Question

Why do organisms look Similar?

Answer 1

All Organisms are made up of different tissues and organs which consist of cells which are all basically made up of genetic material, this genetic material passed down from one generation to another leading to similarity in features of animals.

complete answer:
All Organisms are made up of cells. Inside these cells’ nucleus DNA is present Which determines the development of each individual.
DNA and RNA constitute the genetic material of all living organisms.
We inherit this DNA from Our Parents That is why many times we are so similar.
This Happens in every species of every organism, that is when the DNA passes to the next generation, the same morphology is retained in the new organism.
In human beings These DNA sequences are packed into 23 pairs of chromosomes.
Most of our DNA sequences are the same. In fact, all humans are $99.3\%$ the same. That tiny. $7\%$ difference is what makes each one of us unique.
This is the reason all organisms belonging to the same species look so similar.

Note:
DNA is first replicated (that is duplicate copy of the parents DNA is made).
This involves several chemical processes which require various enzymes.