The sexuality of pteridophytic gametophytes can be classified as follows. Importance of heterospory and seed habit of ferns 581 words abstract the evolution of the seed is one of the major events in the history selaginlela land plants. Such peridophytes are known as homosporous and this phenomenon is known as homospory. It is characterized by morphologically dissimilar spores produced from two types of sporangia. In homosporous pteridophytes, the sex differentiation takes place only during the development of antheridia or archegonia. The sporangia show greater specialization than those of ferns.
Historical the natural presumption has been that the marsiliaceae have. Heterospory and seed habit in pteridophytes botany in order to overcome this problem, the female gametophyte is heteroslory retained in the megasporangium. Olmstead3 summary the origin of the seedplant life history, and subsequent diversification of seed morphology, should be considered two independent, fundamentally distinct evolutionary problems. Most of the pteridophytes produce one kind of similar spore. Seex pteridophytes, selaginella rupestris is the most successful species that completed first four steps towards seed habit. A seed ovule may be defined as an integumented indehiscent megasporangium. Algae alkaloids allelopathy arbuscules aspergillus nidulans bryophytes and pteridophytes celpholeuros chemosynthesis. Since their first appearance in the late devonian, seed plants have come to dominate almost every terrestrial ecosystem. Heterothally and the seed habit versus heterospory, new. David haig and mark westoby, selective forces in the emergence of the seed habit, biological journal of the linnean society, 38, 3, 215238, 2008. Heterospory and seed habitat in pteridophytes easy biology. These two types of spore differ in their formation. A seed consists of an embryo, stored food and a seed coat. Thomson how they may ally, especially to thc conditions in oenothera rubricahx.
Heterospory originated in some pteridophytes like selaginella. Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit. Jul 01, 2019 seed habit is an evolutionary trend in vascular plants where naked megasporangium got covered by a vascular integument and hence a seed was formed. Seed is the ripened ovule with integuments formed after fertilization. Pteridophytes 7 public service commission psc 27 question bank 379 rdna technology 3 research methodology 18 research methodology 2 research methodology ppt 1 scientist jobs in biologylife sciences 3 set botany 7 set botany mock test 3 set environmental science 14 set environmental sciences 3 set life science solved. Ruggles gates and the second, in reply to it by dr d. Some of the characters of pteridophytes are as follows.
Some pteridophytes are aquatic and some are epiphytes. Heterospory and seed habitat in pteridophytes easy biology class. Apr 25, 2020 heterospory and origin and evolution of seed habitat in land plants pteridophytes. Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular. A heterosporous life history occurs in some pteridophytes and in all seed plants. Aug 06, 2019 heterospory and seed habit in pteridophytes pdf.
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. Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral condition, homospory. The smaller of these, the microspore, is male and the larger megaspore is female. Heterospory and gametophytic unisexuality are not necessarily evolu tionary antecedents of endospory. Heterospory and seed habit in pteridophytes ferns plant. Heterospory and seed habitat in pteridophytes easy.
Heterospory and seed habitat in pteridophytes short notes heterospory and seed habitat. Seed habit is an evolutionary trend in vascular plants where naked megasporangium got covered by a vascular integument and hence a seed was formed. Origin and evolution of the seed habit the seed habit is the most complex and evolutionary successful method of sexual reproduction found in vascular plants. However, there are some pteridophytes which produce two different types of. Jan 11, 2018 therefore, the key difference between homosporous and heterosporous pteridophytes is that the homosporous pteridophytes produce one type of spores that are same in size whereas heterosporous pteridophytes produce two types of spores that are different in sizes. Being the first true land plants they include in their bodily features the results of many experiments that nature conducted with the sporophytic plant body on a primordial terrestrial habitat. Heterospory is a condition of the production of more than one type usually two of spores in a single plant. The role of heterochrony article pdf available in taxon 381. S15, 2nd floor uphar cinema market, above red chilli restaurant, green park extension, new delhi, 110016. Evolutionary significance of heterospory and seed development in. Heterospory means production of two different sizes of sporesmegaspore and microspore. According to rashid1976, only 9 genera of pteridophytes show heterospory,i. High concentration of active ingredients are present in oil and seed.
