Before any truly accurate scientific work on evolution and inheritance could be done, the academic community had to accept the notion that the Earth and its species change over time. If species were fixed, then genetic variation, natural selection, and evolution could not be plausible. Once the scientific community acknowledged the changes in organisms, they were able to proceed into studies to determine why and how such changes occur.

Darwin's finches were distinct from one another due to the size and shape of their beaks. Darwin noted that these distinct beaks allowed the different birds to eat specific food groups. The varying food groups allowed the animals to coexist in the same habitat, without resorting to competing for natural food resources. Each species had evolved to occupy a unique ecological niche in order to survive with minimal competition for resources.

Evolution is a theory that accounts for the changing and transformation of organisms throughout history. For evolution to take place, mutations must occur and change the genetic identity of a population. Essentially, evolution is evidenced by changes in genetic diversity and allele frequency. Each of the answer choices contributes towards the theory of evolution.

Natural selection was coined by Darwin, whose work helped with the theory, and describes the tendency for traits that aid in survival to become more prevalent in a population. Vestigial structures are organs in modern organisms that serve no purpose in increasing biological fitness, but may have been useful to ancestral species in history. Common ancestor organisms are different species that share genetic information with modern species, suggesting that genetic changes in the historic species may have produced the modern species. The fossil record provides genetic material and physical evidence of historic species to use for comparison with modern organisms.

All of these are true. There is lots of evidence supporting the endosymbiotic theory. The mitochondrial genes, in addition to the genes in the nucleus, are also needed to make a functional mitochondrion. These genes are contained in a singular circular chromosome, the same way bacterial genes are organized. Also, when translating their mRNA, they use the same ribosome structure as prokaryotes (70s). The mitochondria are not replicated the same way as other organelles or structures; they undergo binary fission.

The correct answer is that mitochondrial DNA is found in the mitochondria, where it takes the form of a plasmid, or ring-shaped structure characteristic of bacterial DNA. (This provides evidence in favor of the endosymbiotic theory.) Furthermore, in humans and in many other organisms, mitochondrial DNA is passed down solely through the maternal line. Note that the answer choice "It is found in a plasmid in the nucleus" is inherently non-sensical; plasmids are characteristic of prokaryotes, which do not have nuclei, as they do not have membrane-bound organelles.

Homologies are physical similarities resulting form common ancestry.  This is the reason that related species share similar features.  Therefore, homologous structures are anatomical similarities in organisms due to a shared ancestry.  On the other hand, analogous structures are the result of convergent evolution.  Convergent evolution is defined as the evolution of similar anatomical features in independent evolutionary lineages. In response to a changing environment, natural selection favored animals with similar traits or features that evolved independently as a result of  adaptation to environmental alterations.