The spores are differentiated into microspores and megaspores borne on the microsporangium and megasporangium. Reference botany for degree students pteridophyta by. Ncert solutions for class 11 biology chapter 3 plant kingdom. The heterosporous pteridophytes represent the highest stage of development in the second or intermediate series of plants.
This means that their leaves originated from the emergences of the stem surface, and therefore are more similar to moss leaves than any other leaves of pteridophytes and seed plants. Heterospory and origin and evolution of seed habitat in land plants pteridophytes. Describe briefly the four major groups of protozoa. In the plant evolution, there was a high need for heterospory because it independently arose in several groups of pteridophytes and even among mosses. Heterospory is a condition of the production of more than one type usually two of spores in a single plant. S15, 2nd floor uphar cinema market, above red chilli restaurant, green park extension, new delhi, 110016. Ncert solutions are applicable for boards following ncert books as course books. The heterosporous fern platyzoma microphyllum has exosporic photosynthetic gametophytes. Heterospory is a crucial first step because it creates a division of labor, enhancing the sedentary nature of one type of gametophyte mega and the. This pdf version does not have an isbn or issn and is not therefore effectively published melbourne code, art. Oct 10, 2019 heterospory and origin and evolution of seed habitat in land plants pteridophytes. Lycopodiopsida, or lycophytes have at least four genera and more than 1,200 species. Some heterosporous pteridophytes do occur in terrestrial habitats, but these plants rely.
Pteridophyta characteristics, life cycle, classification. Most of the pteridophytes are homosporous, produce isospores which are morphologically and physiologically identical. According to rashid1976, only 9 genera of pteridophytes show heterospory,i. Heterospory and seed habitat in pteridophytes easy. Lycophytes belong to microphyllous lineage of pteridohytes. Jan 11, 2018 summary homosporous vs heterosporous pteridophytes pteridophytes or ferns belong to the class of vascular plants. The condition of production of two different types of spores in the same species is known as the heterospory. From certain phenomena that i observed in making a morphological investigation of marsilia quadrijolia, it seemed possible that an experi. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. In this article we will discuss about heterospory and seed habit in pteridophytes. Depending on the life cycle of the pteridophytes, it can undergo alternation of generation based on homospory or heterospory. Pteridophytes biology encyclopedia plant, body, different. Evolutionary significance of heterospory and seed development in. An introduction to pteridophyta top results of your surfing an introduction to pteridophyta start download portable document format pdf and ebooks electronic books free online rating news 20162017 is books that can provide inspiration, insight, knowledge to the reader.
Most pteridophytes are terrestrial plants and thrive well in abundant moisture and shade while some flourish well in open, dry situations especially in xeric conditions. Heterospory and seed habitat in pteridophytes easy biology class. The heterospory also facilitated the sex differentiation in pteridophytes. The origin of heterospory in marsilia the university of. Difference between homosporous and heterosporous pteridophytes. A pteridophyte is a vascular plant with xylem and phloem that disperses spores. In most of the heterosporous plants, the gametophyte is restricted to very few cells. Heterospory and seed habitat in pteridophytes easy biology.
Leaves that produce spores are called sporophyll and leaves that do not produce spores are called tropophyll. However, there are some pteridophytes which produce two different types of spores differing in size. Most of the pteridophytes are homosporous, produce isospores. Pteridophytes introduction, authors and addresses, systematic list, glossary, and key to tribes.
They describe the apportionment of spore dimorphs among different sporangia heterosporangy, the retention. A model for the origin of heterospory is proposed, in which an initially homosporous population is subject to natural selection for increased spore size. The microspores develop into male gametophyte whereas the megaspores give rise to female gametophyte. Download offline apps based on latest ncert books 202021 for new session. Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral condition, homospory. The sori are found on the ventral surface of fern fronds. Ruggles gates and the second, in reply to it by dr d. In both types, the gametophyte obtains the nutrition from the sporophyte. Pteridophytes may represent the closest living relatives sister group to the seed plants. Most pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions. Heterospory and seed habit in pteridophytes ferns plant science. Such peridophytes are known as homosporous and this phenomenon is known as homospory. Each microsporangium contains a large number of microspores whereas.
Heterospory and gametophytic unisexuality are not necessarily evolu. However, there are some pteridophytes which produce two different types of. Ebook an introduction to pteridophyta as pdf download. Heterospory and gametophytic unisexuality are not necessarily evolu tionary antecedents of endospory. The function of tropophyll is to only photosynthesize. Ncert solutions 202021 are updated according to new cbse syllabus 202021 to all boards who are using ncert books. The heterospory also reduced the size of gametophytic generation. Heterospory appears to have conferred a selective advantage under terrestrial conditions. Pdf summary the origin of the seedplant life history, and subsequent diversification of seed morphology. As more nutrition becomes available to less number of spores, the surviving spore grow better, hence increase in their size.
And among the first of the plants to truly live on land were the pteridophytes. Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. Most of the pteridophytes produce one kind of similar spore. Some of the characters of pteridophytes are as follows. Ncert solutions for class 11 biology chapter 3 plant kingdom to study online or free pdf to download updated for new academic session 202021 based on latest ncert books for cbse board.
