EVALUATION

1. EVALUATION XII BOTANY 2019-20

2. REPRODUCTION1.Name the type of ovule in Primulaceae & Leguminosae? Hemianatropous in Primulaceae Campylotropous in Leguminosae

3. Name the type of flower which favours cross pollination? • Chasmogous or Unisexual

4. Although Potato tuber is an underground plant part, it is considered as a stem. Give reasons? [i] The tuber has nodes & internodes [ii] Leafy shoots appear from the nodes

5. [i] Mention the similarity between autogamy & geitonogamy ?[ii] How does geitonogamy differ from xenogamy ? • [i] In both cases pollen grains come from the same plant • [ii] In geitonogamy pollen grains are transferred from the anther to the stigma of another flower of the same plant whereas in xenogamy pollen grains are transferred from the anther to the stigma of a different flower

6. Fertilisation is essential for production of seed, but in some angiosperms, seeds develop without fertilisation [i] Give an example of an angiosperm that produces seeds without fertilisation? [ii] Explain any two ways by which seeds develop without fertilisation • Ans [i] In the members of Asteraceae / grasses seeds develop without fertilisation. It is called apomixis • [ii] The two ways are • In some species the diploid [2n] egg cell is formed without reduction division & develops into embryo without fertilisation • In many varieties of Citrus & Mango fruits some of the nucellar cells surrounding the embryo sac start dividing , protrude into the embryo sac & then develop into embryos

7. Give reasons Why?[i] most zygotes in angiosperms divide only after certain amount of endosperm is formed[ii] groundnut seeds are exalbuminous & castor seeds are albuminous[iii]micropyle remains as a pore in the seedcoat of a seed[iv]integuments of an ovule harden & the water content is highly reduced, as the seed matures[v] apple & cashew are not called true fruits • To obtain nutrition from the endosperm for the developing embryo • The groundnut seeds are exalbuminous because the endosperm is completely consumed. Whereas, in castor seeds endosperm persists. • For the entry of water & oxygen required for germination • To protect the embryo & keep the seed viable ,until favourable conditions return for germination • In apple & cashew ovary does not take part in fruit formation, instead thalamus contributes to fruit formation

8. Although sexual reproduction is a long drawn, energy intensive complex form of reproduction, many groups of organisms in Plantae prefer this mode. Why? Give three reasons? • Sexual reproduction brings about variation in the offspring • Since gamete formation is proceeded by meiosis, genetic recombination occurring during crossing over, lead to a great deal of variation in the DNA of gametes • The organism has better chances of survival in a changing environment

9. GENETICS What is true breeding line? • It means that the organism has undergone continuous self pollination with stable trait inheritance from parent to offspring

10. What is allopolyploidy?Name an allopolyploid that has succeeded as a crop? How does colchicine induce polyploidy? • The presence of two or more copies of different genomes in an organism is referred to as allopolyploidy • Triticale • Prevents the formation of spindle apparatus during mitosis

11. How will you identify the genotype of a phenotypically dominant individual? • By Test cross • The above question can be asked in different manner as follows • Work out a cross to find the genotype of a tall pea plant.Name the type of cross? • How would you find out whether a given tall garden pea plant is homozygous or heterozygous? Substantiate your answer with the help of Punnett square?

12. Name the process which results due to crossing over? What is its importance? • Recombination • Exchange of segments leads to new gene combinations which plays an important role in evolution • It reveals that genes are arranged linearly on the chromosomes • Genetic maps are based on the frequency of crossing over • It helps to understsnd the nature of mechanism of gene action • New combinations are used in plant breeding

13. A plant of Antirrhinum majus with red flowers was crossed with another plant of the same species with white flowers. The plants of the F1 generation bore pink flowers.Explain the pattern of inheritance with the help of a cross ? [OR]The F2 projeny of a monohybrid showed phenotypic & genotypic ratio as 1:2:1, unlike that of Mendels monohybrid F2 ratio. With the help of a suitable example work out a cross & explain how it is possible? • The cross can be drawn clearly • Explanation • Because the gene for red colour is not completely dominant over the recessive gene i.e., white • Pattern of inheritance : Incomplete Dominance

