Evolution, Adaptation, Species, Biology, Climate variability and change 12th Biology Revision
We are revising the entire syllabus of 12th biology in the form of sample paper. Cbsc sample papers and that too, particularly for your batch 2021 batch already, we have solved, we have discussed, we have analyzed, we reflected on sample papers four, so one two four we have done in this session. We are going for sample paper, five, so yesterday’s session. I gave you questions of section a and i have told you to write the answers and if the answers are ready, you can compare your answers with my answers. Number one question number one mention the number of cells in the following stages: embryonic stage. Zygote number of cells, of course zygote – is always single cell morula morula. Of course we know 16 cell stage, blastocyst blastocyst 64 cells will be there. So this is answer for question number. One question number two: during reproduction, the chromosome number 2n reduces to half n in the gametes and again resume the original number 2n in the offspring. What are the processes through which these events take place? Answer the reduction division that is having chromosomal number half of that takes place during gametogenesis genesis means taking, but the gamete taking but sperm and oh and regaining the two in number occur as a result of fertilization. So sperm and o1 will have n number. Two n becomes n and n numbered spawn n numbered woven, joined together. Fertilization takes place resulting in zygote zygote regains the two year number.
That is nothing question number three. A pedigree chart is given below a particular generation shows a trait, irrespective of success present in both male and female. Neither of the parents of the particular generation shows the trait draw your conclusion on the basis of the pedigree chapter that is given now, the trait is, as you guess, autosomal linked, resistive, autosomal recessive in nature. Both the parents are carriers that is heterozygous, hence among offspring. Few show there are in fact, three plus two five offspring out of the five. Only three are showing and irrespective of the sex, both male as well as female, are having this problem, so the other offsprings are either normal or carrier. Not so if the among the offsprings all are suffering as well as carriers and some are healthy, then it is autosomal. Resistive next question number four: what is ectopic pregnancy, ectopic pregnancy, also known as tubal pregnancy, is a complication of pregnancy in which the embryo attaches outside the uterus, particularly in the fallopian tube. Then we say: ectopic pregnancy, question number five pollinating species of wasps show mutualism with specific fig plants, mention the benefits of the female verbs derived from the fig trees from such an interaction. The answer the wasp uses the fig plant ovary for ob portion deposition of the it also uses developing seeds of the fruit to nourish nourish its larvae. So there is a double benefit for the last question. Sixth, define multiple allelism when more than two alternative forms of a gene are present on the same locus, it is said to exhibit multiple alleles of multiple means.
Many alleles question: seven suppose two individuals, one have three chromosomes of a type, while the other have one chromosome effort, type name, this phenomena and give example of each type it’s trisomy. So one is trisomic and monozomic condition is resulted due to non disjunction. It may lead to down syndrome that is one chromosome extra 47 are turner’s syndrome. One chromosome is less instead of 46, 45 or x0 question number eight. Why sharing of injection needles between two individuals is not recommended? Sharing of injection needles may act as a mode of transmission of certain diseases, including aids. Thus it’s not recommended question number nine, for which variety of indian rice the patent was filed by usa company. All of us know it is for basmati rice. The patent was filed for basmati rice later on. Of course, they tried to get the potency for even tulasi oximum sanctum, turmeric, turmeric, okay and they even tried for tamarind. All these question number ten name: the plant whose sap is used in making toddy mention the process involved in that palm tree sap is used in making tidy by the process of fermentation. So it is the palm tree next question number 11 assertion, reasoning, assertion and reasoning. The answer is, a assertion is true, but reason is false. What is that explanation? An organism with a lethal means? Dangerous mutation may not even develop beyond the zygote stage due to change in the gene, but all kinds of mutations are not lethal, whether they’re.
What we said in region all types of genes mutations are lethal, but all are not lethal that’s. Why a is the answer? The mutation is the main source of variation essential for evolution. Next choice is there for that question question number 11 and for that answer also is a both assertion and reason are correct. Explanation in snap dragon flower, a cross between true breeding white and red colored flower produces pink color, so w w was says, small, w, small, w, okay, so white versus pink. You are getting capital w small w right. This happens due to incomplete dominance. So there is, this: dominant gene is not expressing fully that’s how this fellow becomes pink pink flowers, so this happened due to incomplete dominance of aliens with the other. Hence answer a is correct. Question number 12 again: question number one: a both assertion and reason are false. Both are false, that is, drugs, margina and lsd are not used as analgesics or painkillers. These drugs stimulate brain function and create a feeling of happiness under the influence of these drugs that’s. How both are wrong question number 13. Both assertion and reason are true. Answer is a what is the explanation. Uea, that is the terminating codon uae of mrna, does not code for any amino acids, so it is stop codon or terminating codon. If the termination codon is present on mrna, the protein synthesis stops abruptly at that point, because it is top quota.
Question number 14, a again answer, assertion and reason: both are correct statements and the reason is correct explanation for assertion. So here what is the explanation among animals? Insects are the most species, rich taxonomic group, making up more than 70 percent of the total that pays out of every 10 animals on this planet. Seven are insects, that’s. Why uh a is correct and question number 15 there’s a case study. We were talking about the organisms and the vertebrate invertebrate species adaptations and all that. So there was a big paragraph and the paragraph is followed by questions. So, first one an animal that can survive up to 10 degrees centigrade and 40 centigrade 40 degree centigrade both can be placed under the category of. Of course. We know regulators question number one b regulator question two which of the following is an important adaptation of animals to cold climate. Again, it is the d answer: reduced surface area to volume ratio. This is the adaptation question number three. When organisms change their location to escape from harsh environment, it is called as migration. They move from place to place from uncomfortable zone to comfortable zone which of the following is an incorrect match. Now the incorrect is answer d, lizard, east duration and diagram based on fifth one in the given diagrammatic representation of organism response identify a that is you have to identify conformer. So there is a external level and internal level, so conformers will be having the better adaptation.
Now question number 16: again one paragraph is given about the sexual reproduction and almost it is the whole description of the anteridium as well as archaeology. Now there are five questions to be followed question one: each lobe in typical angiosperm anther has two thick. All of us know two means uh thicker means layer. The question two innermost layer of microsporangium is the atom b. The center of the microsporangium is occupied by sporogenous tissue answer c, and the answer for the process of formation of microspores from poland, mother cell through meiosis, is called microsporogenesis and the last question with assertion reasoning. Both assertion reasons are true, but reason is not correct. Explanation of the assertion answer is b. What is the assertion as the answer mature and dehydrate, the microspores dissociate from each other and develop into your pollen rate? So assertion is true reason, as the anther develop, the cell of the sporogenous tissue undergoes neotic extrusion to form microscope attracts so reason. Also true, but reason is not explaining the assertion. That is how dissociation takes place, how pollen brain is developed. That is not there. Hence, answer is b, so this is how you need to explain section a in a specific way. In our next session we will answer section b as well as section c.