Gobezoch › Past exams › Biology
Grade 12 Biology national exam, 2011 E.C. (2019 G.C.)
94 questions · 120 minutes. The first 5 answers are shown with explanations; sit the whole paper timed in the app to get your score and the textbook page behind every question.
- 1.Which of the following is the Greek word for life?
- A. 'Logos'
- B. 'Bios'
- C. 'Cientia'
- D. 'Cell'
Answer: B. The question tests the Greek word that means life. The Greek word is “bios,” which is also part of the word biology. A means “word” or “study”; C is not the Greek word for life; D means a basic unit of living things, not life itself. Textbook: Grade 10, unit 5 · section 5.1. - 2.What is the shape of an enzyme molecule?
- A. Globular
- B. Linear
- C. Branched
- D. Pleated
Answer: A. The question tests the general shape of an enzyme molecule. Enzymes are globular proteins, meaning they fold into compact shapes. B is wrong because linear describes a chain without the enzyme's folded shape. C is wrong because enzymes are not generally branched molecules. D is wrong because pleated describes a protein structure pattern, not the overall enzyme shape. Textbook: Grade 11, unit 3 · section 3.3. - 3.In which of the following groups of organisms are all the members unicellular?
- A. Algae
- B. Fungi
- C. Bacteria
- D. Viruses
Answer: C. The question tests which group is made up entirely of single-celled organisms. Bacteria are unicellular, meaning each organism consists of one cell. A includes algae that can be multicellular; B includes multicellular fungi; D is wrong because viruses are not cells. Textbook: Grade 12, unit 2 · section 2.11. - 4.Which of the following chromosomal errors creates a cell with an extra chromosome?
- A. Non-disjunction
- B. Inversion
- C. Deletion
- D. Duplication
Answer: A. This question tests which chromosome error can give a cell an extra chromosome. Non-disjunction is when chromosomes fail to separate properly during cell division, so a cell can receive an extra chromosome. Inversion reverses a chromosome section; deletion removes a section; duplication copies a section but does not itself mean a whole extra chromosome. Textbook: Grade 10, unit 4 · section 4.2. - 5.What is the type of scientific research that is directly concerned with studies of the way of solving problems related to human needs?
- A. Basic science
- B. Applied science
- C. Space science
- D. Current science
Answer: B. The key idea is that applied science uses scientific knowledge to solve practical problems. Research aimed directly at solving problems related to human needs is applied science. A is wrong because basic science mainly seeks knowledge; C is wrong because space science studies space; D is wrong because current science is not the name for this type of problem-solving research. Textbook: Grade 10, unit 1 · section 1.2. - 6.For which of the following purposes do biologists use centrifuges?
- A. Measuring volume
- B. Magnifying cell parts
- C. Culturing microorganisms
- D. Fractionation of cell contents
Answer, explanation and textbook page: open in the app. - 7.What is the function of DNA polymerase?
- A. It hydrolyzes the DNA molecule.
- B. It forms DNA by joining nucleotides.
- C. It converts the DNA molecule to RNA.
- D. It joins two RNA molecules to form DNA.
Answer, explanation and textbook page: open in the app. - 8.Which one of the following is commonly called the code of life?
- A. Cell
- B. Organelle
- C. Nucleus
- D. DNA
Answer, explanation and textbook page: open in the app. - 9.What is another name for secondary consumer?
- A. Producer
- B. Herbivore
- C. Carnivore
- D. Decomposer
Answer, explanation and textbook page: open in the app. - 10.In which geologic period is the evolution of humans most probably believed to have happened?
- A. Tertiary period
- B. Jurassic period
- C. Quaternary period
- D. Cretaceous period
Answer, explanation and textbook page: open in the app. - 11.Of the following patterns of innate behaviour in animals, which one is considered the simplest?
- A. Instinctive behaviour
- B. Reflex action
- C. Taxis movement
- D. Kinesis movement
Answer, explanation and textbook page: open in the app. - 12.The hypothesis which a scientist tries to disprove is called:
- A. Alternative hypothesis
- B. Ad hoc hypothesis
- C. Null hypothesis
- D. Auxiliary hypothesis
Answer, explanation and textbook page: open in the app. - 13.What are the compounds that have the same chemical composition, but different arrangement of atoms?
