12 Gymnosperms and Angiosperms Gymnosperm Intro and evolution Life cycle and reproduction Uses and significance Angiosperms Flowering plants Intro and evolution Life cycle and reproduction Uses and significance Monocots vs dicots Kingdom Plantae Evolutionary tree of plants From primitive more advanced traits Bryophytes Gymnosperms Flowers Green alga ancestor Vascular Terrestrial GYMNOSPERMS Introduction Gymnosperm means naked seed From the Greek gymnos naked sperm seed More advanced than ferns do not have spores they have seeds The seeds of the gymnosperms lack a protective enclosure unlike flowering plants which have flowers and fruit Examples of gymnosperms Conifers pine trees cycads ginkgo biloba Evolution of gymnosperms Gymnosperms evolved from fern like ancestors Advancements of gymnosperms over ferns 1 plant embryo food storage tissue and seed coat 2 Gymnosperms do not depend on water for fertilization have air borne pollen 3 Have a more dominant generation 4 Have a more efficient vascular system Gymnosperm life cycle Exhibits alternation of generations Sporophyte generation 2n is dominant Gametophyte generation 1n is contained in and dependent on the sporophyte generation Gymnosperm lifecycle Sporophyte generation Sporophyte produces two types of spores heterosporous Megasporangium undergoes meiosis to produce megaspores female gametophyte sporangium undergoes meiosis to produce haploid microspores germinate to produce male gametophyte pollen Many gymnosperms use wind for pollination and seed dispersal Wood produced by gymnosperms Gymnosperms have a very efficient and effective vascular system Usually woody plants Xylem wood of a tree Phloem bark of the tree Wood is formed from secondary growth Primary vs secondary growth 1 Primary growth occurs in apical meristems of shoots and roots Results in increase in length 2 Secondary growth derived from secondary or lateral meristems Results in increase in girth width Common in trees wood and bark Secondary growth The cambium forms secondary xylem and secondary phloem W is secondary xylem cells are dead at maturity and only cell wall remains Bark is secondary phloem conducts food Annual rings Annual rings xylem formed by the vascular cambium during one growth season Early Spring wood vessel diameter is large xylem walls are thinner Late Summer wood vessel diameter is small walls are thicker Tropical trees have no annual rings because seasons are so similar Vascular tissue Trees Vascular tissue is located on the outer layers of the tree bark Vascular cambium wood Gymnosperms Conifers are most important group of gymnosperms Largest and most familiar group Bear seeds in cones Staminate cones male cones Ovulate cones cones Seeds produced on an open scale Do not produce flowers or fruit Gymnosperms Mainly woody plants that include Oldest living trees bristlecone pine 5000 yrs old Most massive trees giant sequoia up to 375 ft tall 41 ft wide Tallest living trees redwoods Conifers Conifers adapted to temperate to cold regions Narrow leaves needles help to conserve water Covered by resins for protection from predators fire etc Other gymnosperms Cycads short shrubs native to tropical regions look like palms Ginkgo biloba a living fossil male and female tree used as a medicinal plant Other gymnosperms Welwitschia a bizarre gymnosperm plant that grows in Namib desert So Africa Live up to 2000 years in these extreme conditions Only makes two leaves throughout its life It takes water from sea mist Significance of gymnosperms Ecological importance Provide food and habitat for wildlife Forests prevent soil erosion Reduce greenhouse effect gasses Economic and commercial importance Lumber for wood paper etc Resins wood furniture etc Ornamental plants trees landscaping Food pine nuts pesto etc ANGIOSPERMS Angiosperm means covered seed Have flowers Have fruits with seeds Live everywhere dominant plants in the world 260 000 species 88 of Plant Kingdom Angiosperms are the most successful and advanced plants on earth Evolution of Angiosperms Advancements over gymnosperms Angiosperms have flowers many use pollinators Fruits and seeds adapted for dispersal Double fertilization of the endosperm in the seed Angiosperm life cycle Flower has male and female sex organs Flower structure Male sex organs Stamens composed of anther organ that produces pollen male gametophyte Female sex organs The carpel Ovary 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 Flower structure Non reproductive parts Sepals green are the outermost whorl of leaf like bracts Petals usually colored are the inner whorl of leaf like bracts Both can have various shapes and colors Tepals Angiosperm life cycle Heterosporous 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 Angiosperm lifecycle Flowering 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 Double fertilization Pollen grain germinates on stigma forming a pollen tube which grows down style to the ovary Pollen has 2 haploid sperm nuclei which travel to the ovary One sperm nucleus fertilizes the haploid egg forming the 2n zygote Another sperm nucleus unites with the 2 polar nuclei forming the triploid 3n endosperm Seeds Fertilized egg grows into a which grows into plant embryo Endosperm is stored food tissue for the embryo to grow Mature ovule becomes the seed coat and or fruit 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 Comparing monocot vs dicot plants FEATURE MONOCOTS DICOTS Cotyledons 1 2 Leaf venation parallel broad Root system Fibrous Tap Number of floral parts In 3 s In 4 s or 5 s Scattered Arranged in a circle Herbaceous Either Vascular bundle position Woody or herbaceous Monocot vs dicot Number of cotyledons one vs two Monocot vs dicot Leaf venation pattern