Examples of heterosporous pteridophytes lifeeasy biology. Heterospory evolved during the devonian period from isospory independently in several plant groups. Heterospory evolved first in pteridophytes such as selaginella and salvinia. 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. Once seeds existed, their early pattern of diversification was not one of gradual change in form. Jul 17, 2019 heterospory and seed habit in pteridophytes botany in microsporangium all the microspores are functional while in magasporangium one megaspore is functional and rest degenerate. Experimental studies described in the book highlight the phenomena of apogamy and apospory, their occurrence, induction and alternate role. Even among seed plants the development of the megaspore is by. Department of palaeontology, british museum natural history london s. Gary pilarchik the rusted garden recommended for you. Heterospory and seed habit in pteridophytes botany. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the.
A seed is that ovule which contains an embryo developed as a result of fertilization. The heterospory also reduced the size of gametophytic generation. Pteridophytes biology encyclopedia plant, body, different. Pteridophyta characteristics, life cycle, classification. They are the second most diverse land plants after angiosperms. Entomycorrhiza epithem essential oils functions of root fungi golden rice guttation gymnosperms hartingnet haustoria heterocysts heterospory and seed habit hydathodes ingo. A model for the origin of heterospory is proposed, in which an initially homosporous population is subject to natural selection for increased spore size. They are differentiated into micro and megasporangia. However, there are some pteridophytes which produce two different types of spores differing in size.
When such attempts lime been made the definitions show striking contrasts in content andor emphasis table i. T h e seed habit was well established by the lowermost mississippian period and quite a large diversity of fossil ovules is now known. The next big step in evolution was heterospory or formation of two different types of spores, the smaller ones. Pteridophytes have many unique characters in both structural and reproductive features. Pteridophytes may represent the closest living relatives sister group to the seed plants. What are the similarities between homosporous and heterosporous pteridophytes. Seed evolution the seed biology place the seed biology. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle.
Importance of heterospory and seed habit of ferns 581 words. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the phenomenon of seed habit, a characteristic feature of the spermatophytes. Each microsporangium contains a large number of microspores whereas each megasporangium contains usually only. The microspores develop into male gametophyte whereas the megaspores give rise to female gametophyte. The book also discusses topics like heterospory, seed habit, leaf phylogeny, stellar system, alternation of generations, regeneration in general and special role of germ cellsegg and sporein life cycle. Rather, we believe that the decisive character in this success is related to pollination. Apr 26, 2020 in this article we will discuss about heterospory and seed habit in pteridophytes. Ncert solutions for class 11 biology chapter 3 in pdf form to free download in english medium updated for new academic session 202021. Most of these have been found as detached organs in the tournaisian basal mississippian of southern scotland heterospory and the origin of the seed habit textfig. In this article we will discuss about heterospory and seed habit in pteridophytes. Thomson department of botany, university of toronto some months ago there were two notes in. Difference between homosporous and heterosporous pteridophytes. The spores are differentiated into microspores and megaspores borne on the microsporangium and megasporangium. Each microsporangium contains a large number of microspores whereas.
Oct 10, 2019 heterospory and seed habit in pteridophytes botany. It furthers the universitys objective of excellence in research. In order to overcome this problem, the female gametophyte is heteroslory retained in the megasporangium. To watch the full class on pteridophytes and gymnosperms for your neet exam for free, click here. They also encompass a greater range of habit than any other group of tracheophytes. Heterospory and seed habit in pteridophytes ferns plant science. Selective forces in the emergence of the seed habit, biological journal of the. Evolution of seed habit in selaginella pdf pdf summary the origin of the seedplant life history, and subsequent should be considered two independent, fundamentally distinct evolutionary. Heterospory and origin and evolution of seed habitat in land plants pteridophytes. Download offline apps based on latest ncert books 202021 for new session.