- A. Anomers
- B. Isomers
- C. Polymers
- D. Monomers
Answer, explanation and textbook page: open in the app. - 14.Which one of the following conditions is least likely to denature an enzyme?
- A. A high temperature
- B. An extreme pH
- C. Heavy metal ions
- D. A low temperature
Answer, explanation and textbook page: open in the app. - 15.Respiration is:
- A. Anabolic and exergonic
- B. Anabolic and endergonic
- C. Catabolic and exergonic
- D. Catabolic and endergonic
Answer, explanation and textbook page: open in the app. - 16.Both photosynthesis and respiration are involved in:
- A. Nitrogen Cycle
- B. Phosphorous Cycle
- C. Water Cycle
- D. Carbon Cycle
Answer, explanation and textbook page: open in the app. - 17.Which of the following statements best describes the role of bacteria in the nitrogen cycle? Bacteria turn:
- A. oxygen into nitrogen for plants to use.
- B. nitrogen into a usable form for plant use called ammonia.
- C. nitrogen into a usable form in a process called transpiration.
- D. carbon dioxide into oxygen during the process of photosynthesis.
Answer, explanation and textbook page: open in the app. - 18.Which one of the following terms best describes the number of different species in the biosphere or in a particular area?
- A. Biodiversity
- B. Genetic diversity
- C. Ecosystem diversity
- D. Species diversity
Answer, explanation and textbook page: open in the app. - 19.The daily cycle of activity that occurs over a 24-hour period of time is called a:
- A. Stimulus-response
- B. Kinesis behavior
- C. Circadian rhythm
- D. Taxis behavior
Answer, explanation and textbook page: open in the app. - 20.Within a few weeks after a heavy rain, pools become teemed with tadpoles. What is the source of the tadpoles?
- A. The rain water
- B. The eggs laid by frogs
- C. The decaying vegetation of the pond
- D. The mud on the floor
Answer, explanation and textbook page: open in the app. - 21.In what way does an antiretroviral drug help AIDS patients? It
- A. stops the multiplication of HIV.
- B. kills opportunistic infectious agents.
- C. stimulates multiplication of T-helper cells.
- D. provides immunity.
Answer, explanation and textbook page: open in the app. - 22.Of the following four elements, which one is the least abundant in living things?
- A. Oxygen
- B. Hydrogen
- C. Carbon
- D. Sulfur
Answer, explanation and textbook page: open in the app. - 23.If a homogenate of eukaryotic cells is spun in a centrifuge, which of the cellular organelles settles out first?
- A. Nucleus
- B. Ribosome
- C. Chloroplast
- D. Mitochondria
Answer, explanation and textbook page: open in the app. - 24.In which part of mitochondria does the Kreb's cycle take place?
- A. In the matrix
- B. On the inner membrane surface
- C. On the outer membrane surface
- D. In the inter-membrane space
Answer, explanation and textbook page: open in the app. - 25.What is the ultimate source of the electrons that replace those lost from the photosystem II during photosynthesis?
- A. Photosystem I
- B. Chlorophyll-b
- C. Chlorophyll a
- D. Water
Answer, explanation and textbook page: open in the app. - 26.Which one of the following human diseases is NOT correctly matched with its mode of transmission?
- A. Malaria - vector
- B. Sleeping sickness- physical contact
- C. Cholera - contaminated water
- D. Influenza - droplet infection
Answer, explanation and textbook page: open in the app. - 27.Which clinical test is routinely performed to diagnose patients for AIDS?
- A. Culturing opportunistic infectious agents
- B. Culturing the virus on a special media
- C. Serological test for anti-HIV antibody
- D. Determining hemoglobin amount
Answer, explanation and textbook page: open in the app. - 28.Which bacterial genus fixes nitrogen in the nodules of leguminous plants?
- A. Agrobacterium
- B. Escherichia
- C. Rhizobium
- D. Azobacter
Answer, explanation and textbook page: open in the app. - 29.One of the following agricultural practices does NOT have a negative effect on biodiversity?
- A. Use of pesticides
- B. Use of insecticides
- C. Growing improved varieties
- D. Growing landraces
Answer, explanation and textbook page: open in the app. - 30.On which of the following points do Lamarck's and Darwin's theories of evolution agree?
