Final answer:
Novel traits in organisms arise primarily due to genetic mutations, which create new phenotypes that can be selected for, and genetic recombination from sexual reproduction, leading to increased genetic diversity.
Step-by-step explanation:
Novel traits in organisms typically arise through mutations in genes. These mutations can result in a new phenotype, which is a new observable characteristic. When this new trait proves to be adaptive and beneficial for the organism, it may be favored by natural or sexual selection, leading to an increased frequency of the trait within the population. Sexual reproduction also contributes to genetic diversity, creating new combinations of alleles that can give rise to novel traits.
For mutations to contribute significantly to evolution, they must occur in gametes, so they can be inherited by the next generation. Mutations can sometimes also be introduced into a population through gene flow, where new genetic material is incorporated from another population. Over time, the accumulation of these changes can lead to the development of new traits that can define new branch points in the evolution of a species, contributing to the biodiversity we see today.
In summary, new traits can appear through gene mutations, which can be random or induced by environmental factors. These mutations are the source of new genetic variation and the raw material for evolution.
The final answer for how novel traits arise is: Through mutations that lead to a new phenotype and genetic recombination due to sexual reproduction, some of which are favored by natural selection or sexual selection, leading to an increase in frequency of these traits in a population.