LO4 Flashcards
Describe challenges biologists face when defining species, including what significance is given to morphological differences, genetic variation, and reproductive isolation. Explain how genetic variation can lead to reproductive isolation and speciation. Distinguish allopatric and sympatric speciation processes, and describe a possible scenario of each. List several pre-zygotic and post-zygotic mechanisms of reproductive isolation and tell how they help to maintain distinct species.
Microevolution
consists of changes in allele frequency in a population over time
Macroevolution
refers to broad patterns of evolutionary change above the species level
biological species concept
a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with members of other populations
Limitations of the Biological Species Concept
The biological species concept cannot be applied to fossils or asexual organisms (including all prokaryotes)
morphological species concept
defines a species by structural features
This applies to sexual and asexual species but relies on subjective criteria
ecological species concept
views a species in terms of its ecological niche
This applies to sexual and asexual species and emphasizes the role of disruptive selection
phylogenetic species concept
defines a species as the smallest group of individuals on a phylogenetic tree
This applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species
Reproductive isolation
is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring
Hybrids
are the offspring of crosses between different species
