Phylogenetic, Functional, and Geological Perspectives on Complex Multicellularity

Knoll, Andrew H.; Hewitt, David

doi:10.7551/mitpress/9780262015240.003.0013

Cited by 24 publications

(21 citation statements)

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“…[9]), as well as how early animal evolution may have connected to the many environmental and ecological changes that occurred in the Neoproterozoic Era [10][11][12]. This same interest also applies to the other complex multicellular clades, whose timing of appearance has also been explored in terms of environmental change in the Neoproterozoic Era -for example, increasing atmospheric oxygen levels and the origin of complex multicellularity in algae [4]. Here, we identify metazoans and florideophytes as the only two complex multicellular clades with likely Neoproterozoic origins (Figure 1).…”

Section: Introduction: the Neoproterozoic Origins Of Complex Multicelmentioning

confidence: 99%

“…775 Ma, within the range of 929-630 Ma, broadly correlating with the 800-750 Ma shift in the Cr isotope record ( Figure 3A). Since algae respire aerobically, and cease oxygen production at night, it has been argued that lowoxygen conditions in the middle Proterozoic could have also impeded the evolution of algal multicellularity [4]. However, the existence of putative stem-group florideophytes ca.…”

Section: Animal Origins In Context: the Tonian Earth Systemmentioning

confidence: 99%

“…Although multicellularity (i.e. any phenotype-based on multiple, attached cells) has evolved at least 25 times across the tree of life [2], a distinction has been made between 'simple multicellularity' and 'complex multicellularity' [3][4][5]. According to this view, simple multicellular phenotypes include filaments, clusters, and sheets of cells, which remain in direct contact with the external environment, and feature little to no functional or structural specialization.…”

Section: Introduction: the Neoproterozoic Origins Of Complex Multicelmentioning

confidence: 99%

“…There is considerable interest in relating the evolution of these complex multicellular clades to changes in Earth's surface environment over geologic time [4][5][6]-particularly the relationship between early animal evolution and possible increases in atmospheric and/or marine oxygen levels in the Neoproterozoic Era [7,8]. This interest is partially motivated to explain why animals originated when they did and not earlier in Earth history (reviewed in ref.…”

Section: Introduction: the Neoproterozoic Origins Of Complex Multicelmentioning

confidence: 99%

“…According to this view, simple multicellular phenotypes include filaments, clusters, and sheets of cells, which remain in direct contact with the external environment, and feature little to no functional or structural specialization. In contrast, complex multicellularity is characterized by the following features: (1) cellular differentiation, including tissues; (2) three-dimensional bodyplans with an inner-outer distinction, where interior cells are segregated from the external environment and reliant on exterior cells for environmental cues and resources; and (3) cytological features and tissue types that facilitate the active transport of signaling molecules and metabolites at rates exceeding those achieved by molecular diffusion [3][4][5]. According to these proposed criteria, complex multicellularity has independently evolved at least six times, represented by the following extant eukaryotic clades: embryophytes, florideophyte red algae, laminarialean brown algae, ascomycete fungi, basidiomycete fungi, and animals (ref.…”

Section: Introduction: the Neoproterozoic Origins Of Complex Multicelmentioning

confidence: 99%

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Animal origins and the Tonian Earth system

Mills

Francis

Canfield

2018

Emerging Topics in Life Sciences

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The Neoproterozoic Era (1000-541 million years ago, Ma) was characterized by dramatic environmental and evolutionary change, including at least two episodes of extensive, low-latitude glaciation, potential changes in the redox structure of the global ocean, and the origin and diversification of animal life. How these different events related to one another remains an active area of research, particularly how these environmental changes influenced, and were influenced by, the earliest evolution of animals. Animal multicellularity is estimated to have evolved in the Tonian Period (1000-720 Ma) and represents one of at least six independent acquisitions of complex multicellularity, characterized by cellular differentiation, three-dimensional body plans, and active nutrient transport. Compared with the other instances of complex multicellularity, animals represent the only clade to have evolved from wall-less, phagotrophic flagellates, which likely placed unique cytological and trophic constraints on the evolution of animal multicellularity. Here, we compare recent molecular clock estimates with compilations of the chromium isotope, micropaleontological, and organic biomarker records, suggesting that, as of now, the origin of animals was not obviously correlated to any environmental-ecological change in the Tonian Period. This lack of correlation is consistent with the idea that the evolution of animal multicellularity was primarily dictated by internal, developmental constraints and occurred independently of the known environmental-ecological changes that characterized the Neoproterozoic Era.

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