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Questions and Answers
What does the term 'pollen grain' refer to?
What does the term 'pollen grain' refer to?
Double fertilization in angiosperms involves the fusion of two sperm cells with two different parts of the female gametophyte: one sperm with the egg cell and the other sperm with the central cell.
Double fertilization in angiosperms involves the fusion of two sperm cells with two different parts of the female gametophyte: one sperm with the egg cell and the other sperm with the central cell.
True
What is the role of the endosperm in a seed?
What is the role of the endosperm in a seed?
The endosperm provides nourishment to the developing embryo.
Which of these is NOT a characteristic of angiosperm gametophytes?
Which of these is NOT a characteristic of angiosperm gametophytes?
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What is the primary function of the tube cell in a pollen grain?
What is the primary function of the tube cell in a pollen grain?
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The process of pollination is necessary for the development of angiosperm fruits.
The process of pollination is necessary for the development of angiosperm fruits.
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What is the difference between the generative cell and the tube cell in a pollen grain?
What is the difference between the generative cell and the tube cell in a pollen grain?
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The union of the two sperm cells with different tissue of the ovule where the egg has been fertilized is called ______ fertilization.
The union of the two sperm cells with different tissue of the ovule where the egg has been fertilized is called ______ fertilization.
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Study Notes
Angiosperm Life Cycle Overview
- Angiosperms have a life cycle focusing on gametophyte development, sperm delivery (pollen tubes), and double fertilization.
- Gametophytes in angiosperms are small, dependent on the sporophyte for nutrients.
- Female gametophytes develop within ovules deep within the ovary.
- Male gametophytes form within pollen grains (anthers).
Female Gametophyte Development (Embryo Sacs)
- Ovules develop within the ovary.
- Megasporangium within ovule produces megaspores via meiosis.
- Only one megaspore survives and divides three times without cytokinesis, resulting in a multinucleate embryo sac with eight nuclei.
- The embryo sac contains an egg cell, two synergids, three antipodal cells, and two polar nuclei.
Male Gametophyte Development (Pollen Grains)
- Microsporangia (pollen sacs) form within anthers.
- Microsporocytes undergo meiosis to form microspores.
- Each microspore develops into a pollen grain with two cells: tube cell and generative cell.
Sperm Delivery by Pollen Tubes
- Pollen grain germinates and forms a pollen tube that grows through the style.
- The generative cell divides to form two sperm cells.
- The tube nucleus leads the way, following chemical attractants to the embryo sac.
- Sperm are released in vicinity of the embryo sac.
Double Fertilization
- One sperm fertilizes the egg, forming a diploid zygote.
- The other sperm fertilizes the two polar nuclei, forming a triploid endosperm.
- Double fertilization ensures that resources are allocated only to fertilized ovules.
Seed Development
- The ovule develops into a seed.
- The ovary develops into a fruit, aiding in seed dispersal.
- Seeds store nutrients (starch, proteins, oils) for the developing embryo, and in some cases cotyledons (seed leaves) take over this role.
- The seed embryo eventually develops into a new sporophyte when the seed germinates.
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Description
Explore the life cycle of angiosperms, focusing on the development of male and female gametophytes. Understand the processes of gametophyte formation, sperm delivery, and double fertilization. Dive into the details of embryo sacs and pollen grains for a comprehensive overview of angiosperm reproduction.
