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Questions and Answers
What is a megaphyll?
What is a megaphyll?
Which types of ferns possess megaphylls?
Which types of ferns possess megaphylls?
Both eusporangiate and leptosporangiate ferns
What are two reasons for the evolution of megaphylls?
What are two reasons for the evolution of megaphylls?
What does the telome theory suggest about megaphyll evolution?
What does the telome theory suggest about megaphyll evolution?
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What is a telome?
What is a telome?
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What is true about fronds?
What is true about fronds?
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What is a compound frond composed of?
What is a compound frond composed of?
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Climbing ferns exhibit determinate leaf growth.
Climbing ferns exhibit determinate leaf growth.
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What defines Polypodiopsida?
What defines Polypodiopsida?
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What are fern sporophytes characterized by?
What are fern sporophytes characterized by?
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What do sori represent on fern fronds?
What do sori represent on fern fronds?
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What does the annulus in a sporangium do?
What does the annulus in a sporangium do?
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What is the structure of a prothallus?
What is the structure of a prothallus?
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How does a new sporophyte initially depend on the gametophyte?
How does a new sporophyte initially depend on the gametophyte?
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What is apogamy?
What is apogamy?
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What is apospory?
What is apospory?
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What describes vegetative reproduction in ferns?
What describes vegetative reproduction in ferns?
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Some fronds look the same when comparing fertile and sterile fronds.
Some fronds look the same when comparing fertile and sterile fronds.
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Study Notes
Ferns and Megaphylls
- Ferns are characterized by the presence of megaphylls, large leaves with multiple veins.
- Both eusporangiate and leptosporangiate ferns possess megaphylls, highlighting their evolutionary significance.
Megaphyll Definition and Function
- Megaphylls are defined by having a leaf trace gap, allowing efficient water conduction and nutrient transport.
- The evolution of megaphylls is linked to environmental adaptations and demands for better vascular systems to prevent overheating.
Evolutionary Theories
- The telome theory proposes that structures in plants evolve due to environmental pressures affecting the development of ultimate branches, or telomes.
Fern Structure and Features
- Fronds, the leaves of ferns, may vary in thickness, typically being one cell layer thick or leathery. They often exhibit dichotomous venation patterns.
- Types of fronds include entire, pinnatifid, and compound, with compound fronds consisting of lamina and petiole along with pinna and petiolule attached to the rachis.
Climbing Ferns and Growth Patterns
- Climbing ferns exhibit indeterminate leaf growth and can create dense thickets, sometimes becoming aggressive invaders in ecosystems.
Polypodiopsida Classification
- True ferns are classified under Polypodiopsida, characterized as homosporous and displaying high diversity.
Sporophyte Characteristics
- Fern sporophytes are the dominant form, featuring rhizomes (underground stems), fronds, and adventitious roots, with siphonostelic rhizomes contributing to their structure.
Reproductive Structures
- Frond surfaces display sori, which may be clustered and are responsible for spore production; these may be exposed or covered by protective structures called indusia.
- In sporangia, the annulus plays a crucial role in spore dispersal; it forms, inverts as it dries, then snaps back to release spores into the wind.
Gametophyte and New Sporophyte Development
- The prothallus, which is the gametophyte stage, is small and membranous, featuring rhizoids and gametangia on its ventral surface.
- Sperm produced by antheridia are multiflagellate, while archegonia develop near the prothallus notch.
- The new sporophyte initially relies on the gametophyte for nutrition during early development stages.
Alternative Reproductive Methods
- Apogamy refers to the formation of a sporophyte directly from a gametophyte, which can occur in either haploid or triploid forms.
- Apospory involves the formation of a 2n gametophyte directly from the sporophyte, showcasing an alternative reproductive strategy.
Vegetative Reproduction
- Some ferns reproduce vegetatively through rhizomes that divide, allowing the emergence of separate plants.
- Certain species generate bulbils, small plantlets that detach and grow independently.
Dimorphism in Ferns
- In dimorphic ferns, there is a notable visual difference between fertile and sterile fronds, which can impact reproductive strategies.
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Description
Test your knowledge on megaphylls and their significance in ferns with these flashcards. Each card provides a definition or important fact about megaphylls and their role in plant biology. Perfect for students of botany and plant sciences.