- A. Evolution produces new species
- B. Evolution occurs by natural selection
- C. All living things tend to over reproduce
- D. New structures arise by use-and-disuse
Answer, explanation and textbook page: open in the app. - 31.What is the behavior that an animal learns to ignore a trivial stimulus that is repeated many times?
- A. Sensitization
- B. Insight learning
- C. Habituation
- D. Latent learning
Answer, explanation and textbook page: open in the app. - 32.One of the following is true about a behavior that has a fixe daction pattern.
- A. It is a learned behavior.
- B. It is always done in the same way.
- C. It can be perfected through experience
- D. It does not need a stimulus to trigger it.
Answer, explanation and textbook page: open in the app. - 33.If a chimpanzee piles up boxes and climbs on it to reach a bunch of banana hanging from a ceiling, which behavior is manifested?
- A. Operant conditioning
- B. Trial and error learning
- C. Insight learning
- D. Latent learning
Answer, explanation and textbook page: open in the app. - 34.Which of these elements is known to have less than 10% occurrence in many cells?
- A. Carbon
- B. Hydrogen
- C. Nitrogen
- D. Oxygen
Answer, explanation and textbook page: open in the app. - 35.One of the following is a non-carbohydrate molecule.
- A. Starch
- B. Cellulose
- C. Glycogen
- D. Collagen
Answer, explanation and textbook page: open in the app. - 36.Which model of enzyme action requires that the shape of the substrate molecule is complementary to that of the active site?
- A. The induced-fit model
- B. The lock-and-key model
- C. The activation energy model
- D. The enzyme function model
Answer, explanation and textbook page: open in the app. - 37.If the average diameter of the human red blood cell is 0.000007 m, which one is its correct diameter when expressed in a smaller unit?
- B. 0.00007μm 0.007 μm
- C. 7 mm
- D. 7000 nm
Answer, explanation and textbook page: open in the app. - 38.Which procedure allows biologists to separate different cellular organelles and study their structures and compositions separately?
- A. Dehydrogenation
- B. Cell fractionation
- C. Phosphorylation
- D. Polymerization
Answer, explanation and textbook page: open in the app. - 39.How many ATP molecules are produced during the complete cellular respiration of one glucose molecule?
- A. 2
- B. 4
- C. 18
- D. 36
Answer, explanation and textbook page: open in the app. - 40.What is the main method of transmission of botulism?
- A. Direct contact
- B. Droplet infection
- C. Eating contaminated food
- D. Drinking contaminated water
Answer, explanation and textbook page: open in the app. - 41.From which group of microorganisms was the first antibiotics produced?
- A. Members of viruses
- B. Members of the fungi
- C. Gram-negative bacteria
- D. Gram-positive bacteria
Answer, explanation and textbook page: open in the app. - 42.What is a capsid?
- A. The genetic material of a virus
- B. The DNA of a virus
- C. The RNA of a virus
- D. The protein shell of a virus
Answer, explanation and textbook page: open in the app. - 43.What is the general name of crop plants that add nitrogen to the soil because of their symbiotic association with certain types of bacteria?
- A. Nodules
- B. Legumes
- C. Cereals
- D. Herbs
Answer, explanation and textbook page: open in the app. - 44.If two parents with genotypes 'Aa' are cross-bred and that there is no codominance in the inheritance pattern, what proportion of the offspring would have genotypes exactly like that of their parents?
- A. 50%
- B. 75%
- C. 100%
- D. 25%
Answer, explanation and textbook page: open in the app. - 45.Which of the following is an example of a cell formed by reduction division?
- A. Nerve cells
- B. Kidney cells
- C. Bone cells
- D. Sperm cells
Answer, explanation and textbook page: open in the app. - 46.One of the following sources of evidence provides a more direct support to the process of Charles Darwin's theory of evolution.
- A. Physiology
- B. Anatomy
- C. Genetics
- D. Geographical distribution
Answer, explanation and textbook page: open in the app. - 47.Which animal behaviour pattern is best illustrated by the famous Pavlov's dog?
- A. Associative learning
- B. Latent learning
- C. Instinctive behaviour
- D. Habituation
Answer, explanation and textbook page: open in the app. - 48.Through which of the following methods can blood be separated into its cellular and fluid parts?
