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Wright BIO 1150 - Evolution of Seed Plants
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BIO 1150 1st Edition Lecture 20Chapter 30 Topic Discussed: Evolution of Seed PlantsDerived Traits of Seed Plants1. Reduced gametophytes- gametophytes nourished and protected by sporophyte (2n)2. Heterospory- a. microspore- male gametophyteb. megaspore- female gametophytec. ovules- integument, megaspore and megasporangium3. Pollen- grains make water unnecessary for fertilization4. Seeds- a. Seed coat, food supply and embryob. Can be transported long distancesc. Survive better than sporesHeterospory- ancestors of seed plants- homosporous- Megasporangia- produce megaspores that give rise to female gametophytes- Microsporangia -produce microspores that give rise to male gametophytesOvules and Production of Eggs- ovule = megasporangium, megaspore, and 1+ protective integuments- Gymnosperm megaspores =one integument- Angiosperm megaspores = two integumentsPollen and Sperm Production- Microspores develop into pollen grains-contain the male gametophytes- Pollen eliminates the need for a film of water- pollen grain germinates- gives rise to a pollen tube that discharges sperm into the female gametophyte within the ovuleEvolutionary advantage of seeds- May remain dormant for days to years, until conditions are favorable for germination- Supply of stored food- Can be transported long distances by wind or animals- Adaptive value- adaptation that gave organism an advantage in certain placesGymnosperms- “naked” seeds, typically on cones- Mostly wind pollinated- Sporangia on strobiliDivision Cycadophyta- Flagellated sperm- Beetle pollinated- Thrived inCenozoic- Only 130 species today- Tropical plants- Need water to germinateDivision Ginkophyta- Flagellated sperm- One species onlyDivision Gnetophyta- Welwitschia-longest leaves ever- Ephedra- drug, banned because of use in weight loss drugs- GnetumDivision Coniferophtya- Most numerous group- Mostly evergreen- Most extreme enviroments, oldest and largestAlternation of Generations- can take up to 2 years to completeAngiosperms- flower and a fruit- Animal/wind/self pollinatedFlower structure- Carpal (female)o Stigma- pollen lands ono Style- pollen grows ono Ovary- Stamen (male)o Anther- produces polleno FilamentHummingbird- long flower, hummingbird reaches in, pollen gets on forehead, then the pollen is transferred to another flowerBat- wants nectarFruit- Can be fleshy or dry- Dispersed by eating, barbs and windAngiosperms originated 140 mya- Most


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Wright BIO 1150 - Evolution of Seed Plants

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