G11.4B 5 – Evolution – Speciation Learning Objectives 11.2.6.5 11.2.6.5

the main mechanisms of speciation
Success Criteria
1. Define species, speciation

and hybrid.
2. State and explain the two parts of speciation with examples.
3. Explain, identify, and give examples of the 4 main mechanisms of speciation

CIE Biology Jones
p402 to 418

Understanding Evolution Website https://evolution.berkeley.edu/evolibrary/article/evo_14

Speciation occurs when populations of the same species evolve to
become so different that they can’t breed with one another to produce fertile offspring.

Bozeman Speciation
http://www.bozemanscience.com/speciation

Extra help

functional role that it plays within an ecosystem. The niche (better

refined as the 'ecological niche') is determined by the abiotic factors (non-living).

Describe and give examples for each type of speciation
Modes of Speciation a group of organisms that is about to become a separate species from other, related individuals. For a lineage to split once and for all, the two species must have genetic differences that are expressed in some way that causes mating’s between them to either not happen or to be unsuccessful. These need not be huge genetic differences. A small change in the timing, location, or rituals of mating could be enough. But still, some difference is necessary. This change might evolve by natural selection or genetic drift. Reduced gene flow probably plays a critical role in speciation. Modes of speciation are often classified according to how much the geographic separation of species can contribute to reduced gene flow.

Geographical barriers
Geographic isolation

more rapidly.
What are the two parts of speciation?

an ecosystem. The niche (better refined as the 'ecological niche') is determined

by the abiotic factors (non-living). New populations develop around new niches – usually due to an adaptation that allows survival.

Genetic isolation  speciation

Barrier causes isolation that leads to evolution by causing genetic differentiation(change) also
Geographic isolation

Formation of a new species due to difference in the same environment forms a (hybrid zone) lives in a new niche adjacent (close) to the original niche. – also genetic polymorphism

Isolation leads to a new species in a new niche outside of the original niche – also the founder effect

Genetic differentiation leads to a new species to evolve within the original niche forming a new niche.

(reproductive)

Cut off

Physical barrier

Genetic polymorphism

Main mechanisms of speciation

fertilization/breeding)

capable of breeding but have different courtship rituals
Common Ancestor

Mountains, Lakes, Oceans, Rivers, Deserts…over time speciation will occur.
Geographic Isolation
Kaibab

squirrel has a black belly and lives on the North Rim.

Abert squirrel has a light colored belly and lives on the South Rim

Grand Canyon, Arizona

Common Ancestor

different times of day or night.
Dural = day
Nocturnal =

night

Common Ancestor

physiological

Examples
Attractive coloring of fur, feathers, scents, mating calls, or

rituals.

can no longer interbreed to produce successful offspring
Examples

Geographic barriers Change in Anatomy or physiology
Behavior- bird mating calls are different
Temporal- mating times have changed seasons, or day to night

the potential to interbreed to produce fertile, viable (living) offspring Members

of a species are unable to produce fertile and viable offspring with members of a different species (hybrid) Hybrids are individuals produced by cross-breeding between two different species, and are reproductively sterile (e.g. ligers, mules) Reproduction Isolation Barriers Pre-zygotic – before fertilization occurs Post-zygotic – after fertilization occurs