Pteridophytes and Gymnosperms Questions

Ans: The scientific study of the structure and specific structural features of either animals or plants is called Morphology.

Ans: Biodiversity is the total variability within and among species of all living organisms and their habitats. Plant diversity is the variety of plant species on the basis of their diagnostic characteristics and their habitats. It is estimated that there are between 300,000 and 500,000 species of higher plants (i.e. flowering and cone-bearing plants).of which approximately 250,000 have been identified or described.

Ans: The term Pteridophyte is derived from two words ‘Pteron’ meaning feather and ‘phyton’ meaning plant. Thus, Pteridophytes are planted with Feather-like leaves. Pteridophytes occupy the intermediate position between Bryophytes and Phanerogams (seed plants)., there are approximately 11,000 different species with the most being found in the tropics. An example of a Pteridophyte is the fern. They reproduce by releasing spores into the air.

Ans: Pteridophytes are cryptogams. Because they produce neither seeds, not flowers. They reproduced by spores.

Ans: Pteridophytes cannot become complete land pants. Because they cannot produce flowers and seeds. They grow or live mostly in moist soil or in the aquatic environment.

Ans: Synangia (three fused sporangia) develop in Psilotum. The leaves which bear synangia in Tmesipteris may be murconate rather than lanceolate. Lycopodium and Equisetum bear cones containing similar spores (homosporous). Selaginella, Marsilea, Salvinia, Azolla, Regnellidium, Pilularia, Stylites, lsoetes and Platyzoma are heterosporous (produce two types of spores-microspores and megaspores. The spores are contained in sporangia which are borne on sporophylls or sporangiophores. These become aggregated into cones or strobili.

 Ans: Microphylls: The sporophytes with small and scale-like leaves, for example, those found in Ephedra.
Megaphylls: These are large and well-developed leaves, for example, those found in Cycas and Pinus. These are foliage leaves and are protected by a thin layer of cuticle or waxy layer.

 Ans: The special type of reproductive leaves which produce sporangium (spore-producing structure) is called sporophylls.
There are two types of sporophylls.
Microsporophyll (Produce Micro-sporangia)
Megasporophyll (Produce mega-sporangia)

Ans: Homosporous Ferns: produce only one type of spore that contains both male and female parts. The resulting gametophyte is monoecious that is both antheridia and archegonia are present on the same plant. E.g.Lycopodium, Equisetum.
Heterosporous Ferns: Produce two types of spores or distinct male and female spores or microspores and megaspores. The resulting gametophyte is dioecious. Microspore germinates to form male gametophyte that bears antheridia. Megaspore germinates to form a female gametophyte that bears archegonia. E.g. Selaginella, Marselia.

Ans: Sporocarp is a Bean shaped structure attached to the petiole through a small stalk called Peduncle in which spores are produced. The young Sporocarp is relatively soft and green but they become hard brown and nut-like at maturity.

Ans: True indusium: A delicate membranous structure arises from the lower side and covers the sorus of sporangia. Seen in Dryopteris.
False indusium: It is formed by the curving of margins of the pinnae or leaflet that protects the marginal sorus. It originates from the upper side of the pinnae. Seen in Pteris, Adiantum etc.

Ans: A form of vernation in which the leaf primordia are rolled in on themselves from the apex to the base so that the apex is in the middle of the coil. It is seen in most ferns (except the Ophioglossales) and in certain cycads and extinct seed ferns. The young leaves are coiled inward in the embryonic state. It is called circinate vernation.

Ans: Brightly coloured complex green leaves of Ferns are called Fronds.

Ans:  Synangium is a trilocular or three-chambered, spore-bearing structure in Psilotum.  It is considered a fusion product of three sporangia. Synangia are characteristic of the ancient group Psilotophyta, some ferns and ferns like gymnosperms (seed ferns). A special type of synangia called microsporangia is found in an ancient group of gymnosperms.

Ans: The type of branching in plants those results when the growing point (apical bud) divides into two equal growing points, which in turn divide in a similar manner after a period of growth, and so on. Dichotomous branching is common in ferns and mosses.

Ans: A rhizoid (such as is found on the gametophytes of bryophytes or ferns) is basically just a filament or a root-like structure that anchors the plant to the ground. Rhizoids absorb water and nutrients from the soil through the process of capillary action
A root, on the other hand, is a sophisticated structure containing many different layers including vascular tissue, playing a key role in water and nutrient uptake.

Ans: They are called club mosses because of their small size and moss-like leaves and aggregation of sporophylls into terminal groups.

Ans: Ligule is a membranous outgrowth present at the base of leaves and considered as water secreting structure that protects the young leaves and sporangia from desiccation.It is present in the members of lycopsids, for example, Selaginella and Isoetes. Those plants in which Ligule is present are known as Ligulates.

Ans: The genus name of the maidenhair fern, Adiantum, is derived from the Greek word ‘Adiantos’ – meaning ‘unwetted’ – as the leaves of the fern repel water, while the species name is taken from the Latin words ‘capillus’ and ‘Veneris’, meaning ‘hair of Venus’, giving this plant its alternative common name, the Venus maidenhair fern. The Petiole of the leaves is shining black and brittle. Due to these characteristics, the Adiantum is also known as maiden hair fern.

Ans: Tapetums is the innermost layer of the microsporangium. It provides nourishment to the developing pollen grains. During microsporogenesis, the cells of tapetum produce various enzymes, hormones, amino acids, and other nutritious materials required for the development of pollen grains.

Ans: Rhizophore is a colourless or leafless structure arising from the rhizome and bears adventitious roots at their like in Selaginella.

