1. P lant D iversity II : T he E volution of S eed P lants Campbell, 5 th Edition, Chapter 30 Nancy G. Morris Volunteer State Community College

2. Evolution of Seed Plants Gametophytes of seed plants continue pattern of reduction Sporophytes continue pattern of dominance (Figure 30.1)

3. R eproductive A daptations of S eed P lants Gametophyte develops within the spore retained in the tissues of the parent sporophyte. (Figure 30.1)

4. Trend in Dominance of Sporophyte

5. R eproductive A daptations of S eed P lants The seed replaced the spore as the main means of dispersing offspring. (Figure 30.2) The seed, which is the fertilized ovule, consists of a sporophyte embryo packaged along with a food supply within a seed coat.

6. Figure 30.2 From Ovule to Seed

7. R eproductive A daptations of S eed P lants Pollen became the vehicles for sperm cells in seed plants. The pollen grain, which is the immature male gametophyte, can be dispersed through the air by wind or transported by animals.

8. G ymosperms Bear their seeds “naked” on the surfaces of sporophylls. Pine Life Cycle -- key reproductive adaptation of seed plants (Figure 30.4) – 1) Dominance of the sporophyte – 2) Development of seed from fertilized ovules – 3) Flagellated sperm replaced by pollen

9. 4 Divisions of Gymnosperms Division Cycadophyta – sago palms Division Ginkgophyta – ginkgo Division Gnetophyta – Welwitshia Division Coniferophyta – pines, firs, redwoods, spruce, hemlock, bald cypress (Figure 30.3)

10. Figure 30.4 Gymnosperm Life Cycle

11. Angiosperms Terrestrial adaptation continued with the refinement of vascular tissue – both xylem vessel elements & fibers evolved from tracheids, a type of xylem. (Figure 30.5)

12. Figure 30.5 Tracheids

13. Angiosperms The flower is the defining reproductive adaptation (Figure 30.6) – Sepals, petals, stamens (which produce pollen), carpels (which produce ovules), are whorls of modified leaves that make up flowers.

14. Figure 30.6 Flower Anatomy

15. Angiosperms Fruits help disperse the seeds of angiosperms (Figure 30.7) – Ovaries ripen into fruits, which when opened disperse seeds to new locations.

16. Life Cycle of the Angiosperm Alternation of Generations Life Cycle Figure 30.8 Double fertilization occurs when a pollen tube discharges two sperm into the embryo sac (the female gametophyte within an ovule). One sperm fertilizes the egg, the other combines with two nuclei to produce the food-storing endosperm.

17. Figure 30.8 L ife C ycle of A ngiosperm

18. Consider this… Angiosperms & animals have shaped one another’s evolution. – Pollination of flowers by animals & transport of seeds by animals are two important relationships in terrestrial ecosystems. Agriculture is based almost entirely on angiosperms. – Human cultures depend on the cultivation & harvest of angiosperms, especially the fruits of grains.

19. Consider this… Plants transform the atmosphere and the climate. – By lowering the concentration of CO 2, plants probably contribute to the cooling of the Earth. Plants are a renewable resource. Plant diversity is a nonrenewable resource. – Destruction of the tropical rainforests is an especially urgent problem because they contain the greatest diversity of plants on Earth.

20. Embryological Development of a Plant