Bryophyte Evolution and Anatomy Quiz
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Questions and Answers

What is the primary descent hypothesis regarding bryophytes according to Campbell?

Bryophytes have descended directly from Chara, based on the similarity of their sex organs.

What do Frye and Clark suggest about the relationship between Chara and ancient hepatics?

They suggest that Chara and primitive hepatics arose on parallel lines from ancient algae.

How did the Pteridophytean hypothesis explain the evolution of bryophytes?

It posits that bryophytes descended from pteridophytes through a process of reduction.

Identify two features that support the Pteridophytean hypothesis.

<p>Close similarity in sex organs between bryophytes and pteridophytes, and resemblance of sporogonium structures.</p> Signup and view all the answers

What distinct characteristic of bryophytes is highlighted in their life history?

<p>Bryophytes display a distinct and well-defined heteromorphic alternation of generations.</p> Signup and view all the answers

What anatomical similarity exists between Chara and bryophytes?

<p>Both groups have sex organs that contain a sterile enveloping jacket.</p> Signup and view all the answers

Discuss the role of sexual reproduction in the relationship between bryophytes and pteridophytes.

<p>Both bryophytes and pteridophytes share similar methods of reproduction, particularly regarding their sex organs.</p> Signup and view all the answers

How do the pigments of bryophytes relate to their affinity with pteridophytes?

<p>Both groups exhibit similarity in their pigments, which supports their evolutionary connection.</p> Signup and view all the answers

What distinguishes the structure of Plectostele from other types of stele?

<p>Plectostele is characterized by masses of xylem in the form of plate-like lobes, with a cylinder of phloem surrounding the xylem masses.</p> Signup and view all the answers

Describe the central structure found in Siphonostele.

<p>Siphonostele contains parenchymatous pith at the central region of xylem.</p> Signup and view all the answers

How does Ectophloic siphonostele differ from Amphiphloic siphonostele?

<p>Ectophloic siphonostele has phloem surrounding the peripheral side of xylem, while Amphiphloic siphonostele has phloem on both the peripheral and inner sides of xylem.</p> Signup and view all the answers

What is a characteristic feature of Solenostele?

<p>Solenostele has non-overlapping leaf gaps and consists of two vascular strands, including a horse-shoe-shaped principal vascular strand.</p> Signup and view all the answers

What defines the Dictyostele type of stele?

<p>Dictyostele is a type of amphiphloic siphonostele with overlapping leaf gaps that occur in parallel and are closely spaced.</p> Signup and view all the answers

What type of plant structure can you find in Eustele?

<p>Eustele consists of ectophloic siphonostele characterized by overlapping leaf gaps that are parallel to each other.</p> Signup and view all the answers

Explain the arrangement of phloem in Amphiphloic siphonostele.

<p>In Amphiphloic siphonostele, phloem is arranged both on the outer peripheral side and the inner side of the xylem.</p> Signup and view all the answers

Identify an example of a plant exhibiting Siphonostele.

<p>An example of a plant with Siphonostele is ferns like Osmunda and Schizaea.</p> Signup and view all the answers

What is the main argument presented by Kashyap in 1919 regarding the origin of hepatics?

<p>Kashyap proposed that hepatics may have originated from pteridophytes, citing similarities in thallus structure, sexual organs, and methods of spore formation.</p> Signup and view all the answers

According to Christensen's view in 1954, from where did bryophytes potentially derive?

<p>Christensen suggested bryophytes may have derived from either leaf-bearing pteridophytes, leafless pteridophytes like Rhyniaceae, or through polyphyletic origins from various pteridophytes.</p> Signup and view all the answers

Define 'stele' in the context of plant structure and mention its significance.

<p>A stele is the central vascular core of a plant axis composed of xylem, phloem, and other tissues, serving as a vital unit for nutrient transport and support.</p> Signup and view all the answers

What distinguishes a protostele from a siphonostele?

<p>A protostele features a solid core of xylem surrounded by phloem with no pith, while a siphonostele typically has a hollow central region and additional tissues.</p> Signup and view all the answers

What is a haplostele, and provide an example of a plant that exhibits this structure.

<p>A haplostele is characterized by a solid core of xylem surrounded by a cylinder of phloem, as seen in plants like Selaginella and Lygodium.</p> Signup and view all the answers

Describe the structure of an actinostele and how it differs from a haplostele.

<p>An actinostele consists of a star-like mass of xylem with radiating ribs, surrounded by phloem, differing from a haplostele which has a smooth core of xylem.</p> Signup and view all the answers

Explain the concept of exarch protoxylem found in protosteles.

