Lecture 4: Chapter 24

1. Lecture 4: Chapter 24 Evolution and Diversity of Plants

2. Outline • Evolutionary History • Alternation of Generations • Nonvascular Plants • Vascular Plants • Seedless • Seed • Angiosperms • Monocots and Eudicots • Flowers

3. Evolutionary History of Plants • Plants are thought to have evolved from freshwater algae • Among the adaptations of plants to life on land are: • Protection of the embryo from drying out. • Waxy cuticle on leaves to prevent drying out. • Internal skeleton (in flowering plants) to oppose gravity. • Vascular system (in most plants) to move water internally.

4. Other Terrestrial Adaptations • Vascular tissue transports water and nutrients to the body of the plant. • Cuticle provides an effective barrier to water loss. • Stomata bordered by guard cells that regulate opening, and thus water loss.

6. Four Major Plant Groups

7. Alternation of Generations • Plant life cycle(s) include alternation of generations cycle only. • Sporophyte produces spores by the process of meiosis and represents diploid generation. • Gametophyte produce gametes and represents haploid generation.

8. Alternation of Generations

9. Alternation of Generations

10. Nonvascular Plants • Nonvascular plants (bryophytes) lack specialized means of transporting water and organic nutrients. • Do not have true roots, stems, and leaves. • Produces eggs in archegonia • Produces flagellated sperm in antheridia

11. Nonvascular Plants • Liverworts have either flattened thallus (body) or leafy appearance with no true root, no stem. • Asexualy reproduce by gemmae (group of cells that detach from the thallus and can start a new plant)

13. Nonvascular Plants • Mosses usually have a leafy shoot. • Can reproduce asexually by fragmentation. • Mosses prefer dump, moist and shaded location, but could survive in deserts too

14. Vascular Plants • They contain vascular tissue (Xylem and Phloem). • Xylem transports water and dissolved minerals up from roots. • Phloem transports sucrose and other organic compounds throughout the plant. • Vascular plants are divided into plants with seed and seedless plants

15. Seedless Vascular Plants • Vascular seedless plants are homosporous. • Ferns are example of seedless vascular plant. • Most abundant in warm, moist, tropical regions, • An egg is produced in an archegonium. • A sperm is produced in an antheridium.

16. Seed Plants • Vascular plants with seed are heterosporous ( have two kind of spores) • Microspores develop into pollen grain • Megaspore develop into egg • Vascular plants with seed are classified into Gymnosperms and Angiosperms

17. Gymnosperms • Gymnosperms have ovules and seeds exposed on the surface of sporophylls. • Examples of Gymnosperms are Conifers and Ginkgoes • Conifers - bear cones • Ginkgoes - some trees produce seeds and some produce pollen.

18. Pine Life Cycle

19. Pine Life Cycle In the pine life cycle, female cones remain on the tree over two years.

20. Angiosperms (flowering plants) • Angiosperms are an exceptionally large and successful group of plants. • live in all sorts of habitats, from fresh water to desert, and from rigid north to the torrid tropics.

21. Monocots and Eudicots • Two classes of flowering plants. • Monocotyledones (Monocots) • Flower parts in three or multiple of three. • Usually parallel venation in leaves • Eudicotyledones (Dicots) • Flower parts in four or fives or multiples of fours or five . • Usually net venation

22. The Flower • Flower consists of petals, sepals, stamen (male reproductive organs) and carpel (female reproductive organs). • Each stamen consists of an anther (produce pollen) and a filament (stalk). • Carpel has three major regions. • Ovary • Style • Stigma

24. Flowering Plant Life Cycle

25. Flowering Plant Life Cycle