Question

A major mechanism of speciation in plants but not in animals is a adaptation to new environments. b polyploidy. c hybrid breakdown. d genetic changes that alter the organism's niche. e both a and d.

Short answer

The major mechanism of speciation in plants but not in animals is polyploidy.

Step-by-step solution

Understanding the Options

Understanding each of the options provided is crucial to answer the question correctly. \n a) Adaptation to new environments: Both plants and animals can undergo speciation due to adaptation to new environments. \n b) Polyploidy: Polyploidy refers to duplication of the entire set of chromosomes, a phenomenon seen especially in plants. \nc) Hybrid breakdown: Hybrid breakdown is a type of postzygotic barrier that reduces the viability or fertility of hybrid offspring. This can occur in both plants and animals. \nd) Genetic changes that alter the organism's niche: Both plants and animals can undergo speciation due to genetic changes that alter the organism's niche. \ne) Both a and d: As explained, both plants and animals can undergo speciation due to adaptation to new environments and genetic changes that alter the organism's niche.

Identifying the Correct Answer

Knowing that the correct answer is a major mechanism of speciation in plants, but not in animals, now it's necessary to eliminate the options that are applicable to both. Options a, c, d, and e are applicable to both plants and animals, while option b, polyploidy, is a major mechanism of speciation seen specifically in plants and not in animals. Thus, the correct answer is option b.

Verifying the Answer

After identifying the right answer, verify this by cross-checking with your understanding or available resources. Polyploidy being a major mechanism of speciation in plants but not in animals is a verified fact in biology, hence confirming the choice.

Key concepts

Polyploidy

Polyploidy stands out as a fascinating evolutionary strategy predominantly observed in plant species. It involves the duplication of the entire set of chromosomes, resulting in organisms with more than two complete sets of chromosomes. Occurring during cell division when errors in meiosis or mitosis cause a doubling of the chromosome number, polyploidy can lead to instant speciation since polyploid individuals can often only mate with other polyploid individuals, setting them on a separate evolutionary path from their diploid counterparts.

Polyploidy is significant because of its potential to create new species in a single generation. It provides variation on which natural selection can act, fostering diversity within plant kingdoms. Polyploid plants are also often larger and more robust, possibly giving them an edge in survival and adaptation. While polyploidy can occur in animals, it is much less common and does not generally contribute to speciation due to complications in animal developmental processes.

Postzygotic Barriers

The term 'postzygotic barriers' describes reproductive obstacles that occur after the fusion of gametes (sperm and egg). These barriers can take many shapes, such as hybrid inviability, where the offspring fail to develop properly, or hybrid sterility, where the offspring are unable to reproduce. Another example is hybrid breakdown, which may occur in successive generations after the initial hybrid is viable and fertile.

These postzygotic barriers play a critical role in maintaining species integrity by preventing the merging of species gene pools. They are essential mechanisms by which closely related species remain distinct despite their ability to mate and produce offspring. In plants, postzygotic barriers can be bypassed through mechanisms like polyploidy, which allows the establishment of new species despite hybridization events, showcasing an alternative route of speciation in plants that is less prevalent in animals.

Adaptation to New Environments

Species often encounter new environments that demand significant adjustments for survival. Adaptations arise through natural selection, which favors the propagation of beneficial traits. In the context of plants, adaptation to new environments can be swift due to their immense genetic variation and ability to undergo phenomena like polyploidy. This capability permits plants to establish new ecological niches and to continue evolving separately from their parent populations.

Understanding adaptation in plants involves considering their sessile nature; being rooted to one spot, plants must adapt to the conditions where they find themselves or perish. This has led to a vast array of specialized forms and functions within the plant kingdom, from the water-conserving cacti of arid deserts to the epiphytic orchids of humid rainforests. Such adaptations in response to environmental pressures underscore the creative potential of evolutionary processes and highlight the resilience and plasticity of plant life.