Evolution of Sporophytes and the Interpolation Hypothesis

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Questions and Answers

What does the interpolation hypothesis suggest about the origin of sporophytes?

A simple sporophyte existed when a zygote germinated mitotically. (correct)

Sporophytes emerged from zygotes that germinated meiotically.

Sporophytes originated from gametophytes through meiotic processes.

Sporophytes developed from complex forms of vascular plants.

How did the structure of sporophytes evolve according to the interpolation hypothesis?

Both sporophytes and gametophytes became progressively complex.

Sporophytes became progressively more elaborate while gametophytes simplified. (correct)

Sporophytes became simpler while gametophytes became complex.

Sporophytes remained constant in structure throughout evolution.

What was one of the initial forms of the sporophyte according to the interpolation hypothesis?

A simple sporophyte that included a sporangium and a foot. (correct)

A multicellular organism with roots and leaves.

A robust gametophyte with elaborate reproductive structures.

A complex vascular structure similar to flowering plants.

In the context of the interpolation hypothesis, what is the role of the zygote?

It undergoes mitotic germination to initiate sporophyte development. Signup and view all the answers

Which characteristic is highlighted in the evolution of sporophytes as described in the interpolation hypothesis?

Sporophytes gradually gained complexity through evolutionary stages. Signup and view all the answers

What type of protostele is characterized by the protoxylem being located on the edges of the xylem mass?

Exarch protostele Signup and view all the answers

Which early vascular plant is known to have lateral sporangia that opened transversely?

Zosterophyllum Signup and view all the answers

Which of the following statements about Horneophyton is correct?

It possessed naked access that branched dichotomously. Signup and view all the answers

What morphological feature is NOT typical of Zosterophyllum plants?

Branching from a central trunk Signup and view all the answers

What is suggested about the evolutionary relationship between hornworts and vascular plants?

Vascular plants arose from hornwort-like ancestors. Signup and view all the answers

Which feature distinguishes early vascular plant xylem structures?

Solid mass of xylem with no pith called a protostele Signup and view all the answers

How did sporangia in Zosterophyllum open?

They opened by a suture that passed over the top. Signup and view all the answers

Which of the following characteristics is true about the xylem organization in endarch protostele?

Metaxylem is located in the center. Signup and view all the answers

What does the transformation theory propose about the evolution of vascular plants?

Both gametophyte and sporophyte became larger and more complex. Signup and view all the answers

How did early land plants' gametophytes evolve, according to the transformation theory?

They developed into upright structures with vascular tissues. Signup and view all the answers

What is described as an important step in the evolution of embryophytes?

The conversion of a monobiontic ancestor into dibiontic plants. Signup and view all the answers

Which feature characterized the early gametophytes of vascular plants?

They were upright structures with vascular tissues. Signup and view all the answers

Which line of evolution is mentioned in the context of vascular plants?

Microphyll Line of Evolution Signup and view all the answers

What significant change occurred to sporophytes over time in early land plants?

They became larger and more complex. Signup and view all the answers

What is the relationship between gametophyte and sporophyte in the context of dibiontic plants?

They represent alternating generations in a life cycle. Signup and view all the answers

What concept is crucial in understanding the evolution of vascular plants?

The transition from a monobiontic to dibiontic life cycle. Signup and view all the answers

What is the term used for the small circular areas found on the underside of fern fronds?

Sori Signup and view all the answers

What role does water play in the fertilization process of ferns?

It stimulates release of sperm from antheridium. Signup and view all the answers

What is the function of the indusium in some ferns?

To cover the sorus Signup and view all the answers

What structure releases sperm cells during the fertilization process in ferns?

Antheridium Signup and view all the answers

What type of cell is formed when the sperm and egg nuclei fuse during fertilization?

Zygote Signup and view all the answers

How do sperm attractants function during fertilization in ferns?

They stimulate sperm to swim toward the archegonium. Signup and view all the answers

What is the first structure that forms from germinating spores on a moist surface?

Rhizoid Signup and view all the answers

What is indicated by the term 'bisexual hermaphroditic individuals' in relation to gametophytes?

They are capable of producing both sperm and eggs. Signup and view all the answers

What unique feature of lycophyte sporophytes allows them to grow to tremendous size?

Secondary growth Signup and view all the answers

Which of the following characteristics distinguishes extinct lycophytes like Lepidodendron from modern seed plants?

Formation of wood resembling pines Signup and view all the answers

What type of sporangia arrangement is commonly found in many lycophytes?

Clusters called cones or strobili Signup and view all the answers

Which evolutionary advancement is associated with the division Trimerophytophyta?

Unequal branching of stems Signup and view all the answers

What limitation was observed in vascular cambium cells of ancient lycophytes?

