Explain why organisms reproduce only their own kind and why offspring more closely resemble their parents than unrelated individuals of the same species.

Answer: Heredity

Explanation: organisms can reproduce only their own kind due to heredity. Heredity is the transmsion of traits and characters from a parent to its offspring through what is known as gene (a unit of heredity carried by chromosomes of cells)

Now that takes us to the second part of the question,

Traits of the parents are carried in a form of 'genetic information' and passed-on to the offspring thereby making them have a unique resemblance of their parents compared to the other individuals.