Ancestral polyploidy in seed plants and angiosperms. Jiao et al

Nature 473, 97–100 (05 May 2011)

Millions of years ago

P-Tr

Apparent extinction intensity, i.e. the fraction of genera going extinct at any given time

Tr-J K-T

Mass Extinctions

Location of Chicxulub crater(180-300 km in diameter)

Dinosaur Demise at the K-T Boundary

Plants with double genomes might have had a better chance to survive the Cretaceous-Tertiary extinction event. Fawcett et al. PNAS (2009) 106: 5737-5742

• Gymnosperm means “naked seed” (From the Greek: gymnos = naked; sperm = seed)

• More advanced than ferns – do not have spores, they have seeds.

• The seeds of the gymnosperms lack a protective enclosure (unlike flowering plants which have flowers and fruit).

• Examples of gymnosperms: • Conifers (pine trees), cycads,

ginkgo biloba

Gymnosperms

Angiosperms are regarded as one of the greatest terrestrial radiations of recent geological times. This occurred in the Cretaceous era (see MYBP time scale figure): The major lineages originated 130-90 MYBP, following by a dramatic rise to ecological dominance 100-70 MYBP, and >250000 angiosperm species are known today. Charles Darwin described the rapid rise and early diversification within the angiosperms as 'an abdominable mystery'. This diversification is also manifested on the level of the seed, it's longevity and germination control is part of the species adaptation to environmental factors, e.g. to the season: temperature, light and water.

THE PLANT TREE OF LIFE: AN OVERVIEW AND SOMEPOINTS OF VIEWPalmer et al American Journal of Botany 91(10): 1437–1445. (2004)

THE PLANT TREE OF LIFE: AN OVERVIEW AND SOMEPOINTS OF VIEWPalmer et al American Journal of Botany 91(10): 1437–1445. (2004)

Schematic representation of the evolutionary relationships and divergence times for the red, green, glaucophyte and chromist algae. The branches on which the cyanobacterial (CB) primary and red algal chromist secondary endosymbioses occurred are shown. Divergence times in the evolution of eukaryotic phototrophs; Mya, million years ago; Paleo, Paleozoic.

The evolution of photosynthesis and chloroplasts. Björn and Govindjee (2009) CURRENT SCIENCE, VOL. 96: 1466-1474