A nucleic acid composed of four nitrogenous bases--adenine, thymine, cytosine, and guanine; it is the carrier of genetic information; controls cell activities; and exists as a double-stranded molecule held together by hydrogen bonds
A small section of DNA that codes for a particular trait or protein
A long section of DNA that can have many genes on it.
The building block of nucleic acids, such as DNA, that is made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
A theory where organisms undergo gradual change over time to become different from their ancestors
The exchange of genetic information between two organisms of the same species. Leads to variation and diversity
A permanent change in the DNA
The preserved remains (or an impression) of a plant or animal that existed in a past geological age and that has been dug up from the soil
All of the fossils that have been found anywhere on Earth and that have been formally described in the scientific literature.
The process nature determines those individuals that are better suited to (adapted) their environment. These organisms survive and reproduce and are then able to pass on their genes (gene selection occurs here). Decreases variation in a population
survival of the fittest
The process by which individuals that are better suited to (adapted) their environment survive and reproduce and are then able to pass on their genes (gene selection occurs here)
An inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment
adaptive radiation or speciation
Where one species will evolve (give rise to) one or more other species
A group of similar organisms that can breed and produce fertile offspring
One or more different forms of a gene. ex) eye colour can be the allele for brown or blue....
Having two different alleles - you received one type from mom and one type from dad
Having two of the same alleles - you received the same one from mom and dad
Where individuals choose their mates based on a preference for one or more phenotypic traits. This can be seen where there is a dominant male that mates with many females
allelic / relative frequency
How often an allele occurs in a population
All of the alleles in all the individuals that make up a certain population
The movement of alleles into or out of a population due to the migration of individuals to or from the population. Increases variation in a population
recombination (crossing over)
The exchange of genetic material between homologous chromosomes that increases variation - occurs during meiosis
A chance or random event (flood, earthquake) occurs that causes the death of part of the population and therefore, decreases the gene pool of a small population. Tends to reduce genetic variation.
Where different species evolve to have the same adaptation. They have analogous structures which have the same function but a different structure. Ex) birds wing and an insects wing
Where there was a common body plan (from a common ancestor) that was adapted for different uses by different species of organisms. They have homologous structures which have the same structure but a different function. This one leads to speciation / adaptive radiation
A remnant of a structure, or left over part, that may have had an important function in a species' ancestors, but has no clear function in the modern species.
A theory or model of evolution in which gradual change occurs over a long period of time leads to biological diversity - evolution occurred gradually
A theory where there is a pattern of evolution in which there are long stable periods where no evolution occurs followed by brief periods of rapid evolution and then stability (no change) again
a species whose numbers are so small that the species is at risk of extinction
The complete disappearance of a species from the Earth
When natural selection that favours an average for individuals in a population ex) birth weight - extremes rare
When natural selection favours one of the extreme variations of a trait ex) horses evolving to become bigger
When natural selection that favours individuals with either extreme of a trait ex) two different banding patterns occurring for snail shells - leads to speciation
A technique used to determine the actual age of a fossil on the basis of the amount of a radioactive element it contains
The age of a rock compared to the ages of rock layers - based on its position in the sedimentary rock. The older layers are at the bottom and the younger layers are at the top.