Recent questions tagged medium

In flower (of angiosperm) : 1. Each of the cells of an embryo-sac is haploid. 2. Each embryo-sac has a three-celled egg apparatus – one egg cell and two synergids, two antipodal cells and three polar nuclei. 3. The two synergids fuse to produce a diploid secondary nucleus. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In flower (of angiosperm) : 1. The anthers, following meiosis, produce pollen grains. 2. The embryo-sac formation preceeds meiosis. 3. Each of the cells of an embryo-sac is haploid. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In angiosperms : 1. The pollen grains and ovules are developed in specialised structures called flowers. 2. In angiosperms, the seeds are enclosed by fruits. 3. The angiosperms are an exceptionally large group of plants occurring in wide range of habitats. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The pollen grain is released from the microsporangium. 2. Pollen grains are carried in air currents and come in contact with the opening of the ovules borne on megasporophylls. 3. The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharge their contents near the mouth of the archegonia. 4. Following fertilisation, zygote develops into an embryo and the ovules into seeds. 5.The seeds are not covered. Regarding 1,2,3,4 and 5:

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The megaspore mother cell divides mitotically to form four megaspores. 2. All the four megaspores are enclosed within the megasporangium (nucellus) develop into a multicellular female gametophyte 3. Female gametophyte bears one archegonium or female *** organ. 4. The multicellular female gametophyte is also retained within megasporangium. Regarding 1,2,3 and 4:

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The megaspore mother cell is differentiated from few of the cells of the nucellus. 2. The nucellus is protected by envelopes and the composite structure is called an ovule. 3. The ovules are borne on megasporophylls which may be clustered to form the female cones. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The microspores develop into a male gametophytic generation 2. Male gametophytic generation is highly reduced and is confined to a unicellular form. 3. The reduced gametophyte is called a pollen grain. 4. The development of pollen grains take place outside the microsporangia.

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The gymnosperms are heterosporous. 2. They produce diploid microspores and megaspores. 3. The two kinds of spores are produced within sporangia 4. Sporangia are borne on sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones. Regarding 1,2,3 and 4:

asked Jan 6, 2014 by pady_1

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In gymnosperms : 1. The roots are generally tap roots. 2. Roots in some genera have fungal association in the form of mycorrhiza 3. Some others small specialised roots called coralloid roots are associated with N2- fixing cyanobacteria.

asked Jan 6, 2014 by pady_1

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In pteridophytes: 1. The megaspores and microspores germinate and give rise to male and female gametophytes, respectively. 2. The female gametophytes in these plants are retained on the parent sporophytes for variable periods. 3. The development of the zygotes into young embryos take place within the female gametophytes. 4. The development of the zygotes into young embryos within the female gametophytes is a precursor event to the seed habit considered an important step in evolution.

asked Jan 6, 2014 by pady_1

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In pteridophytes: 1.The gametophytes of the pteridophytes bear male and female * organs called archegonia and antheridia, respectively. 2. Water is required for transfer of antherozoids – the male gametes released from male * organ, to the mouth of female *** organ. 3. Fusion of male gamete with the egg result in the formation of zygote. 4. Zygote thereafter produces a multicellular well-differentiated sporophyte 5. Sporophyte is the dominant phase of the pteridophytes.

asked Jan 6, 2014 by pady_1

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In pteridophytes: 1. Pteridophytes are the first terrestrial plants to possess vascular tissues – xylem and phloem. 2. The pteridophytes are found in cool, damp, shady places 3. They can never grow in sandy-soil conditions.

asked Jan 6, 2014 by pady_1

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In Mosses: 1. After fertilisation, the zygote develops into a sporophyte 2. Sporophyte consists of a foot, seta and capsule. 3. The seta contains spores. 4. Spores are formed after mitosis.

asked Jan 6, 2014 by pady_1

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In liverworts: 1. During sexual reproduction, male and female *** organs are produced either on the same or on different thalli. 2. The sporophyte is differentiated into a foot, seta and capsule. 3. After meiosis, spores are produced within the capsule. 4. These spores germinate to form free-living gametophytes.

asked Jan 6, 2014 by pady_1

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In liverworts: 1. Asexual reproduction takes place by fragmentation of thalli 2. Sexual reproduction takes place by formation of gemmae 3. Gemmae are green, unicellular, buds 4. Gemmae develop in small receptacles - gemma cups located on the thalli. 5. The gemmae become detached from the parent body and germinate to form new individuals. Regarding 1,2,3,4 and 5:

asked Jan 6, 2014 by pady_1

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1. Mosses are some of the first organisms to colonise rocks 2. Mosses decompose rocks making the substrate suitable for the growth of higher plants. 3. Mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In Bryophytes: 1. The zygotes produce a multicellular body called a sporophyte. 2. The sporophyte is free-living 3. Some cells of the sporophyte undergo division to produce diploid spores. 4. These spores germinate to produce gametophyte.

asked Jan 6, 2014 by pady_1

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Regarding sexual reproduction in Bryophytes : 1. The female *** organ called archegonium is pyriformin shape 2. Archegonium produces a single egg. 3. The antherozoids are released into water where they come in contact with archegonium. 4. An antherozoid fuses with the egg to produce the zygote. 5. Zygotes undergo reduction division immediately.

