These two types of spore differ in their formation. Being the first successful colonisers in land habit pteridophytes show both the homospory and heterospory. The origin of heterospory in marsilia the university of. Pteridophytes may represent the closest living relatives sister group to the seed plants. Key difference homosporous vs heterosporous pteridophytes pteridophyta is the largest phylum of the kingdom plantae. Gary pilarchik the rusted garden recommended for you. The heterospory also reduced the size of gametophytic generation. Download offline apps based on latest ncert books 202021 for new session. Slowly in higher organisms sexual dimorphism started to occur. Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. 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 pteridophytes are terrestrial and grow in moist and shady places while some flourish well in open, dry places especially in xeric conditions.
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. Selective forces in the emergence of the seed habit, biological journal of the. In homosporous pteridophytes, the sex differentiation takes place only during the development of antheridia or archegonia. They are the second most diverse land plants after angiosperms. The evolution of the seed habit is related to the retention of the megaspore.
Heterospory evolved during the devonian period from isospory independently in several plant groups. 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 sporophyte is the conspicuous and familiar plant body. 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.
Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral condition, homospory. Apr 26, 2020 in this article we will discuss about heterospory and seed habit in pteridophytes. Seex pteridophytes, selaginella rupestris is the most successful species that completed first four steps towards seed habit. Heterothally and the seed habit versus heterospory, new. A seed consists of an embryo, stored food and a seed coat. Evolution of the seed habit consists of at least two independent problems. Heterospory and seed habitat in pteridophytes easy biology class. Evolutionary significance of heterospory and seed development in. It furthers the universitys objective of excellence in research, scholarship, and education by publishing worldwide. The seed habit is the most complex and evolutionary successful method of sexual reproduction. Heterospory and seed habitat in pteridophytes easy biology. Oct 10, 2019 heterospory and seed habit in pteridophytes botany. Ncert solutions for class 11 biology chapter 3 in pdf form to free download in english medium updated for new academic session 202021.
Since their first appearance in the late devonian, seed plants have come to dominate almost every terrestrial ecosystem. Seed evolution the seed biology place the seed biology. 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. 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. 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. Heterospory and seed habit in pteridophytes botany in microsporangium all the microspores are functional while in magasporangium one megaspore is functional and rest degenerate. According to rashid1976, only 9 genera of pteridophytes show heterospory,i.
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. A model for the origin of heterospory is proposed, in which an initially homosporous population is subject to natural selection for increased spore size. Thomson how they may ally, especially to thc conditions in oenothera rubricahx. They also encompass a greater range of habit than any other group of tracheophytes. High concentration of active ingredients are present in oil and seed. 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. Heterospory and seed habit in pteridophytes botany in order to overcome this problem, the female gametophyte is heteroslory retained in the megasporangium. David haig and mark westoby, selective forces in the emergence of the seed habit, biological journal of the linnean society, 38, 3, 215238, 2008. This is the form in which in 1929 he had found that the size of the mother cells was al. The microspores develop into male gametophyte whereas the megaspores give rise to female gametophyte. Such peridophytes are known as homosporous and this phenomenon is known as homospory. The evolution of the seed is one of the major events in the history of land plants. The heterospory also facilitated the sex differentiation in pteridophytes.
Moreover, surprisingly few authors have attempted to formally define heterospory or its presumed ancestral. Experimental studies described in the book highlight the phenomena of apogamy and apospory, their occurrence, induction and alternate role. A heterosporous life history occurs in some pteridophytes and in all seed plants. Selective forces in the emergence of the seed habit. Heterospory and seed habit in pteridophytes ferns plant science. 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. The role of heterochrony article pdf available in taxon 381. What is the difference between homosporous and heterosporous pteridophytes. Most of the pteridophytes are homosporous, produce isospores.
Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit. In the seed bearing plants there are two kinds of spores. Heterospory and seed habit in pteridophytes ferns plant. Department of palaeontology, british museum natural history london s. Rather, we believe that the decisive character in this success is related to pollination. To watch the full class on pteridophytes and gymnosperms for your neet exam for free, click here. The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the.
Seed habit is an evolutionary trend in vascular plants where naked megasporangium got covered by a vascular integument and hence a seed was formed. Heterospory is a condition of the production of more than one type usually two of spores in a single plant. 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. However, there are some pteridophytes which produce two different types of spores differing in size. What are the similarities between homosporous and heterosporous pteridophytes.