<p>Exarch protoxylem in protosteles means that the protoxylem develops at the outermost part of the xylem core, facilitating support as the plant matures.</p> Signup and view all the answers

What role does the endodermis play in relation to the stele?

<p>The endodermis encases the stele on the peripheral side, helping to regulate the movement of water and nutrients into the vascular system.</p> Signup and view all the answers

What are the two types of sporangia found in heterosporous plants, and what do they produce?

<p>The two types of sporangia are microsporangia, which produce microspores, and megasporangia, which produce megaspores.</p> Signup and view all the answers

How does the origin of the endodermis differ between Selaginella and other plants?

<p>In Selaginella, the endodermis is of stelar origin, while in other plants, Jeffrey suggests it penetrates through leaf and branch gaps.</p> Signup and view all the answers

Describe the structural features of sporangia in ferns.

<p>In ferns, sporangia are typically aggregated into sori, which appear as dots on the underside of fronds.</p> Signup and view all the answers

What is the role of a sporangiophore in relation to sporangia?

<p>A sporangiophore is a stalk that elevates the spore-containing sac, allowing for better spore dispersal.</p> Signup and view all the answers

Where are microsporangia located in angiosperms?

<p>In angiosperms, microsporangia are located within the anther of the stamen.</p> Signup and view all the answers

What structural changes occur in the vascular strand during the transition from haplostele to actinostele?

<p>The smooth core of the vascular cylinder folds at different places, leading to a stellate formation.</p> Signup and view all the answers

How does plectostele differ from haplostele in terms of xylem arrangement?

<p>Plectostele involves complete folding and separation of xylem masses, surrounded by living cells.</p> Signup and view all the answers

What is the main idea behind the Expansion Theory regarding the origin of pith?

<p>The Expansion Theory posits that pith has originated from stelar tissues that have not fully differentiated into non-living xylem.</p> Signup and view all the answers

What does the Invasion Theory suggest about the origin of pith?

<p>The Invasion Theory suggests that pith is extrastelar in origin, formed from cortical parenchyma cells invading the xylem core.</p> Signup and view all the answers

Explain the relationship between non-living conducting cells and living cells in vascular plants.

<p>Non-living conducting cells like tracheids are closely associated with living cells, suggesting an unexplained relationship.</p> Signup and view all the answers

Describe the evolution of stele forms leading to siphonostele.

<p>The evolution begins with stele without pith, progresses to mixed pith, and culminates in a stele with pith as seen in siphonostele.</p> Signup and view all the answers

What evidence supports the Invasion Theory proposed by Jeffrey?

<p>Jeffrey cited the presence of an inner endodermis between pith and the vascular cylinder as evidence for cortical invasion.</p> Signup and view all the answers

How does the structure of protostele differ from siphonostele?

<p>Protostele consists of a solid central core of xylem primarily made of tracheids, while siphonostele has a parenchyma center surrounded by tracheids.</p> Signup and view all the answers

What defines an atactostele, and where is it commonly found?

<p>An atactostele is defined as a type of eustele where collateral vascular bundles are irregularly arranged. It is commonly found in monocotyledonous stems.</p> Signup and view all the answers

Describe what polystele is and provide an example of where it can be observed.

<p>Polystele is characterized by having more than one protostele, as seen in species like Selaginella willdenowii. Each protostele has xylem surrounded by phloem.</p> Signup and view all the answers

What is a polycyclic stele and how does it differ from other types of steles?

<p>A polycyclic stele comprises two or more coaxial cylinders of vascular strands interconnected at the base. It differs from other steles by having multiple layers of vascular tissue separated by parenchyma.</p> Signup and view all the answers

What defines a protostele and what significance does it hold in plant evolution?

<p>A protostele is defined as a cylindrical stele where phloem surrounds a solid core of xylem. It is significant because it represents the most primitive form of vascular system in plants.</p> Signup and view all the answers

Explain the evolutionary progression from haplostele to plectostele.

<p>The evolutionary progression involves a transition from haplostele, the most primitive form, to actinostele and ultimately to plectostele, which is the most advanced type. Each stage reflects increasing complexity in vascular structure.</p> Signup and view all the answers

How does the structure of tracheids in Rhynia relate to the concept of protostele?

<p>In Rhynia, the tracheids form the central core of the protostele, surrounded by phloem tissue. This simple vascular organization exemplifies the primitive vascular structure of early land plants.</p> Signup and view all the answers

Identify and describe the significance of one advanced type of protostele.

