Pteridophytes (General) Questions in English

(B) In Pteridophytes,the sporangia are subtended by leaf-like appendages called sporophylls.
In some cases,such as in $Pteris$ (fern),the sporophylls may form distinct,separate structures.
In many other cases,such as in $Selaginella$ and $Equisetum$,the sporophylls may form distinct compact structures called strobili or cones.
Therefore,$P$ represents $Pteris$ and $Q$ represents $Selaginella$ and $Equisetum$.

(D) The prothallus in Pteridophytes is the gametophytic stage.
$1$. It is a small,inconspicuous,multicellular,free-living,and photosynthetic structure,which is haploid $(n)$.
$2$. Because of its specific growth requirements,it is restricted to cool,damp,and shady places.
$3$. Pteridophytes require water for the transfer of male gametes (antherozoids) to the archegonium for fertilization.
$4$. The prothallus develops from a haploid spore $(n)$ produced by the sporophyte via meiosis,not from a diploid spore. Therefore,the statement that it is formed from a diploid spore is incorrect.

(A) Pteridophytes are classified based on the type of spores they produce:
$1$. Homosporous: These plants produce spores of only one kind. Examples include Equisetum and Dryopteris (Ferns).
$2$. Heterosporous: These plants produce two kinds of spores,macro (large) and micro (small) spores. Examples include Selaginella and Salvinia.
Therefore,the correct classification is: Homosporous ($Equisetum$,$Dryopteris$) and Heterosporous ($Selaginella$,$Salvinia$).

(C) Pteridophytes that produce two different kinds of spores,known as microspores and megaspores,are called heterosporous.
$Selaginella$ and $Salvinia$ are well-known examples of heterosporous pteridophytes.
In contrast,$Psilotum$,$Lycopodium$,and $Equisetum$ are homosporous,meaning they produce only one type of spore.

(A) The life cycle of pteridophytes follows these steps:
$1$. $B.$ Meiosis occurs in spore mother cells to produce haploid spores.
$2$. $A.$ These spores germinate to form a multicellular,free-living,photosynthetic thalloid gametophyte called the prothallus.
$3$. $D.$ The prothallus bears sex organs,namely the archegonia (female) and antheridia (male).
$4$. $E.$ Antherozoids are released from antheridia and transferred to the archegonia in the presence of water.
$5$. $C.$ Fertilisation occurs to form a zygote,which develops into a sporophyte.
Therefore,the correct sequence is $B \rightarrow A \rightarrow D \rightarrow E \rightarrow C$.

(B) Heterospory is the production of two different types of spores,namely microspores and megaspores.
Among the given options,$Salvinia$ and $Selaginella$ are heterosporous.
However,$Selaginella$ is a pteridophyte belonging to the class Lycopsida,often called a 'spike moss',and is not considered a true fern.
$Salvinia$ is a member of the class Pteropsida and is a true aquatic fern that exhibits heterospory.
$Salvia$ is an angiosperm (flowering plant).
Therefore,$Salvinia$ is the correct answer.

(B) In homosporous pteridophytes,the spores germinate to produce a small,inconspicuous,photosynthetic,and free-living (independent) gametophyte known as the prothallus.
This prothallus is multicellular and bears the sex organs,namely the antheridia (male) and archegonia (female).
Therefore,the correct answer is an independent multicellular prothallus.

(D) The phenomenon of producing two different types of spores,microspores and megaspores,is known as heterospory.
Among the given options,$Psilotum$,$Equisetum$,and $Dryopteris$ are homosporous,meaning they produce only one type of spore.
$Azolla$ is a genus of aquatic ferns that is heterosporous,producing both microspores and megaspores.
Therefore,the correct option is $D$.

(C) In Pteridophytes,such as ferns,the main plant body is a sporophyte.
When the spores germinate,they produce a small,inconspicuous,multicellular,free-living,mostly photosynthetic thalloid structure called the prothallus.
The prothallus represents the gametophytic generation in ferns.
It bears the sex organs,namely antheridia and archegonia,which produce gametes.

