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Speciation | Zoology Optional Notes for UPSC PDF Download
A species is an ecological unit.
A species is a group of potentially interbreeding natural populations which share a common gene pool. Species are reproductively isolated from other such groups. A species consists of several populations. Speciation is the evolution of a new species from a pre-existing one through gradual modification. To create a new species, a mechanism is required to produce reproductive isolation between two populations.
Speciation Categories
- Convergent speciation: Two species that have not developed enough reproductive isolation but have maintained their independent existence due to geographical isolation can merge and produce a new species through hybridization if the geographical barrier separating them is removed. Migrations or accidental carriage by wind or storm can also cause the two populations to merge into one species.
- Divergent speciation: When two or more species are produced by splitting from a single species, either through migration or adaptive radiation. Each population gradually gives rise to an independent species, as seen in the case of Darwin's finches.
- Phyletic speciation: Also known as sequential evolution or transformation, this occurs when a species changes gradually over a long period of time to become entirely different from its ancestor. The evolution of the horse from Hyracotherium and the elephant from Moeritherium are examples of phyletic speciation.
- Quantum speciation: This involves the sudden formation of a new species through rapid changes or saltation, caused by megamutation and disruptive selection, hybridization, or polyploidy. When new areas are colonized, all niches are vacant, which leads to the rapid production of new types through isolating mechanisms.
Types of Speciation based on Mode, Habitat, and Geographical Distribution
- Allopatric speciation: Also known as geographical speciation. A physical barrier divides a population into smaller units, leading to different genetic changes, translocations, inversions, etc. over time. This can occur when sea levels rise and separate islands from the mainland or when populations are accidentally carried into a new area.
- Parapatric speciation: This type of speciation occurs in widely distributed species with continuous distribution and no geographical barriers. Populations have overlapping boundaries, resulting in zones of hybridization or ecological escarpment.
- Stasipatric speciation: This type of speciation occurs through chromosomal rearrangement within the geographical range of the parent species, followed by parapatric distribution. Zones of hybridization can be observed.
- Sympatric speciation: This type of speciation occurs in freely interbreeding populations without geographical isolation. Reproductive isolation is produced by polyploidy or hybridization.
Quantum Speciation
This is the sudden emergence of new groups by saltation. Small, scattered populations or populations that have migrated to new areas experience rapid speciation through genetic drift and chance events or mega mutations. Disruptive natural selection then makes the species distinct and diverse. Mass extinctions can also lead to speciation as surviving species find vacant ecological niches and split into small populations in new environmental pockets.
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FAQs on Speciation - Zoology Optional Notes for UPSC
| 1. What is a species and why is it considered an ecological unit? |  |
Ans. A species refers to a group of organisms that are able to interbreed and produce fertile offspring. It is considered an ecological unit because it plays a crucial role in the functioning of ecosystems. Species interact with other species and their environment, influencing the flow of energy and nutrient cycling within an ecosystem. They also occupy specific ecological niches, contributing to the overall biodiversity and stability of the ecosystem.
| 2. How does speciation occur? | |
Ans. Speciation is the process by which new species arise. It occurs when a population of organisms becomes reproductively isolated from another population of the same species, leading to the development of distinct genetic traits and characteristics over time. This reproductive isolation can happen through various mechanisms such as geographic isolation, behavioral isolation, or genetic isolation. Over generations, the accumulation of genetic differences can result in the formation of a new species.
| 3. What are the factors that can lead to speciation? | |
Ans. Several factors can contribute to speciation. Geographic isolation, where populations become physically separated by natural barriers such as mountains or bodies of water, can lead to genetic divergence and eventually speciation. Behavioral isolation occurs when individuals within a population develop distinct mating behaviors or preferences, preventing them from successfully reproducing with individuals from other populations. Genetic isolation can occur through genetic mutations or changes in chromosome numbers, leading to reproductive barriers between populations.
| 4. How does speciation contribute to biodiversity? | |
Ans. Speciation is a key driver of biodiversity. As new species arise, they add to the overall diversity of life on Earth. Each species occupies a unique ecological niche, playing a specific role in the ecosystem. This diversity of species increases the stability and resilience of ecosystems, as different species have varying responses to environmental changes. Biodiversity also provides numerous ecological services, such as pollination, nutrient cycling, and pest control, which are essential for the functioning of ecosystems and the well-being of human societies.
| 5. Can speciation occur within a short time frame? | |
Ans. Yes, speciation can occur within a relatively short time frame, depending on the circumstances. While speciation is often seen as a gradual process that takes place over thousands or millions of years, there are instances where it can happen rapidly. This is known as "rapid speciation" or "instantaneous speciation." It can occur through mechanisms such as polyploidy, where an organism possesses multiple sets of chromosomes, allowing for rapid genetic divergence and reproductive isolation. Other factors such as natural selection, genetic drift, and hybridization can also contribute to the acceleration of speciation processes.
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Oct 31, 2024 Last updated |
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