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In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. [1] In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific ...
An organ system is a biological system consisting of a group of organs that work together to perform one or more functions. [1] Each organ has a specialized role in an organism body, and is made up of distinct tissues .
Human organs and organ systems develop in a process known as organogenesis. This begins in the third week of embryonic development, when the gastrula forms three distinct germ layers, the ectoderm, mesoderm and endoderm. The ectoderm will eventually develop into the outer layer of skin and nervous system.
In biology, a biological life cycle (or just life cycle when the biological context is clear) is a series of stages of the life of an organism, that begins as a zygote, often in an egg, and concludes as an adult that reproduces, producing an offspring in the form of a new zygote which then itself goes through the same series of stages, the ...
Biologists can study life at multiple levels of organization, [1] from the molecular biology of a cell to the anatomy and physiology of plants and animals, and the evolution of populations. [1] [6] Hence, there are multiple subdisciplines within biology, each defined by the nature of their research questions and the tools that they use.
Multiple macromolecules form a cell, like a club cell. A group of cells functioning together as a tissue, for example, Epithelial tissue. Different tissues make up an organ, like a lung. Organs work together to form an organ system, such as the Respiratory System. All of the organ systems make a living organism, like a lion.
Scientists think genetically-modified animals could one day be the solution to an organ supply shortage that causes thousands of people in the U.S. to die every year waiting for a transplant.
Plants constantly produce new tissues and structures throughout their life from meristems [36] located at the tips of organs, or between mature tissues. Thus, a living plant always has embryonic tissues. By contrast, an animal embryo will very early produce all of the body parts that it will ever have in its life. When the animal is born (or ...