Lesson - Speciation

Lesson Objectives

Content Objective: Explain how different types of isolation can result in the formation of a new species.

Language Objective: Create a set of notes on the syllabus details below.

Syllabus Statements:

A3.1.4—Biological species concept - "According to the biological species concept, a species is a group of organisms that can breed and produce fertile offspring. Include possible challenges associated with this definition of a species and that competing species definitions exist."

A3.1.5—Difficulties distinguishing between populations and species due to divergence of noninterbreeding populations during speciation - "Students should understand that speciation is the splitting of one species into two or more. It usually happens gradually rather than by a single act, with populations becoming more and more different in their traits. It can therefore be an arbitrary decision whether two populations are regarded as the same or different species. "

A4.1.6—Speciation by splitting of pre-existing species "Students should appreciate that this is the only way in which new species have appeared. Students should also understand that speciation increases the total number of species on Earth, and extinction decreases it. Students should also understand that gradual evolutionary change in a species is not speciation."

A4.1.7—Roles of reproductive isolation and differential selection in speciation - "Include geographical isolation as a means of achieving reproductive isolation. Use the separation of bonobos and common chimpanzees by the Congo River as a specific example of divergence due to differential selection."

A4.1.8—Differences and similarities between sympatric and allopatric speciation - "Students should understand that reproductive isolation can be geographic, behavioural or temporal."

A4.1.9—Adaptive radiation as a source of biodiversity "Adaptive radiation allows closely related species to coexist without competing, thereby increasing biodiversity in ecosystems where there are vacant niches."

A4.1.10—Barriers to hybridization and sterility of interspecific hybrids as means of preventing the mixing of alleles between species - "Courtship behaviour often prevents hybridization in animal species. A mule is an example of a sterile hybrid."

A4.1.11—Abrupt speciation in plants by hybridization and polyploidy - "Use knotweed or smartweed (genus Persicaria) as an example because it contains many species that have been formed by these processes."