- A. Separating funnel
- B. Fractional distillation
- C. Centrifuging
- D. Simple distillation
Answer, explanation and textbook page: open in the app. - 49.The most abundant inorganic molecule in the atmosphere that traps heat is:
- A. H₂S
- B. O₂
- C. H₂O
- D. CO₂
Answer, explanation and textbook page: open in the app. - 50.Which of the following statements is NOT correct about the effect of temperature on enzymes.
- A. Raising the temperature increases the kinetic energy of molecules.
- B. A ten degree centigrade increase in temperature may increase the activity of most enzymes by 50% to 100%.
- C. Most enzymes are insensitive to temperature at low pH.
- D. Most enzymes are denatured at 40 Degree Centigrade.
Answer, explanation and textbook page: open in the app. - 51.Organelles in the cytoplasm that are known as 'power house' of the cell are:
- A. mitochondria
- B. chloroplast
- C. ribosome
- D. cellulose
Answer, explanation and textbook page: open in the app. - 52.Which of the following is NOT a function of lysosomes?
- A. Autophagy
- B. Autolysis
- C. Digestion
- D. Synthesis
Answer, explanation and textbook page: open in the app. - 53.The different steps for complete aerobic respiration are:
- A. Glycolysis and oxidative phosphorylation.
- B. Glycolysis and Krebs cycle.
- C. Glycolysis. Krebs cycle and terminal oxidation.
- D. Krebs cycle and terminal oxidation.
Answer, explanation and textbook page: open in the app. - 54.Which of the following processes indicate the process of photosynthesis?
- A. Reductive, exergonic and catabolic
- B. Reductive, endogenic and catabolic
- C. Reductive, exergonic and anabolic
- D. Reductive, endergonic and anabolic
Answer, explanation and textbook page: open in the app. - 55.The active sludge method of Sewage treatment is based on the principle of
- A. decomposition and removal of organic matter.
- B. removal of polluting organic matter through filtration.
- C. denitrification.
- D. anaerobic respiration.
Answer, explanation and textbook page: open in the app. - 56.When an organism containing a gene which does NOT belong to it and is derived from Somewhere else, the organism is said to be:
- A. hybrid.
- B. transgenic.
- C. mutant.
- D. clonal.
Answer, explanation and textbook page: open in the app. - 57.When is reverse transcriptase a useful enzyme? When:
- A. nutrients are scarce.
- B. there are no host cells present
- C. spikes are forming in the new virus.
- D. an RNA virus converts its RNA to DNA.
Answer, explanation and textbook page: open in the app. - 58.If you were to travel from the Arctic Circle to the Equator, what sequence of biomes would you most likely pass through?
- A. Tundra, temperate forest, taiga, tropical rain forest
- B. Taiga, tundra, temperate forest, tropical rain forest
- C. Tundra, taiga, temperate forest, tropical rain forest
- D. Tropical rain forest, temperate forest, taiga, tundra
Answer, explanation and textbook page: open in the app. - 59.The fact that Ethiopia is a regional center of biological diversity which of the following diversity is expressed?
- A. The many mountain, valleys, rivers and scenic beauty.
- B. High number of endemic wild and domestic plant species.
- C. Wide range of altitude and climate.
- D. The number of different biomes in the country.
Answer, explanation and textbook page: open in the app. - 60.Under ideal conditions and unlimited resources, continuous population growth pattern is known as:
- A. density dependent growth
- B. logistic growth
- C. exponential growth
- D. population distribution growth
Answer, explanation and textbook page: open in the app. - 61.If colour blindness is sex linked and a colour-blind man marries the daughter of a colour-blind person, which of the following is their progeny?
- A. None of her daughters are colour-blind
- B. All her sons are colour-blind
- C. All her daughters are colour-blind
- D. Half of her sons are colour-blind
Answer, explanation and textbook page: open in the app. - 62.Transfer of a gene or genes through a virus is called:
- A. transformation
- B. transduction
- C. genetic engineering
- D. conjugation
Answer, explanation and textbook page: open in the app. - 63.Which of the following concept is attributed to Charles Darwin?
- A. Use and disuse of organs is of great importance in evolution.
- B. Every cell must come from a pre-existing cell.
