Chapter 30 BSC 120
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This 4 page Class Notes was uploaded by fwmartin on Friday February 19, 2016. The Class Notes belongs to BSC 120 at University of Alabama - Tuscaloosa taught by Dr. Martha Powell in Spring 2016. Since its upload, it has received 13 views. For similar materials see Honors Gen Biology II in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 02/19/16
Chapter 30: Gymnosperms (Cone-Bearing Seed Plants) Adaptations 1. Seeds a. Flagellated sperm is replaced by pollen b. Pollen is very successful at spreading- Trees make tons of pollen 2. Roots a. Roots spread out and help anchor the tree in place providing the opportunity to grow much taller. In the Carboniferous Period (305Million years ago) the Earth began to dry out and became colder. As ferns and mosses died, seed plants began to dominate. Gymnosperms = naked seed. This is because the seed has no exterior covering and is exposed to the environment. The Cone protects both the sperm and the egg. There is additional reduction in the gametophyte (off the ground now in a cone) and diploid (sporophyte 2N) is dominant. Located up; hence protected. Pollen is used to carry the (male) sperm (really a reduced male gametophyte). The wind blows the pollen off of its cone and through the air until it lands on a female, ovule producing cone (really a female gametophyte). After Fertilization a seed is produced. Seeds contain the plant embryo and food for germination. It stays locked away and protected from the outside until the time is right to germinate. The seed helped advance the colonization of land by protecting the embryo from drying out and other hazards. Gymnosperms have thick layers of cutin that waterproofs the pine needles from drying out during cold, dry winters by slowing the process of transpiration and retaining more water. Most are Gymnosperms are evergreens, and stay green all year long. Gymnosperms are the first plant to have secondary growth. After growing tall, the plants then grow outward and gain girth allowing them to become much bigger and taller as they will have a larger base to support them. Gymnosperms are the prominent plant in many land areas of the world still. 3 types of Gymnosperms: Conifers, Cycads, Ginkgo (totally exposed seed) Conifers: The US has 190 million acres of coniferous forest designated as US National forests. Conifers are among the tallest, largest and oldest organisms on earth. Coastal redwoods and sequoias (northern California coast) are the world's tallest trees 370 feet) Cycads: These were around when dinosaurs were here. There is a long fossil history that they were formerly more abundant and more diverse than they are today. They typically have a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. Ginkgo: Used in many Asian cuisines, especially to make jelly. However, the plant gives off an odder; they stink very bad. The seed is also completely exposed Chapter 30: Angiosperms (Flower-bearing Seed Plants) First appear in the cretaceous period (125 million years ago). They come in two types: Monocots and Eudicots (Dicots) Monocots have: • Parallel veins • Vascular bundles are scattered • Flowers come in multiples of 3 • Fibrous root system • Usually grasses, corn, grains, and palm trees. They depend on wind for pollination Eudicots (Dicots) • Branched veins • Vascular bundles are arranged in ring • Flowers come in 4s and 5s • Usually has a taproot • Usually fruits, vegetables, and oaks, maples. They depend upon insects, birds and bats for pollination Angiosperms = contained seeds. Most living plants are angiosperms -> 250,000 species A flower is complex reproductive structure that is too look sexy in order to promote reproduction. The flower produces seeds within a protective compartment (the ovary). The flower is designed to interact with animals (pollinators) to be spread. After being fertilized, the ovary becomes a fruit, and the seed is protected within the covering of the fruit. Intended to be eaten by animals to be spread. The female gametophyte (=the embryo sac) is located inside an ovule. The male gametophyte is located in the pollen which is in the anther. They dominate the modern landscape • 250,000 species (gymnosperms have 700). Over 90% of the Plant Kingdom • Supply nearly all of our food as well as the food eaten by domesticated animals. • They typically have three organs: roots, stems, and leaves. • Flowers are just modified leaves Angiosperm characteristics • The gametophytes (N) are protected (off the ground) • The sporophyte (2N) (mostly what you see) is dominant • A flower is actually a short stem with four whorls of modified leaves: sepals, petals, stamens, and carpels • Advantages of a reduced gametophyte- pgs. 618-619. Flowers • Petals attract insects and other animals (bats, birds) that transfer the pollen (sperm) to egg. • Flowers came from the co-evolution of plants and pollinators. • Plants with inconspicuous flowers generally use the wind to disperse pollen. (oaks) Pollination • Pollination involves the transport of pollen from an anther, where pollen is produced, to the stigma portion of the carpel. • Some plants are self-pollinated; others are cross-pollinated. • If flower has both male and female reproductive parts, it is said to be a perfect flower. If male or female only than its an imperfect flower Ways to pollinate • Wind • Animals • Bees • Moths • Hummingbird • bats Lifecycle: Once transferred to the sticky stigma of a carpel, the pollen grain germinates and produces a pollen tube. The tube grows down through the style and into the ovary, where there are ovules just waiting to be fertilized (each containing an egg). The pollen tube then releases two sperm nuclei within the embryo sac. One sperm fertilizes an egg in the ovule, forming the zygote, which develops into an embryo (baby plant). The second sperm fertilizes a polar cell which becomes nutrient storage material of the seed, the endosperm which nourishes the embryo. This process is known as double fertilization and is characteristic of angiosperms. The whole ovule develops into a seed. As seeds are developing from ovules, the ovary wall thickens forming the fruit that encloses the seeds. The ovary develops into a fruit. Fruits protect and help disperse seeds. Seed Dispersal By: • Animals, o Either by eating or by carrying seed • Water • Wind
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