GYMNOSPERMS%20

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GYMNOSPERMS THE LIFE CYCLE OF THE PINES

• Packet 72
• Chapter 30

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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.

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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

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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

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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.

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LIFE CYCLE OF A PINE
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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.

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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.

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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.

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REVIEW
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REVIEW

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