BIOL 2P93 Lecture Notes - Lecture 29: Symmetry In Biology, Malnutrition, Gymnosperm
24 Jan 2016
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4 evolutionary trends by number + arrangement of floral patterns: trait: number of flower parts, primitive flower: many indefinite parts, advanced flower: few parts, fixed numbers. Flowers w/ few-many parts w/ specific #, flowers evolved to having few parts of fixed #. (ex. flower of wintergreen: sepals + petals limited to 5, stamens. Lotus plant: numerous tepals (perianth undistinguished into sepals + petals) + stamens spirally arranged; carpels embedded in flat-topped receptacle = floral parts fused): trait: location of ovary, Primitive flower: superior, advanced flower: inferior. ovary position become inferior than superior, perianth differentiated w/ distinct calyx + corolla. (ex. Chaparral honeysuckle: ovary of plant inferior + has 2-3 locules. Sepals reduced to small teeth at ovary apex: trait: symmetry of flower parts, primitive flower: radial, advanced flower: bilateral. Radial symmetry (regularity)/actinomorphy of early flowers led to bilateral symmetry (irregularity)/zygomorphy in advanced plants. Plants can"t move growth responses + by structures produced.