(A) In $Pteridophytes$ like $Selaginella$ and $Salvinia$, the development of the zygote into young embryos takes place within the female gametophyte.
This retention and germination of the megaspore within the parent sporophyte is a significant evolutionary step.
This phenomenon is considered a precursor to the $Seed \text{ } habit$, which is a characteristic feature of higher plants like $Gymnosperms$ and $Angiosperms$.

(A) The classification of Pteridophytes is as follows:
$1$. Psilopsida: Includes primitive forms like $Psilotum$ $(A \rightarrow iv)$.
$2$. Lycopsida: Includes club mosses like $Selaginella$ $(B \rightarrow iii)$.
$3$. Sphenopsida: Includes horsetails like $Equisetum$ $(C \rightarrow ii)$.
$4$. Pteropsida: Includes ferns like $Dryopteris$ $(D \rightarrow i)$.
Therefore,the correct matching is $A \rightarrow iv, B \rightarrow iii, C \rightarrow ii, D \rightarrow i$.

(D) Pteridophytes require water for fertilization,as their male gametes (antherozoids) are flagellated and need a medium to swim to the female gamete (egg) in the archegonium.
Additionally,the gametophyte stage,known as the prothallus,is free-living but delicate and requires cool,damp,and shady places to survive and develop.
Because of these specific environmental requirements for fertilization and the growth of the prothallus,Pteridophytes are restricted to specific,moist habitats,which limits their geographical distribution.
Therefore,both the Assertion and the Reason are true,and the Reason is the correct explanation of the Assertion.

(C) The correct answer is $C$.
$Salvinia$ is a heterosporous pteridophyte,meaning it produces two different types of spores: microspores and megaspores.
$Pinus$ is monoecious,meaning both male and female cones are present on the same plant.
$Equisetum$ is homosporous,meaning it produces only one type of spore.
$Cycas$ is dioecious,meaning male and female reproductive structures are present on separate plants.

(B) The gametophyte of pteridophytes,also known as the prothallus,is a small,free-living,mostly photosynthetic thalloid structure.
Because pteridophytes require water for fertilization (as the male gametes are flagellated and need to swim to the female gametes),their gametophytes are restricted to specific environmental conditions.
They require cool,damp,and shady places to grow and survive,as these conditions prevent desiccation and facilitate the movement of sperm to the egg.

(B) $Azolla$ is a genus of seven species of aquatic ferns in the family $Salviniaceae$.
$(a)$ $Azolla$ is a free-floating aquatic fern. (True)
$(b)$ It has bilobed leaves,where each leaf consists of a dorsal lobe and a ventral lobe. (True)
$(c)$ It has a symbiotic relationship with the cyanobacterium $Anabaena$ $azollae$,which fixes atmospheric nitrogen. (True)
$(d)$ It is not a climber; it is a free-floating plant. (False)
$(e)$ The dorsal lobe contains the cyanobacteria,while the ventral lobe is thin and lacks Aerenchyma. (False)
Therefore,statements $(a)$,$(b)$,and $(c)$ are true.

(C) $Azolla$ is a free-floating aquatic fern that maintains a symbiotic relationship with the nitrogen-fixing cyanobacterium $Anabaena$ $azollae$.
This cyanobacterium resides within the specialized leaf cavities of the $Azolla$ plant.
The provided figure clearly labels the filaments within the leaf cavity as $Anabaena$.
Therefore,the correct option is $C$.

(A) - xylem and phloem.
Pteridophytes are known as vascular cryptogams because they are seedless plants that possess a well-developed vascular system consisting of both xylem and phloem.
The xylem is responsible for the conduction of water and minerals,while the phloem is responsible for the translocation of food materials.
This vascular tissue allows them to grow taller and survive in diverse terrestrial habitats compared to bryophytes.