Chapter 8.5 - Speciation

The formation of a new species

small changes in gene (allele) frequencies and phenotypic traits within a population and species

reproductive isolating mechanism prezygotic mechanism postzygotic mechanism

a reproductive isolating mechanism that prevents maturation and reproduction in offspring from interspecies reproduction

a reproductive isolating mechanism that prevents interspecies mating and fertilization (for example, ecological isolation, temporal isolation, and behavioural isolation)

any behavioural, structural, or biochemical trait that prevents individuals of different species from reproducing successfully together

Allopatric and Sympatric

When a new species evolves within a large population due to reproductive isolation Commonly caused by genetic changes such as mutations and polyploidy (extra set of chromosomes)

Occurs when a population is geographically divided into isolated subpopulations Over time, these groups evolve independently, and form new species Eventually members of the different populations can no longer interbreed even if they come back into contact.

Human activities like Agriculture expansion Construction on roads etc Can cause large habitats to move into smaller areas human activities influence the evolution of new species

behavioral, temporal, ecological, mechanical, gametic

different species use different courtship and other mating clues to find and attract males

different species breed at different times of the year

very similar species may occupy different habitats within a region

differences in morphological features may make 2 species incompatible

male gametes may not be able to recognize and fertilize an egg of a different species

zygotic, hybrid unviability, hybrid infertility

Mating and fertilization is possible but genetic differences result in a zygote that is unable to develop properly

a hybrid individual develops but either dies before birth, or if born alive, cannot survive to maturity

Hybrid offspring remain healthy and viable but are sterile