summative assessment- 1 cbse class x science, revision sample paper.

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”Read the instructions carefully before answering”

·         Try to answer in your own words as far as possible.

·         Include diagrams wherever required.

·         Diagrams should be drawn and  labeled with pencil only.

·         

1 marks X 9 = 9 marks (A)

1.      Why should a magnesium ribbon be cleaned before burning in air?

2.      Why do ionic compounds have high melting points?

3.      Why does an aqueous solution of an acid conduct electricity?

4.      What processes would you consider essential for maintaining life?

5.      Which part of the brain maintains posture and equilibrium of the body?

6.      What is meant by saying that the potential difference between two points is 1 V?

7.      What is a good source of energy?

8.      What is a good fuel?

9.      What is the role of the acid in our stomach?

2 marks X 9 =  18 marks (B)

10.  Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

11.  Why should curd and sour substances not be kept in brass and copper vessels?

12.  What are plant hormones? Give two examples?

13.  Why is the use of iodised salt advisable?

14.  How is the small intestine designed to absorb digested food?

15.  A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Find the amount of electric charge that flows through the circuit.

16.  Draw magnetic field lines around a bar magnet.

17.  If you could use any source of energy for heating your food, which one would you use and why?

18.  what are the disadvantages of fossil fuels?

3 marks x 6 = 18 marks (C)  

19.  3. Identify the substances that are oxidised and the substances that are reduced in the following reactions.

20.  (i) 4Na(s) + O2(g) → 2Na2O(s)

(ii) CuO(s) + H2(g) → Cu(s) + H2O(l)

21.  What are the different ways in which glucose is oxidized to provide energy in various organisms?

22.  What is a balanced chemical equation? Why should chemical equations be balanced?

23.  What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

24.  Compare and contrast bio-mass and hydro electricity as sources of energy.

5 marks X 3 = 15 marks (D)

25.  Write the balanced chemical equations for the following reactions.

(a)   Calcium hydroxide + Carbon dioxide  →  Calcium

carbonate + Water

(b) Zinc + Silver nitrate  →  Zinc nitrate + Silver

(c) Aluminium + Copper chloride  →  Aluminium chloride +

      Copper

(d) Barium chloride + Potassium sulphate → Barium sulphate

      + Potassium chloride

26.  Describe double circulation in human beings. Why is it necessary?

27.  (1) The potential difference between the terminals of an electric heater is 60 V when it draws a current of 4 A from the source. What current will the heater draw if the potential difference is increased to 120 V?

(2)  Resistance of a metal wire of length 1 m is 26 Ω at 20°C. If the diameter of the wire is 0.3 mm, what will be the resistivity of the metal at that temperature? Using Table 12.2, predict the material of the wire.

Total marks = 9(A) + 18(B) + 18(C) + 15(D)   = 60 marks

“Best of luck”           
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adaptations in insects part 1

1.       Cybister

a.       Habit: it feeds on small fishes. It is positively phototropic. It is an active swimmer.

b.      Habitat: aquatic, occurs in deep water.

c.       Role in ecosystem: it is a secondary consumer.

d.      Adaptations:

i.                     Strucrural adaptations: forewings modified into horny elytra, hind wints are membranous, folded beneath the elytra.

ii.                   Feeding adaptations: mouth parts consists of strong mandibles.

iii.                  Respiratory adaptations: antennae are hydrofuge structures and can hold air balls containing oxygen for respiration.

iv.                 Flight adaptations: wing muscles of both sides are not fused together below the scutellum, therefore it is an active flier.

2.       hydrophilus olivaceous:

a.       habit: predacious, carnivorous.

b.      Habitat: aquatic habitat. It lives near vegetation. It is shade loving.

c.       Role in ecosystem: it is secondary consumer.

d.      Adaptations:

i.                     Structural adaptation: forewings modified into horny elytra, hind wings membranous, folded beneath elytra, body stream linexd.

ii.                   Feeding adaptations: mouth parts mandibulate adapted for biting.

iii.                  Respiratory adaptations: ventral surface of the body is with a set of hydrofuge hairy structures. It can hold an air film for respiratory purpose. Antennae are above hudrofuge structures and can hold air balls near the spiracles.

iv.                 Swimming adaptations: it is an active swimmer. Appendages are fringed with hairs.

v.                   Adaptations for defence: it has a metasternal keel for defence.

