1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Characteristics of Plants Section 1 Adaptations of Plants Chapter 23

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Establishment of Plants on Land Plants are the dominant group of organisms on land, based on weight. Plants probably evolved from multicellular aquatic green algae that could not survive on land. *Before plants could thrive on land, they had to be able to do three things: absorb nutrients from their surroundings, prevent their bodies from drying out, and reproduce without water to transmit sperm. Section 1 Adaptations of Plants Chapter 23

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evolutionary Relationships Between Plants and Green Algae Section 1 Adaptations of Plants Chapter 23

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Establishment of Plants on Land Preventing Water Loss * A watertight covering, which reduces water loss, made it possible for plants to live on land. This covering, called a cuticle, is a waxy layer that covers the nonwoody aboveground parts of most plants. Pores called stomata permit plants to exchange oxygen and carbon dioxide. A pair of specialized cells called guard cells border each stoma. Stomata open and close as the guard cells change shape. Section 1 Adaptations of Plants Chapter 23

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Stomata and Guard Cells Section 1 Adaptations of Plants Chapter 23

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Establishment of Plants on Land Reproducing on Land* In most plants, sperm are enclosed in a structure that keeps them from drying out. The structures that contain sperm make up pollen. Pollen permits the sperm of most plants to be carried by wind or animals rather than by water. Section 1 Adaptations of Plants Chapter 23

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vascular Tissue, Seeds, and Flowers Advantages of Seeds A seed is a structure that contains the embryo of a plant. An embryo is an early stage in the development of plants and animals. Most plants living today are seed plants—vascular plants that produce seeds. Section 1 Adaptations of Plants Chapter 23

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vascular Tissue, Seeds, and Flowers Advantages of Seeds* Seeds offer a plant several survival advantages: 1. The seed coat protects the embryo from drying out, injury, and disease. 2. Most kinds of seeds store a supply of nutrients. 3. Seeds disperse the offspring of seed plants. 4. Seeds make it possible for plant embryos to survive through unfavorable periods such as droughts. Section 1 Adaptations of Plants Chapter 23

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Structure and Function of Seeds Section 1 Adaptations of Plants Chapter 23

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vascular Tissue, Seeds, and Flowers Advantages of Flowers* The last important adaptation to appear as plants evolved was the flower, a reproductive structure that produces pollen and seeds. Most plants living today are flowering plants—seed plants that produce flowers. Flowering plants that are pollinated by animals produce less pollen, and cross-pollination can occur between individuals that live far apart. Section 1 Adaptations of Plants Chapter 23

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Parts of a Fern Section 2 Kinds of Plants Chapter 23

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Angiosperms Kinds of Angiosperms Botanists divide the angiosperms into two subgroups—monocots and dicots. The monocots are flowering plants that produce seeds with one seed leaf (cotyledon). The dicots are flowering plants that produce seeds with two seed leaves. Section 2 Kinds of Plants Chapter 23

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Characteristics of Monocots and Dicots Section 2 Kinds of Plants Chapter 23

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Comparing Characteristics of Monocots and Dicots Section 2 Kinds of Plants Chapter 23