<p>Plectostele is an advanced type of protostele characterized by a complex arrangement of vascular tissues, allowing for efficient transport and support. Its significance lies in representing a key evolutionary adaptation in vascular plants.</p> Signup and view all the answers

In what way does the vascular system evolve with the complexity of vascular plants?

<p>As vascular plants evolve, their vascular systems become more elaborate, transitioning from simple forms like protostele to more complex structures such as siphonosteles and polycyclic steles. This evolution enhances their ability to transport water and nutrients.</p> Signup and view all the answers

Flashcards

Pteridophytean Hypothesis

The theory that bryophytes evolved from pteridophytes by simplifying features.

Campbell's View

Bryophytes are thought to have evolved directly from Chara, a type of green algae, due to similarities in their sexual organs.

Frye & Clark's View

Ancestral bryophytes and Chara are believed to have evolved independently from ancient algae, but with very different paths.

Spore Formation

The process of spore formation in both bryophytes and pteridophytes.

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Pigment Similarity

The similarity of pigments found in bryophytes and pteridophytes.

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Alternation of Generations

The alternating stages of a plant's life cycle, including a dominant gametophyte and a sporophyte stage.

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Reproduction Methods

The methods by which bryophytes can reproduce, including both sexual and asexual forms.

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Spore Mother Cells

The process of how spores are produced from cells called spore mother cells in both bryophytes and pteridophytes.

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Plectostele

A type of stele where xylem forms plate-like lobes that are of various sizes and can be joined at one end. Phloem encircles the xylem and also exists between the xylem plates.

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Siphonostele

A type of stele where xylem forms a hollow cylinder with parenchyma tissue in the center. Phloem surrounds the xylem and is enclosed by pericycle. The entire stele is surrounded by endodermis.

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Ectophloic siphonostele

A type of siphonostele where phloem is found only outside the xylem cylinder.

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Amphiphloic siphonostele

A type of siphonostele with phloem both inside and outside the xylem cylinder. The outside phloem is called outer phloem, and the inside is called inner phloem.

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Solenostele

A type of amphiphloic siphonostele with non-overlapping leaf gaps, meaning the gaps are spaced apart.

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Dictyostele

A type of amphiphloic siphonostele with overlapping leaf gaps, meaning the gaps are close together and overlap each other.

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Eustele

A type of ectophloic siphonostele with overlapping leaf gaps similar to dictyostele. The gaps are close together and overlap in a parallel pattern.

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Protostele

A type of stele where xylem forms a solid core surrounded by phloem, pericycle, and endodermis. It lacks a central pith.

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Haplostele

A type of protostele where the xylem core is circular or oval in cross-section with phloem surrounding it.

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Actinostele

A type of protostele where the xylem core has a star-like appearance in cross-section, with phloem filling spaces between the xylem 'arms'.

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Radial stele

A type of protostele where the xylem core has a radial arrangement with no central pith. It's found in dicotyledonous roots.

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Endodermis

The outermost layer of the stele, surrounding the vascular tissues. It plays a role in regulating water and nutrient movement.

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Protoxylem

The point where the protoxylem first differentiates.

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Atactostele

A type of stem structure where vascular bundles are arranged irregularly, common in monocots, with no clear distinction between pith and cortex.

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Polystele

A stele with more than one protostele, as seen in the cross-section of a stem. An example is in the plant Selaginella willdenowii.

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Polycyclic stele

A stele with two or more concentric cylinders of vascular tissue, interconnected at the base. The innermost cylinder is often an amphiphloic siphonostele.

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Protostele Evolution

The evolutionary progression from the simplest form of protostele (haplostele) to more complex forms (actinostele and then plectostele).

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What is heterospory?

Two different types of spores produced by plants, microspores and megaspores, are analogous to male and female gametes respectively.

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What is homospory?

Production of a single type of spore that gives rise to bisexual gametophytes.

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What is a sporangiophore?

A stalk that supports a sporangium, elevating the spore chamber.

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What are sori?

Clusters of sporangia, often found on the underside of fern fronds.

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What is the anther?

The male reproductive structure in flowering plants, which contains microsporangia where microspores develop into pollen grains.

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Expansion Theory

The theory that the pith, or central parenchyma tissue, originates from the vascular tissues in the stele. Living cells differentiate and remain within the central core.

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Invasion Theory

The theory that the pith is of cortical origin, meaning it originated from the outer layers of the stem and invaded the center of the stele.

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Leaf gap

A kind of siphonostele with leaf gaps where leaves attach to the stem. These gaps interrupt the vascular cylinder.

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Association of non-living and living cells

The close association between non-living conducting cells like tracheids and living cells in vascular tissues. The reasons behind this association are still being investigated.

