There are several levels of biological organization, each building upon the previous level and encompassing a more complex organization of living things. These levels include:
Molecules with biological activity: living things are made of molecules. For example, the biphospholipid layer forms the backbone of the cell membrane and proteins are embedded in it. This structure effectively separates the internal environment from the outside world and controls the entry and exit of substances.
Organelles: They are microscopic units with specific shapes and functions scattered within the cell. They are all wrapped by membrane, except for the ribosomes. The common organelles: ribosomes, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus and lysosomes.
Cell: It is the smallest unit of life and they cooperate to carry out all the functions necessary for life, such as metabolism, growth, and reproduction.
Tissue: It is groups of similar cells and their extracellular matrix that work together to perform a specific function. The animal tissue includes muscle tissue, nervous tissue, connective tissue and epithelial tissue.
Organ: It is groups of tissues that form a specific structure and work together to perform a common function. Examples include the heart, liver, and brain.
Organ system: It is groups of organs that work together to perform one or more functions. Examples include the digestive system, respiratory system, and circulatory system.
Organism: It is a single living entity that is made up of organ systems. Examples include deer and plants.
Population: It is all groups of the same species organisms that live in the same area and interbreed with each other. Examples include all the deer in the meadow.
Community: It is all groups of different populations that live in the same area and interact with each other. For example, all the animals, plant, fungus and bacterium in the meadow. You can also think that all the life in the meadow make up community.
Ecosystem: Ecosystem contains community (all the lives) and its abiotic (non-living) environment, such as a forest ecosystem, a meadow ecosystem, or a desert ecosystem.
Biosphere: It is the sum of all ecosystems on Earth (or all life on Earth and their surroundings). Here, ecosystems interact with each other to form a more complex system. For example, water vapor from the ocean becomes rainfall for forests, and warm ocean currents significantly affect the temperature of nearby terrestrial ecosystems.