1. 1 Chap 30: Plant Diversity II The Evolution of Seed Plants Overview of Seed Plant Evolution So in this section you are answering the essay question: What reproductive adaptations did seed plants (gymnosperms and angiosperms) make to be successful terrestrial organisms?

2. 2 Reduction of the gametophyte generation The gametophyte generation was getting pretty small with the ferns (seedless) but it is even smaller and more “insignificant” with the seed plants. It is microscopic and cannot be seen with the naked eye. In seed plants the female gametophyte develops from a spore that is retained within the sporangia. See Fig 30.1c. Advantage: no environmental stress is experienced. The gametophyte and embryo are protected from drought and UV radiation. Nutrients can also be gotten from the parent. Why has the gametophyte not disappeared from the life cycle? screening of new mutations gametophyte helps to nourish the sporophyte embryo

3. 3 Figure 30.1 Three variations on gametophyte/sporophyte relationships

4. 4 Seeds became an important means of dispersing offspring A spore is a single cell whereas a seed an embryo plus food supply. The seed develops within the female gametophyte which is retained on the parent plant (sporophyte) Within the ovule develops one or more egg cells which when fertilized develops into a zygote and remains protected. The seed’s protected coat develops from the integument of the ovule.

5. 5 Figure 30.2 From ovule to seed

6. 6 Figure 30.3 Winged seed of a White Pine (Pinus strobus)

7. 7 Pollen eliminated the liquid-water requirement for fertilization So this is an important point since one of the main aspects of coming onto land was keeping a moist environment for the sperm to find the egg. Now we can get rid of this adaptation. Pollen grains develop from the microspores which produce the male gametophyte. Pollen is protected by the sporopollenin coats. When pollen nears the ovule it produces a pollen tube through which sperm travel to reach the female gametophyte. Most of these sperm lack flagella Airborne pollen not swimming of sperm

8. 8 The two clades of seed plants are gymnosperms and angiosperms Different ancestors of gymno- and angiosperms but both came from the progymnosperms. Two key reproductive adaptations of seed plants: seeds pollen

9. 9 Gymnosperms The Mesozoic era was the age of gymnosperms Gymnosperms replaced the club mosses, horsetails and ferns as arid conditions increased on Earth some 250 million years ago. Gymnosperms were a main food for dinosaurs Gymnosperms persisted when dinosaurs went extinct. Four Phyla Ginkgo (Ginkgo biloba) Cycads Gnetophyta Conifers

10. 10 Figure 30.5c Phylum Ginkgophyta: Ginkgo biloba

11. 11 Figure 30.6 Phylum Cycadophyta: cycads

12. 12 Figure 30.7a Phylum Gnetophyta: Welwitschia

13. 13 Figure 30.8a Phylum Coniferophyta: Douglas fir

14. 14 Figure 30.9 The life cycle of a pine (Layer 3)

15. 15 Angiosperms Angiosperm Clades Phylum: anthophyta Not simply divided into monocots and dicots anymore Monocots: lilies, orchids, palms, grasses venation in leaves runs parallel Eudicots includes the majority of dicots Netlike venation Roses, peas, sunflowers, oaks and maples Other lineages

16. 16 What contributed to the success of the angiosperms? Xylem tissue with tracheids for mechanical support and transport Fiber cells also for support Vessel elements which are more efficient at transporting water than tracheids. Reproductive adaptations of flowers and fruits. The flower is the defining reproductive adaptation of angiosperms Know fig 30.13

17. 17 Fruits help disperse the seeds of angiosperms What you are eating is an ovary. The ovule develops around the seed Pericarp: wall of the ovary/fruit Fruit Classification Simple fruit: derived from one ovary; cherries, soybean pod and pea pod Aggregate fruit: single flower with several carpels, each carpel having an ovary and therefore producing lots of “little fruits” and since these carpels are close together they form an aggregate; blackberries Multiple fruit: the flowers of this fruit are so close together that there fertilized ovaries fuse as they develop and become one fruit; pineapples.

18. 18 Figure 30.17 The life cycle of an angiosperm

19. 19 The radiation of angiosperms marks the transition from the Mesozoic era to the Cenozoic era Oldest fossils are about 130 million years ago They became the dominant plants within 65 million years and are still the dominant plant today. Angiosperms and animals have shaped one another’s evolution Coevolution: the influence two different species have on each other’s evolution through their interactions and thus affecting the selected adaptations of each organism. insects were favored to evolve with those plants that kept their reproductive parts off of the ground. animals that carried a plant’s pollen or seeds were selected for by obtaining food on the one hand and helping the plant to reproduce on the other.

20. 20 Plants and Human Welfare So what is the value of plants to humans? Agriculture is based almost entirely on angiosperms Flowering plants provide most of our food. Vegetables and fruits are both angiosperms Selective breeding of plants became a way to improve crop productivity and quality. Table 30.2: Angiosperms are also valuable as medicines Plant diversity is a nonrenewable resource

21. 21 Table 30.2 A Sampling of Medicines Derived from Plants

22. 22 Figure 30.12 Xylem cells in angiosperms

23. 23 Figure 30.13a The structure of a flower

24. 24 Figure 30.4 Hypothetical phylogeny of the seed plants