Multicellularity
Multicellular organisms are composed of multiple cells operating in unison to support the total lifeforms
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All plant and animal species are multicellular, along with most fungi and several species of eukaryotic algae
Multicellularity has evolved repeatedly and offers several distinct survival advantages
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Being multicellular allows an organism to exceed size limits normally imposed by SA:Vol ratio limitations
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Multicellular organisms can have longer lifespans as the organism can survive the death of an individual cell
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Multicellularity fosters complexity by allowing the differentiation of cell types within a single organism
One challenge faced by multicellular organisms is the occurrence of cancer – whereby cells fail to regulate their normal pattern of growth within the organism
Multicellular Specialisation
Multicellullar organisms are capable of completing functions that unicellular organisms could not undertake – this is due to the collective actions of individual cells combining to create new synergistic effects
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These new functions are called emergent properties and arise as a consequence of cell specialisation
In a multicellular organism, the differential expression of genes causes cells to become specialised and develop unique functions
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The differing patterns of gene expression may be coordinated by extracellular signals or triggered by changes in the environment
In multicellular organisms:
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Cells of the same type may be grouped together to form tissues
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The functional grouping of multiple tissues results in the formation of organs
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Organs may interact to form organ systems capable of carrying out specific body functions
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Organ systems collectively carry out the life functions of the complete organism
Cell Organisation
