Final answer:
Life on Earth is described as carbon-based because carbon forms the fundamental components of many molecules that are essential to living things. Its four-valent bonding property allows for a diverse array of complex organic molecules. The carbon cycle and the extensive use of carbon compounds in biochemistry are key aspects of Earth's life systems.
Step-by-step explanation:
The statement that life on Earth is described as carbon based because this element forms essential molecules is true. Carbon atoms are fundamental to many biomolecules because their four electrons in the outer shell allow them to form up to four covalent bonds. This bonding capability makes carbon uniquely suited to be the backbone of organic molecules, including hydrocarbons which are pivotal to our biochemistry. Through a process known as chemical evolution, carbon became a central element in life on Earth, and its importance continues in structures and functions of macromolecules that are vital to living organisms.
Carbon's prevalence in organic chemistry is due to its ability to form complex molecules with itself and other elements such as hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These elements together are used as the building blocks of life through what is often referred to by the acronym CHNOPS. Furthermore, the role of carbon in the environment extends beyond biology, as evidenced by the carbon cycle, highlighting how carbon moves through biotic and abiotic parts of our ecosystem.
Our understanding of organic chemistry began to solidify when chemists realized organic molecules obey the same natural laws as inorganic substances. This led to the recognition that life is indeed carbon-based, as shown by the synthesis of organic compounds from nonliving materials, rebuking the old concept of vitalism.