W18 L1 - Speciation and Molecular Clocks

Flashcards about speciation, molecular clocks, and key evolutionary concepts.

Molecular Clock

Converts measures of genetic distance between sequences into estimates of the time that this lineage is separated or diverged.

Paralogous genes

Genes where nucleotide substitutions are proportional to the time since the genes became duplicated and do not help with timing.

Molecular Clocks Calibration

Number of genetic distances are plotted against the dates from the fossil record to calibrate phylogenetic trees.

Speciation

The origin of new species and the focal point of evolutionary biology.

Micro evolution

Changes in allele frequency that affect populations over time.

Macro evolution

Broad patterns of change between species or groups of species.

Species

Groups of populations that can interbreed and produce fertile offspring.

Reproductive isolation

The existence of biological factors or barriers that impede two species from producing viable and fertile offspring.

Pre zygotic barrier

Factors that affect the creation of a zygote or embryo.

Prezygotic barriers

Species cannot create a zygote or an embryo.

Post zygotic barrier

They manage to create an embryo, but it is not fertile, doesn't develop fully, or is not fertile.

Reduced hybrid viability

The embryo cannot develop into a full grown adult.

Hybrid breakdown

Usually happens in plants, the first generation of hybrids are fertile, but the second generation does not work.

Hybrids

Result of mating different species.

Hybrid zone

Species with incomplete reproductive barriers come into contact.

Allopatric speciation

Geographic isolation restricts gene flow between populations.

Sympatric speciation

Reproductive barrier that stops the population from breeding.

Allopathic expreciation

A geographic barrier.

Sympatric expreciation

No geographic barrier.

Periopathic expedition

Geographical barrier plus founder effect makes the species very fast.

Symbiotic exposition

Symbiotic exposition happens when there is no geographic barrier.