an active learning technique in which an instructor poses a question and students write a brief response in one to three minutes. The responses can be reviewed to assess student understanding or graded with a check/check-minus/check-plus system.
Myriapods (myria = ten thousand, pod = foot) are a group of arthropods distinguished by the following characters:
- a body built from a head and long, repeating trunk
- one pair of antennae (number of other appendages on head varies), many (but not 10,000!) limbs on trunk
Examples of myriapods include centipedes and millipedes.
Centipede photo by James T. Johnson © California Academy of Sciences; Millipede photo © 2003 John White
A segment of muscle.
A species interaction in which both of the interacting species profit from the interaction.
most recent common ancestor
(abbr: MRCA) The youngest common ancestor that two taxa share. On a phylogenetic tree, one can locate the most recent common ancestor of two terminal taxa by tracing each lineage back in time until they meet. The node at which the lineages meet represents the most recent common ancestor of the taxa.
The study of the form and structure of organisms. For example, comparing the shape of the femur in different grazing mammals is a morphological study.
A process in which an animal sheds all or part of its outer covering, which is then regenerated in some way. For example, arthropods molt their exoskeletons in order to grow, and birds molt their feathers in order to replace worn out feathers or to prepare for a different season or for breeding.
In evolutionary biology, having to do with DNA sequences or the amino acid sequences of proteins.
The idea that some stretches of DNA evolve at a constant enough rate that they can be used to estimate the dates of past events. Learn more about molecular clocks.
A conception of the processes and mechanisms of evolution that builds on Darwin’s original ideas about evolution by incorporating advances in our understanding of Mendelian genetics, molecular genetics, and population genetics. The modern synthesis was developed in the 1930s and 40s and integrates the work of Charles Darwin, Theodosius Dobzhansky, Ronald Fisher, Sewall Wright, and others. For more details, see our historical essay on the topic.
A change in a DNA sequence, usually occurring because of errors in replication or repair. Mutation is the ultimate source of genetic variation. Changes in the composition of a genome due to recombination alone are not considered mutations since recombination alone just changes which genes are united in the same genome but does not alter the sequence of those genes. For a more detailed explanation, see our resource on mutation in Evolution 101.
Aspects of genetics associated with the molecules responsible for inheritance: DNA and RNA. The field involves, for example, the sequence of bases on a DNA molecule, the copying of DNA, the transcription of DNA into RNA, and the translation of RNA into amino acids.
In science, the term model can mean several different things (e.g., an idea about how something works or a physical model of a system that can be used for testing or demonstrative purposes). However, as a research method, modeling often means creating a mathematical model — a set of equations that indirectly represents a real system. These equations are based on relevant information about the system and on sets of hypotheses about how the system works. Given a set of parameters, a model can generate expectations about how the system will behave in a particular situation. A model and the hypotheses it is based upon are supported when the model generates expectations that match the behavior of its real-world counterpart. Modeling often involves idealizing the system in some way — leaving some aspects of the real system out of the model in order to isolate particular factors or to make the model easier to work with computationally.
In evolution, lack of fit between an organism’s traits and its environment. A mismatch is likely to occur if a species that evolved in one environment moves to a different environment or if a species’ environment changes rapidly and the species does not experience natural selection and adapt to these changes. Evolutionary mismatches are frequently used to explain aspects of human biology that are problematic in modern life, but that may have been beneficial over the course of our evolutionary history.
The movement of individuals between populations.
Changes in gene frequency in a population from one generation to the next.
The collection of microbial organisms that live internally and externally upon larger organisms.
A small (under about one meter across), rocky or metallic object traveling through space. If a meteoroid enters the Earth’s atmosphere it may heat up and glow as a meteor, or “shooting star.”
A piece of meteoroid, asteroid, or comet that survives its journey through the atmosphere and hits the ground.
Aspects of genetic inheritance documented by Gregor Mendel. Mendelian genetics mainly refers to the ideas that (1) traits are influenced by discrete heritable elements (now known as genes) that come in different varieties (now known as alleles), (2) for a particular gene, each individual carries two alleles, one inherited from each parent, (3) during reproduction, one allele from each pair is randomly selected to be passed to the offspring and united with the other parent’s alleles, (4) because of these characteristics, trait ratios among offspring are predictable if the parental genotypes are known. For more details, see our historical essay on the topic.
Event in which many different lineages go extinct around the same time. Mass extinctions involved higher rates of extinction than the usual rate of background extinction that is going on all the time. For a more detailed explanation, see our resource on mass extinctions in Evolution 101.
A mammal, such as an opossum or kangaroo, whose young are suckled and protected inside a maternal pouch.
Evolution above the species level. The adaptive radiation of a lineage into many different niches is an example of macroevolution. Since evolutionary change above the species level, means that populations and species must be evolving, macroevolutionary change entails microevolutionary change.
An organelle in eukaryotic cells where cellular respiration takes place. Mitochondria contain a short loop of DNA that is distinct from the DNA contained in the cell’s nucleus.
Group of two or more atoms bonded together.