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The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
The average 70 kg (150 lb) adult human body contains approximately 7 × 10 27 atoms and contains at least detectable traces of 60 chemical elements. [5] About 29 of these elements are thought to play an active positive role in life and health in humans.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
The hierarchy of biological classification's eight major taxonomic ranks.A domain contains one or more kingdoms. Intermediate minor rankings are not shown. In biology, a kingdom is the second highest taxonomic rank, just below domain.
A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1]
Cells are the structural and functional units of life. [1] The smallest organisms are single cells, while the largest organisms are assemblages of trillions of cells. DNA, double stranded macromolecule that carries the hereditary information of the cell [ 2 ] and found in all living cells; [ 3 ] each cell carries chromosome(s) having a ...
4.7 to 6.1 million (male), 4.2 to 5.4 million (female) erythrocytes: [13] Red blood cells contain the blood's hemoglobin and distribute oxygen. Mature red blood cells lack a nucleus and organelles in mammals. The red blood cells (together with endothelial vessel cells and other cells) are also marked by glycoproteins that define the different ...
Nuclear DNA is known as the molecule of life and contains the genetic instructions for the development of all eukaryotic organisms. It is found in almost every cell in the human body, with exceptions such as red blood cells. Everyone has a unique genetic blueprint, even identical twins. [7]