology, genetic variation is one of the components of the process of natural selection.

analogous trait

A trait that is similar in two different species or taxa, not because of common descent, but rather as a result of natural selection operating in similar ways along separate evolutionary lineages.

characters

Measurable aspects of an organism. Characters may be anatomical, physiological, morphological, behavioral, developmental, molecular genetic, and more.

chronograms

A phylogenetic tree on which absolute time is denoted.

clade

A taxonomic group including an ancestor and all of its descendants.

cladograms

A phylogenetic tree in which cladistic (historical evolutionary) relationships are represented but in which branch lengths do not indicate the degree of evolutionary divergence. See also clade, phylogram.

convergent evolution

The process in which natural selection acts in similar ways in different taxa, driving the independent evolution of similar traits in each taxon. See also analogous trait.

divergent evolution

The process in which natural selection operates in different ways in each of two or more taxa that share a recent common ancestor, leading to different traits in these taxa.

homologous trait

A trait shared by two or more species because those species have inherited the trait from a shared common ancestor.

monophyletic group

A group that consists of a unique common ancestor and each and every one of its descendant species, but no other species.

node

A branch point on a phylogenetic tree, representing an ancestral population or species that subsequently divided into multiple descendant populations or species.

paraphyletic group

A group that includes the common ancestor of all its members but does not contain every species that descended from that ancestor.

phylogenetic systematics

An approach to classifying organisms based on their evolutionary histories.

phylogeny

The branching pattern of relatedness among populations (or occasionally, individuals) in a group or taxon.

phylograms

A phylogenetic tree in which the length of each branch represents the amount of evolutionary change that has occurred along that branch.

polyphyletic group

A group that does not contain the common ancestor of its members and/or all descendants of that common ancestor.

polytomy

A node on a phylogenetic tree that has more than two branches arising from it. Polytomies are often used to represent uncertainty about phylogenetic relationships on a phylogenetic tree.

root

The basal (most ancestral) lineage on a phylogenetic tree.

rooted tree

A phylogenetic tree in which the root is indicated and thus the direction of time is specified.

sister taxa

Two taxa that are immediately derived from the same ancestral node on a phylogenetic tree.

taxon

A group of related organisms.

traits

Any observable characteristics of organisms, such as anatomical features, developmental or embryological processes, behavioral patterns, or genetic sequences.

unrooted tree

A phylogenetic tree in which the root, and thus the direction of time, is unspecified.

vestigial trait

Traits that have no known current function but that appear to have had a function in the evolutionary past.

Bayesian inference

A statistical approach often used to model evolutionary processes. Bayesian inference selects as "best" the tree that is most probable given both the observed data and some prior assumptions about possible trees.

bootstrap resampling

A statistical technique for quantifying how strongly a data set supports a given phylogeny.

derived trait

A trait that over evolutionary time has changed form or state from the ancestral form or state.

homoplasy

A trait that is similar in two species because of convergent evolution rather than common ancestry.

independent contrasts

A technique for accounting for shared common ancestry when using the comparative method to access evolutionary trends and patterns.

long-branch attraction

The tendency of some phylogenetic inference methods to incorrectly infer too close a relationship among rapidly evolving taxa.

maximum likelihood

A statistical approach often used to model the evolutionary process. This approach selects as "best" the phylogenetic tree that would have the highest probability of generating the observed data.

odds ratio testing

A statistical technique for quantifying how strongly a data set supports a particular hypothesis. Applied to phylogenetics, odds ratio testing is sometimes used to determine how strongly the data support the hypothesis that a given group represents a monophyletic clade.

outgroup

A distantly related group with a known evolutionary relationship to the taxon being studied. Outgroups are used in rooting phylogenetic trees.

parsimony

An approach to selecting the best phylogenetic tree given some set of character data. Parsimony methods assume that the best tree is the one that requires the fewest character changes to explain the data.

phylogenetic distance methods

Methods of constructing phylogenetic trees based on measurements of pairwise "distances" between species, where distance is a measurement of morphological or genetic differences between species.

phylogeography

The use of phylogenetic and population-genetic tools to study the geographic distributions of populations or species.

polarity

The order in which different variants of a trait evolved over evolutionary time.

sequence divergence

A measure of the extent to which two DNA sequences differ from one another.

symplesiomorphy

A derived trait that has arisen so recently that it appears in only one of two sister taxa.

synapomorphy

A derived trait that is shared in two populations because it was inherited from a recent common ancestor.

alleles

Gene variants; that is, alternate forms of the same gene.

amino acids

Specified by nucleotide triplets, these molecules are the building blocks of proteins.

chromatin

DNA wrapped around histone proteins on chromosomes.

chromosomal deletion

A mutation involving the loss of a section of a chromosome.

chromosomal duplication

A mutation involving the duplication of a section of a chromosome.

codons

A sequence of three consecutive nucleotides specifying an amino acid product.

crossing-over

The physical exchange of segments of DNA on homologous chromosomes during meiosis.

distribution of fitness effects

The distribution of fitness effects of random mutations to a wild-type genome.

dominant

An allele A₁ is said to be dominant over another allele A₂ if its effects on phenotype mask those of A₂; that is, if the A₁A₂ heterozygote manifests the same phenotype as the A₁A₁ homozygote.