Evolution of Angiosperms Topic 8 Learning Objectives Plant Biology BOT 3015 Dr Mast On Exam 3 you will not be tested on relationships of the angiosperms to other phyla of seed plants or characteristics of extinct angiosperms 1 What are the synapomorphies of the angiosperms Synapomorphy Synapomorphies Character states that arose in the most recent common ancestor of a group and are present in all of its members meaning the recent common ancestor s own ancestor did not possess the trait A shared derived characteristic Synapomorphies of Phylum Anthophyta the angiosperms 1 Flowers 2 Closed carpels the vessel containing the seeds 3 Double fertilization that leads to endosperm formation 4 Three 3 nucleate microgametophyte 5 Eight 8 nucleate megagametophyte seven cells and eight nuclei 6 Stamens the microsporophylls with two pairs of pollen sacs contain the pollen 7 Sieve tube elements and companion cells in the phloem Main function Transport carbohydrates 2 What are the two major groups of angiosperms What differentiates them from one another Table 19 1 Are all angiosperms either monocots or eudicots Why is it important for there to be at least one pollen aperture Monocots Eudicots pollen aperture cotyledon Two major groups Monicots and Eudicots Comprise 97 of the Angiosperms Monocots The second major lineage of angiosperms Still retain some of the archeic features Recently found that they are NOT monophyletic Eudicots Third major lineage of angiosperms Some angiosperms 3 of the total species are NOT monocots or eudicots Therefore the answer is NO not all angiosperms are monocots or eudicots Arose before the split between monicots and eudicots Typically have some of the most archaic features Amborellaceae have only ONE species Sister species to ALL other angiosperms Flowers lack distinct sepals and petals Staminate and carpellate flowers are borne on separate plants Magnolias Water lily Characters Eudicots Monocots In threes Monoaperturate Primitive State Flower Parts Pollen Aperture Thinning or opening in the wall of a pollen grain through the exine and the intine Why is it important that there be at least one pollen aperture For pollination to occur a pollen tube must erupt through the pollen wall and transport the pillen to the egg in the pistil The aperture is the only place that the pollen tube is able to break through the elsewhere very tough pollen wall In fours or fives Triaperturate This is the derived state synapomorphy that defines Eudicots Increased aperture number in angiosperm pollen grains offers a selective advantahe because it increases the number of prospective germination sites Facilitating contact between at least one aperture and the stigmatic surface Cotyledons A leaf life structure of the embryo Two One This is the derived state synapomorphy that defines Monicots Leaf Venation Usually netlike Usually parallel Arrangement of veins in the leaf blade Primary vascular bundles in stem In a ring Complex arrangement True secondary growth with vascular cambium Commonly present Rare 3 What are the four major evolutionary trends in floral evolution that are presented in the text Recognize both the primitive and derived states there is a shift from a primitive to one or more derived Superior ovary inferior ovary actinomorphic zygomorphic radial symmetry bilateral state s in each statement symmetry Evolutionary Trend A persistent happening several times directional change in a character state or set of character states resulting in a significant change through time 1 Primitive Flowers with an indefinite amount of parts meaning that there could be a few or there could be many Ex Waterlily Nymphaea odorata Derived Flowers with few parts that are definite in number Ex Lance leaf trillium Trillium lancifolium with 3 parts whorl 2 Primitive Spiral arrangement of parts with free flower parts Ex Waterlily Nymphaea odorata flower parts are free not fused to any other adjacent whorls in any of there length Parts are spirally arranged and intergrade gradual transition in appearance The arrow is pointing to a structure that is gradually transitioning from a stamen to a petal Derived Distinct whorls with fused flower parts Fusion forms the corolla and or sepals into a tubular structures Ex Apalachicola false rosemary has petals fused to one another produce a tube the controls the behavior of the pollinator 3 Primitive Ovary is superior Ovary is free and separate from the calyx Sepals petals and stamens are attached below the ovary Derived Ovary is inferior Ovary is completely or partially attached to the calyx Sepals petals and stamens appear to be attached above the ovaries 4 Primitive Radial symmetry Actinomorphy Can cut through flower in a number of different ways and get 2 perfect halves Derived Bilateral symmetry Zygomorphy Can only be cut one way to get 2 symmetric halves 5 Primitive Flower is comprised of four whorls Petals sepals stamen and carpels Derived Fewer whorls Arose through loss Ex Staminate flowers of Amborella trichopoda do NOT have carpels And the same is true for carpellate flowers they do not have stamens The perianth was NOT divided undifferentiated into calyx sepals and corolla petals 6 Primitive Derived The perianth IS differentiated into two distinct and separate whorls the calyx sepals and corolla petals Ex Scarlett rosemallow Hibiscus coccinea has distinct sepals and petals 4 Describe the flowers of the two largest flowering plant families the Asteraceae sun flowers and Orchidaceae orchids Why does delivery of many pollen grains at a time in the orchids have a positive Asteraceae Orchidaceae connate and connation adnate and adnation pappus disk flowers ray flowers column pollinium phyllary effect on their fitness Two largest families of Angiosperms Asteraceae and Orchidaceae Family Asteraceae Eudicot lineage Sunflowers These are located everywhere there is now where on land except Antartica where they do not exist a Two different kinds of flowers that are very small and aggregate to each other to form a single head 1 Disk flowers Make up the central portion of the aggregate Corolla is actinomorphic radial symmetry Primarily location of reproduction 2 Ray flowers Arranged on the outer part Corolla is zygomorphic Bilateral symmetry and fused May be carpellate or sterile Function in attracting a pollinator Therefore a head is NOT one single flower it is an inflorescence Some flowers are composed of only ray flowers or only disk flowers b In both of these
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