They could not undergo radial longitudinal division Signup and view all the answers

How does the morphology of fossil lycophytes demonstrate convergent evolution?

By sharing characteristics like secondary growth with seed plants Signup and view all the answers

In the context of sporophytes, what is a common characteristic of many lycophytes regarding their reproductive strategy?

Remaining predominantly homosporous with some heterosporous Signup and view all the answers

What determines the failure of cambial cells in ancient lycophytes?

Cells stretching too much to function effectively Signup and view all the answers

What is the primary role of rhizoids in the gametophyte?

To anchor the gametophyte to the soil Signup and view all the answers

Where are male gametangia called antheridia formed?

At the posterior end of the gametophyte Signup and view all the answers

What does an archegonium consist of?

A neck and a swollen venter Signup and view all the answers

What role does the hormone antheridiogen play in gametophyte development?

Stimulates adjacent plants to form male gametangia Signup and view all the answers

What is the function of the foot in the embryo of the sporophyte?

To absorb water from the soil Signup and view all the answers

What event occurs when the venter tissue ruptures during embryonic development?

A root begins to grow into the soil Signup and view all the answers

What determines whether self-fertilization or cross fertilization will occur?

The timing of the appearance of gametangia Signup and view all the answers

How does a bisexual gametophyte enhance the chances of cross fertilization?

By surrounding itself with multiple male gametophytes Signup and view all the answers

Study Notes

Seedless Vascular Plants

Seedless vascular plants lack seeds, flowers, and fruits
Include ferns, horsetails, and club mosses
They are a significant evolutionary step after non-vascular plants.

Topic Outline

Vascular plants without seeds
Early vascular plants
Microphyll line of evolution
Megaphyll line of evolution
Ferns

Interpolation Hypothesis

Suggests a small sporophyte arose when a zygote germinated mitotically, not meiotically
Early sporophytes were simple, with sporangia and a foot, resembling liverworts
Sporophyte became more complex, while gametophytes became simpler over time.

Transformation Theory

Proposes gametophytes and sporophytes grew larger and more complex, becoming more vascularized after the bi-bionic life cycle began
Early land plants had upright, dichotomously branched gametophytes resembling sporophytes
Sporophytes increased in size and complexity while gametophytes simplified over time

Early Vascular Plants

Rhyniophytes were early vascular plants
Cooksonia is a genus of extinct plants
Dichotomous branching (equal sized branches)
Large multicellular sporogenous tissue at the ends of branches

Xylem Structure

Early vascular plants had two xylem types.
Protostele: a solid center xylem mass without a pith
Endarch Protostele: metaxylem differentiates on the xylem's outer edge, with protoxylem in the center
Exarch Protostele: metaxylem is in the center, protoxylem on the edges as groups next to the phloem

Zosterophyllophytes

Similar to Rhyniophytes
Sporangia are lateral
Sporangia open transversely along the top edge
Exarch protostele xylem
Some had smooth surfaces, others had enations (small to long, thin scales)

Microphyll Line of Evolution

Lycophytes: A distinct evolution line of early land plants
Resemblance to zosterophyllophytes (lateral sporangia, exarch protosteles)
Early lycophytes were Drepanophycus and Baragwanathia
Drepanophycus and Baragwanathia had leaf-like structures that were large

Megaphyll Line of Evolution

Trimerophytes: A distinct advancement from rhyniophytes
Unequal branching (overtopping)
Trimerophyton, Psilophyton, and Pertica as extinct plant genera
Pertica: Displays pseudomonopodial branching
Ancestors to seed plant stems

Ferns

Diverse group with over 12,000 species
Leptosporangiate ferns are a common type
Often have rhizomes, leaves (fronds) and roots
Sporangia clustered in sori
Sori are often protected by an indusium

Sporangia

Sporangia (spore containers) cluster in sori on the fern's underside
Two types: eusporangia (contain multiple cell types) and leptosporangia (have a single protective layer)
Annulus: a ring of cells that dries out and contracts to expel spores

Spore Release

Dehydration of the annulus causes the sporangium to split open
Spores are then scattered by air currents
Gametophytes grow from spores

Gametophyte

A multicellular haploid structure
Develops from a spore
Some gametophytes are bisexual, bearing both male (antheridia) and female (archegonia) gametangia
Fertilization occurs when sperm swim to the egg.

Embryo and Young Sporophyte

Fertilized egg develops into an embryo
Embryo is attached to the gametophyte and absorbs nutrients
Young sporophyte grows and matures into a mature sporophyte.

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Description

This quiz explores the interpolation hypothesis regarding the origin and evolution of sporophytes. It covers key characteristics, structural developments, and the evolutionary relationships of early vascular plants and their morphology. Test your knowledge on early plant evolution concepts and related structures.