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Flowering plants, the dominant plant group, [9]: 168 reproduce both by sexual and asexual means. Their distinguishing feature is that their reproductive organs are contained in flowers. Sexual reproduction in flowering plants involves the production of separate male and female gametophytes that produce gametes.
The flower is the characteristic structure concerned with sexual reproduction in flowering plants (angiosperms). Flowers vary enormously in their structure (morphology). A perfect flower, like that of Ranunculus glaberrimus shown in the figure, has a calyx of outer sepals and a corolla of inner petals and both male and female sex organs.
Sexual selection is described as natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. Sexual selection is a common concept in animal evolution but, with plants, it is often overlooked because many plants are hermaphrodites.
ABC model of flower development guided by three groups of homeotic genes. The ABC model of flower development is a scientific model of the process by which flowering plants produce a pattern of gene expression in meristems that leads to the appearance of an organ oriented towards sexual reproduction, a flower.
Sexual systems play a key role in genetic variation and reproductive success, and may also have led to the origin or extinction of certain species. [4] In flowering plants and animals, sexual reproduction involves meiosis, an adaptive process for repairing damage in the germline DNA transmitted to progeny. [5]
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (/ ˌ æ n dʒ i ə ˈ s p ər m iː /). [5] [6] The term 'angiosperm' is derived from the Greek words ἀγγεῖον / angeion ('container, vessel') and σπέρμα / sperma ('seed'), meaning that the seeds are enclosed within a fruit.
In 2013, flowers dating from the Cretaceous (100 million years before present) were found encased in amber, the oldest evidence of sexual reproduction in a flowering plant. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma.
Sexual reproduction in flowering plants involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamens and is carried to the pistil or carpel , which has the ovule at its base where fertilization can take place.