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Edexcel IAL biology Unit 2 Exam Questions and Answers, Exams of Biology

Edexcel IAL biology Unit 2 Exam Questions and Answers

Typology: Exams

2023/2024

Available from 04/07/2024

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Download Edexcel IAL biology Unit 2 Exam Questions and Answers and more Exams Biology in PDF only on Docsity!

Questions and Answers

protein synthesis - correct answer the ribosomes in the rough endoplasmic reticulum make the proteins. the RER has a large surface area for the synthesis of the proteins. the polypeptide chain is folded into a 3-D shape and then packaged into vesicles to be transported to the Golgi apparatus. the proteins are modified in the Golgi apparatus/enzyme is activated in the Golgi apparatus. carbohydrate is added to some proteins to form glycoproteins. the proteins/enzymes are then enclosed in vesicles to form lysosomes. the lysosomes fuse with the cell membrane and release the enzymes out of the cell by exocytosis. cellulose microfibrils - correct answer many beta-glucose units are held together by 1,4-glycosidic bonds to form cellulose in a condensation reaction. every alternative monomer unit has to be turned round/inverted so the bonding can take place. the cellulose molecules formed are unbranched chains and these chains are held together by hydrogen bonds. this is called cross-linking (holding neighbouring bonds together) need for seedbanks - correct answer 1. food crop such as wheat, barley, rice and corn (horticulture).

  1. medicinal value.

Questions and Answers

  1. materials, such as paper, clothing and building materials.
  2. food for wildlife as plants are the base of all food chains.
  3. recycling carbon dioxide and producing oxygen.
  4. transpiration gives rise to rainfall. pros for seedbank - correct answer 1. since seeds are small, they take up less space when storing.
  5. if large numbers of seed are stored there is greater genetic diversity.
  6. seeds can also be stored for along time. because they can stay dormant for a long time.
  7. many different species of plants seeds can be stored easily and in similar conditions.
  8. growing plants require more regular maintenance.
  9. they are less expensive to keep than growing plants. cons for seedbank - correct answer 1. are not of interest to public.
  10. cannot spread awareness/raise funds easily.

Questions and Answers

seedbank collection - correct answer 1. seeds are collected from a large number of individual plants to ensure a high genetic diversity.

  1. seeds are x-rayed to check for fully formed embryos so that only viable seeds are stored.
  2. seeds are dried to prolong viability/survival and stored at -20dC to stop enzyme activity and prevent germination and decomposition.
  3. seeds are periodically germinated to make new seeds, replace dead and decaying seeds and check for viability. seedbank conditions - correct answer low temperatures and dry atmosphere-
  4. reduces the enzyme activity and respiration in seeds.
  5. the seed will thus be less likely to germinate/seed kept dormant.
  6. this also reduces the enzyme activity and growth of bacteria/fungi/microorganisms.
  7. this also decreases the rate of decomposition. seedbanks and genetic diversity - correct answer 1. harvest the seeds from different plants of the same species.

Questions and Answers

  1. collect seeds from plants growing in different locations/countries.
  2. this all will increase the variety of alleles in the plants by doin gthis a large gene pool can be obtained. zoos - correct answer 1. prevent extinction.
  3. maintains breeding populations when habitats are lost.
  4. breeding programmes increase numbers so endangered animals can be introduced back into the wild.
  5. zoos are used for research to gain a better understanding for conservation. 5.zoos raise awareness to educate the public on endangered species. captive breeding and genetic diversity - correct answer 1. '18 individuals is a small population/small gene pool/low genetic diversity/may have been closely related.
  6. captive breeding will increase population.
  7. the animals can be taken care of in zoos.
  8. they can also be exchanged from different zoos and may mate with other animals of different zoos.
  9. this will lead to an increase in their population size as more offspring will be produces.

Questions and Answers

  1. there will also be more genetic diversity.
  2. stud books can be kept to select mates.
  3. inbreeding must be prevented to avoid genetic drift.
  4. IVF (pg 144) can be done to make sure fertilization is successful. the zygote can be implanted into a surrogate mother.
  5. genetic diversity can be measured using DNA profiling. meiosis importance - correct answer 1. meiosis reduces the chromosome number in gametes from diploid to haploid.
  6. genetic variation is brought about in two ways :- crossing over and independent assortment.
  7. in crossing over, alleles/sections are exchanged between chromatids.
  8. this leads to the formation of recombinants.
  9. moreover, in independent assortment, the maternal and paternal genetic material is completely randomly distributed into the gametes. genetic variation in a species - correct answer 1. genetic variation is brought about in two ways in meiosis.
  10. in crossing over, sections of chromatids are exchanged.

