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