Plant Diversity

Chapter 22

Miller & Levine TextBiology 112

Introduction to Plants

Plants…• Provide the base for food chains on

land• Provide shade, shelter and oxygen

for all animalsOldest 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

What do Plants Need?

1. Sunlight

2. Water & Minerals

3. Gas Exchange

4. Movement of Water and Nutrients

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”

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 KingdomBotanists divide the plant kingdom

into 4 groups based on three important features:

1. Water-conducting tissues

2. Seeds

3. Flowers

Types of Plants

235,000 Flowering Plants (Angiosperms)

Mosses & Relatives

15,600 species

Cone-bearing plants 760 species (gymnosperms)

Ferns & Relatives 11,000 species

Bryophytes (Non-Vascular)

• 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

No Xylem or Phloem

Liverwort

Hornwort

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

Moss

Seedless Vascular Plants (Ferns & Relatives)• Dominant land plant 300 million

years ago

• Most are now extinct

Seed Plants - Gymnosperm

• Divided into 2 groups: Gymnosperms & Angiosperms

GYMNOSPERMS:

• The most ancient surviving seed plants are the gymnosperms (naked seeds)

• Seeds often found in a cone

Gymnosperms: The 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

Seed Plant – Angiosperms: Flowering Plants• There are thousands of different kinds of

flowering plants• Angiosperms ALL produce seeds in

reproductive structures called flowers.• Flowers contain ovaries, which surround and

protect the seed. 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

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

**See other **See other characteristics on characteristics on page 570page 570

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. 

• Make a plant hard to pull from the ground• Go far underground to reach water• Ex: dandelions, carrots, beets, radish 

Taproot

#2. Fibrous Roots – • Characterized by having a mass of

similarly sized roots.    • Most monocots have fibrous root

systems. • Ex: grasses • 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:

1. Produce leaves, branches, flowers

2. Hold leaves up to sunlight

3. Transport substances between roots and leaves

Leaves – (focus for Friday’s Lab)• The structure of a leaf is optimized

for absorbing light and carrying out photosynthesis.

Leaves• Photosynthetic organ of the plant, used

to convert sunlight into food • Photosynthesis Equation:

• Stomata: pores within the leaf that open to let CO2 in and O2 out. Guard cells open and close.

• Cuticle: waxy covering on leaf that prevents water loss

All Plants

Nonvascular plants

vascular plants

seedless plants seed

plants

gymnosperms angiosperms

monocots dicots

•Vascular tissue= veins for the plant

•Phloem- transports food (sugar- 2ways)

•Xylem- transports water (1 way)

Seeds = embryo surrounded by endosperm (food for the baby plant)

Flowering plants

Non-flowering plants

•Make cones, but no fruit or flowers

•Example: conifers, fir trees, pine trees, etc.

•No vascular tissue

•No true roots, stems or leaves

•Example: Moss

•Flower parts in 3 or multiples of 3

•Parallel veins in leaf

•Scattered vascular bundles in stem cross section

•1 cotyledon (seed leaf

•Ex. Tulip

•Flower parts in 4/5 or multiples of 4/5

•Netted veins in leaf

•Ring of vascular bundles in stem cross section

•2 cotyledon (seed leaf

•Ex. Sunflower