Chapter 22 Miller & Levine Text Biology 112 Plant Diversity Chapter 22 Miller & Levine Text Biology 112

What Do You Already Know??? PLANTS

Introduction to Plants Provide the base for food chains on land Provide shade, shelter and oxygen for all animals Oldest fossil evidence of plants dates from about 470 million years ago! What is the name of the science of studying plants??

Kingdom Plantae Multicellular Eukaryotic Carry out photosynthesis using green pigments called chlorophyll Include trees, shrubs, grasses, mosses and ferns Most are autotrophs Cell Walls made of cellulose

Plant Life Cycle Two alternating phases, a diploid (2N) phase called the sporophyte generation and a hapoid (N) known as gametophyte generation These alternating phases are known as “alternation of generations”

What do Plants Need? 1. Sunlight 2. Water & Minerals 3. Gas Exchange 4. Movement of Water and Nutrients

Early Plants For most of Earth’s history plants did not exist. Life was concentrated in oceans, lakes and streams…Oxygen came from algae and cyanobacteria The first plants evolved from an organism much like the multicellular green algae living today.

Overview of the Plant Kingdom Botanists divide the plant kingdom into 4 groups based on three important features: Water-conducting tissues Seeds 3. Flowers

Types of Plants 235,000 Flowering Plants (Angiosperms) Cone-bearing plants 760 species (gymnosperms) Ferns & Relatives 11,000 species Mosses & Relatives 15,600 species

Bryophytes (Non-Vascular) No Xylem or Phloem Confined to moist habitats b/c they need water for sexual reproduction Commonly found in wetlands, rain forests, and roadside ditches Generally less than 20cm tall 3 classes: mosses, liverworts, and hornworts

Bryophytes Have leaflike, stemlike and rootlike organs Have rhizoids (fine-like roots) that anchor the plant Water and nutrients move from cell to cell by diffusion Mosses are the most common and they hold a lot of water – this sponge like feature makes them useful in oil spills, and potting soils

Seedless Vascular Plants (Ferns & Relatives) Dominant land plant 300 million years ago Most are now extinct

Seed Plants - Gymnosperms Represent all seed plants that DO NOT form flowers (therefore do not have seeds enclosed within a fruit) The most numerous and widespread are the conifers Reproductive Adaptations and an improved vascular system largely account for the success of seed plants The most widely distributed and complex group of plants on Earth 270 000 known seed plants Have separate male and female gametophytes, as well as roots, stems and leaves.

Gymnosperms cont… Seed type is the main criterion for distinguishing the two major seed-bearing groups; gymnosperms and angiosperms Greek: sperma “seed”, gymnos “naked”, and angeion “vessel” Gymnosperms produce unprotected or “naked” seeds in conelike structures, and Angiosperms produce seeds that are enclosed and protected inside the fruit, which is formed by the flower. Seeds ensure the survival of seed plants by resisting desiccation.

Conifers Cone bearing woody trees and shrubs Leaves are usually needlelike Most are evergreen (don’t drop their leaves in the Autumn) Conifers DO shed their needles, just not all at once – usually 2 to 4 years Grow in many different environments 600 species (pine, fir, spruce, cedar, hemlock, sequoias Produce useful products, ie. lumber/paper

Angiosperms – Flowering Plants There are thousands of different kinds of flowering plants They range from tiny pond-surface plants, which are less than 1mm long to trees 100m tall. Angiosperms ALL produce seeds in reproductive structures called flowers. Then, as the seeds mature, the flower changes into a fruit. The name angiosperm means “covered seed” Mature seeds are scattered, or dispersed, along with the fruit http://www.biology.ualberta.ca/facilities/multimedia/?Page=271

Monocots & Dicots Botanists are able to divide the 235,000 species of angiosperms into two large groups based on the structure of their seeds Inside the seeds of angiosperms are tiny embryonic leaves called cotyledons. The seeds of one group of angiosperms have one cotyledon, called monocotyledons or monocots. Other angiosperms have two cotyledons. These are called dicotyledons or dicots

The veins of monocot leaves are parallel to each other The leaves of dicots usually have netlike veins

Monocot Examples Tulips, daffodils, irises, lilies, palm trees

Dicot Examples Buttercups, peas, roses, sunflowers, maple trees, and dandelions

Grass? The leaf blade of grasses indicates whether they are monocots or dicots based on leaf veins. To which group to grasses belong? You are right if you said monocots!

Roots, Stems & Leaves “Principal organs of seed plants”

Roots – Try This: http://www.virted.org/Plants/RootsQuiz.html Absorbs water and dissolved nutrients Anchors plants to ground Prevents erosion Protection from soil bacteria and fungus Transports water & nutrients Holds plants upright against forces such as wind and rain

Roots – Two main types: Plants have taproots, fibrous roots or both #1 Taproots - Characterized by having one main root (the taproot) from which smaller branch roots emerge.  When a seed germinates, the first root to emerge is the radicle, or primary root.  In conifers and most dicots, this radicle develops into the taproot.   Taproots can be modified for use in storage (usually carbohydrates) such as those found in sugar beet or carrot.  Taproots are also important adaptations for searching for water, as those long taproots found in mesquite and poison ivy.

Taproot

#2. Fibrous Roots – Characterized by having a mass of similarly sized roots.  In this case the radicle from a germinating seed is short lived and is replaced by adventitious roots. Adventitious roots are roots that form on plant organs other than roots.  Most monocots have fibrous root systems.  Some fibrous roots are used as storage; for example sweet potatoes form on fibrous roots.  Plants with fibrous roots systems are excellent for erosion control, because the mass of roots cling to soil particles.

Fibrous Roots - A cabbage seedling with white, fibrous roots snaking through the soil

Root Overview

STEMS Stems have 3 important functions: Produce leaves, branches, flowers Hold leaves up to sunlight Transport substances between roots and leaves

Leaves – (see handout for additional notes) The structure of a leaf is optimized for absorbing light and carrying out photosynthesis.