Grade 12 books

Which part of the nervous system is made up of the brain and spinal cord? A) Central nervous system B) Peripheral nervous system C) Autonomous nervous system D) None of the above 2. What is the function of supporting cells (glial cells)? A) Conduct information away from the cell B) Aid the function of neurons C) Receive signals from sensory receptors D) Insulate the axons 3. What is the function of the axons in a neuron? A) Receive signals from sensory receptors B) Transmit information away from the cell C) Protect the axons with a myelin sheath D) Insulate the dendrites 4. What are the gaps in the myelin sheath called? A) Nodes of Ranvier B) Dendritic Trees C) Axon terminals D) Schwann cells 5. What is the function of motor neurons? A) Conduct impulses from sensory organs B) Send impulses from the brain to effector organs C) Only found in the central nervous system D) Help in speeding up impulse transmission

@grade_11_books1 Evolution 1,B 2, C 3, B 4. C 5. B 6, C or biochemical theory 7, ____ 8, D 9. C 10. B

Biology detailed explanation about half life fossil dating as per your request 50% of the existing c-14 will decay after each successful half-life. Half-life is the time needed for half of the atoms of a radioactive element to decay After one half – life 50% will still be radioactive After a second half-life, 75% will be decayed, 25% of the original will still be radioactive This means for example if the half life is given as 100 years the fossil remained undecayed is 50% ,then after another 100 year it remains 25% after third 100 year it remains 12.5% for the fourth 100 year it remains 6.25%.it will continoue like that. I hope you understand it well Thanks

BIOLOGY QUESTIONS FOR GRADE 12 1. Suppose a fossil initially contains 100,000 atoms of a certain radioactive element whose half-life is 10,000 years, after how many years would the number of the atoms be12500? A, 10,000 years B. 30,000 years C, 20,000 years D, 40,000 years 2, How many years have passed since Darwin’s book on the theory of evolution was published? A, About 50 years B, About 120 years C, About 160 years D. About 100 years 3, In his theory of evolution, the cause of which of the following of concepts was MISSING in Darwin’s explanation? A, Over reproduction B, Hereditary variation C, Struggle for survival D. Survival of the fittest 4, Which of the following characteristics can show the evolutionary relationships among organisms? A, Structures having similar functions B, Presence of analogous structures C. Presence of homologous structure D, Structures of having different structures 5, Which of the following evolutionary theory believes there is no beginning and ending of life? A, Cosmozoan theory B. eternity of life C. spontaneous generation D. special creationism 6, In the process of the evolution of life on earth , which of the following processes evolves last? A, Photosynthesis B. aerobic respiration C. chemosynthesis D. photo auto tropism 7, In which of geological period does the fossil record show more diverse and relatively higher forms of organisms? A, Devonian B. Permian C. Jurassic D. Cretaceous 8, If a radioactive substance that weighs one kilogram has a half-life of 100 years. What would be the percentage of the substance left after 400 years? A,50 B. 25 C. 12.5 D. 6.25 9, According to Lamarck’s theory of evolution, what is the mechanism by which evolving organisms acquire new structures? A, Mutation B. Hereditary variation C. use and dis use of body parts D. recombination of ancestral genes 10, The half life of carbon-14 is about 7680. If a fossil is 1970 years old, about what percent of its original carbon-14 is still present in the fossil? A, 50% B. 12.5% C. 6.25% D. 25%