14. Mention the role of ribosomes in peptide bond formation? How does ATP facilitate It? • There are two sites in the large subunit of the ribosome, for subsequent aminoacids to bind & thus ,be close enough to each other for the formation of a peptide bond. The ribosome also acts as a catalyst for the formation of peptide bond. Amino acids become activated by binding with its tRNA in the presence of amino acyl synthetase & ATP

15. Draw a schematic sketch of replication fork of DNA. Explain the role of the enzymes involved in DNA replication? • Diagram • Enzymes involved in DNA replication • Helicase –To unzip the DNA strand • Topoisomerase- To maintain the fork • DNA dependent DNA polymerase to catalyse the polymerisation of nucleotides • DNA Ligase- To join the discontinuous strand or okazaki fragments formed on one of the template strands

16. Give a genetic explanation for the following cross. When a tall peaplant with round seeds was crossed with a dwarf pea plant with wrinkled seeds then all individuals of F1 population were tall with round seeds.Howeverselfing among F1 population led to a 9:3:3:1 phenotypic ratio. • Dihybrid cross to be drawn clearly • Genetic explanation will be: • Law of Dominance • Law of Segregation • Law of Independent Assortment

17. BIOTECHNOLOGY • How has the development of bioreactor helped in biotechnology? • ANS: Production of larger biomass, under controlled conditions

18. Explain the importance of a selectable marker with the help of a suitable example? • For example if a recombinant DNA bearing gene for resistance to an antibiotic [e.g, ampicillin] is transferred inti E.Coli cells, the host cells become transfoemed into ampicillin resistant cells.If these cells are spread on agar plates containing ampicillin, only transformants will grow, & the untransformed recipient cells will die as they do not contain the gene for ampicillin resistance. Thus transformed cells can be selected.The gene for ampicillin resistance, in this case is a useful selectable marker.

19. Why is Agrobacterium tumifaciens a good cloning vector ? Explain. • Agrobacterium is a soil bacterium which causes disease in many dicot plants. It is able to deliver a piece of DNA known as T-DNA to transform the normal cells into tumour cells &direct these tumour cells to produce the chemicals required by the pathogen. The tumour inducing [Ti] plasmid of Agrobacterium tumefaciens has now been modified into a cloning vector which is no more a pathogenic to the plants but still deliver genes of interest into a variety of plants.

20. You have chosen a plasmid as vector for cloning your gene. However this vector plasmid lacks a selectable marker. How would it affect your experiment? • In a gene cloning experiment ,first a recombinant DNA molecule is constructed,where the gene of interest is ligated to the vector & introduced inside the host cell[transformation]. Since, not all the cells get transformed with the recombinant/plasmid DNA, in the absence of selectable marker, it will be difficult to distinguish between transformants & non-transformants, because role of selectable marker is in the selection of transformants.

21. A mixture of fragmented DNA was electrophoresed in agarose gel.After staining the gel with ethidium bromide, no DNA bands were observed. What could be the reason? • The reasons could be • [i] DNA sample that was loaded on the gel may got contaminated with nuclease & completely degraded • [ii] Elactrodes were put in opposite orientation in the gel assembly [ie]anode towards the wells. Since DNA molecules are negatively charged, they move towards anode & hence move out of the gel instead of moving into the matrix of gel. • [iii] Ethidium bromide was not added at all or was not added in sufficient concentration & so DNA was not visible.