asked Jan 6, 2014 by pady_1

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Regarding Rhodophyceae: 1. Majority of them are marine 2. Greater concentrations of Rhodophyceae are found in the warmer areas 3. They occur in well-lighted regions close to the surface of water 4. They can not grow at great depths in oceans where relatively little light penetrates

asked Jan 6, 2014 by pady_1

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Regarding the members of phaeophyceae or brown algae: 1. possess chlorophyll a, c, carotenoids and xanthophylls. 2. Food is stored as complex carbohydrates, which may be in the form of laminarin or mannitol. 3. The vegetative cells have a cellulosic wall. 4. cellulosic wall usually covered on the outside by a gelatinous coating of algin. 5. The protoplast contains, in addition to plastids, a centrally located vacuole and nucleus.

asked Jan 6, 2014 by pady_1

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In Chlorophyceae: 1. Vegetative reproduction usually takes place by fragmentation or by formation of different types of spores. 2. Asexual reproduction is by non flagellated zoospores produced in zoosporangia. 3. Zoospores produced in zoosporangia. 4. The sexual reproduction shows considerable variation 5. Sexual reproduction may be isogamous, anisogamous or oogamous.

asked Jan 6, 2014 by pady_1

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In Chlorophyceae: 1. The pigments are not localised in chloroplasts. 2. The chloroplasts may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon-shaped in different species. 3. Most of the members have one or more storage bodies called pyrenoids located in the chloroplasts. 4. Pyrenoids contain only starch. 5. Some algae may store food in the form of cholesterol.

asked Jan 6, 2014 by pady_1

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1. Vegetative reproduction is by fragmentation. 2. Each fragment develops into a thallus. 3. Asexual reproduction is by the production of different types of spores, the most common - oospores. 4. The spores are non flagellated and on germination give rise to new plants.

asked Jan 6, 2014 by pady_1

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1. Numerical Taxonomy which is now easily carried out using computers is based on all observable characteristics. 2. Number and codes are assigned to all the characters and the data are then processed. 3. Some important characters are given more importance 4. Cytological information like chromosome number are aslo included 5. At the same time hundreds of characters can be considered.

asked Jan 6, 2014 by pady_1

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1. Fungi, and members of the Monera and Protista having cell walls have now been excluded from Plantae 2. Earlier classifications also have placed them in Plantae 3. The cyanobacteria that are also referred to as blue green algae are not ‘algae’ any more. Regarding 1,2 and 3:

asked Jan 6, 2014 by pady_1

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In Phycomycetes: 1. Asexual reproduction takes place by zoospores (non-motile) or by aplanospores (motile). 2. These spores are exogenously produced in sporangium. 3. A zygospore is formed by fusion of two gametes; if these gametes are similar in morphology (isogamous or oogamous) or dissimilar (anisogamous)

asked Jan 6, 2014 by pady_1

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The sexual cycle involves the following three steps: (i) Fusion of protoplasms between two motile or non-motile gametes called plasmogamy. (ii) Fusion of two nuclei called karyogamy. (iii) Meiosis in zygote resulting in diploid spores. Regarding (i), (ii) and (iii)

asked Jan 6, 2014 by pady_1

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1. Archaebacteria differ from other bacteria in having a different cell wall structure 2. Methanogens live in marshy areas and halophiles live in hot springs. 3. Methanogens are present in the gut of several ruminant animals

asked Jan 6, 2014 by pady_1

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Regarding Linnaeus' time : 1. a Two Kingdom system of classification with Plantae and Animalia kingdoms was developed. 2. This system is still used till 3. This system did not distinguish between the eukaryotes and prokaryotes, & photosynthetic (green algae) and non-photosynthetic (fungi) organisms; yet this system distinguishes unicellular and multicellular organisms

asked Jan 6, 2014 by pady_1

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Regarding Aristotle: 1. used floral characters to classify plants 2. divided animals into two groups, those which had red blood and those that did not 3. a Two Kingdom system of classification with Plantae and Animalia kingdoms 4. earliest to attempt to classify organisms more on a scientific basis 5. classified plants into trees, shrubs and herbs

asked Jan 6, 2014 by pady_1

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1. Families are characterised only on the basis of reproductive features of plant species 2. Lion, tiger, leopard is put along with cats and dogs in the family Felidae 3. Three different genera Solanum, Petunia and Datura are placed in the family Solanaceae

asked Jan 6, 2014 by pady_1

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A determinant is chosen at random from the set of all determinants of order 2 with elements 0 and 1 only. The probability that the determinant chosen is non-zero is

asked Jan 6, 2014 by thanvigandhi_1

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A variable plane is at a distance $k$ from origin and meets the coordinate axes at the points $A,B,C$ respectively. then the locus of centroid of the $\Delta\:ABC$ is ?

asked Jan 6, 2014 by rvidyagovindarajan_1

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The equation of the plane passing through the point $(1,1,1)$ and having direction ratios $b,c,a$ $(a < b < c)$, where $a,b,c$ are prime factors of $2001$ is ?

asked Jan 6, 2014 by rvidyagovindarajan_1

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