Final answer:
Defining a species is difficult because species are constantly evolving and because the standard definition involving interbreeding does not apply to asexually reproducing organisms. The interbreeding definition of species is generally accepted for sexually reproducing organisms but presents challenges for asexually reproducing ones, necessitating alternative definitions such as phylogenetic or genetic species concepts. Option 4 is correct answer.
Step-by-step explanation:
Defining the concept of a species is a challenging task for several reasons. Firstly, species are constantly evolving, which means their characteristics can change over time as they adapt to new environments. This evolutionary process makes it difficult to draw precise boundaries around a species.
Additionally, the concept of a species is complicated when considering organisms that reproduce asexually, since the standard biological definition involving interbreeding doesn't apply. Furthermore, the environment, both of which are in a state of constant flux, influences the traits that evolve within a species. This can result in new species but can also cause extant ones to vanish, making the tracking and defining of species more complex.
The most widely accepted scientific definition of a species is a group of actually or potentially interbreeding organisms capable of producing fertile offspring. However, with the presence of asexually reproducing organisms, determining their species status can become particularly difficult. For example, bacteria reproduce asexually, so the interbreeding definition of species does not work for them. This leads to alternative species concepts, such as the phylogenetic or genetic species concepts, which are used to categorize these organisms.
Therefore, when answering the question about why defining the concept of species is such a difficult task, all given options contribute to the complexity. However, with the considerations of both evolving species and the issues surrounding asexually reproducing organisms as critical factors in this difficulty, the correct option is 4) Both a and c.