22. [i] Mention the property that enables the explants to regenerate into a new plant?[ii] A banana herb is virus infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant? [OR]How is it possible to recover healthy banana plants from a diseased but desirable quality banana plant.Explain? • [i] Totipotency • [ii] Healthy banana plants can be obtained from diseased plants by meristem culture. Although the plant is virus infected the apical & axillary meristem is free of virus. This meristem is removed from the plant & grown in vitro by micropropagation. The plants produced are virus free

23. What is single cell protein? What is the significance of such a protein? • The biomass produced from microorganisms can be treated or processed in industry to be used as food & is called single cell protein. • Significance of single cell protein: • [i] Its production reduces pollution as it uses organic wastes & industrial effluents. • [ii] Single cell protein provides a protein –rich diet • [iii] It fulfils the demand of protein for human diet & takes off pressure on agricultural system

24. ECOLOGY • What does ecological niche of an organism represent? • ANS:Ecological niche of an organism refers to the ranges of tolerance it utilises & itsfuntional role in the ecosystem.

25. Name two basic types of competition found amongst organisms. Which one of them is more intense & why? • The two types are • [i] Interspecific competition • [ii] Intraspecific competition • The intraspecific competition is more intense because the requirements of the individual of the species are similar

26. Why is predation required in a community of different organisms? • [i]It keeps prey population under control • [ii]It helps in maintaining species diversity in a reducing the intensity of competition among competing prey species • [iii]It acts as a conduit for energy transfer across trophic levels • [iv]Biological control methods adopted in agricultural pest control are based on the ability of the predator to regulate prey population.

27. Sometimes due to biotic /abiotic factor the climax remain in a particular seral stage {pre-climax} without reaching the climax . Do you agree with this statement, If yes give a suitable example • This can happen in cases of forest fires, landslide, in soil characteristics, &increase in herbivore population leading to over-grazing.

28. What will happen to an ecosystem ifAll producers are removedAll organisms of herbivore level are eliminatedAll top carnivore population is removed • [i] Reduction in primary productivity. No biomass available for consumption by higher trophic levels/heterotrophs • [ii]Increase in primary productivity &biomass of producers.Carnivore population will dwindle due to shortage of food • [iii]Increase in number of herbivores which leads to over grazing by herbivores, finally resulting in desertification

29. Differentiate between ‘bad ozone’ & ’good ozone’? • The ozone found in the lower atmosphere is called bad ozone • It harms both plants & animals • The ozone found in the stratosphere is called good ozone • It absorbs UV radiation & protects the living organisms from its harmful effects

30. What is an incomplete ecosystem? Explain with an example? • An ecosystem is a functional unit with biotic abiotic factors interacting with one another resulting in a physical structure. Absence of any component will make an ecosystem incomplete as it will hinder the functioning of the ecosystem.Examples of such an ecosystem can be a fish tank or deep aphotic zone of the oceans where producers are absent.

31. Explain the process of artificial hybridisation to get improved crop variety in [i] plants bearing bisexual flowers [ii] femake parent producing unisexual flowers? ORWhy is it necessary to emasculate a bisexual flower in a plant breeding programme? Mention the condition under which emasculation is not necessary? • In plants bearing bisexual flowers,the anthers are removed from the flower before they dehise. This is called emasculation. The emasculated fdlowers are covered with a bag of butter paper to prevent contamination of stigma with unwanted pollen. This process is called bagging. When this stigma attains receptivity, mature pollen grains are dusted on the stigma & the flowers are rebagged to allow the fruits to develop. • If the female parent produces unisexual flowers, emasculation is not necessary.The flower buds are bagged before the flowers open. When the stigma becomes receptive, pollen is dusted on stigma & the flower is rebagged.

32. Give two examples of biofortified crops. What benefits do they offer to the society? • Maize, Wheat, Rice ,pulses have biofortifiedvarieties. Maize hybrids have twice the amount of aminoacids, fortified wheat variety has high protein content, fortified rice has high quantity of iron. Consumption of such biofortified foods will enrich the nutritive value of our common foods & will vastly improve public health. It may even help overcome several nutrient deficiency disorders latent in our country.