T h e seed habit was well established by the lowermost mississippian period and quite a large diversity of fossil ovules is now known. Ebook an introduction to pteridophyta as pdf download. They are a type of vascular plants which possesses xylem and phloem tissues. Ncert solutions for class 11 biology chapter 3 plant. Entomycorrhiza epithem essential oils functions of root fungi golden rice guttation gymnosperms hartingnet haustoria heterocysts heterospory and seed habit hydathodes ingo. Pteridophytes have many unique characters in both structural and reproductive features. It furthers the universitys objective of excellence in research. Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular plants. Importance of heterospory and seed habit of ferns 581 words. Ncert solutions 202021 are updated according to new cbse syllabus 202021 to all boards who are using ncert books. 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. A seed is that ovule which contains an embryo developed as a result of fertilization. Moreover, surprisingly few authors have attempted to formally define. Examples of heterosporous pteridophytes lifeeasy biology.
In both types, the gametophyte obtains the nutrition from the sporophyte. Some of the characters of pteridophytes are as follows. The spores are differentiated into microspores and megaspores borne on the microsporangium and megasporangium. To watch the full class on pteridophytes and gymnosperms for your neet exam for free, click. 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. Pteridophyta characteristics, life cycle, classification. Even among seed plants the development of the megaspore is by.
Heterospory and gametophytic unisexuality are not necessarily evolu tionary antecedents of endospory. 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. In order to overcome this problem, the female gametophyte is heteroslory retained in the megasporangium. Heterospory and seed habitat in pteridophytes short notes heterospory and seed habitat. Biology question bank 80 mcqs on plant kingdom answered. In most lower plants like algae fertilization takes place outside the plant body. Algae alkaloids allelopathy arbuscules aspergillus nidulans bryophytes and pteridophytes celpholeuros chemosynthesis. However, the pteridophytes differ from mosses and seed plants in that both generations are independent and freeliving. Nonetheless, dioicy can undoubtedly occur in homosporous pteridophytes. A model for the origin of heterospory sciencedirect. 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 pteridophytes, majority are homosporous, but selaginella, marselia, salvinia, azolla etc are heterosporus showing tendency towards seed habit. Study of plant seed seed habit seed habit a seed consists of an embryo, stored food and a seed coat. S15, 2nd floor uphar cinema market, above red chilli restaurant, green park extension, new delhi, 110016.
Today, seed plants, gymnosperms and angiosperms flowering plants are the most diverse lineage within the vascular. The condition of production of two different types of spores in the same species is known as the heterospory. Thomson department of botany, university of toronto some months ago there were two notes in. When such attempts lime been made the definitions show striking contrasts in content andor emphasis table i. 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.
A seed may be defined as an integumented surrounded by integument and indehiscent not ruptured o. A seed ovule may be defined as an integumented indehiscent megasporangium. Each microsporangium contains a large number of microspores whereas each megasporangium contains usually only. Some pteridophytes are aquatic and some are epiphytes. Full text of the origin of gymnosperms and the seed habit. A few pteridophytes are aquatic while still others are epiphytes. Pteridophytes biology encyclopedia plant, body, different. Historical the natural presumption has been that the marsiliaceae have. Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants. Heterospory and origin and evolution of seed habitat in land plants pteridophytes. The smaller of these, the microspore, is male and the larger megaspore is female. Heterospory and seed habitat in pteridophytes easy.
However, there are some pteridophytes which produce two different types of. The microsporangia contain microspores whereas megasporangia contain megaspores in them. 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. In selaginella, nutritive tissue called tapetum is present.
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. 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. Heterospory and seed habit in pteridophytes botany. Heterospory originated in some pteridophytes like selaginella. Similar to the life cycle of seed plants, the pteridophytes also involves the alternation of generations in its life cycle. In this paper, we consider the suite of characters that define the seed habit, and discuss the probable selective pressures that produced each character. 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. When such attempts lime been made the definitions show striking contrasts in content and or emphasis table i. 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 these have been found as detached organs in the tournaisian basal mississippian of southern scotland heterospory and the origin of the seed habit textfig.
Seed is the ripened ovule with integuments formed after fertilization. The sporangia show greater specialization than those of ferns. Heterospory evolved first in pteridophytes such as selaginella and salvinia. 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 seed habit is the most complex and diverse means of sexual reproduction in vascular land plants. 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 means production of two different sizes of sporesmegaspore and microspore. Heterospory and seed habit in pteridophyts youtube. They are differentiated into micro and megasporangia.
Most of the pteridophytes produce one kind of similar spore. Aug 06, 2019 heterospory and seed habit in pteridophytes pdf. Apr 25, 2020 heterospory and origin and evolution of seed habitat in land plants pteridophytes. The sexuality of pteridophytic gametophytes can be classified as follows. In this article we will discuss about heterospory and seed habit in pteridophytes.