BIOL 240W 1st Edition Lecture 12Outline of Last Lecture I. Alternation of GenerationsII. Flower Structure and FunctionIII. Development of GametophytesIV. Development of Embryo SacsV. Development of Pollen GrainsVI. PollinationOutline of Current Lecture I. Development of a Eudicot EmbryoII. MorphologyIII. GerminationIV. FruitsV. Sexual ReproductionVI. Asexual ReproductionVII. Monoecious and Dioecious FlowersCurrent LectureI. Development of a Eudicot Embryoa. Fertilization has already taken placeb. Endosperm develops firstc. First division is asymmetric, producing basal and terminal celli. Basal cell creates suspensor that anchors embryo to parental tissue and transfers nutrients from endosperm to embryoii. Terminal cell gives rise to most of the embryo. Globular ball of cells is created to create a pro-embryo, which differentiates into a heart shape with cotyledons at the topiii. Growth continues along apical-basal axis as endosperm begins to disappeariv. Cotyledon take over inside of the seeds, and they contain the nutrients needed by the seed (absorb endosperm material because there is no endosperm at maturity)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.v. Shoot and apical meristem are visiblevi. Seed stockpiles proteins, oil, and starch so it can remain dormant and then start to grow during germinationd. Seed Maturationi. Seed desiccates/ loses water to slow metabolism while the embryo is not growing.ii. Germination waits to occur until there are favorable conditionsiii. Seed is surrounded by a hard coat formed from integumentsII. Morphology (garden bean)Castor Beana. Maize Seed III. Germinationa. Once seeds are ready to be germinated, they maintaina low metabolic rateb. Long periods of cold weather, fire, copious rainfall, and digestion signal a seed to germinatec. Seed bank- all of the different dormant seeds in the environmentd. Imbition- uptake of water by dried seeds, re-restarting metabolism, stored energy sources mobilized by enzymese. Ex: brewing beer. Malted barley germinates, complex carbohydrates (starches, etc) are broken down by seed enzymes. Germinated seedlings are roasted. Mixture is boiled, sugars are extracted, allowed to fermentf. Hypocotyl forms a hook for protection of shoot apical meristem during germinationIV. Fruitsa. Ovule develops into the seedb. Mature ovary becomes the fruit that protects seeds and attracts animals to aid in seed dispersali. Hormones released result in edible fruits that attract animals, change colors, andbecome sweeterc. Fruits are based on where they come fromi. The carpel is the female part of a flowerii. Simple fruits develop from a single carpeliii. Aggregate fruits are a cluster of fruits which each developed from a separate carpeliv. Multiple fruits are derived from multiple carpels born on separate flowers. Each develops into part of a fruit, so the whole fruit is a bunch of little fruitsInflorescence: group of flowers tightly clustered together.v. Accessory fruits are tissues besides the over that contribute to major portions (ex: apples). These do not have to do with reproductionV. Sexual reproduction a. Allows for variation in offspring where conditions changeb. Seeds that are sexually produced are dormant until ideal conditions, but production of enormous numbers of seeds requires a lot of energyVI. Asexual reproductiona. Genetically identical cloneb. Fragmentation- parent plants become separated that develop into whole plantsc. Modified stems or roots produce new individualsi. Stolon- above ground stems (strawberries)ii. Rhizome-below ground stemiii. Roots- can propogate by rootsd. Advantages of asexual reproductioni. Do not have to worry about pollinators or fertilization. ii. Good for rapid colonization in stable environments where genetic differences are not needede. Disadvantages for asexual reproductioni. No diversity createdii. Cannot adapt to changes in environmentiii. Susceptible to sudden, catastrophic disease outbreaksiv. Hermaphrodites- problems with inbreeding because it reduces genetic diversityf. Apomixis i. Asexual production of a seed that produces genetically identical seeds without fertilization (ex:dandelions). ii. They can clone themselves and have the advantage of seed dispersaliii. Apo- away fromiv. Mixis- mixing because there is no mixing of male and female partsv. Requires 3 events1. Apomeiosis: the production of a female gametophyte without meiosis (uses mitosis)2. Parthenogenesis- fertilization independent of embryo and endosperm formation VII. Monoecious and Dioecious Flowersa. Monoecious plants produce both male and female flowersb. Dioecious plants, on the other hand, produce only one type of flower, which means they are either male or female. They do not have the problem of self fertilizationc. Overcome the possible of self-fertilization by timing their pollen release and carpel development so their maturity does not overlap. i. Can also be self incompatible1. Rejection of genetically identical pollen2. Determined by genes in male gametophyte and female
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