Transcript 06-Plants
The Wonderful World of Plants The Basics All plants are eukaryotic autotrophs • 6H20 + 6CO2 → C6H12O6 + 602 • Reaction takes place in the chloroplast with the help of a photosynthetic pigment such as chlorophyll. The Life Cycle of Plants Life Cycle of Plants • Plants have an alternation of generations. • The diploid (2N) phase is the sporophyte. The sporophyte makes spores. • The haploid (1N) phase is the gametophyte. The gametophyte makes gametes. For mosses, the gametophyte is the dominant form. For ferns, gymnosperms, and angiosperms, the sporophyte is the dominant form. The Divisions of Plants Plant Divisions Plants are divided into groups based on: 1. whether or not they have vascular conducting tissues. Xylem – moves water from the roots up to the leaves Phloem – moves sugars made in the leaves down to the roots. 2. whether or not they make seeds. 3. whether or not they have flowers. The four groups are: 1. bryophytes (mosses) 2. seedless vascular plants (ferns) 3. gymnosperms (cone bearers) 4. angiosperms (flowering plants) Plant Kingdom Bryophytes • Examples include mosses and liverworts. Characteristics of Bryophytes • Bryophytes do not have special tissues to conduct food and water. • They rely on osmosis to move water around their bodies. Because of this, they don’t get very tall. • They rely on water to be able to reproduce because the sperm swim through water to the eggs. Moss sporophyte and gametophyte Mosses & Horsetails Seedless Vascular Plants • Ferns are vascular which means they have xylem and phloem. • Xylem and phloem allow these plants to grow taller than mosses. • Ferns are seedless plants. They make spores. Ferns Ferns reproduce with spores Horsetails and club mosses are close relatives of ferns Horsetail & Ferns The Seed Plants Gymnosperms and Angiosperms Gymnosperms • • • • Have vascular tissue. Make seeds. Do not have flowers, but do have cones. The 1N gametophyte stage is enclosed entirely within the 2N sporophyte structure. Gymnosperm cones…male and female. Which is which? Gymnosperms include conifers and ginkgoes Angiosperms • • • • Have vascular tissue. Make seeds. Do have flowers. The 1N gametophyte stage is pretty much enclosed entirely within the 2N sporophyte structure. Angiosperms include any flowering plant…tulips, cherry trees, zinnias Flower Structure and Seed Dispersal Higher Plants Angiosperms • Flowers contain ovaries which protect the egg. • Somehow, sperm needs to get to the egg. • Once the egg is fertilized, it turns into a seed. • Somehow the seeds need to be dispersed – spread away from the parents. Flower Structure Seed dispersal Angiosperms can be Further Divided Angiosperms can be divided into Monocots and Dicots Monocots Single cotyledon Dicots Two cotyledons Parallel leaf veins Branched leaf veins Flower petals in 3’s Flower petals in 4’s or 5’s Roots are fibrous One big tap root http://trc.ucdavis.edu/biosci10v/bis10v/week8/dicotmonocot.gif Leaf Vein Patterns Dicot leaf Flowers Roots Monocot-roots are fibrous Dicot-one big tap root Plants Do Cool Stuff Plants can maintain homeostasis Phototropism • Phototropism is the movement of plants towards light. Gravitropism/Geotropism • Roots move down and shoots grow up in the dark in response to gravity. These plants were situated in various positions, but the shoots continued to move against gravity. Thigmotropism • Thigmotropism is a plant’s response to touch. This plant responds to a stationary object by wrapping its stem around it to anchor itself. This plant responds to touch by wilting. What advantage may this be to the plant? Photoperiodism - Some plants respond to the amount of daylight – Poinsettia turn red and flower in response to shorter days Some plants “eat” animals Monkey cup A.K.A. Tropical pitcher plant Monkey drink as the plants trap water, insects fall in and get digested by enzymes Sundews – insects are attracted to surface and get stuck on mucus Venus Fly Trap