Plant Diversity Ii

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angiosperm

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A flowering plant, which forms seeds inside a protective chamber called an ovary.

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basal angiosperm

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Member of a clade of three early-diverging lineages of flowering plants. Examples are Amborella, water lilies, and star anise and its relatives.

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carpel

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The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary.

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conifer

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Member of the largest gymnosperm phylum. Most conifers are cone-bearing trees, such as pines and firs.

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cotyledon

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A seed leaf of an angiosperm embryo. Some species have one cotyledon, others two.

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cross-pollination

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in angiosperms, the transfer of pollen from an anther of a flower on one plant to the stigma of a flower on another plant of the same species.

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dicot

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A term traditionally used to refer to flowering plants that have two embryonic seed leaves, or cotyledons. Recent molecular evidence indicates that dicots do not form a clade; species once classified as dicots are now grouped into eudicots, magnoliids, and several lineages of basal angiosperms.

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double fertilization

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A mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte (embryo sac) to form the zygote and endosperm.

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endosperm

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In angiosperms, a nutrient-rich tissue formed by the union of a sperm with two polar nuclei during double fertilization. The endosperm provides nourishment to the developing embryo in angiosperm seeds.

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eudicot

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Member of a clade consisting of the vast majority of flowering plants that have two embryonic seed leaves, or cotyledons.

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filament

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In an angiosperm, the stalk portion of the stamen, the pollen-producing reproductive organ of a flower.

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flower

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In an angiosperm, a short stem with up to four sets of modified leaves, bearing structures that function in sexual reproduction.

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fossil

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A preserved remnant or impression of an organism that lived in the past.

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fruit

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A mature ovary of a flower. The fruit protects dormant seeds and often aids in their dispersal.

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gymnosperm

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A vascular plant that bears naked seeds—seeds not enclosed in specialized chambers.

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indeterminate cleavage

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A type of embryonic development in deuterostomes in which each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo.

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integument

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Layer of sporophyte tissue that contributes to the structure of an ovule of a seed plant.

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magnoliid

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Member of the angiosperm clade most closely related to eudicots. Extant examples are magnolias, laurels, and black pepper plants.

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monocot

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Member of a clade consisting of flowering plants that have one embryonic seed leaf, or cotyledon.

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ovary

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In flowers, the portion of a carpel in which the egg-containing ovules develop.

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ovule

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A structure that develops within the ovary of a seed plant and contains the female gametophyte.

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petal

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A modified leaf of a flowering plant. Petals are the often colorful parts of a flower that advertise it to insects and other pollinators.

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pollen grain

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In seed plants, a structure consisting of the male gametophyte enclosed within a pollen wall.

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pollination

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The transfer of pollen to the part of a seed plant containing the ovules, a process required for fertilization.

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progymnosperm

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An extinct seedless vascular plant that may be ancestral to seed plants.

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radial symmetry

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Symmetry in which the body is shaped like a pie or barrel (lacking a left side and a right side) and can be divided into mirror-imaged halves by any plane through its central axis.

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seed

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An adaptation of some terrestrial plants consisting of an embryo packaged along with a store of food within a protective coat.

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sepal

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A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens.

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sporangium (pl., sporangia)

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A multicellular organ in fungi and plants in which meiosis occurs and haploid cells develop.

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spore

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In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis. A spore can divide by mitosis to develop into a multicellular haploid individual, the gametophyte, without fusing with another cell.

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sporophyte

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In organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes. The sporophyte produces haploid spores by meiosis that develop into gametophytes.

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stamen

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The pollen-producing reproductive organ of a flower, consisting of an anther and a filament.

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stigma (pl., stigmata)

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The sticky part of a flower’s carpel, which traps pollen grains.

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style

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The stalk of a flower’s carpel, with the ovary at the base and the stigma at the top.