Because the minimum costs of mate reproduction are less than the minimum costs of female reproduction, larger food reserves evolve principally for the use of female reproduc tion. That is they produce spores of equal size that germinate into gametophytes that produce both male and female gametes. The role of heterochrony article pdf available in taxon 381. Examples include ferns, h slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit. Pteridophytes have little leaves microphyll and large leaves macrophyll. Importance of heterospory and seed habit of ferns 581 words. When such attempts lime been made the definitions show striking contrasts in content andor emphasis table i. It is characterized by morphologically dissimilar spores produced from two types of sporangia. A seed consists of an embryo, stored food and a seed coat.
The key difference between homosporous and heterosporous pteridophytes is that homosporous pteridophytes produce one type of spores that. For many years it has been generally assumed by botanists that in angiosperms, as in the heterosporous pteridophytes, the megaspores are larger than the microspores. The next big step in evolution was heterospory or formation of two different types of spores, the smaller ones. The smaller one is known as microspore and the larger one is known as megaspore. The terms pteridophytes, ferns and fern allies and vascular cryptogams continue to be used informally by botanists who wish to avoid becoming enmeshed in the. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. Heterospory evolved during the devonian period from isospory independently in several plant groups. Spores that are produced by pteridophyta are located in spore box which is known as sporangium. Their results indicate that polar auxin transport is not involved in shoot development the haploid.
The sexuality of pteridophytic gametophytes can be classified as follows. Ncert solutions for class 11 biology chapter 3 in pdf form to free download in english medium updated for new academic session 202021. In homosporous pteridophytes, the sex differentiation takes place only during the development of antheridia or archegonia. Size marsileaceae and salviniaceae, is called heterospory. A heterosporous life history occurs in some pteridophytes and in all seed plants. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as cryptogams, meaning that their means of reproduction is hidden. In ferns the spores are produced in sporangia that are found in clusters called sori. The sporangia show greater specialization than those of ferns.
Oct 26, 2019 division of labor allows resources to be used more efficiently and also restricts selffertilization. Heterospory evolved first in pteridophytes such as selaginella and salvinia. The seed habit is the most complex and evolutionary successful method of sexual reproduction. The microsporangia contain microspores whereas megasporangia contain megaspores in them. Stelar evolution of pteridophytes sporangial organization. Pteridophytes are vascular plants and have leaves known as fronds, roots and sometimes true stems, and tree ferns have full trunks. Those from the small spores are filamentous, with few rhizoids and produce. Heterospory the most iterative key innovation in the evolutionary history of the plant kingdom pdf. Pteridophyte reproduction christian brothers university. Embryophytes bryophytes rhynia fossil lycopodiophyta pteridophytes transition to land megaphylls equisetales. A few pteridophytes are aquatic while still others are epiphytes. Stelar evolution of pteridophytes, sporangial organization homospory and heterospory.
Some pteridophytes are aquatic and some are epiphytes. A first checklist of the pteridophytes of togo west africa. Lycopsids all species of selaginella are heterosporous. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and freeliving. As in seed plants, the greatest diversity of pteridophytes is found in the tropics, with only about six hundred species adapted for life in temperate climates. Under conditions of low light intensity, the photosynthetic activity of selaginella was retarted and it produced microsporangia. A model for the origin of heterospory sciencedirect. Summary homosporous vs heterosporous pteridophytes pteridophytes or ferns belong to the class of vascular plants. Aug 06, 2019 under conditions of low light intensity, the photosynthetic activity of selaginella was retarted and it produced microsporangia.
Pteridophytes ferns and lycophytes are freesporing vascular plants that have a life cycle with alternating, freeliving gametophyte and sporophyte phases that are independent at maturity. However, there are some pteridophytes which produce two different types of spores differing in size, structure and function. Ncert solutions for class 11 biology chapter 3 plant. They are differentiated into micro and megasporangia.
The term heterosporous is applied to plants in which there are two kinds of nonsexual spores, large and small, called respectively megaspores and microspores. Once seeds existed, their early pattern of diversification was not one of gradual change in form. The printed version, however, was effectively published on 6 june 20. These two types of spore differ in their formation. The body of the sporophyte is well differentiated into roots, stem and leaves. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the. Thomson department of botany, university of toronto some months ago there were two notes in.
Each microsporangium contains a large number of microspores whereas each megasporangium contains usually only. Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants. Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. Such ferns are referred to as homosporous pteridophytes. Ferns, horsetails often treated as ferns, and lycophytes clubmosses, spikemosses, and quillworts are all pteridophytes. Such pteridophytes are known as heterosporous and the phenomenon is known as heterospory. Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular plants.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. The smaller of these, the microspore, is male and the larger megaspore is female. What are the similarities between homosporous and heterosporous pteridophytes. Pteridophytes should be kept distinct from the heterosporous, since the development of heterospory represents one of the advancing waves of. Pteridophytes, also known as vascular cryptogams and ferns and fern allies, comprise about 12 000 species of vascular plants that do not produce. Pteridophyta, ferns and allies, have approximately 12,000 species and six classes figure \\pageindex1\. Life cycles of lycopodium, selaginella, equisetum, adiantum and marsilea.
Examples of heterosporous pteridophytes lifeeasy biology. Heterospory and seed habit in pteridophytes botany. It is speculated that life began in the oceans, and through millions of years of evolution, life slowly adapted on to dry land. The earliest tracheophytes were homosporous, but heterospory arose independently in many later lineages, including progymnosperms, the ancestors of seed plants. The sporophyte is the conspicuous and familiar plant body.
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