• Why plants are important -• http://www.enviro-explorers.com/wildflowers/

importance_of_plants_and_plant_c.htm

• Cool plant Facts:• http://hubpages.com/hub/plantfacts

• http://www.youtube.com/watch?v=igkjcuw_n_U

• http://www.youtube.com/watch?v=fc50QniIzVM

• Pretest• The World of Plants (15 minutes)

Plant Diversity

Chapter 22

Miller & Levine TextBiology 112

Introduction to Plants(Chapter 22)Plants…• Provide the base for food chain 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?? Botany

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. Sunlight2. Water & Minerals3. Gas Exchange4. Movement of Water and Nutrients

Plant Life Cycle• Two alternating phases, a diploid

(2N) phase called the sporophyte generation and a haploid (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 tissues2. Seeds3. Flowers

Water-Conducting Tissues• Evolved as an adaptation to land• Absence – no xylem or phloem• Presence of tissue:

– Xylem• Carries water and nutrients that enter

the plant in the roots up through the stem and out to all parts of the leaves

– Phloem• Parallel to the xylem• Carries sugar (energy) produced in

leaves (site of photosynthesis) to all parts of the plant

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– Do not flower so no seeds– They produce spores

• 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

Mosses

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 osmosis / 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 (Vascular)• Divided into two groups

– Gymnosperms (naked seed)– Angiosperms (covered seed)

• What makes them different?– 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”

• Why are they successful?– 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.

Seed Plants - Gymnosperms

• The most ancient surviving seed plants are the gymnosperms

• Seeds are often found in a cone• 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

Gymnosperms: 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 Plants – Angiosperms (Flowering Plants)• There are thousands of different kinds of

flowering plants• They range from tiny pond-surface plants, which

are less than 1 mm long to trees 100 m tall.• Angiosperms ALL produce seeds in

reproductive structures called flowers. Then, as the seeds mature, the flower changes into a fruit.

• Angiosperms produce seeds that are enclosed and protected inside the fruit, which is formed by the flower.

• Mature seeds are scattered, or dispersed, along with the fruit