Organismal size, metabolism and the evolution of complexity in metazoans

Megan C. McCarthy, Brian Enquist

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Questions: What is the macroevolutionary relationship between body size, number of cell types and metabolism? Furthermore, why does the relationship between body size and the number of cell types hold between major metazoan clades but not within closely related taxa? Mathematical methods: Expand the allometric relationship between size and metabolism to include (1) the energetic costs of supporting an increased number of cell types and (2) the phylogenetic constraints governing the number of cell types. Key assumptions: An increase in organismal size selects for additional cell types. This is due to biophysical constraints and transport demands. The increase in cell types allows the organism to perform new functions. The extra cell types also require more intercellular networks. Therefore, the amount of energy required per unit of body mass should increase with the number of cell types. Phylogeny may also constrain the number of cell types within taxa. This constraint will limit the number of cell types to be approximately constant within a bauplan (a unique organismal form comprised of an anatomical and physiological design). Predictions: Organismal size should be positively correlated to the number of cell types across metazoan taxa. However, this relationship will not hold within clades due to energetic and phylogenetic constraints. The energetic constraint leads to a positive correlation between the number of cell types and metabolic intensity (the mass-specific rate of energy processing standardized to a given body size) across metazoan bauplans. Available data support these predictions. Metabolic intensity is positively related to the number of cell types in metazoan clades.

Original languageEnglish (US)
Pages (from-to)681-696
Number of pages16
JournalEvolutionary Ecology Research
Volume7
Issue number5
StatePublished - Jul 2005

Fingerprint

metazoan
Cell Count
metabolism
body size
energetics
cells
phylogenetics
Body Size
prediction
body mass
numerical method
energy
phylogeny
cost
Phylogeny
Costs and Cost Analysis

Keywords

  • Allometry
  • Evolutionary trends
  • Macroevolution
  • Multicellularity
  • Number of cell types
  • Organismal energetics

ASJC Scopus subject areas

  • Ecology
  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Genetics(clinical)

Cite this

Organismal size, metabolism and the evolution of complexity in metazoans. / McCarthy, Megan C.; Enquist, Brian.

In: Evolutionary Ecology Research, Vol. 7, No. 5, 07.2005, p. 681-696.

Research output: Contribution to journalArticle

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