Lower Cretaceous – Recent
Flowering plants (also called Angiosperms or Magnoliophyta) are the dominant land plants today. Together with the gymnosperms they make up the seed plants. They are different from the gymnosperms because angiosperms bear flowers, and have enclosed ovules. Gymnosperms bear naked seeds on cones or open structures.
Typical adaptations[change | change source]
Angiosperms have a number of derived characters, which evolved as they split off from the gymnosperms.
Flowers, the reproductive organs of flowering plants, are the most remarkable feature distinguishing them from other seed plants. Flowers, with their colour and their nectar, act to attract pollinators, which are mostly insects and birds. Whereas gymnosperms are almost entirely wind-pollinated, early flowers were probably all insect-pollinated. Some present-day flowering plants are wind-pollinated, but that is a secondary feature.p182
The fertilized angiosperm ovule develops into a seed, and the ovary develops into the fruit. The fruit is often a way to use animals to spread the seeds far and wide. The fruit is made out of the carpel and some tissue round it. The carpel hold inside itself the ovules.
In general, endosperms form after fertilization and before the first division of the zygote. Endosperm is a highly nutritive tissue that can provide food for the developing embryo, the cotyledons, and sometimes the seedling when it first appears.
- Sexual parts
Specialised sexual parts have led to co-evolution in fertilization and seed dispersal. The stamens, and the male and female gametophytes, have been adapted in many ways to suit particular pollinators. The smaller pollen grain shortens the time between pollination and fertilization, which can be up to a year in gymnosperms. The small female gametophyte also allows rapid seed production, which led to annual herbaceous life-cycles.
Phylogeny[change | change source]
A whole genome duplication (doubling) at 160 million years ago (mya) may have started the ancestral line that led to all modern flowering plants. That event was studied by sequencing the genome of an ancient flowering plant, Amborella trichopoda. Amborella, found on the Pacific island of New Caledonia, belongs to a sister group of the other flowering plants. Studies suggest that it has features that may have been characteristic of the earliest flowering plants.
The earliest known fossil confidently identified as an angiosperm, Archaefructus liaoningensis, is dated to about 125 mya in the Lower Cretaceous. Pollen probably of angiosperm origin takes the fossil record back to about 130 mya.
References[change | change source]
- Bakker, Robert T. 1986. The dinosaur heresies: new theories unlocking the mystery of the dinosaurs and their extinction. Morrow, New York.
- Callaway, Ewen (2013). "Shrub genome reveals secrets of flower power". Nature. doi:10.1038/nature.2013.14426. http://www.nature.com/news/shrub-genome-reveals-secrets-of-flower-power-1.14426?WT.mc_id=GPL_NatureNews.
- Keith Adams (December 2013). "Genomic Clues to the Ancestral Flowering Plant". Science 342 (6165): 1456–1457. doi:10.1126/science.1248709. http://www.sciencemag.org/content/342/6165/1456.summary.
- South Pacific plant may be missing link in evolution of flowering plants — Public release date: 17-May-2006
- Sun G. et al 2002. Archaefructaceae, a new basal Angiosperm family. Science 296 (5569): 899–904. doi:10.1126/science.1069439. PMID 11988572. http://www.sciencemag.org/cgi/content/abstract/296/5569/899?ck=nck&siteid=sci&ijkey=8dZ6zTqF606ps&keytype=ref.
- Angiosperm Phylogeny Group 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141: 399-436 An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II - 2003 - Botanical Journal of the Linnean Society - Wiley Online Library
- Angiosperm phylogeny website Angiosperm Phylogeny Website Archived 19 April 2006 at WebCite
|Wikispecies has information on: Angiosperms.|