- C. In the struggle for existence, the fittest would survive.
- D. The gametes will carry only one of a pair of contrasting characters.
Answer, explanation and textbook page: open in the app. - 64."Skinner box" is used for experiments in:
- A. operant conditioning
- B. classical conditioning
- C. migration
- D. taxis
Answer, explanation and textbook page: open in the app. - 65.Which of the following factors affects enzyme activity without denaturing the enzyme molecule?
- A. High temperature
- B. Low temperature
- C. High pH
- D. Low pH
Answer, explanation and textbook page: open in the app. - 66.Which of the following can reverse or reduce an allosteric enzyme inhibition?
- A. Adding more substrate
- B. Adding more end products
- C. Depleting the substrate
- D. Depleting the end product
Answer, explanation and textbook page: open in the app. - 67.In what way do retro viruses differ from the other RNA viruses?
- A. Their genetic material is RNA.
- B. They are parasitic.
- C. They copy RNA to DNA.
- D. They are smaller in size.
Answer, explanation and textbook page: open in the app. - 68.As an ecological succession passes from a lower to a higher seral stage, which of the following will NOT happen?
- A. The community gets more complex
- B. Ecological niches increase
- C. Species get more diverse
- D. Soil nutrient is depleted
Answer, explanation and textbook page: open in the app. - 69.What is the population growth phase of the current world population?
- A. Exponential phase
- B. Lag phase
- C. Decline phase
- D. Static phase
Answer, explanation and textbook page: open in the app. - 70.If allowed to self-pollinate, which of the following pea genotype would produce progeny with 9 : 3 : 3 : 1 phenotypic ratio?
- A. RRYy
- B. RrYY
- C. RRYY
- D. RrYy
Answer, explanation and textbook page: open in the app. - 71.How many nucleotides are needed to form codons for a protein that is 100 amino acids long?
- A. 100 nucleotides
- B. 200 nucleotides
- C. 300 nucleotides
- D. 640 nucleotides
Answer, explanation and textbook page: open in the app. - 72.Which of the following is the common idea held by all the creationists?
- A. Life is eternal.
- B. Life was created by a supernatural being.
- C. All life was created in six days.
- D. Life came to earth from elsewhere in the universe.
Answer, explanation and textbook page: open in the app. - 73.Among the following, which one had the cranial capacity of about the same size as that Of Homo sapiens?
- A. Homo habilis
- B. Homo erectus
- C. Lucy
- D. The Neanderthal man
Answer, explanation and textbook page: open in the app. - 74.One of the following behavioral pattern of human babies is more or less similar to the imprinting of newly hatched goose?
- A. Fixed action pattern
- B. Attachment-formation
- C. Habituation
- D. Breast suckling
Answer, explanation and textbook page: open in the app. - 75.In the human body, which conditions are generally considered optimum for most enzymes? 37 C ∘ 90 C ∘
- A. and pH 1.0
- B. and pH 7.0 5 C ∘ 37 C ∘
- C. and pH 9.0
- D. and pH 7.0
Answer, explanation and textbook page: open in the app. - 76.Which of the following has the highest water potential than all the other?
- A. Animal cells
- B. Different solutions
- C. Pure liquid water
- D. Different suspensions
Answer, explanation and textbook page: open in the app. - 77.Which of the four stages in the aerobic respiration of glucose does NOT produce ATP?
- A. Glycolysis
- B. The link reaction
- C. Krebs cycle
- D. Electron transport & chemiosmosis
Answer, explanation and textbook page: open in the app. - 78.In an experiment to study photosynthesis, a plant was provided with radioactive carbon dioxide as a metabolic tracer and the radioactive carbon was incorporated first into oxaloacetate. Which one of the following would best characterize this plant?
- A. C4 plant
- B. C3 plant
- C. CAM plant
- D. Heterotrophic plant
Answer, explanation and textbook page: open in the app. - 79.Which of the following is a correct statement about the difference between a bacterium and a virus?
- A. DNA is present in the former, but absent in the latter.
- B. The former is cellular, but the latter is a cellular.
- C. Protein is absent in the former, but present in the latter.
- D. The former causes malaria, but the latter causes cholera.
Answer, explanation and textbook page: open in the app. - 80.Which of the following statements about transgenic organisms is correct?
