Final answer:
The components or entities that are less complex than a cell are hemoglobin, oxygen, and the heart.
Step-by-step explanation:
In this question, the term 'less complex than a cell' refers to components or entities that have a simpler structure or organization compared to a cell. Among the options provided, the correct answers are:
- Hemoglobin: Hemoglobin is a protein found in red blood cells that carries oxygen to cells and carbon dioxide to the lungs. It consists of four symmetrical subunits and four heme groups.
- Oxygen: Oxygen is a molecule necessary for cellular respiration, during which it is used to produce energy in the form of ATP.
- Heart: The heart is a complex organ composed of cardiac muscle tissue, blood vessels, and other components. It is more complex than a single cell.
The options 'Blood' and 'Cardiac muscle' are not less complex than a cell because they are composed of multiple cells and have a higher level of organization.