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Chapter 22 Plant Diversity
Transcript of Chapter 22 Plant Diversity
What is a Plant?
The Plant Life Cycle
Plants have life cycles that are characterized by alternation of generations.
The two generations are he Gametophyte and the Sporophyte.
Gametes are haploid cells that fuse together to produce a new individual by mitosis.
To be fuly terrestrial , plants must be able to reproduce in dry environments where there is no water.
The first plants envolved from an organism much like the multicellular green algae living today.
The first true plants were still dependent on water to complete their life cycle.
One of the earliest fossil plants was Cooksonia.
Cooksonia had simple branched stalks that bore reproductive structures at their tips.
What Plants Need To Survive
Plants will need sunlight, water, minerals, gas change, movement of water, and nutrients to survive.
Plants need energy from sunlight to carry out photosynthesis.
All cells require a constant supply of water.
Plants require oxygen to support respiration as well as carbon dioxide to carry out photosynthesis.
Plants are multicellular eukaryotes that have cell walls made of cellulose.
Plants include trees,shrubs, and grasses plants.
Plants are so different from animals that sometimes there is a tendency to think of them as not being alive. Plants can neither run away from danger nor strike blows against an adversary.
Groups Of Bryophtes
Life Cycle of Bryophytes
In Bryophytes, the gametophyte is the dominant , recognizable stage of the life cycle and is the stage that carries out the most of the plant's photosynthesis.
Protonema- a moss spore lands in a moist , it germinates and grows into a mass of tangled green filaments.
Antheridia-sperm with whiplike tails are produced.
Human Use Of Mosses
Spahagnum mosses are group of mosses that thrive in the acidic water of bogs.
Dried spahagnum moss absorbs many times its own weight in the water and thus acts as a sort of natural sponge.
in certain environments the dead remains of sphagnum accumulate to form thick deposits of peat.
22-3 Seedless Vascular Plants
Evolution Of Vascular Tissue
Ferns and The Relatives
Seedless vascular plants include club mosses, horsetails and ferns.
Roots are underground organs that absorb water and minerals.
Leaves are photosynthetic organs that contain one or more bundles of vascular tissue.
Overview of the Plant Kingdom
Botanist divide the plant kingdom into four groups based on three important features: water-conducting tissues,seeds,and flowers.
Bryophytes include mosses,liverworts, and hornworts.
The most common bryophytes are mosses.
Mosses grow most abundantly in areas with water.
When mosses reproduce ,they reproduce in stalks, each containing a capsule.
The first vascular plants had a new type of cell that was specialized to conduct water.
Tracheids were one of the great evolutionary innovations of the plant kingdom.
Xylem- a form of vascular tissue that carries water upward from the roots to every part of a plant.
Vascular plants also possess a second type of vascular tissue called phloem.
Life Cycle of Ferns
Ferns and other vascular plants have a life cycle in which the diploid sporophrie is the dominant stage.
When the spores germinate , they develop into haploid gametphytes.
The small gametophyte first grows a set of rootlike rhizoids.
22-4 Seed Plants
Reproduction Free From Water
Evolution of Seed Plants
Ancestors of seed plants evolved a variety of new adaptions that enabled them to survive in many places in which most mossses and ferns could not from frigid mountains to scorching deserts.
The early seed plants reached every landmass on Earth.
Their remains now exist in the form of coal deposits.
Gymnosperms include gnetophytes , cycads, ginkgoes, and conifers.
About 70 present -day species of the phylum gnetophyta are known , placed in just three genera.
The genus ephedra grows in the american southwest and is sometimes known as mormon tea.
Cycads-members of the phylum cycadophyta , are beautiful palm-like plants that reproduce with large cones.
Ginkgoes were common dinosaurs were alive,but today the phylum ginkgophyta contains only one species.
By far the most common gymnosperms , with more than 500 known species , are the conifers.
Flowers and Fruits
Angiosperms have unique reproductive organs known as flowers.
In general, flowers are an evolutionary advantage to plants because they attract animals such as bees , moths, or hummingbirds, which then transport pollen from flower to flower.
There are three categories of plant life spans: annual,biennial, and perennial.
Some plants grom from seed to maturity ,flower,produce seeds, and die all in the course of one growing season.
Angiosperms that complete their life cycle in two years are called bienials.
Flowering plants that live for more than two years are called perennials.
Like all plants , seed plants have a life cycle that alternates between a gametophye stage and a sporophyte stage.
As a result , seed plants can live just about anywhere.
Adaptations that allow seed plants to reproduce without water include flowers or cones ,the transfer of sperm by pollination , and the protection of embryos in seeds.
Diversity of Angiosperms
There are two classes within the angiosperms: the Monocotyledonae, or monocots.
Monocots and dicots are named for the number of seed leaves , or coytyledons, in the plant embryo.
Monocots have one seed leaf, and dicots have two.
22 Plant Diversity