Warm-Up #30

1. Warm-Up #30 • Complete the Analyzing Data on page 620 of your textbook.

2. Leaf Lab Review

3. Reproduction of Seed Plants

4. Objectives • Identify the reproductive structures of gymnosperms and angiosperms. • Describe the development of seeds and fruits. • Explain how seeds are dispersed. • List the factors that influence the dormancy and germination of seeds.

5. Seeds—Reproductive Adaptations • The gametes of seedless plants, such as ferns and mosses, need water for fertilization. • The water allows the gametes to move from plant to plant. • The gametes of seed plants, however, can achieve fertilization even when the plants are not wet from rain or dew. • They can reproduce anywhere—this has allowed them to survive the dry conditions on land.

6. Alternation of Generations • In seed plants, the familiar, recognizable form of the plant is the diploid sporophyte. • The gametophyte of seed plants are hidden deep within the tissues of the sporophyte plant. • In gymnosperms they are found inside cones, and in angiosperms they are found inside flowers.

7. Life Cycle of Gymnosperms • Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant. • Two types of cones: • Pollen cones—male cones, produce the male gametophytes, which are called pollen grains. The pollen grain is the entire male gametophyte stage. • Seed cones—produce the female gametophytes. Near the base of each scale are two ovules in which the female gametophytes develop. Meiosis produces haploid cells that grow into female gametophytes.

8. Figure 24-4 on page 611 • Discuss the stages of the gymnosperm life cycle with your partner.

9. Structure of Flowers • Flowers are reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens and carpels

10. Life Cycle of Angiosperms • Reproduction in angiosperms takes place within the flower. Following pollination and fertilization, the seeds develop inside protective structures. • Discuss Figure 24-7 on page 614 with your partner. • Once the gametes have developed inside the flower, pollination takes place.

11. Pollination • Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals. • insects • Birds • Bats

12. Fertilization in Angiosperms • If a pollen grain land son the stigma of an appropriate flower, it grows a pollen tube. • The nucleus within the pollen grain divides and forms two sperm nuclei. • Once the pollen grain reaches the embryo sac, two fertilizations take place (double fertilization) • One sperm nucleus fuses with the egg nuclei to form the diploid zygote. • The other sperm nucleus fuses with two of the polar nuclei in the embryo sac to form a triploid (3N) cell. This cell grows into the endosperm

13. Seed and Fruit Development • Once fertilization is complete, nutrients flow into the flower tissue and support the development of the growing embryo within the seed. • As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seeds • The fruit may be fleshy as in grapes and tomatoes or tough like the pod of a bean. • In some the inner wall of the ovary is attached rigidly to the surface of the seed, while others form an aerodynamic shape for wind dispersal. • Page 618—Figure 24-10

14. Seed Dispersal • Animals—seeds dispersed by animals are typically contained in fleshy, nutritious fruits. • Wind and Water—seeds dispersed by wind or water are typically lightweight, allowing them to be carried in the air or to float on the surface of the water • Maple twirlers • Tumbleweeds • Coconuts

15. Seed Dormancy • Some seeds sprout so rapidly that they are practically instant plants—like bean seeds. • Many seeds will not grow when they first mature. Instead they enter a period of dormancy. • Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.

16. Seed Germination • Seed germination is they early growth stage of the plant embryo. • When seeds germinate they absorb water, this causes food-storing tissues to swell, cracking open the seed coat. • Through the cracked seed coat, the young root emerges and begins to grow.

17. Summary • What are the reproductive structures of gymnosperms? • Angiosperms? • What are seeds? • What are fruits? • How are seeds dispersed? • What factors influence dormancy and germination of seeds?

18. Flower Lab • Study Guide 94—Flower Lab only

19. Homework • Read Text 633-645 • Complete Study Guide 96-97 • Finish Flower Lab