Answer:
Genetic drift
Explanation:
Genetic drift can also be referred to as allelic drift, it refers to the variation in allelic frequencies within a particular population over a period of time. It can also be referred to as the random fluctuations in the number of genotypes within a population. Genetic drift is not influenced by the environment and is usually more pronounced in a small population of organisms.
For example, a population of birds can consist of green feathers and blue feathers with the green feathers as the dominant allele, but as a result of random fluctuations, the offspring may all be with green feathers and hence could eliminate or reduce the allele responsible for blue feathers over time.
Organ system is the answer according to me if it is one word question
Nucleic acid is the answer for this problem
I only have an answer for number 24, I'm sorry! But one piece of evidence is the DNA sequences, they have discovered that humans and monkeys/apes share a common ancestor through DNA. Another would be fossils, scientists have fossils to show great similarities in the skull and jaw structure, along with the legs, comparing to humans.