Questions and Answers

  1. this leads to the formation of recombinants.
  2. errors in the progress lead to mutation which also introduces new combinations into the genetic make-up of the species.
  3. furthermore, in independent assortment, the maternal and paternal genetic material is distributed completely at random.
  4. moreover, a completely random ovum is fertilized by a completely different random sperm. specialized cells - correct answer 1. give a stimulus to the cell (e.g. chemical).
  5. some genes are activated while others are deactivated.
  6. only the active genes are transcribed to produce mRNA at those genes.
  7. the mRNA is then translated to make a protein/polypeptide.
  8. this protein permanently modifies the cell (and determines the structure and function of the cell). potential risks of stem cell treatment - correct answer 1. infection from donor/unsterilized equipment.
  9. increased suspectibility due to immunosuppressants.

Questions and Answers

  1. risk of cancer/abnormal growth.
  2. rejection. role of the cell cycle - correct answer 1. in the cell cycle the organism grows as the number of cells increase.
  3. asexual reproduction or mitosis leads to the production of clones or genetically identical daughter cells.
  4. tissues are also repaired and the cells are replaced. (in phase- )
  5. cell division is also controlled at checkpoints by enzymes called CDKs... prophase - correct answer 1. nuclear membrane is disintegrated.
  6. nucleolus is disintegrated.
  7. chromosomes become shortened and thickened and more visible.
  8. each chromosome now has two chromatids joined to a centromere.
  9. centrioles start moving to the pole at late prophase. metaphase - correct answer 1. centrioles reach the poles and form

Questions and Answers

spindles. (plants do not have centrioles but can form spindle fibres)

  1. chromatids line up along the metaphase plate (equator) of the spindle.
  2. centromeres of each chromatids attach with a separate microtubule of the spindle. anaphase - correct answer 1. the overlapping microtubules (spindle fibres) contract - this uses energy, pulling chromatids from each pair to opposite poles.
  3. pairs of chromatids have been separated to opposite ends. telophase - correct answer 1. spindle fibres break down.
  4. nuclear membrane and nucleolus reforms.
  5. centrioles reform and chromosomes unravel. acrosome reaction - correct answer 1. when the sperm touches the ovum, acrosome releases acrosin.
  6. the acrosome fuses with cell surface membrane of sperm.

Questions and Answers

  1. the acrosin will be released by exocytosis and will digest the zona pellucida and allow the sperm to penetrate through the barrier. cortical reaction - correct answer when the sperm cell fuses with the egg cell membrane, cortical granules in the cytoplasm of the ovum release enzymes into the zona pellucida. these enzymes destroy the sperm-binding sites and also thicken and harden the jelly of the zona pellucida to form a tough fertilisation membrane. the ion channels in the cell membrane of the ovum open and close inside the cell, instead of being electrically negative with respect to the outside, becomes positive. these all prevent polyspermy. drug testing protocols - correct answer 1. computers used to model effects.
  2. tested on human tissue in labs.
  3. tested on animals.
  4. clinical trial. testing drugs on whole animals (instead of just tissues) - correct answer 1. the drug may have an effect on other tissues.
  5. the effect on organs and systems by the drug must also be found.

Questions and Answers

  1. drug metabolism...
  2. whether the drug is toxic must also be found. clinical trials/contemporary drug testing protocols - correct answer phase 1 : tested on small group of healthy volunteers. phase 2 : larger group of patients with the disease. must be split into two groups. one group will be given the placebo. (neither the doctor or patient will know who got the new drug) - mine phase 3 : compared to existing treatments on thousands of patients (double blind trials) placebo - correct answer it is an inactive drug that is used as a control. it is compared with the actual drug and used to find the psychological effect of taking the drug or placebo. double blind trial - correct answer 1. a large group of patients are taken.
  3. they must be of the same age, gender, non-smokers, etc.
  4. the group is divided into two- one group is given the new drug , while the other is given a placebo or an existing drug.