3.       Laccotrephes maculatus:

a.       Habit: it is phytophagous, positively phototrophic.

b.      Habitat: aquatic; is a bottom dweller and liver in mud.

c.       Role in ecosystem: primary consumer.

d.      Adaptations:

i.                     Structural adaptations: fore wings are chitinized to form hemielytra.

ii.                   Feeding adaptation: first pair of legs are pre-hensile and adapted for catching food. Mouth parts of piercing and sucking type.

iii.                  Respiratory adaptation: respiratory tube consists of 2-spine like processes.

iv.                 Swimming adaptations: body is slender, appendages are fringed with hair.

4.       Ranatra elongata

a.       Habit: it feeds upon sap of plants. It is positively phototropic.

b.      Habitat: aquatic; swims on the surface of water,

c.       Role in ecosystem:  it is primary consumer.

d.      Adaptations:

i.                     Structural adaptation: for wings are chitinized to form hemielytra.

ii.                   Feeding adaptations: mouth parts are of piercing and sucking type.

iii.                  Respiratory adaptation: respiratory siphon present.

iv.                 Swimming adaptation: body is slender, appendages are ringed with hair. Walking legs are prominent and are also adapted for walking on bottom of the aquatic habitat,

5.       Lethocerus indicus (giant water bug)

a.       Habit: it feed rapaciously upon small fishes, tadpole, youngs, frogs, and insects. It is positively phototropic.

b.      Habitat: aquatic habitat; it clings to vegetation submerged in the bottom.

c.       Role in the ecosystem: pest of fishes, it is secondary consumer

d.      Adaptations:

i.                    Feeding adaptations: mouth parts are of piercing and sucking type.

ii.                  Respiratory adaptation:  it has a pair of respiratory siphons at the hind end. It breaths oxygen by piercing the surface film with the apex of the abdomen

iii.                Swimming adaptation:  body is stream lined, dorsoventrally flattened, so it overcomes friction in water easily, appendages are oar-like and fringed with hair.

iv.                 Colonization: it flies readily from one water piece to the another and just occupy a different habitat. But it is restricted flier. This is because wing muscles of both sides fuse together below the scutellum.

6.       Diplonuchus annulatum:

a.       Habit:  it feeds upon plant sap, mainly on hydrilla. It is positively phototropic.

b.      Habitat: aquatic; fresh water.

c.       Role in ecosystem:  it is primary consumer.

d.      Adaptations:

i.                    Structural adaptations: body is oval in shape. Forewings modified into horny hemielytra. Hind wings are membtanous. Folded bjeath the elytra.

ii.                  Feeding adaptations: mouth parts of piercing and sucking type.

iii.                Respiratory adaptation: it has a pair of respiratory siphon at the hind end. It takes oxygen through this siphon.

iv.                 Appendages are oar like and fringed with hair.

v.                   Parental care: the male carries eggs on it back till they are hatched;

adaptations in insects

Adaptations in insescts.

1.       Cybister

a.       Habit: it feeds on small fishes. It is positively phototropic. It is an active swimmer.

b.      Habitat: aquatic, occurs in deep water.

c.       Role in ecosystem: it is a secondary consumer.

d.      Adaptations:

i.                     Strucrural adaptations: forewings modified into horny elytra, hind wints are membranous, folded beneath the elytra.

ii.                   Feeding adaptations: mouth parts consists of strong mandibles.

iii.                  Respiratory adaptations: antennae are hydrofuge structures and can hold air balls containing oxygen for respiration.

iv.                 Flight adaptations: wing muscles of both sides are not fused together below the scutellum, therefore it is an active flier.

2.       hydrophilus olivaceous:

a.       habit: predacious, carnivorous.

b.      Habitat: aquatic habitat. It lives near vegetation. It is shade loving.

c.       Role in ecosystem: it is secondary consumer.

d.      Adaptations:

i.                     Structural adaptation: forewings modified into horny elytra, hind wings membranous, folded beneath elytra, body stream linexd.

ii.                   Feeding adaptations: mouth parts mandibulate adapted for biting.

iii.                  Respiratory adaptations: ventral surface of the body is with a set of hydrofuge hairy structures. It can hold an air film for respiratory purpose. Antennae are above hudrofuge structures and can hold air balls near the spiracles.

iv.                 Swimming adaptations: it is an active swimmer. Appendages are fringed with hairs.

v.                   Adaptations for defence: it has a metasternal keel for defence.

3.       Laccotrephes maculatus:

a.       Habit: it is phytophagous, positively phototrophic.

b.      Habitat: aquatic; is a bottom dweller and liver in mud.

c.       Role in ecosystem: primary consumer.

d.      Adaptations:

i.                     Structural adaptations: fore wings are chitinized to form hemielytra.

ii.                   Feeding adaptation: first pair of legs are pre-hensile and adapted for catching food. Mouth parts of piercing and sucking type.

iii.                  Respiratory adaptation: respiratory tube consists of 2-spine like processes.

iv.                 Swimming adaptations: body is slender, appendages are fringed with hair.

