Recent questions tagged class11

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 Bryophytes : 1.The plant body is thallus-like and prostrate or erect 2. The plant body is attached to the substratum by unicellular or multicellular rhizoids 3. They have true roots, stem or leaves. 4. They may possess root-like, leaf-like or stem-like structures. 5. The main plant body of the bryophyte is diploid.

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. Vegetative reproduction takes place by fragmentation. 2. Sexual reproduction in most brown algae is by biflagellate zoospores. 3. Zoospores are pear-shaped and have two equal laterally attached flagella

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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1. Lichens are symbiotic associations between algae and fungi. 2.The algal component is known as mycobiont and fungal component as phycobiont 3. Algal component is autotrophic and fungal component is heterotrophic 4.Algae absorb water and prepare food for fungi and fungi provide shelter and absorb mineral nutrients for its partner. 5. Lichens are very good pollution indicators – they grow well in polluted areas Regarding 1,2,3,4 and 5:

asked Jan 6, 2014 by pady_1

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1. In 1979, T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. 2. It was found to be a free RNA; 3. it lacked the protein coat that is found in viruses, hence the name viroid. 4.The RNA of the viroid was of high molecular weight. Regarding 1,2,3 and 4:

asked Jan 6, 2014 by pady_1

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Regarding 1,2 and 3: 1. Life cycle of plants has two distinct phases 2. The diploid gametophytic phase and the haploid sporophytic phase - that alternate with each other. 3. This phenomenon is called alternation of generation.

asked Jan 6, 2014 by pady_1

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In Basidiomycetes: 1.The asexual spores are generally not found 2. Vegetative reproduction by fragmentation is common. 3. The *** organs are present 4. plasmogamy is brought about by fusion of two vegetative or somatic cells of same strain or genotype. 5. The resultant structure of plasmogamy is dikaryotic which ultimately gives rise to basidium. 6.Karyogamy and meiosis take place in the basidium producing four basidiospores. The basidiospores are exogenously produced on the basidium . 7. The basidia are arranged in fruiting bodies called basidiocarps.

asked Jan 6, 2014 by pady_1

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In Ascomycetes: 1.The asexual spores are conidia produced endogenously on the special mycelium called conidiophores. 2. Conidia on germination produce mycelium. 3. Sexual spores are called ascospores which are produced exogenously in sac like asci 4. These asci are arranged in different types of fruiting bodies called ascocarps.

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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The herbarium sheets carry a label providing information about (i)date of collection (ii)place of collection (iii)botanical names, family names (iv)English, local names (v)collector’s name

asked Jan 6, 2014 by pady_1

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1.As one goes higher from species to kingdom, the number of common characteristics goes on increasing. 2. Lower the taxa, more are the characteristics that the members within the taxon share. 3.Higher the category, determining the relationship to other taxa at the same level becomes easy.

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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1. The scientific names need not always ensure that each organism has only one name. 2. Description of any organism should enable the people (in any part of the world) to arrive at the same name. 3. While naming a new organism suh a name may have been used for some other closely related known organism.

asked Jan 6, 2014 by pady_1

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If $ P(A)=0.65\: P(B)=0.80$ then $ P(A \cap B)$ lies in the interval

asked Jan 6, 2014 by thanvigandhi_1

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A line with direction ratio $(2,1,2)$ meets the lines $x=y+a=z\:\;and\:\:x+a=2y=2z$. The coordinates of the points of intersections are ?

asked Jan 6, 2014 by rvidyagovindarajan_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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Two dice are thrown, the probability that the sum of the points on the dice is 7 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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Ram shares a photo link on facebook with 3 persons and requests each of them to share with 3 more persons and continue the chain. For every share of the photo link if Rs 100 is donated to the Adyar Cancer society, what is the total amount collected by the society till the $b^{th}$ set of shares.

asked Jan 6, 2014 by yamini.v

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Given $4$ numbers, the first $3$ numbers are in $AP$ and the last $3$ numbers are in $GP$. The $1^{st}$ and $3^{rd}$ terms add upto $2$ and the $2^{nd}$ and $4^{th}$ terms add to $17$. Find the numbers.

asked Jan 6, 2014 by yamini.v

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If $P(0,1,0)\:and\:Q(0,0,1)$ are two points in space, then the projection of $PQ$ on the plane $x+y+z=3$ is ?

asked Jan 6, 2014 by rvidyagovindarajan_1

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If $a, b, c$ are in $AP, a, x, b$ and $b, y, c$ in $GP$, what is the progression type for $x^2,b^2,y^2$?

asked Jan 6, 2014 by yamini.v

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Find the sum of the series upto 20 term 1+(1+2)+(1+2+3)+--------

asked Jan 6, 2014 by yamini.v

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Find the sum of 8 terms of the series whose $n^{th}$ term is given by $n^2+2^n$

asked Jan 6, 2014 by yamini.v

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For what value of n , the $n^{th}$ term of the GPs 2560,1280,640 ----- and 10,20,40 ------ are equal.

asked Jan 6, 2014 by yamini.v

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The first term of a $GP$ is $4$ and the sum of its $3^{rd}$ and $5^{th}$ terms is $360$. Find the common ratio.

asked Jan 6, 2014 by yamini.v

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Find three numbers in AP whose sum is 33 and the sum of whose squares is 395

asked Jan 6, 2014 by yamini.v

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Two cars start at a point A at the same time. The first car goes with a uniform speed of 100 Km/hr and the second car starts at 80 for the first hour and increases the speed by 10 km/hr every hour. After how much time does the second car overtake the first car, assuming these are no stops in between.

asked Jan 6, 2014 by yamini.v

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