What determines the similarities in anatomical features among organisms?

The most common example that determines the similarities in anatomical features among organisms is the bone structure, commonly used in comparative anatomy. For example, the forelimbs or appendages of bats, humans, cats and whales have the same basic parts but they differ in function. Fins of whales and wings of bats have the same skeletal parts, but fin is used for swimming while wing is for flight. These structures could be termed as homologous, analogous, or homoplastic. However, recent developments have been made than just basing to the skeleton - the main reason why we have comparative genomics today. 

The three elements make up most of the human body are

1. Oxygen

2. Carbon

3. Hydrogen

Explanation

The human body is made up of many different elements, but oxygen, carbon, and hydrogen these elements are present in abundance.

Oxygen: oxygen is the first major element that is present in the abundant, about 65 percent total weight of a human body is made up of oxygen. Oxygen is consumed by both inhalation and exhalation process.Carbon: It is the second most important element of the human body, about 18 percent total weight of a human body is made up of carbon.carbon is consumed by the food material.hydrogen: It is the third major element of the human body, about 9 percent of the total weight of the human body is made of hydrogen. In a water molecule, two hydrogen are there.