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13.3 Nonflowering Vascular Plants

13.3 Nonflowering Vascular Plants. Gymnosperms. Nonflowering vascular plants that produce seeds are called gymnosperms. Conebearing trees, such as pine and redwood, are the most common gymnosperms alive today.

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13.3 Nonflowering Vascular Plants

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  1. 13.3 Nonflowering Vascular Plants Gymnosperms

  2. Nonflowering vascular plants that produce seeds are called gymnosperms.

  3. Conebearing trees, such as pine and redwood, are the most common gymnosperms alive today.

  4. Because of their seeds and other adaptations, these plants live and reproduce in places where ferns, horsetails, and club mosses cannot.

  5. A seed is an adaptation for protecting and nourishing a plant embryo.

  6. The embryo inside a seed may remain dormant for a long period of time. Then, when the conditions are right, it can begin growing.

  7. Sperm cells develop inside protective cases that can be carried by moving air. (Pollen)

  8. As a result, gymnosperms grow in deserts and on dry, windy mountaintops.

  9. There are four main groups of gymnosperms alive today.

  10. The most common living gymnosperms, the conifers, have needle-shaped leaves and seeds produced in cones.

  11. Cycads (SY kadz) are relics of the ancient forests.

  12. This gnetophytes (NEE toh FYTS) has long straplike leaves and bears clusters of small cones on short stalks.

  13. The ginkgo, also called the maidenhair tree, has fan-shaped leaves and fleshy seeds. Unlike other gymnosperms, the leaves of a ginkgo fall from the tree in autumn.

  14. Life Cycle of Gymnosperms Example – Pine Tree

  15. The life cycles of gymnosperms differ greatly from the life cycles of ferns, horsetails, and club mosses.

  16. The pine tree is the sporophyte generation. It has two types of cones.

  17. The large woody cones produce spores that develop into female gametophytes.

  18. Smaller, nonwoody cones produce spores that develop into male gametophytes.

  19. The female gametophyte remains in the cone. It grows into a many-celled mass in which several egg cells begin to develop.

  20. The male gametophyte is packaged into a tiny pollen grain. These are released and carried by the wind.

  21. When the wind-borne pollen reaches a cone where the female gametophyte is developing, pollination occurs.

  22. The male gametophyte grows a pollen tube through which sperm can reach the egg cell. Fertilization occurs as the sperm and egg fuse. The fertilized egg then develops into an embryo.

  23. The embryo is packaged into a seed, along with a food supply.

  24. When the seed sprouts and grows into a young sporophyte, the cycle is complete.

  25. In this life cycle, the gametophyte generation is very small. • For this reason, reproduction in gymnosperms appears to involve only one generation producing male and female sex cells.

  26. End

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