[Biology Class Notes] on Speciation Evolution Factors Pdf for Exam

What is Evolution?

Evolution is essentially the change of a species’ characteristics over many generations. The evolution theory was first offered by Charles Darwin. Evolution is a variation on the heritable properties of biological species over subsequent generations. Those characteristics are gene variations that are transferred from parent to offspring during reproduction. Specific traits tend to occur within any particular population as a result of mutation, genetic recombination, and other causes of genetic variation. Evolution is a result of a number of factors, which includes environmental factors as well.

What is Speciation?

Speciation is how to establish a new kind of animal or plant species. Speciation happens when a group distinguishes its species from other members within a species and creates its own unique characteristics. The demands of another environment or features of the new group members will differentiate the new species from their ancestors.

Examples of Speciation

There are several examples of speciation in nature; some of them are:

• Three-spined sticklebacks

• Greenish Warbler

• Cichlid fishes in Lake Nagbago

• Ensatina salamanders

• Larus gulls

• Petroica multicolor

• Mayr bird fauna

• Squirrels in the north and south rims of the Grand Canyon

• Finches

• Faeroe Island house mouse

• Croatian lizards

Types of Speciation

The causes of speciation are:

Allopatric Speciation

This is one of the most common forms of speciation. It occurs when the members of a specific population get geographically isolated from one another. It occurs to such an extent that genetic exchange via mating is prevented. It may be a result of the formation of mountains, volcanos, islands, glaciers, etc. It can also occur due to human activities as well. 

Parapatric Speciation

Parapatric speciation happens when species are isolated by a significant habitat shift rather than by a physical boundary, such as a body of water. Example-Plants that live on boundaries between extremely distinct climates may form flowers in response to the different environments at different time periods, making them unable to interbreed.

Sympatric Speciation

When there is an evolution of new species, even though there has been no geographical isolation of the species, it is called Sympatric Speciation. It is far more prevalent in plants and rare in animals. For example, in British Columbia speciation of 3-spined sticklebacks, freshwater fishes.

Peripatric Speciation

Peripatric speciation occurs when a small group of individuals breaks away from the main group to form a new species. Similar to allopatric speciation, physical barriers such as mountain ranges or waterways separate the two groups, making it almost impossible for the two groups to interbreed. One example is the Mosquito on the London Underground.

Artificial Speciation

Artificial speciation is the speciation form, which can be achieved through the intervention of human beings. By artificially separating populations and thus restricting any form of breeding, or deliberately breeding individuals with specific morphological or genotypic characteristics, humans can create new, distinct species.

[]

Factors Responsible for Speciation

These factors help in determining how speciation takes place:

Geographical Isolation

Separation of two populations of the same species or breeding community, such as a mountain or body of water or any other physical boundary. Geographic isolation will eventually contribute to the adaptive radiation making different species for the populations.

Natural Selection

Natural selection is a pressure which in the course of time causes changes in organism groups. Animals inherit their DNA from their parents or ancestors, while the environment constantly changes. So, no organism is completely adjusting to its environment. Thus, species evolution is continuously affected by natural selection.

Genetic Drift

Caused by chance alone when there are drastic changes in the frequencies of specific genes. Genetic drift with gene flow changes imposed by the insulation mechanism acts as a speciation agent.

Hybridization

Hybrid speciation is a speciation form in which hybridization between two different species results in a new species, isolated reproductively from the parent species. Previously, it was thought that reproductive isolation between hybrids and their parents was particularly difficult to achieve, and therefore it was thought that hybrid species were extremely rare.

Fun Facts

• No two animals are identical even though they belong to the same species.

• Within one species, small changes can add up and create a whole new species.

• There are more than 340 dog breeds, and they all come from one kind of wild wolf which existed many years ago.

• The slightest change in color or design will help a plant or animal grow, survive and better reproduce in the wild. That is called natural selection.

• Birds have evolved from birds, and they also originate from reptiles. The crocodile is the closest living reptilian relation to a bird.