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What is a taxon in biological classification?
A group of organisms treated as a unit, such as a genus or all insects.
What are the hierarchical levels in taxonomic classification?
Genera, families, order, classes, phyla, kingdoms.
What does monophyletic mean?
A taxon that includes one ancestor and all of its descendants, with no other organisms.
What is problematic about historical taxonomy?
Many names were given before detailed phylogenetic information was available.
What is the difference between paraphyletic and polyphyletic taxa?
Paraphyletic taxa include a common ancestor but not all its descendants, while polyphyletic taxa lack a common ancestor.
What does the molecular clock hypothesis suggest?
It allows prediction of evolutionary divergence timing because rates of molecular change are consistent.
What is a molecular clock calibrated by?
Independent data such as the fossil record and known divergences.
What is neutral molecular evolution?
Most mutations are neutral and can fix in populations via genetic drift.
What is the probability of fixation for a new neutral mutation?
1/2N, where N is the population size.
What is a pseudogene?
Duplicate copies of genes that are no longer functional.
What is the difference between synonymous and nonsynonymous substitutions?
Synonymous substitutions do not change the amino acid specified, while nonsynonymous substitutions do.
What are gap genes in segmentation?
Genes that organize broad areas during the development of an embryo.
What defines the morphology of each segment in an embryo?
HOX genes, which are expressed in different combinations along the length.
What is heterometry in developmental genetics?
Altered quantity of gene expression of a developmental gene.
How does modularity relate to evolution?
It allows genes affecting development to evolve independently in form or expression.
What is the role of BMP4 and CaM in Darwin's finches?
They affect beak shape by influencing gene expression during early development.
What is heterochrony?
Altered timing of gene expression during development.
What causes ducks to have webbed feet?
Altered spatial expression pattern of the developmental gene BMP4 and its inhibitor Gremlin.
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