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Questions and Answers
What are gymnosperms?
What process initiates the formation of male gametophytes (pollen grains) in the Pine Life Cycle?
Meiosis to form microspores
Explain pollination in the Pine Life Cycle.
The wind carries a pollen grain to the micropyle at the base of an ovulate cone scale.
What happens while the pollen tube is growing in the megasporocyte?
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What brings the sperm to the eggs in the Pine Life Cycle?
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Explain fertilization in the Pine Life Cycle.
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What is the embryo in the Pine Life Cycle?
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Study Notes
Gymnosperms
- Seed plants lacking enclosed chambers around their seeds
- Majority are conifers, also known as cone-bearing trees
Formation of Male Gametophytes
- Initiated by meiosis producing microspores (n)
- Pollen cones contain numerous microsporangia within sporophylls
- Microsporangia cells undergo meiosis to yield haploid microspores
- Microspores develop into pollen grains equipped with tiny wings, representing male gametophytes
Pollination Process
- Pollination occurs when wind transports a pollen grain to the micropyle located at the base of an ovulate cone scale
- A pollen tube begins to grow, extending from the pollen grain into the megasporangium
- This process can exceed one year in duration
Pollen Tube Growth Dynamics
- While the pollen tube extends, the megasporocyte (2n) undergoes division into four haploid megaspores (n); typically, only one survives
- The surviving megaspore divides mitotically multiple times to form the female gametophyte (n)
- Formation of two or three archegonia, each housing an egg, occurs within the gametophyte
Sperm Delivery to Eggs
- The completion of the pollen tube facilitates sperm delivery
- Sperm cells arise within the pollen tube, breaking through the megasporangium, and reaching the female gametophyte
- Sperm nuclei are released into the megasporangium
Fertilization Process
- Fertilization occurs when sperm and egg nuclei combine, resulting in a 2n zygote
- Generally, one sperm nucleus fuses with each egg, leading to survival of typically one zygote
- Zygote undergoes mitosis to develop into an embryo
- The seed is formed from the embryo, surrounding gametophyte tissue (n), and the seed coat (2n)
Structure of the Seed
- Contains an embryo that is an immature sporophyte
- Comprises a food supply sourced from gametophyte tissue and a seed coat derived from the parent tree
- The seed disperses, germinates, and the embryo develops into a seedling
- The seedling matures into a mature sporophyte (2n), completing the Pine Life Cycle
Studying That Suits You
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Description
Explore the intricate details of the Pine Life Cycle through these flashcards based on Chapter 30. Test your knowledge on key terms such as gymnosperms and the processes involved in male gametophyte formation. Perfect for students looking to enhance their understanding of plant biology.