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Study Notes

Unit 7: Origin of Land Plants

  • Land plants originated from terrestrial algae and bryophytes, exhibiting alternation of generations.
  • Early vascular plants show stelar evolution, sporangium evolution, seed development, and seed evolution.
  • Angiosperms are studied through phylogeny of major groups.

Origin of Land Plants

  • Bryophytes are small, non-vascular land plants with jacketed sex organs.
  • Bryophyte life cycles alternate between haploid and diploid generations, with a dominant branched gametophyte stage.
  • Bryophytes lack fossil records and intermediate forms, resulting in ongoing debate about their origin.
  • Origin hypotheses are based on comparative morphology, ontogeny, and analogies with other plant groups.
  • Bryophytes exhibit affinities with algae, including amphibian nature, lack of vascular tissues, autotrophic nutrition, prominent gametophytic life cycle, flagellated spermatozoid, and water dependence for fertilization.

Algal Hypothesis

  • Supported by several researchers (Church, Campbell, Frye & Clark, Fritsch).
  • Suggests bryophytes evolved from algae, particularly semi-terrestrial algal ancestors.
  • Transition to land was facilitated by scarcity of water, prompting adaptation of the sporophyte to land habitats.
  • Cytological alternation of generations in algae and bryophytes supports this view.

Pteridophytean Hypothesis

  • Supported by various researchers (Kashyap, Christensen, Andrews, Proskauer).
  • Suggests bryophytes descended from pteridophytes through reduction.
  • Argues for close similarities in sex organs and sporangia between the two groups.
  • Emphasizes resemblance between sporogonites and Horneophyton.

Stelar Evolution

  • Stele is the vascular cylinder of a plant, primarily composed of xylem, phloem, interfascicular tissues, medullary rays, and pith (if present).
  • Stelar tissue is primarily seen in pteridophytes, and less frequently in angiosperms and gymnosperms.
  • Endodermis encircles the stele.
  • Different stele types exist:
    • Protostele: solid core of xylem surrounded by phloem. (Haplostele, Actinostele, Plectostele). Further subdivided into different types (Haplostele, Actinostele, Plectostele) based on the organization of xylem and phloem surrounding the xylem core.
    • Siphonostele: hollow xylem cylinder with pith and concentric layers of xylem and phloem. (Ectophloic siphonostele, Amphiphloic siphonostele, Solenostele, Dictyostele, Eustele, Atactostele, Polycyclic stele). Further subdivided into various sub-types (Ectophloic siphonostele, Amphiphloic siphonostele, Solenostele, Dictyostele, Eustele, Atactostele, Polycyclic stele). Each type has a unique organization of vascular tissues.

Sporangium Evolution

  • Heterospory exhibits diverse sporangium function in plants.
  • Plants with heterospory have both microsporangia (producing microspores) and megasporangia (producing megaspores).
  • Spores are analogous to male and female gametes in heterosporous plants.
  • Homosporous plants (equisetophytes and most bryophytes) produce a single spore type.
  • Sporangia location varies across species, positioned at stem/leaf apices or along sides. Some may have sporangiophores (stalks) and columella (supporting structure).
  • Sporangia in ferns are aggregated into sori (dots).
  • In flowering plants, sporangia are in the stamen's anther. This houses microspores that develop into pollen grains.
  • Sporangia are crucial for spore production and dispersal (important for reproduction and reproduction mechanisms). They are enclosures, protecting developing spores, aiding in their adaptation to environmental conditions.
  • Sporangia presence and structure are diverse, reflecting evolutionary adaptations of spore dispersal and dispersal mechanisms.

Theories of Stelar Evolution

  • Expansion theory: pith originates from stelar tissues. Living cells in the center of the stem do not transform into xylem but remain as pith tissue.

  • Invasion theory: pith arises from the cortex invading the stele through leaf gaps.

  • Many different and diverse types of steles exist. Each demonstrating different evolutionary paths across various plant lineages.

General Notes on the Topic

  • The notes cover the origin of land plants, evolution of steles, and sporangia. These are important topics in plant biology.
  • Detailed subcategories (protostele types, siphonostele types) are provided, increasing the comprehension of the material.
  • Numerous supporting facts and figures related to different hypotheses, stele types, and sporangium components are incorporated.

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Description

Test your understanding of bryophyte evolution and anatomy based on Campbell's concepts. This quiz covers hypotheses about bryophytes, their relationship with pteridophytes, and various types of stele. Dive into the distinctive features and life history of these fascinating plants.

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