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classification of amino acids

classification of amino acids

chemical reaction during 5'capping.

An overview of polyadenylation of 3’ end: post transcriptional modification, prior to the nuclear export.

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The final RNA processing event, i.e. the polyadenylation of the 3’ end of the mRNA is linked with the termination of the transcription.

The CTD tail of the polymerase is involved in the recruiting of the enzymes necessary for the polyadenylation.
The DNA contains a poly-A signal sequence. Once the polymerase has reached the sequence and transcribed the poly-A signal sequence into the RNA, the poly-A signal sequence (these sequences once transcribed into RNA, triggers transfer of the CPSF and CstF from the CTD tail of the polymerase to the RNA, described in the text later) in the RNA triggers the transfer of polyadenylation enzymes to RNA leading to three events.
1. Cleavage
2. Addition of the “A” residues.
3. Termination of transcription.
The CTD tail of the polymerase carries two protein complexes as it reaches the end of the gene.
1. CPSF (cleavage and polyadenylation specificity factor)
2. CstF (cleavage stimulation factor)

The binding of the CPSF (cleavage and polyadenylation specificity factor) and CstF (cleavage stimulation factor) is followed by the recruitment of other proteins as well. This leads to RNA cleavage and then polyadenylation.
The poly-A polymerase mediates the process of polyadenylation and adds about 200 adenines to the RNA’s 3’ end produced by the cleavage.
The poly-A polymerase uses ATP (adenosine triphosphate) as a precursor and adds the nucleotides using the same chemistry as that of RNA polymerase, but here in the absence of a template. Thus long “A” tail is only present in RNA (and not in the DNA)
After polyadenylation (the final step in post transcriptional modification, prior to the nuclear mRNA transport) the mature mRNA is then transported from the nucleus to the cytosol.
At present, not more is known about the relation of the polyadenylation with the termination of the transcription. Two basic models have been proposed to explain the link between polyadenylation and termination.
· First: the transfer of the enzymes responsible for the polyadenylation from the CTD tail of the polymerase to the RNA triggers a conformational change in the polymerase that reduces the processivity of enzymes leading to spontaneous termination soon afterwards.
· Second: after cleavage of the RNA transcript the polymerase keeps on transcribing the DNA short while, the polymerase senses the absence of the 5’ cap on the second RNA molecule; as a result, the RNA recognizes the transcript as improper and terminates the transcription.

INSECT ENDOCRINE SYSTEM: ENTOMOLOGY (HEXAPODOLOGY)

FIGURE: CEPHALIC ENDOCRINE SYSTEM (diagrammatic)

hypersensetivity

·         It is an exaggerated response of immune system that leads to the damage of the tissue and cells, and is shown by an individual on a second contact with the antigen.

·         Coombs and Gell classified the hypersensitivity reactions in four classes of reactions

Type I hypersensitivity:

·         The type I hypersensitivity is also known as allergic reaction. It is induced by antigens which are referred to as allergens.

·         Allergens are specifically non parasitic antigens capable of stimulating type I hypersensitivity responses.

·         The type I hypersensitivity reactions are IgE mediated reactions.

·         The reaction is stimulated by IgE to high affinity IgE-specific Fc receptors expressed on the mast cells and the basophil cells

·         When activated by the antigens (allergens) the IgE antibodies stimulates the mast cells and basophil cells to release primary mediators: vasoactive amines, stored in the granules (degranulation)

·         The chief mediators are the proteases, heparin and histamines etc..

·         The mediators are responsible for all the normal consequences of an acute inflammatory reaction. I.e. granulocyte chemotaxis, vascular permeability and all sorts of the consequences of inflammations.

·         The type I hypersensitivity is further classified as :

Ø  Anaphylaxis: this type of the type I hypersensitivity is highly rapid, life threatening, severe and are spread to whole body, they are caused due to the re-exposure of the individual to the antigen (allergens)

Ø  Atopy: if the tendency to develop allergic reactions is inherited genetically, they are called the atopic hypersensitivity reactions.

Type II hypersensitivity:

·         The type II hypersensitivity reactions cause the destruction of the host cells and tissues; by lysis or toxic mediators, hence they are also called as cytotoxic or cytolytic reactions.

·         It is an IgM and IgG mediated response.

