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A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. [1] All species of animals , land plants and most fungi are multicellular, as are many algae , whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium .
A human cell has genetic material contained in the cell nucleus (the nuclear genome) and in the mitochondria (the mitochondrial genome). In humans, the nuclear genome is divided into 46 linear DNA molecules called chromosomes, including 22 homologous chromosome pairs and a pair of sex chromosomes. The mitochondrial genome is a circular DNA ...
An extensive listing of human cell types was published by Vickaryous and Hall in 2006, collecting 411 different types of human cells (with 145 types of neuron among those). [ 11 ] The Human Cell Atlas project, which started in 2016, had as one of its goals to "catalog all cell types (for example, immune cells or brain cells ) and sub-types in ...
The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. ... In humans, as in most multicellular organisms, ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 8 February 2025. Process in which chromosomes are replicated and separated into two new identical nuclei For the type of cell division in sexually reproducing organisms used to produce gametes, see Meiosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Algae-like multicellular land plants are dated back to about 1 billion years ago, [112] although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2.7 billion years ago. [113] Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician period.
Except for placozoans, multicellular animals including humans have a variety of organ systems. These specific systems are widely studied in human anatomy. The functions of these organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus.
By contrast, gametes of diploid organisms contain only half as many chromosomes. In humans, this is 23 unpaired chromosomes. When two gametes (i.e. a spermatozoon and an ovum) meet during conception, they fuse together, creating a zygote. Due to the fusion of the two gametes, a human zygote contains 46 chromosomes (i.e. 23 pairs). [citation needed]