How do new species arise? Speciation
What is a species? • Biological concept of species • a population or group whose members have the potential to interbreed and produce fertile offspring • Ecological concept of species • identifies species in terms of their ecological niches, focusing on unique adaptations to particular roles in biological communities
SPECIATION • The formation of new species • As new species evovlve, populations become reproductively isolated • Reproductive barriers keep species separate • Reproductive isolation – members of 2 populations cannot interbreed & produce fertile offspring.
Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Tigers and lions are eparated both geographically and ecologically.
Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.
Fig. 23.6 Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.
These squirrels live on opposite sides of the Grand Canyon. This is an example of speciation.
SPECIATION IN DARWIN’S FINCHES • Speciation in the Galapagos finches occurred by: • founding of a new population, • geographic isolation which led to reproductive isolation • changes in the new population’s gene pool due to competition.
Hawaiian Honeycreepers An example of adaptive radiation – these species all diverged from a common ancestor (founder species) FOUNDER SPECIES
Phylogeny • the evolutionary history of a group • based on homologous structures and molecular sequences