Questions and Answers

  1. a placebo is an inactive substance which is used to compare the effect of the psychological effect and "medical?" effect of the drug.
  2. neither the doctor nor the patients know who is in which group. natural selection - correct answer random sampling - correct answer 1. form a grid using 2 tape measures perpendicular to each other.
  3. obtain random coordinates by generating random numbers from a calculator and place the quadrat at these coordinates to reduce bias.
  4. repeat in 2 different habitats in order to compare the number of individuals or the different number of species in 2 different habitats. taxonomic classification - correct answer 1. organisms with common features are placed in a group.
  5. the characteristics are assessed by observing the characteristics, (e.g. behavioural, physiological and but mainly, anatomical adaptations similarities in DNA, molecular phylogeny.)

Questions and Answers

critical evaluation of scientific ideas - correct answer 1. scientific findings can be published in a journal or newspaper.

  1. they can also be presented in a scientific conference.
  2. peer review can be done, in which other scientists can repeat the experiments to confirm or validate the findings (test reliability of data) investigating need for mineral salts for plants - correct answer - take 5 plants.
  • the plants must be planted from seedlings of the same parent plant.
  • they must be of the same age and size at the start.
  • each plant will have a different concentration of the mineral salt. the concentrations are 1%, 2%, 3%, 4% and 5%.
  • the temperature and type of soil the plants are exposed must be the same. the concentration of all the other minerals in the soil must be the same. they must be kept in the same area so they are exposed to the same light intensity and temperature
  • after every week/month, measure the growth of the plants by finding the mass/number of leaves/length of roots/height of plant.

Questions and Answers

  • repeat the investigation 5 more times , keeping all the variables the same.
  • then calculate the mean mass/number/height... investigating totipotency - correct answer investigating tensile strength. for example : suggest how a valid investigation could be carried out to produce reliable data to compare the tensile strength of white fibres and brown fibres (4) -june 14 - correct answer 1.take 9 white fibre and 9 brown fibre strings of the same length of 10cm and of same diameter.
  1. clamp one of the strings between two retort stands. ensure it is held securely.
  2. place the cushioning underneath the string. ensure the tray is kept beneath the masses, so they do not strike the bench when the string breaks.
  3. hang masses 10g at a time to the string until the string breaks. record the mass required to break the string in the results table.
  4. repeat the procedure with each of the other strings and calculate the mean mass required to break a white fibre string and a brown fibre string.

Questions and Answers

investigating tissue culture - correct answer investigating antimicrobial properties. for example : describe an investigation to determine the effect of the concentration of garlic extract on other species of bacteria. - correct answer 1. use a mortar to grind a garlic into a paste and then mix the paste with alcohol. make several mixtures like this of different garlic concentrations. the concentrations are 1%, 2%, 3%, 4% and 5%. soak a disk in each of the beakers of garlic extract. then soak one disc in only ethanol.

  1. use a marker to mark 6 places on the agar plate that has been seeded with bacteria (or take 2 agar plates and label 3 places in both of them..); label five according to the concentrations of the garlic extracts and one control.
  2. then using forceps place the discs according to their labels in the agar plate. use clean forceps for each disc.
  3. place one piece of tape on each side of the petri dish to hold it down.
  4. invert the plate and incubate at a temperature of 25dc for 48 hours.
  5. finally, use a ruler to measure the diameter of the clear zones around each disc. record your results in a suitable table. clear away all the equipment. petri dishes should be returned for sterilization.

Questions and Answers

  1. do the whole procedure, keeping everything the same, but using different species of bacteria. make sure to use garlic of the same size and parent plant. do this with atleast 4 more different species of bacteria. then repeat each of the experiments 5 more times to find the mean diameter of each of the discs. preparing root tip squash. for example : describe how to prepare a root tip squash so that the chromosomes can be seen. (4)- june 15 - correct answer 1. soak the roots in hydrochloric acid at 55dc for 5 minutes. then rinse it with tap water. cut root tips of 5-10mm in length. let them fall in a vial of acetic orcein standing on a white tile. place a lid over the vial. place the vial containing the root tips in acetic orcein in the 55dc water bath for 5 minutes to intensify the staining. after 5 minutes, use forceps to remove the tips from the vial and place them on a microscope slide. use the blunt edge of a knife to gently press on a coverslip on to the slide. gently clean slide with a paper towel. use an electron microscope to observe. describe the structure of the plasmodesmata - correct answer these are cytoplasmic bridges and are pores in the cell wall between adjacent cells. there is cytoplasm running through the plasmodesmata.

