Chapter 24 ~ The Origin of Species. Introduction. Evolutionary theory also explains macroevolution , the origin of new taxonomic groups (new species, new genera, new families, new kingdoms) Speciation is the keystone process in the origination of diversity of higher taxa.
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Today, differences in body function, biochemistry, behavior, and genetic makeup are also used to differentiate species.
ex. two species of garter snakes, genus Thamnophis, live in same areas but one lives in water and other is terrestrial
ex. female fireflies only flash back and attract males who first signaled to them with a species-specific rhythm of light signals
ex. Eastern and western spotted skunk- geographic ranges overlap, yet one mates in late summer, other in late winter
ex. reproductive isolation of flowering plants that are pollinated by insects/animals
ex. many insects, the male and female copulatory organs do not fit together, preventing sperm transfer
ex. may be due to differences in chromosome number or structure
mule, the hybrid between a horse and donkey cannot mate (except very rarely) with either horses or donkeys
ex. The sequences of nucleic acids and proteins provide data that are used to define species by unique genetic markers.
Modes of speciation (based on how gene flow is interrupted)
Can separated populations interbreed and produce fertile offspring when they come back in contact?
Ring species ex. salamander, Ensatinaescholtzii, expanded south from Oregon to California, USA
Diane Dodd studied Drosophila, demonstrating a prezygotic barrier to interbreeding developing from adaptive diveregence
However, under light conditions showing no color differences, females will mate with males of the other species
Changes accumulated in
resulting in speciation
Species seen in fossil record
Evolution is a response between organisms and their current environments, leading to changes in evolutionary trends as conditions change
ex. differences in the feet of tree-dwelling versus ground-dwelling salamanders
mutation in the alleles that control the timing of foot development
Ex. a sexually mature stage can retain juvenile structures - a process called paedomorphosis
This axolotlsalamander hasthe typical externalgills and flattenedtail of an aquaticjuvenile but hasfunctioning gonads