How Do Evolutionary Factors Lead to the Formation of New Species?
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.
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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.
FAQs on Speciation Evolution Factors: Key Causes, Types & Examples
1. What are the primary factors that lead to speciation?
Speciation, the formation of new and distinct species, is driven by several key evolutionary factors that prevent gene flow between populations. The primary factors include:
- Geographic Isolation: Physical barriers like mountains, rivers, or oceans divide a population, preventing interbreeding.
- Natural Selection: Separated populations adapt to different environmental pressures, leading to divergent traits.
- Genetic Drift: Random changes in the frequency of genes in small, isolated populations can lead to significant differences over time.
- Mutation: The ultimate source of new genetic variation, providing the raw material upon which other evolutionary forces act.
- Reproductive Isolation: The development of barriers (pre-zygotic or post-zygotic) that prevent members of different populations from producing viable, fertile offspring.
2. What are the main types of speciation, with examples?
Speciation is broadly classified based on the geographical separation between the diverging populations. The main types are:
- Allopatric Speciation: Occurs when a population is split by a geographic barrier. For example, the formation of the Grand Canyon separated a squirrel population, leading to the evolution of the distinct Kaibab and Abert's squirrels on opposite rims.
- Sympatric Speciation: Occurs without a physical barrier, within the same geographic area. An example is seen in apple maggot flies, where some populations shifted to feeding on apples instead of the native hawthorn fruit, leading to reproductive isolation over time. This can also occur via polyploidy in plants.
- Parapatric Speciation: Occurs when populations are not completely separated but have a narrow contact zone. Gene flow is limited, and strong selective pressures in their respective environments lead to divergence. An example is the grass Anthoxanthum odoratum growing on and off mine tailings.
- Peripatric Speciation: A specific type of allopatric speciation where a small group becomes isolated at the edge of the main population's range. Genetic drift plays a significant role here due to the small population size.
3. How does adaptive radiation lead to speciation?
Adaptive radiation is a process where a single ancestral species rapidly evolves into multiple new species, each adapted to a specific ecological niche. This process directly leads to speciation by creating reproductive isolation. When a population enters a new environment with unoccupied niches (like an island), different groups adapt to different food sources or habitats. For instance, Darwin's finches in the Galápagos Islands evolved different beak shapes to exploit various food sources (seeds, insects, etc.). This specialisation led to changes in mating signals and preferences, eventually resulting in them becoming distinct species unable to interbreed.
4. What is the difference between speciation and evolution?
While related, evolution and speciation are not the same. Evolution is the broader process of change in the heritable characteristics of biological populations over successive generations. It happens at all scales, from microevolution (changes in gene frequency) to macroevolution (large-scale changes). Speciation, on the other hand, is a specific outcome of macroevolution. It is the 'species-forming' event, where a lineage splits into two or more distinct species. In essence, speciation is a result of evolution, but not all evolutionary change results in speciation.
5. Can speciation occur without a physical barrier separating populations?
Yes, speciation can occur without a physical barrier through a process known as sympatric speciation. This happens when populations living in the same area become reproductively isolated through other means. Key mechanisms include:
- Polyploidy: A condition where an organism has more than two complete sets of chromosomes. This is common in plants and instantly creates a new species because the polyploid individuals can no longer successfully mate with the original diploid individuals.
- Disruptive Selection: When natural selection favours extreme phenotypes over intermediate ones, leading to subgroups that specialise on different resources or habitats within the same area, eventually causing them to stop interbreeding.
6. Why is reproductive isolation considered the most crucial factor for speciation?
Reproductive isolation is the most crucial factor because it is the ultimate barrier that prevents gene flow between diverging populations. Even if populations are geographically separated and have evolved different traits, they are not considered distinct species until they can no longer produce viable, fertile offspring together. Reproductive isolation solidifies the genetic differences that have accumulated through mutation, natural selection, and genetic drift, ensuring that the two populations follow separate evolutionary paths. It is the final step that confirms the formation of a new species.
7. How does genetic drift contribute to the formation of new species, especially in small populations?
Genetic drift refers to random fluctuations in allele frequencies from one generation to the next, purely by chance. In small populations, its effects are magnified. When a small group gets isolated (the founder effect), its gene pool may, by chance, be very different from the source population. Over time, genetic drift can lead to the random fixation of certain alleles and the loss of others. This random divergence, independent of natural selection, can lead to significant genetic differences between the small, isolated population and its ancestral population, contributing to the development of reproductive barriers and ultimately, speciation.