Questions and Answers

describe the role of the sperm tail (2) - correct answer it makes whip-like movements and allows the sperm to move and swim to transfer the male genetic material from the cervix to the ovum ultraviolet light has been shown to increase the risk of skin cancer. suggest how skin cancer is the result of an interaction between genotype and the environment (3) - correct answer 1. ultraviolet light is an environmental factor that causes skin cancer.

  1. ultraviolet light causes mutations in the genetic makeup, 4. affecting DNA replication in the cell cycle.
  2. this results in the formation of an oncogene and tumours.
  3. the control of the cell cycle is then lost. explain the meaning of the term totipotent stem cells. (2)

correct answer these are undifferentiated cells which can be given a stimulus to become any type of specialized cell and divide continuously by mitosis.

Questions and Answers

explain the role of mitosis and the cell cycle in the formation of the morula from the zygote. (3) - correct answer 1. increase in cell number.

  1. cells will be genetically identical.
  2. there will be an increase in the number of cell organelles during interphase.
  3. DNA replication during S-phase explain how endemic lemurs evolved in Madagascar (3) - correct answer the group of early monkeys from Africa, after arrived to Madagascar, had a mutation in their genes as they continued to in live in Madagascar. the alleles from these genes helped the lemurs better adapt to and survive in the climate with the type and amount of food they get in Madagascar. as a result these new species called lemurs were naturally selected for and reproduced to make more lemurs which also had the mutated gene. this increased the allele frequency of the mutated gene. these lemurs also survived and they never left Madagascar and so are only found there. what are the structures formed as a result of double fertilisation - correct answer diploid zygote and triploid endosperm nucleus

Questions and Answers

explain why scientists tool samples of tissue from very specific parts of the S. chirata plant (to investigate...) - correct answer this is because only certain parts of the plant can grow by mitotic division. this is usually the meristem of the root of a plant. name the three domains - correct answer Bacteria, Archaea, Eukaryota suggest two applications of the use of stem cell therapy - correct answer 1. to treat Parkinson's disease.

  1. produce transplant organs.
  2. replace/repair damaged tissue. critical evaluation of this paper by the scientific community did not fully support the conclusions. there were calls for the paper to be withdrawn. suggest how the process of critical evaluation failed to support the conclusions of this paper. (3) - correct answer 1. reference to peer review - many peer scientists individually repeated the investigation?
  3. the other scientists repeated the experiment.
  4. the results they achieved was not the same

Questions and Answers

suggest why it is difficult for a specialized cell to be reprogrammed to become a stem cell. (1) - correct answer the cells are permanently modified and so it is hard to reprogram the genes. suggest how these programmes can help conserve the lion-tailed macaque. (5) - correct answer macaques can be exchanged between zoos. a stud book can be used for the selection of mated and the macaques can mate with other macaques from different zoos and outbreeding can also be encouraged. this will result in an increase in their population size and increase their genetic diversity. the macaques can be prepared to be re-introduced into the wild by reducing their food intake. this will reinforce their wild behavior. they can then be released into a national park or reserve and can be protected from predators and poachers. describe what is meant by the tensile strength of fibres - correct answer this is measured by force required to break the fibres suggest why calcium ions affect the tensile strength of plant fibres. (2) - correct answer if there are more calcium ions, more calcium pectate will strongly bind adjacent cellulose microfibrils in the middle lamella and so the fibres will be stronger and harder to break.

Questions and Answers

describe the process of double-fertilisation in flowering plants (3) - correct answer 1. one haploid male gamete fuses with haploid egg cell.

