Which Best Describes Biogeographic Isolation

Question- Which best describes biogeographic isolation? 

1. A) It always leads to the formation of new species.
2. B) It only happens as a result of geographic factors.
3. C) It cannot lead to evolution.
4. D) It is a mechanism for evolution.

Answer: A) It always leads to the formation of new species.

Biogeographic isolation is best described as the separation of different members of a species because of geographical and biological factors.

Geographical factors include:

• Rise of new mountains
• Change in a river course
• Earthquakes
• Content drifts

Meanwhile, biological factors include:

• Prezygotic barriers
• Postzygotic barriers

Distinguishing between two species of the same organism can be quite challenging. For exmaple, if you were to put pictures of the bald eagle and the African fish eagle side by side, it'll be impossible to find differences between the two.

To any common person, they would look the same.

On the other hand, some animals' physical characteristics are so different that people assume they are of different species. For example, many people mistake a Great Dane and a Beagle to be of different species.

Hence, scientists usually club organisms to a particular species if they are compatible for reproduction.

Interbreeding is a process in which organisms of different species breed together to produce offspring, creating an entirely different species. For example, a mule is born out of interbreeding between a female horse and a male donkey. Now, this mule does not contain the genes of either the horse or the donkey, thereby leading it to be infertile. This proves that the donkey and horse are of different species.

Now, biogeographic isolation often results in the formation of new species that originate from one parent species of an organism.

Also known as allopatric speciation, the parent species of an organism get separated into two or multiple populations because of geographical factors. Often, the changing of the course of a river or an earthquake completely transforms the landform and causes a split in the population.

When these groups are isolated, they undergo genetic divergence. Their genetic composition keeps changing and, over the years, finds more expression in the features of the offspring. These genetic changes occur due to the organisms adapting to their changed environment in order to survive.

As the different populations continue to thrive separately from each other, they may develop prezygotic or postzygotic barriers that might make them incompatible for reproduction. For example, one population might have adapted to newer mating rituals, which are completely different from the other population. As a result, they won’t be compatible for breeding even if the geographical barrier separating them were to be removed.

Sometimes, you don’t need geographical factors to create a separate species. Initially, it seems odd that organisms of the same species living in the same area won’t try to interbreed. However, let’s study the case of the North American apple maggot fly.

As the name suggests, the North American apple maggot flies feed on apple trees. However, originally, the hawthorn tree was their host.

When European settlers started planting apple trees in the area, some of these flies began to use the apple trees as their source of food. The flies that were born in the apple trees exclusively fed on them and did not venture into the hawthorn territory. As a result, two distinct species of flies came about – one that stuck to their original food source of the hawthorn tree and another that chose the apple tree.

Nothing stops these two species from interbreeding. The apple flies can choose the hawthorn as their food source and vice versa. But they don’t, thereby leading to isolation despite the absence of geographical factors.

In conclusion,

Based on all these examples, it is safe to say that biogeographic evolution leads to speciation and not evolution.

Speciation is significantly different from evolution.

While evolution is the process in which heritable features undergo changes in a population through successive generations, speciation only leads to the formation of a new species.

The process of speciation results in certain variations that prevent the different species of an organism from interbreeding. However, over the course of many generations, these variations might continue to increase and lead to the evolution of the species. Therefore, assuming that biogeographic isolation cannot lead to evolution is incorrect.

However, there’s no guarantee that these variations might lead to evolution. So, claiming that biogeographic isolation is a mechanism of evolution won’t be most appropriate.

The discussion has already stated that biogeographic isolation occurs due to both geographical and biological factors. Therefore, option B, which states that it is a result of only geographical factors, is incorrect.

Hence, the only correct or most appropriate answer is option A - biogeographic isolation always leads to the formation of new species.

Frequently Asked Questions

1. How does biogeographic isolation lead to the birth of a new species?

Ans: Biogeographic isolation leads to the separation of different species into different populations. This forces the organisms to sustain themselves through tough environmental conditions. As a result, each of these populations undergo reproduction isolation and genetic differentiation to produce a new species.

2. What causes biogeographic isolation?

Ans: Biogeographical isolation usually occurs due to both biological and geographical factors. Sometimes, compatible species cannot interbreed because of geographical barriers. For example, if a species of apes live on the mainland, they won’t have any contact with those that live on an island far away. Meanwhile, biological factors, like different mating calls, size difference, etc. prevent animals of the same species from mating.

3. Whats is 'island biogeography'?

E.O. Wilson and

Ans: Robert H. MacArthur came up with the term 'island biogeography' in the 1960s. The ecologists noticed the uneven distributions of flora and fauna species on islands and proposed the 'island biogeography' theory. According to this, the current species on any island is a balance between the rate of colonization of the new species and the rate of extinction of established species.

4. What are some examples of biogeographic isolation?

Ans: Some examples of biogeographic isolation include:

• The Appalachian Mountains, which run through Maine to Georgia, create a geographical barrier between various species of flora and fauna.
• The Galapagos Islands are so far off the main coast of Ecuador (600 miles) that several different species of plants and animals have evolved thanks to the diverse habitats.

5. Who is known as the ‘Father of Biogeography’?

Ans: Alfred Russel Wallace is often referred to as the ‘Father of Biogeography’. His study of the diverse flora and fauna and their distribution across the Amazon Basin and the Malay Archipelago was crucial to the development of studies on biogeography. His research focused on the breeding habits, migration tendencies, and distribution of birds and animals in the presence and absence of geographical barriers.