1. Plant Diversity I: How Plants Colonized Land
Chapter 29 Notes
Plant Diversity I: How Plants Colonized Land

2. Concept 29.1
More than 280,000 species of plants inhabit the earth today
Although some are aquatic, most are terrestrial: deserts, grasslands, forests
Land plants evolved from certain green algae called charophyceans

3. Concept 29.1
There are four main groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms
Bryophytes: mosses; distinguished from algae by advances that allow for life on land

4. Concept 29.1
Pteridophytes: ferns; contain vascular tissue (transport water and food); “seedless plants”
Gymnosperms: conifers; “naked seed” (seeds are not enclosed in a special chamber)
Seed: consists of a plant embryo packaged with food and a protective coat

5. Concept 29.1
Angiosperms: flowering plants; “container seed”; most modern-day plants
algal ancestors  bryophytes  vascular plants  the origin of seeds  the evolution of flowers

6. Concept 29.1

7. Concept 29.1
Charophyceans are the green algae most closely related to land plants
Plasma membranes contain rosette cellulose-synthesizing complexes
- synthesize the cellulose of cell walls
Same enzymes in peroxisomes that help minimize the loss of product due to photorespiration

8. Concept 29.1

9. Concept 29.1
Several terrestrial adaptations distinguish land plants from charophycean algae
- growth in length is from apical meristems
- multicellular, dependent embryos
- alteration of generations: gametophyte and sporophyte

10. Concept 29.1

11. Concept 29.1

12. Concept 29.1

13. Concept 29.2
There are other adaptations that are common in many land plants
Adaptations for water conservation:
- formation of a cuticle
- stomata contain guard cells

14. Concept 29.2

15. Concept 29.2 Adaptations for water transport:
Except for bryophytes, land plants have true roots, stems, and leaves with vascular tissue
- xylem: carry water and minerals up from root
- phloem: distribute sugars and amino acids throughout the plant

16. Concept 29.2

17. Concept 29.2 Land plants evolved from charophycean algae over 500 mya
- chloroplasts: chlorophyll b and beta-carotene
- homologous cell walls
- peroxisomes

18. Concept 29.2
Alteration of generations in plants may have adapted by delayed meiosis
Charophycean zygote undergoes meiosis to produce haploid spores
Plant zygote undergoes mitosis to produce a multicellular sporophyte to produce haploid spores by meiosis

19. Concept 29.2
Adaptations to shallow water preadapted plants for living on land
- natural selection would favor those that could withstand occasional drying

20. Concept 29.3 Bryophytes are represented by 3 phyla:
Hepatophyta (liverwarts), Anthocerophyta (hornworts), and bryophyta (mosses)

21. Concept 29.3

22. Concept 29.3
The gametophyte is the dominant generation in the life cycle of bryophytes
- sporophytes are typically smaller and present only part of the time
- up to 50 million spores can be generated in one spore capsule

23. Concept 29.3

24. Concept 29.3

25. Concept 29.3

26. Concept 29.3 Mosses are able to exist in very harsh climates
- able to loose most of their body water without dying, then rehydrate later
Bryophytes were the only plants on earth for 100 million years

27. Concept 29.4
Modern vascular plants include ferns (pteridophytes), gymnosperms, and flowering plants (angiosperms)
Differ from bryophytes
- contain phloem and xylem
- dominant sporophyte generation

28. Concept 29.4
2 phyla of seedless vascular plants: phylum Lycophyta and phylum Pterophyta (ferns)
Pteridophytes provide clues to the evolution of roots and leaves

29. Concept 29.4
Most pteridophytes have true roots with lignified vascular tissue
Lycophytes have small leaves with only a single unbranched vein; known as microphylls
- modern leaves are known as megaphylls

30. Concept 29.4

31. Concept 29.4
A sporophyte-dominant life cycle evolved in seedless vascular plants
Homosporous plants: produce one type of spore
Heterosporus plants: produce megaspores (female) and microspores (male)

32. Concept 29.4