Final answer:
All living things are composed of cells, which are the fundamental units of life. These cells facilitate various life functions and can come as single cells in simple organisms or trillions in complex multicellular organisms. The vast diversity in living organisms is a result of evolution.
Step-by-step explanation:
All Living Things Are Composed of Cells
All living things are composed of one or more cells, which are considered the basic units of life. Whether organisms are single-celled, like bacteria and amoebae, or complex, multicellular entities such as plants and animals, they all share the common feature of being cellular. As per the Cell Theory, cells are not only the structural unit of living organisms, but they are also alive themselves and always arise from other living cells.
Organisms, through their cellular structure, carry out essential life processes. They need energy to function, they grow and reproduce, respond to their environment, and work to maintain a stable internal environment. Some organisms are made of just one cell that carries out all life functions, while others are made of trillions of cells that specialize and work together to form tissues and organs.
The amazing diversity of life on Earth—from tiny fungi to sprawling forests and complex animal life—stems from the long history of evolution, which has led to the vast array of organisms we see today. Within these organisms, all life functions occur within their cells, and all cells have originated from pre-existing cells, ensuring the continuity of life forms over generations.