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Timeline of plant evolution

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**Earliest Plant Evolution**:
– Land plants evolved from charophytes.
– Chloroplasts evolved from an endosymbiotic relationship.
– Fossil evidence dates plants back to around 3000 Ma.
– Cyanobacteria played a crucial role in oxygen production.
– Stromatolites provide evidence of cyanobacteria presence.

**Paleozoic Flora**:
– **Cambrian**:
– Small, unicellular early plants.
– Calcareous green algae existed.
– Land plants with vascular tissues appeared in the mid-Silurian.
– Ordovician saw the first embryophyte spores.
– Trilete spores resembling modern plants in the Late Ordovician.
– **Silurian**:
– First fossil records of vascular plants.
Genus Cooksonia represented early vascular plants.
– Zosterophylls diversified.
– Primitive lycopods like Baragwanathia widespread.
– **Devonian**:
– Mycorrhizal symbioses in early Devonian plants.
– Late Devonian forests of large, primitive plants.
– Seed-forming plants by the end of the Devonian.
– The Devonian Explosion marked rapid plant evolution.

**Carboniferous Flora**:
– Early Carboniferous plants similar to Late Devonian plants.
– New plant groups like Equisetales and Lycopodiales appeared.
– The greening of continents acted as a carbon dioxide sink.
– Atmospheric CO2 concentrations may have dropped.
– Vertebrates and arthropods established on land.

**Dominant Plant Groups**:
– **Carboniferous**:
– Dominated by Lepidodendron, Sigillaria, Filicales, etc.
– Sphenophyllum, Cordaites, and true coniferous trees appeared.
– Cycadophyta, Callistophytales, and Voltziales emerged.
– **Permian**:
– Transition from lycopod trees to conifers.
– Radiation of important conifer groups.
– Appearance of ginkgos and cycads.
– **Triassic**:
– Lycophytes, cycads, Ginkgophyta, and glossopterids dominant.
– Conifers flourishing in the northern hemisphere.
– Dicroidium dominant in the southern hemisphere.

**Plant Evolution in Later Periods**:
– **Jurassic**:
– Conifers dominating, with extant families flourishing.
– Cycads, ginkgos, and tree ferns common.
– Podocarps successful in the Southern Hemisphere.
– **Cretaceous**:
– Flowering plants spreading, becoming predominant.
– Evolution aided by the appearance of bees.
– Extant conifers thriving alongside flowering plants.

This article attempts to place key plant innovations in a geological context. It concerns itself only with novel adaptations and events that had a major ecological significance, not those that are of solely anthropological interest. The timeline displays a graphical representation of the adaptations; the text attempts to explain the nature and robustness of the evidence.

Plant evolution is an aspect of the study of biological evolution, predominantly involving evolution of plants suited to live on land, greening of various land masses by the filling of their niches with land plants, and diversification of groups of land plants.

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