This is the form in which in 1929 he had found that the size of the mother cells was al. Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral. Ebook an introduction to pteridophyta as pdf download. The seed habit is the most complex and evolutionary successful method of sexual reproduction. Selective forces in the emergence of the seed habit.
The evolution of the seed is one of the major events in the history of land plants. In both types, the gametophyte obtains the nutrition from the sporophyte. In the seed bearing plants there are two kinds of spores. Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular plants. The origin of heterospory in marsilia university of chicago. Heterospory and seed habit are often exhibited by a plant possessing a petiole b ligule c bract d spathe. Origin of seeds and seed habitat in vascular plants from heterospory heterospory is a condition of the production of more than one type usually two of spores in a single plant. Jul 20, 2019 importance of heterospory and seed habit of ferns 581 words abstract the evolution of the seed is one of the major events in the history selaginlela land plants. Study of plant seed seed habit seed habit a seed consists of an embryo, stored food and a seed coat. A few pteridophytes are aquatic while still others are epiphytes. Wiley online library divya darshan pant and rita singh, on the possible occurrence of anisospory in some hepaticae, botanical journal of the linnean society, 100, 2, 183, 1989.
Slowly in higher organisms sexual dimorphism started to occur. The heterospory also facilitated the sex differentiation in pteridophytes. Pteridophytes reproduction mainly occurs via the spores. The next big step in evolution was heterospory or formation of two different types of spores, the smaller ones called microspores and the larger ones known as megaspores. Ncert solutions for class 11 biology chapter 3 plant. The evolution of the seed habit is related to the retention of the megaspore. Ncert solutions 202021 are updated according to new cbse syllabus 202021 to all boards who are using ncert books. The microsporangia contain microspores whereas megasporangia contain megaspores in them. A model for the origin of heterospory sciencedirect. 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. Full text of the origin of gymnosperms and the seed habit see other formats stop early journal content on jstor, free to anyone in the world this article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in the world by jstor. The condition of production of two different types of spores in the same species is known as the heterospory.
It furthers the universitys objective of excellence in research, scholarship, and education by publishing worldwide. Moreover, surprisingly few authors have attempted to formally define. Being the first successful colonisers in land habit pteridophytes show both the homospory and heterospory. Heterospory and seed habit in pteridophytes botany in microsporangium all the microspores are functional while in magasporangium one megaspore is functional and rest degenerate.
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 the origin of the seed habit deepdyve. A seed may be defined as an integumented surrounded by integument and indehiscent not ruptured o. Some heterosporous pteridophytes do occur in terrestrial habitats, but these plants.
In this paper, we consider the suite of characters that define the seed habit, and discuss the probable selective pressures that produced each character. Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. In most lower plants like algae fertilization takes place outside the plant body. To watch the full class on pteridophytes and gymnosperms for your neet exam for free, click. In selaginella, nutritive tissue called tapetum is present. The origin of heterospory in marsilia the university of.
Biology question bank 80 mcqs on plant kingdom answered. There is further elaboration of the megasporangium so as to enable it to be an ideal starting point for the development of a new plant. What is the difference between homosporous and heterosporous pteridophytes. Heterospory and seed habit in pteridophytes ferns evolution of the seed is one of the most crucial adaptations in phanerogams for successful survival in terrestrial habitat. Most of the pteridophytes are homosporous, produce isospores. The sporophyte is the conspicuous and familiar plant body. Full text of the origin of gymnosperms and the seed habit.
In pteridophytes, majority are homosporous, but selaginella, marselia, salvinia, azolla etc are heterosporus showing tendency towards seed habit. From certain phenomena that i observed in making a morphological investigation of marsilia quadrijolia, it seemed possible that an experi. 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. Nonetheless, dioicy can undoubtedly occur in homosporous pteridophytes. Heterospory and seed habit in pteridophyts youtube. They are a type of vascular plants which possesses xylem and phloem tissues. Key difference homosporous vs heterosporous pteridophytes pteridophyta is the largest phylum of the kingdom plantae. Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants.
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