Presentation on theme: "ANGIOSPERMS Angiosperm means “covered seed” Have flowers"— Presentation transcript:
1 ANGIOSPERMS Angiosperm means “covered seed” Have flowers Have fruits with seedsLive everywhere – dominant plants in the world260,000 species (88% of Plant Kingdom)Angiosperms are the most successful and advanced plants on earth
2 Evolution of Angiosperms Advancements over gymnosperms:Angiosperms have flowers – many use pollinatorsFruits and seeds – adapted for dispersalDouble fertilization of the endosperm in the seed
3 Angiosperm life cycleFlower has male and female sex organs
4 Flower structureMale sex organs: Stamens, composed of anther – organ that produces pollen (male gametophyte)Female sex organs: The carpelOvary is the enlarged basal portion of carpel that contains the ovules (female gametophyte)The stigma is the receptive portion of the carpel for pollen grains to adhere
5 Flower structure Non-reproductive parts: Sepals (green) are the outermost whorl of leaf-like bractsPetals (usually colored) are the inner whorl of leaf-like bractsBoth can have various shapes and colors
6 Angiosperm life cycleHeterosporous: forms two different types of spores (micro- and megaspores; male and female spores)Male – pollen grains contain tube nucleus and generative cell (2 sperm nuclei)Female – female gametophyte contains egg and 2 polar nuclei
7 Angiosperm lifecycleFlowering plants exhibit alternation of generations. The large, familiar flowering plant is the diploid sporophyte, while the haploid gametophyte stages are microscopic. The unique feature about the life cycle of flowering plants is a double fertilization that produces a diploid zygote and a triploid endosperm or nutritive tissue.
8 Anthers contain microsporangia Anthers contain microsporangia. Each one contains microsporocytes that divide by meiosis, producing microspores.2) Microspores form pollen grains (containing male gametophytes). The generative cell will divide to form two sperm. The tube cell will produce the pollen tube.3) In the megasporangium of each ovule, the megasporocyte divides by meiosis and produces four megaspores.
9 The surviving megaspore in each ovule forms a female gametophyte (embryo sac).4) After pollination, eventually two spermnuclei are discharged in each ovule.5) Double fertilization occurs. One sperm fertilizes the egg, forming a zygote. The other sperm combines with the two polar nuclei to form the nucleus of the endosperm.
10 6) The zygote develops into an embryo that is packaged along with food into a seed.7) When a seed germinates, the embryo develops into a mature sporophyte.
12 Double fertilizationPollen grain germinates on stigma forming a pollen tube, which grows down style to the ovaryPollen has 2 haploid sperm nuclei, which travel to the ovaryOne sperm nucleus fertilizes the haploid egg forming the 2n zygoteAnother sperm nucleus unites with the 2 polar nuclei, forming the triploid (3n) endosperm
13 Seeds Endosperm is stored food tissue – for the embryo to grow Mature ovule becomes the seed coat and/or fruit
14 Monocot vs. Dicot Angiosperms are divided into monocots and dicots As the zygote grows into the embryo, the first leaves of the young sporophyte develop and are called as cotyledons (seed leaves)Monocots have one cotyledon (corn, lily, etc).Dicots have two cotyledons (bean, oak, etc).
15 Comparing Monocot vs. Dicot Plants FEATUREMONOCOTSDICOTSCotyledons12Leaf venationparallelbroadRoot systemFibrousTapNumber of floral partsIn 3’sIn 4’s or 5’sVascular bundle positionScatteredArranged in a circleWoody or herbaceousHerbaceousEither
16 Monocot vs. DicotNumber of cotyledons: one vs. two
17 Monocot vs. Dicot Leaf venation pattern: Monocot is parallel Dicot is net pattern
18 Monocot vs. Dicot RootMonocot: Fibrous rootDicot: Tap root
19 Monocot vs. Dicot Flower parts: Monocot: in groups of three Dicot: in groups of four or five
20 Monocot vs. Dicot Vascular bundle position: Monocot: Scattered Dicot: Arranged in a circle
21 Monocot vs. Dicot Stem type: Monocot: Herbaceous Dicot: herbaceous or woody