GYMNOSPERMS & THE LIFE CYCLE OF THE PINES

1. GYMNOSPERMS & THE LIFE CYCLE OF THE PINES Packet #72 Chapter #30

2. INTRODUCTION • Gymnosperms are vascular plants with seeds that are totally exposed or borne on the scales of cones. • Ovules and seeds develop on the surface of specialized leaves called sporophytes. • Familiar to most people are the conifers • The cone-bearing plants (pines). • Gymnosperms produce wind-borne pollen grains. • Feature that seedless vascular plants lack. • Gymnosperms, according to the theory of evolution, appear earlier in the fossil record than the angiosperm.

3. PHYLA OF GYMNOSPERMS • Ginkgophyta • One extant species • Cycadophyta • Large cones and palm-like leaves • 130 extant species • Gnetophyta • 3 very different genera • Coniferophyta • Pines, firs & spruces • 600 species identified

4. PHYLA OF GYMNOSPERMS • Ginkgophyta • One extant species • Cycadophyta • Large cones and palm-like leaves • 130 extant species • Gnetophyta • 3 very different genera • Coniferophyta • Pines, firs & spruces • 600 species identified

5. PHYLUM CONIFEROPHYTA • Largest phylum of the gymnosperms • Conifers (refers to cone) are woody plants that bear needles • Leaves that are usually evergreen • The needles are a result of adaptations to dry conditions. • Produce seeds in cones. • Most conifers are monoecious • Have male and female reproductive parts in separate cones on the same plant. • Most of the wood used today is from conifers • Conifers are among the largest and oldest organisms on the earth.

6. LIFE CYCLE OF A PINE

7. LIFE CYCLE OF A PINEINTRODUCTION • The pine tree is a mature sporophyte. • Pine gametophytes are extremely small AND are nutritionally dependent on the sporophyte generation. • Pine trees are hetereosporous and produce microspores and megaspores in separate cones.

8. LIFE CYCLE OF A PINE Step #1Page 597 Figure 30.6Page 597 • Male cones produce microspores that develop into pollen grains (immature male gametophytes) that are carried by air currents to female cones. • Female cones produce megaspores. One of each four megaspores produced by meiosis develops into a female gametophyte within an ovule (megasporangium). • Once the male and female cones appear, female is normally bigger, it takes approximately three years to produce male and female gametophytes, get pollinated and form mature seeds.

9. LIFE CYCLE OF A PINE II Steps 2 – 8Page 597 Figure 30.6Page 597 • After pollination, the transfer of pollen to the female cones, a pollen tube grows through the megasporangium to the egg within the archegonium. • After fertilization, the zygote develops into an embryo encased inside a seed adapted for wind dispersal. • The scales of the ovulate cone open and the seeds travel by wind.

10. REVIEW

11. REVIEW • Students • List potential examination questions and/or here, and on following slides, based on the packet.