Chapter 22 Plant Diversity 1 22 1 Introduction

Chapter 22 Plant Diversity 1

22– 1 Introduction to Plants 2

Objectives • Explain what a plant is • Describe what plants need to survive • Describe how plants first evolved 3

What Is a Plant? • Plants are members of the kingdom Plantae • Plants are multicellular eukaryotes that have cell walls made of cellulose. They develop from multicellular embryos and carry out photosynthesis using the green pigments chlorophyll a and b 4

The Plant Life Cycle • Plants have life cycles that are characterized by alternation of generations • the two generations are the haploid (N) gametophyte, or gamete-producing plant, and the diploid (2 N) sporophyte, or sporeproducing plant. 5

6

7

8

What Plants Need to Survive 1. 2. 3. 4. Sunlight Water and Minerals Gas Exchange Movement of water and nutrients 9

Early Plants • The first plants evolved from an organism much like the multicellular green algae living today. 10

The First Plants • The first true plants were still dependent on water to complete their life cycles, similar to today’s mosses in that they were simple in structure and grew close to the ground. 11

• From these plant pioneers, several major groups of plants evolved. 12

Mosses 13

Ferns 14

Cone Bearing Plant 15

Flowering plant 16

Overview of the Plant Kingdom • Botanists divide the plant kingdom into four groups based on three important features: 1. Water conducting tissues 2. Seeds 3. Flowers 17

18

19

22 – 2 Bryophytes a. k. a (Non-vascular plants) 20

Objectives • Describe the adaptations of Bryophytes 21

bryophytes • Type of early plant with no vascular tissue that draw water in their cells by osmosis. 22

Moss 23

Liverwort 24

Hornwort 25

• During at least one stage of their life cycle, bryophytes produce sperm that must swim through water to reach eggs of other individuals. • Therefore, they must live in places where there is rainfall or dew for at least part of the year 26

Asexual Reproductive Part Sexual Reproductive/ Photosynthetic Part 27

22– 3 Seedless Vascular Plants 28

Objectives • Explain how vascular tissue is important to ferns and their relatives • Describe three phyla of sporebearing plants • Identify the stages in the cycle of ferns 29

• In just a few million years, plants grew to a whole new scale on the landscape. Q: What caused this increase in size? A: Vascular Tissue 30

Vascular tissue • A type of tissue that is specialized to conduct water and nutrients through the body of the plant 31

Evolution of Vascular Tissue • Both forms of vascular tissue— xylem and phloem—can move fluids throughout the plant body, even against the force of gravity. 32

Xylem • Carry water upwards from the roots to every part of the plant 33

Phloem • Transports nutrients and carbohydrates produced by photosynthesis from the leaves down to the roots 34

35

• Vascular plants also evolved the ability to produce lignin, a substance that makes cell walls rigid. • The presence of lignin allows vascular plants to grow upright and tall 36

Ferns and Their Relatives • Seedless vascular plants include club mosses, horsetails, and ferns. • Like other vascular plants, ferns and their relatives have true roots, leaves, and stems. 37

Roots • Absorb water and minerals 38

Leaves • Collect light for photosynthesis 39

Veins • Made of xylem and phloem 40

Stems • Used for support, connect roots and leaves, carry water between them 41

Club Mosses 42

Horsetails 43

Ferns Underground Stem 44

45

22 – 4 Seed Plants 46

Objectives • Describe the reproductive adaptations of seed plants • Describe the evolution of seed plants • Identify the four groups of gymnosperms 47

• Over millions of years, plants with a single trait—the ability to form seeds—became the most dominant group of photosynthetic organisms on land. • Seed plants are divided into two groups: 48

Gymnosperms • Cone plants • Bear their seeds directly on the surfaces of cones Ex. ) conifers, pines, spruces, cycads, ancient ginkgoes and gnetophytes 49

Angiosperms • Flowering plants • Bear their seeds within a layer of tissue that protects the seed Ex. ) grasses, flowering trees shrubs, wild flowers 50

Reproduction Free From Water • Unlike mosses and ferns, however, seed plants do not require water for fertilization of gametes. Q: Why was this an advantage? A: They could live further away from water • 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. 51

Cones and Flowers 52

Cones • Seed bearing structures of gymnosperms 53

Flowers • Seed bearing structures of angiosperms 54

Pollen 55

Pollen grain • Contains the male gamete 56

57

Pollination • The transfer of pollen from the male gametophyte to the female gametophyte 58

59

Seeds 60

seed • An embryo of a plant that is encased in a protective covering and surrounded by a food supply 61

embryo • Early development stage of a sporophyte plant • The seed’s food supply provides nutrients to the embryo as it grows 62

Seed Coat • Surrounds and protects the embryo and keeps the contents of the seed from drying out • Can be specialized for dispersal 63

64

65

Evolution of Seed Plants • Over a period of millions of years, continents became much drier, making it harder for seedless plants to survive and reproduce. • For that reason, many moss and fern species became extinct. They were replaced by seed plants with adaptations that equipped them to deal with drier conditions. 66

Gymnosperms—Cone Bearers • The most ancient surviving seed plants are the gymnosperms. • Gymnosperms include: 67

Gnetophytes 68

Cycads 69

Ginkgos 70

71

Conifers 72

22– 5 Angiosperms - Flowering Plants 73

Objectives • Identify the characteristics of angiosperms • Explain what monocots and dicots are • Describe three different life spans of angiosperms 74

• Flowering plants originated on land quickly came to dominate Earth’s plant life. • The vast majority of living plant species reproduce with flowers. 75

76

Flowers and Fruits • Angiosperms have unique reproductive organs known as flowers. Q: Why are flowers evolutionary adaptations? A: they attract animals that pollinate them 77

78

• Flowers contain ovaries, which surround and protect the seeds • After pollination, the ovary develops into a fruit, which protects the seed and aids in its dispersal. 79

Fruit • Ripened ovary, thick wall of tissue that surrounds the seed 80

Diversity of Angiosperms • The angiosperms are an incredibly diverse group. Not surprisingly, there are many different ways of categorizing these plants. 81

Monocots and Dicots • Monocots and dicots are named for the number of seed leaves, or cotyledons, in the plant embryo. Monocots have one seed leaf, and dicots have two seed leafs 82

83

Woody and Herbaceous Plants • Woody plants – Have woody stems Ex. ) trees, shrubs, vines 84

Herbaceous Plants • Plant stems that are smooth and nonwoody Ex. ) dandelions, petunias, and sunflowers 85

Annuals, Biennials, and Perennials 86

Annuals • Angiosperms that complete a life cycle within one growing season 87

Biennials • Angiosperms that complete their life cycle in two years • In the first year, biennials germinate and grow roots, stems, leaves • During their second year, biennials grow new stems and leaves and then produce flowers and seeds 88

Perennials • Flowering plants that live for more than two years 89