Macroevolution and Evolutionar y Anthro 21:06
Macroevolution refers to large-scale changes at or above the species level, extending
over a geological era, and resulting in the formation of new taxonomic groups.
What’s a Species?
- a single, distinct class of living creature with features that distinguish it from
Biological Species Concept (BSC)
a species represents a population of individuals that varies from other species in a
variety of ways and that individuals in a population exchange genes by
biological features prevent one species from breeding with another species
Phylogenetic Species Concept (PSC)
a species is the smallest aggregation of (sexual) populations diagnosable by unique
combination of character states.
it requires a researcher to measure and analyze character states of a sample of
individuals in and between populations.
- Allopatric speciation: some form of physical barrier causes geographic isolation
and reduces gene flow between populations. The barrier only has to limit gene flow;
complete isolation is not necessary. Thus, a barrier can operate in very small
geographic scales for some organisms.
- Two major models of allopatric speciation:
vicariant speciation: occurs when a physical barrier creates large, geographically
separated populations, which then diverge from each other and can no longer
Peripatric spetiation: occurs when a small, peripherally isolated colony of the main
population diverges to become a new species.
Intro to Cladistics
- the study of evolutionary relationships within and between organisms on our
- a cladogram, also known as a phylogeny or evolutionary tree, is a graph used to
visualize hypothesized evolutionary relationships.
- thus, a cladogram is a graphical representation of the evolutionary relationships
among organisms, whether extinct or extant.