BSC2011 -- ANGIOSPERMS AND FETILITY

Angiosperms

Seed plants characterized by flowers, seeds enclosed within an ovary/carpel, and fruits

Sepals

Outermost sterile whorl protecting the flower bud

Petals

Inner sterile whorl adapted to attract animal pollinators

Stamen

Male organ composed of a slender filament and pollen-bearing anther

pistil

one or more fused carpels, containing the ovaries (organs that make the ovules) as well as the style and stigma(s) that receive and transmit pollen to the ovaries

Double Fertilization

Key angiosperm synapomorphy where one sperm nucleus fertilizes the egg to form a diploid (2n) zygote, while the second sperm nucleus fuses with two polar nuclei to form triploid (3n) endosperm

Endosperm (3n)

Triploid nutritive tissue in angiosperm seeds that feeds the embryo

Cotyledons

Embryonic seed leaves that absorb endosperm nutrients or perform early photosynthesis upon germination.

Pollination Syndromes

Suites of floral traits (color, shape, odor, nectar rewards) co-evolved to attract specific pollen vectors (wind, insects, birds, bats)

Inbreeding Depression vs. Outcrossing

reduced biological fitness from self-fertilization vs. enhanced genetic variation resulting from cross-fertilizatio