Ans: Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content. Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide. It can only be used to date fossils younger than about 75,000 years.

Ans: Stele is the central cylinder or core of vascular tissue in higher plants. The stele consists of the xylem, phloem, pericycle and medullary rays and pith if present. The term ‘stele’ was for the first time used by Van Tieghem and Douliot in 1886 in their stellar Theory’.

Ans: i) Protostele ii) Poly cyclic Stele iii) Siphonostele iv) Solenoste v) Dictyostele

Ans: When the sporangia are borne on the leaves then the condition is known as phyllosporous. When sporangia are borne in the axils of the leaves then the condition is known as stachyosporous.

Ans: The largest group of the Geological time chart is called Era. There are Four Eras in the Geological time chart. (i) CENOZOIC (ii) MESOZOIC (iii) PALEOZOIC
(iv) PRECAM BRAIN/PRPTEROZOIC

Ans: The period is the basic unit of geological time in which a single type of rock system is formed. Two or more periods comprise a geological Era. Two or more Eras form an Eon, the largest division of geologic time. Some periods are divided into epochs.

Ans: Scale leaves: Scaly leaves are thin, brown-coloured and scale-like and develop only on long as well as dwarf shoots, these are small undeveloped leaves which are sessile and rarely green. Their function is usually protection.
Foliage leaves: Normal leaves attached to aerial stems and branches are called foliage leaves. Foliage leaves are large, needle-like, and vary in number from 1 to 5 in different species. These are usually green-coloured. The main function of these leaves is to take part in photosynthesis, respiration and transpiration-The word ‘leaf is normally used for foliage leaves.

Ans: Each Megasporophyll of Pinus consists of two types of scales, known as bract scales and ovuliferous scales.
Bract scales are thin, dry, membranous, brown-coloured structures having fringed upper parts. These are also called carpellary scales.
An ovuliferous scale is present on the upper surface of each bract scale. Each ovuliferous scale is woody, bigger and stouter than the bract scale and it is triangular in shape. A broad sterile structure, with a pointed tip, is present at the apex of these scales. This is called the apophysis. At the base of the upper surface of each ovuliferous scale are present two sessile and naked ovules.

Ans: The prothallus is the fern gametophyte. It is a green, photosynthetic structure that is one cell thick, usually, heart or kidney-shaped 3 – 10 mm long and 2 – 8mm broad. It is very difficult to find in the bush as it is so tiny. It doesn’t have roots, stems or leaves, but it does have rhizoids that anchor it to the soil and help with absorption. The underside of the prothallus is where the gametes are produced.

Ans: Manoxylic wood: The wood is porous, soft and contains more parenchyma. This type of wood is found in the members of Cycadophyta usually. It is less important commercially.
Pycnoxylic wood: It is compact and hard with narrow medullary rays. This kind of wood is more important commercially than manoxylic wood. This type of wood is found in the members of the Coniferophyta.

Ans: The psilotales have often been called ‘living fossils’. In some respects, the order Psilotales, with its two genera of primitive vascular plants, Tmesipteris and Psilotum. Primitive characters of Psilotum are dichotomous branches, the Presence of Scale Leaves, and Underground Rhizome.

Ans: The leaves which bear the sporangia are called Sporophylls. In Ferns the sporophylls are foliage leaves, but in other plants the sporophylls are modified and arise in specialized structures such as the strobili (cones) of club mosses, horsetails, and gymnosperms and the flower of angiosperms.Sporophyll bearing microsporangia are called microsporophyll and Sporophylls bearing megasporangia are called megasporophyll

Ans: Annules is a ring like structure of jacket of sporangium of Pteris, consist of radially elongated thick walled cells helping in spore dispersal. Stomium is the weak region in the jacket where the sporangium is broken transversely to liberate the spores.

Ans: Cycas revoluta species of gymnosperm in the family Cycadaceae. The pith of the Cycas revoluta yields Sago and the fruit can be eaten being rich in proteins and soluble non nitrogenous substances. The leaves of the Sago are called palm leaves.
Sago palm is a common name for several plants which are used to produce a starchy food known as sago. It is one of several species used for the production of sago, as well as an ornamental plant.

Ans: Petrifaction or petrification is the process by which the plant material when laying in water has become infiltrated with mineral matter such as lime, silica, magnesium and other similar substances. These salts penetrate the minute cell and the organic matter is being replaced by Mineral salts. The original organic matter is completely or partially changed but its outline and general structure is left in the form of these infiltrated substances.

Ans: Medicines produced by gymnosperms are as follows
1. Ephedrine (alkaloid) extracted from Ephedra used in treating asthma, cough, cold, bronchitis etc.
2. Tincture of Ephedra is a cardiac stimulant.
3. The juice extracted from young leaves of Cycas revoluta is used for curing blood vomiting and flatulence.
4. Anti-cancerous drug called taxol, is obtained from the bark of Taxus.

Ans: (i) Eusporangiate Type: Sporangium develops from group of superficial cells. These cells divide periclinally into primary wall layers and inner primary sporogenous cells.
(ii) Leptosporangiate Type: This type of sporangium arises from a single superficial cell. It divides transversely to form an outer and an inner cell.

Ans: A: Any of the thin brownish often fringed or laciniate scales that are borne upon the leaves or young shoots of many ferns and that consist of a single layer of cells. B: the armor of a fossil cycad stump that suggests in appearance the ramenta of existing ferns. One of the thin, chafflike scales covering the shoots or leaves of certain ferns are called Ramenta.