Recent questions tagged ch3

The male reproductive system : 1. The testes are situated outside the abdominal cavity within a pouch called . 2. The helps in maintaining the high temperature of the testes, 2–2.5o C higher than the normal internal body temperature. 3. 2–2.5o C higher than the normal internal body temperature is necessary for spermatogenesis. Regarding 1,2 and 3 :

asked Mar 20, 2014 by pady_1

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Plant life cycle and alternation of generations: 1. The haploid gametophytic plant body produces gametes by mitosis. 2. Following fertilisation the zygote divides by mitosis to produce a diploid sporophytic plant body. 3. Haploid spores are produced by this plant body by meiosis. Regarding 1,2 and 3:

asked Mar 20, 2014 by pady_1

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1. Double fertilisation is an event unique to angiosperms and gymnosperms. 2. The zygote develops into an embryo 3. Primary endosperm nucleus (PEN) develops into endosperm which provides nourishment to the developing embryo. 4. The synergids and antipodals degenerate after fertilisation. 5. During these events the ovules develop into seeds and the ovaries develop into fruit. Regarding 1,2,3,4 and 5:

asked Mar 20, 2014 by pady_1

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In angiosperm : 1. After pollination, the pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule. 2. The pollen tubes enter the embryo-sac where two male gametes are discharged. 3. One of the male gametes fuses with the egg cell to form a zygote (syngamy). 4. The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus (PEN). 5. This event is termed as double fertilisation Regarding 1,2,3,4 and 5:

asked Mar 20, 2014 by pady_1

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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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 2014 by pady_1

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In gymnosperms :

asked Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 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 Mar 20, 2014 by pady_1

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In which of the following arrangements is the order not according to the property indicated against it?

asked Mar 16, 2014 by balaji.thirumalai

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The ionization enthalpy of hydrogen atom is $1.312 \times 10^{6} \; J/mol$. The energy required to excite the electron in the atom from $n=1 \rightarrow n = 2$ is:

asked Mar 16, 2014 by balaji.thirumalai

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Which metal is obtained commercially by the electrolysis of salt?

asked Mar 15, 2014 by meena.p

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At $STP,$ which substance is the best conductor of electricity?

asked Mar 15, 2014 by meena.p

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Which of the following elements' atom has the greatest ability to attract electrons?

asked Mar 15, 2014 by meena.p

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The first ionization energy of an element is 736 kJ per mole of atoms. An atom of this element in the ground state has a total of how many valence electrons?

asked Mar 15, 2014 by meena.p

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As atoms of elements in Group 16 are considered in order from top to bottom, the electronegativity of each successive element

asked Mar 15, 2014 by meena.p

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Atoms of elements in a group on the Periodic Table have similar chemical properties. This similarity is most closely related to the atoms'

asked Mar 15, 2014 by meena.p

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Which set of elements contains a metalloid?

asked Mar 15, 2014 by meena.p

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When combining with nonmetallic atoms, metallic atoms generally will

asked Mar 15, 2014 by meena.p

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Arrange the following in order of increasing ionization energies: Ar, Se, S.

asked Mar 15, 2014 by balaji.thirumalai

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Which halogens are gases at $STP?$

asked Mar 15, 2014 by meena.p

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Which element in Group 15 has the strongest metallic character?

asked Mar 15, 2014 by meena.p

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Linus Pauling defined electronegativity as the power of an atom in a molecule to attract electrons. Given the bond disassociation enthalpies, $\varepsilon_{C-C} = 348\; \text{ kJ/mol}, \varepsilon_{C-H} = 412 \; \text{ kJ/mol}, \varepsilon_{H-H} = 436 \; \text{ kJ/mol}$, what is the Pauling elctronegativity of $C$? (Electronegativity of $H$ is $2.1$)

asked Mar 15, 2014 by balaji.thirumalai

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Given the following assertion and reason, choose the correct answer:

asked Mar 15, 2014 by balaji.thirumalai

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According to periodic table, which of the following elements has the smallest atomic radius?

asked Mar 14, 2014 by meena.p

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When a metal atom combines with a nonmetal atom, the nonmetal atom will

asked Mar 14, 2014 by meena.p

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Which compound forms a colored aqueous solution?

asked Mar 14, 2014 by meena.p

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Which element has the highest first ionization energy?

asked Mar 14, 2014 by meena.p

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