- A. A bacterium that contains genes from another organism.
- B. A plant that has been cross-pollinated with another plant.
- C. An animal that has been reared in isolation in the laboratory.
- D. Any organism in which a foreign gene is added to its genome.
Answer, explanation and textbook page: open in the app. - 81.If a radioactive substance that weighs 5,600 grams and has a half-life of 100 years is left with 700 grams, for how long has the decaying activity been undergoing?
- A. 100 years
- B. 200 years
- C. 300 years
- D. 500 years
Answer, explanation and textbook page: open in the app. - 82.What is the survival value of a social behaviour in which some birds move in large groups?
- A. Protection of a territory
- B. Protection from predators
- C. Technique for trapping prey
- D. Displaying courtship activities
Answer, explanation and textbook page: open in the app. - 83.What is the biome of the world where succulent plants are commonly found?
- A. Hot deserts
- B. Thorn forests
- C. Deciduous forests
- D. Temperate grasslands
Answer, explanation and textbook page: open in the app. - 84.Which of the following statements is NOT correct?
- A. Employers may not dismiss an employee because of his/her HIV status.
- B. HIV-positive people are forced by law to disclose their HIV status.
- C. There is no medication that can reduce your chances of contracting HIV.
- D. Mothers can give their babies HIV by means of breastfeeding.
Answer, explanation and textbook page: open in the app. - 85.Lipids to become sphingolipids must contain:
- A. Glycerol
- B. Nitrogen
- C. Alcohol
- D. Triglycerides
Answer, explanation and textbook page: open in the app. - 86.If other conditions were to remain constant, which one of the following changes would explain a reduced rate of activity in an enzyme-controlled reaction? Increase in
- A. concentration of end-product.
- B. substrate concentration.
- C. enzyme concentration.
- D. temperature towards the optimum.
Answer, explanation and textbook page: open in the app. - 87.Which of the following statements best describes an induced fit-model?
- A. an active site alters shape such that it is ready to accept a substrate.
- B. a substrate adopts the correct binding conformation before entering an active site.
- C. a substrate binds to an active site and alters the shape of the active site.
- D. an active site alters the shape of the substrate such that it can adopt the necessary active conformation for binding.
Answer, explanation and textbook page: open in the app. - 88.Which of the following happens if a nucleolus is missing in a cell?
- A. Nuclear pores will be blocked
- B. Endoplasmic reticulum will be unfolded
- C. DNA synthesis will be enhanced
- D. Ribosomal functions will be disrupted
Answer, explanation and textbook page: open in the app. - 89.Which one is first inhibited if a cell contains excess of ATP?
- A. Krebs cycle
- B. Oxidative phosphorylation
- C. Glycolysis
- D. Electron transport
Answer, explanation and textbook page: open in the app. - 90.Which of the following results in the production of oxygen during photosynthesis?
- A. Reducing NADP+
- B. Splitting of the water molecules
- C. Electron transfer system of photosystem I
- D. Electron transfer system of photosystem II
Answer, explanation and textbook page: open in the app. - 91.Which one of the following happens during integration of viruses in host cells?
- A. The virus takes over the host cell machinery.
- B. The viral DNA enters the host cell.
- C. The virus attaches to a host cell repector.
- D. The viral DNA is inserted into the host DNA.
Answer, explanation and textbook page: open in the app. - 92.The following statements are correct regarding ecological succession EXCEPT:
- A. Ecological succession is a random process.
- B. The food chain relationship becomes more complex.
- C. The role of decomposers becomes more and more important.
- D. Species diversity increases as succession proceeds
Answer, explanation and textbook page: open in the app. - 93.Which one of the following phenomena supports Darwin’s concept of natural selection in organic evolution?
- A. Development of transgenic animals
- B. Production of ‘Dolly’, the sheep by cloning
- C. Prevalence of pesticide resistant insects
- D. Development of organs from ‘stem cells’ for organ transplantation
Answer, explanation and textbook page: open in the app. - 94.One of the following is NOT true about operant conditioning.
- A. It is based on innate behaviors.
- B. It is based on reward and punishment.
- C. It is concerned with learnt behavior.
- D. It is based on consequences of actions.
Answer, explanation and textbook page: open in the app.