  1. to produce a diploid zygote.
  2. one haploid male gamete fuses with two polar nuclei.
  3. to produce a triploid endosperm nucleus to soften or marcerate the tissue before staining the cells, the root tips may be placed in - correct answer hydrochloric acid the technique Woese used to classify organisms - correct answer molecular phylogeny Sclerenchyma (note) - correct answer - dead
  • supporting plant
  • not involved in transporting water and mineral ions parenchyma (note) - correct answer - living
  • packing tissue and stores food

Questions and Answers

describe a process that would not occur with the ICSI technique. - correct answer the cortical reaction would not occur as the sperm head will not touch the surface of the egg cell. cortical granules are released in this reaction which destroy the sperm binding sites on the secondary oocyte membrane(recheck) and that harden the zona pellucida. (the ion channels on the ovum also open and close to make the ovum positively charged like the outside. this all prevents polyspermy. woese suggested that bacteria and archaea were two separate groups of prokaryotic organisms. describe the evidence woese used to make this suggestion. (2) - correct answer he used molecular phylogeny and DNA profiling. woese looked at DNA. explain how secondary thickening in the cell wall contributes to the physical properties of xylem vessels. (3) - correct answer 1. secondary thickening provides greater tensile strength.

  1. secondary thickening provides extra rigidity.
  2. lignin provides waterproofing.

Questions and Answers

  1. pits present for movement of water into or out of xylem. explain the importance of nitrate ions to plants. (2) - correct answer nitrate ions are required to make amino acids and proteins. the amino acids are used for the synthesis of proteins such as enzymes, bases for synthesis of DNA, nucleic acids, for cell division, ATP as an energy source. explain how a tissue culture technique can be used to grow pitcher plants - correct answer 1. meristem cells are used in the tissue culture as only these cells can divide by mitosis.
  2. grow the explants in agar nutrient mediums.
  3. which has a low nitrate concentration.
  4. the agar also contains growth hormones.
  5. make sure to use sterilized equipment. state what is meant by the term biodiversity (2) - correct answer the number or variety of species suggest how scientists could find out if biodiversity within the town of Pripyat has increased or decreased since the Chernobyl disaster in 1986. (2) -

Questions and Answers

correct answer measure the species richness in Pripyat and compare it with the species richness of Pripyat in 1986 and over time (compare over time) explain what is meant by the term genetic diversity - correct answer the number of alleles within a gene pool or species or population. explain how a decrease in population size can result in a reduced genetic diversity. (2) - correct answer inbreeding or mating with closely related individuals such as siblings reduces the gene pool in a population the fur of koalas is not affected by their environment. koalas that live in habitats between the north and south of Australia have a range of fur colouration from grey to brown. suggest one reason for this range of fur colour. (1) - correct answer polygenic inheritance or more than one gene codes for fur colour. name two substances found in the secondary cell wall that provide support. (2) - correct answer lignin and hemicellulose

Questions and Answers

explain what is meant by the term tissue. (2) - correct answer this is a group of cells with a similar structure or function or origin explain how the structure of the cell walls in this tissue enables it to be strong and flexible. (2) - jan 15 - correct answer the cell walls consist of many cellulose microfibrils which lay parallel to one another in layers for flexibity. there is also a mesh of microfibrils in secondary cell wall for strength. the cellulose microfibrils are also bound together by calcium pectate bonds which make the fibre very strong. - look at book and rewrite suggest how molecular phylogeny can be used to determine the evolutionary relationships between the different species of penguin. (3) - jan 15 - correct answer the more sequences of bases two different species have in common, the more closely related they are. DNA profiling is used to study the sequence of the bases - recheck with book suggest how damage to the acrosome membrane could affect the fertilisation of an egg. (4) - correct answer the acrosome cannot fuse with cell surface membrane of sperm. no acrosin will be released

Questions and Answers

from the acrosome by exocytosis and so the zona pellucida will not be digested by the acrosin. explain how damage to the mitochondria could affect the ability of sperm to fertilize an egg. (3) - correct answer the mitochondria provides energy by respiration to enable the sperm to swim to the ovum. so without the mitochondria the sperm cannot move and reach the ovum to fertilize it using information in the table, comment on the relative contributions of genotype and the environment to the probability of developing lung cancer. (4) - correct answer niche - correct answer the role of an organism within the habitat in which it lives species richness - correct answer it is the number of different species in an area suggest why it is better to store seeds from several individual plants of one species rather than seeds from one individual plant. (2) -