·         It is caused by the binding of the antibodies to the cell or tissue antigens.

·         They (IgG and IgM) cause cell destruction by Fc-mediated mechanisms, either directly or indirectly activating the complement via the classical pathway.

·         Example of the hypersensitivity class ii reaction is the hypersensitivity shown by an individual who has been transfused blood of blood group other than that of the individual.

·         The antibodies attach to the cell membrane component, leading to complement fixation; this activates the complement chain and leads to either lysis or oposonization of the cell.

·         Lysis of target cell is analogous to that of cytotoxic T cells and involves the release of cytoplasmic granules, containing perforin and granzymes that activates the event leading to the apoptosis.

Type III hypersensitivity:

·         It is mediated by immune complexes of IgG antibodies with soluble antigens.

·         The circulating immunity complexes may accumulate at various tissue sites, where they activate complement and subsequently cause tissue cell lysis.

·         Normally these complements are phagocytized by the monocyte-macrophage system.

Type IV hypersensitivity:

·         Commonly it is known as delayed type of hypersensitivity.

·         Only class of hypersensitivity that is triggered by antigen-specific T cells. (cell mediated immunity reactions)

·         This is mediated by T-cell dependent effector mechanisms involving T_H cells.

·         This reaction has nothing to do with the antibodies.

PCR: polymerase chain reaction.

·         PCR is a very simple process.

·         All that happens in PCR is a short region of DNA molecule, let’s take for example a single gene, and is copied many times by DNA polymerase enzyme.

·         The PCR has a variety of applications in genetics, research and in broader areas of biology.

An outline of polymerase chain reaction:

·         It results in selective amplification of chosen reaction of the DNA molecule.

·         For amplification, a region of DNA is chosen (whose sequences in border regions are known)

·         The border sequences of the DNA fragment to be amplified must be known, because in order to carry PCR, two short oligonucleotides must hybridize to the DNA molecule, one to each strand of double helix.

·         These oligonucleotides are used as DNA primers for DNA synthesis reaction.

·         Amplification is usually carried out by DNA polymerase I enzymes derived from thermus aquaticus (this bacteria inhabits the hot streams)

·         The polymerase is named taq polymerase after the name of bacteria from which it is derived.

·         Taq polymerase is thermostable and can withstand temperature up to 96 ⁰ C.

·         The PCR is a very sensitive technique; it can even start from a single target molecule.

·         The size of DNA that can be amplified by this technique is 10 to 40 Kb.

Components required to carry out polymerase chain reaction (PCR):

·         DNA template (with known end sequence)

·          Primers ( the primers complementary to the known sequence of target DNA molecule,

·          taq DNA polymerase (isolated from bacteria thermus aquaticus) living in hot springs. It can withstand temperature up to 96 ⁰ C),

·          fixed buffer( to maintain favourable environment during the PCR),

·          Divalent cations (Mg²⁺ is used in general. Mn²⁺ can be also used, but at higher concentration it causes mutation),

·          monovalent cations (K⁺ is used in general)

·         Large number of DNA nucleotides

Procedures of PCR:

·         The PCR consists of 20 to 40 thermal cycles.

·         Each cycles has discrete steps

1.       Hold: the cycle starts with a temperature of 96 ⁰ C. the hold lasts for a brief period.

2.       Initializing step: the temperature is raised further to 94 to 96 ⁰ C. (if the DNA polymerase to be used is highly thermostable then the temperature can be raised up to 98 ⁰ C.)

This step lasts up to 1 to 6 minutes.

3.       Denaturation step: at the 94⁰ C to 96 ⁰ C the tubes containing the target DNA is placed in the machine.

At this temperature the DNA melts—the strands get separated by breading of hydrogen bonds. At the end of the denaturation step the result is the 2 separated ssDNA molecules.

4.       Annealing step: in this step the temperature is decreased down to 50 to 60 ⁰ C and primers are added and are carried out for 20 to 40 seconds.

Also the DNA polymerase is added too. The primers pair with the complementary sequences on target DNA molecules.

Note: annealing temperature should always be 2 to 3 ⁰ C less than melting temperature of primers, to prevent the primers from melting down.

At this temperature H-bonds are formed and DNA polymerase binds to end of primers.

5.       Elongation: at this step the temperature is raised to 70 to 75 ⁰ C.

At this temperature taq DNA polymerase acts at its best (best temperature is 72 ⁰ C)

6.       Final elongation: at this step the temperature is maintained from 70 to 74 ⁰ C for 5 to 15 minutes after last cycle of PCR, to ensure that all last DNA are fully extended.