A2 Biology Revision Checklist. Name..

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1 A2 Biology Revision Checklist Name.. 1

2 Unit 4 Index Unit 5 Populations and ecosystems Investigating populations Variation in population size Competition Predation Human populations Energy and ATP Overview of photosynthesis The light-dependent reaction The light-independent reaction Factors affecting photosynthesis Glycolysis Link reaction and Krebs cycle Electron transport chain Anaerobic respiration Food chains and food webs Energy transfer between trophic levels Ecological pyramids Agricultural ecosystems Chemical and biological control of agricultural pests Intensive rearing of domestic livestock The carbon cycle and global warming The nitrogen cycle Succession and Conservation of habitats Monohybrid inheritance Sex inheritance and sex linkage Allelic frequencies and population genetics Selection and speciation Sensory reception Nervous control Control of heart rate Role of receptors Coordination Neurones The nerve impulse Passage of an action potential and its speed Synaptic transmission Muscle contraction Principles of homeostasis Regulation of body temperature Hormones and the regulation of blood glucose Diabetes and its control Control of the oestrous cycle Genetic control of protein structure and function Polypeptide synthesis transcription and splicing / translation Gene mutation Totipotency and cell specialisation Regulation of transcription and translation Producing DNA fragments In vivo / in vitro cloning Use of recombinant DNA technology Gene therapy Locating and sequencing genes Screening for clinically important genes Genetic fingerprinting 2

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4 Unit 4 Populations and environment *(page numbers from Biology A2 book by Glenn Toole, Susan Toole) Populations and ecosystems (pages 4-5) Populations A population is all the organisms of one species in a habitat. Populations of different species form a community. Within a habitat a species occupies a niche governed by adaptation to both biotic and abiotic conditions. What is meant by the terms environment, biotic, abiotic and biosphere? What is an ecosystem? What is meant by the terms population, community and habitat? What is a niche? Investigating populations (pages 6-9) candidates should carry out experimental and investigative activities, including appropriate risk management consider ethical issues arising when carrying out fieldwork, particularly those relating to the organisms involved and their environment analyse and interpret data relating to the distribution of organisms, recognizing correlations and causal relationships appreciate the tentative nature of conclusions that may be drawn from such data. Random sampling with quadrats and counting along transects to obtain quantitative data. The use of percentage cover and frequency as measures of abundance. The use of mark release recapture for more mobile species. What factors should be considered when using a quadrat? How is a transect used to obtain quantitative data about changes in communities along a line? How is the abundance of different species measured? How can the mark-release-recapture method be used to measure the abundance of mobile species? 4

5 Variation in population size (pages 10-12) Population size may vary as a result of the effect of abiotic factors interactions between organisms: interspecific and intraspecific competition and predation. Human population size and structure, population growth rate, age-population pyramids, survival rates and life expectancy. interpret growth curves, survival curves and age-population pyramids calculate population growth rates from data on birth rate and death rate. relate changes in the size and structure of human populations to different stages in demographic transition. Competition (pages 13-16) - The effects of interspecific competition on population size - Competing to the death - Effects of abiotic and biotic factors on population size Predation (pages 17-19) - Effect of predator prey relationship on population size - Example - The Canadian lynx and the snowshoe hare Human populations (pages 20-23) - Factors affecting the growth and size of human populations - Factors affecting birth rates / Factors affecting death rates / Population structure / Survival rates and life expectancy - The demographic transition of the human population What factors determine the size of a population? Which abiotic factors affect the size of a population? How do each of these factors influence population size? What is intraspecific competition? What factors do different species compete for? What is interspecific competition? How does interspecific competition influence population size? What is predation? How does the predator prey relationship affect the population size of the predator and prey? How does the human population growth curve differ from that of most other organisms? What factors affect the growth and size of human populations? 5

6 Energy and ATP (pages 28-31) How ATP stores energy Synthesis of ATP from ADP and phosphate Roles of ATP as the immediate source of energy for biological processes. Overview of photosynthesis (pages 32-34) Site of photosynthesis - Structure of the leaf Structure and role of chloroplasts in photosynthesis The light-independent and light-dependent reactions in a typical C3 plant. The light-dependent reaction (pages 35-37) The light-dependent reaction in such detail as to show that light energy excites electrons in chlorophyll energy from these excited electrons generates ATP and reduced NADP the production of ATP involves electron transfer associated with the electron transfer chain in chloroplast membranes photolysis of water produces protons, electrons and oxygen. The light-independent reaction (pages 38-40) The light-independent reaction in such detail as to show that carbon dioxide is accepted by ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP) ATP and reduced NADP are required for the reduction of GP to triose phosphate RuBP is regenerated in the Calvin cycle Triose phosphate is converted to useful organic substances. Factors affecting photosynthesis (pages 41-44) Effect of light intensity on the rate of photosynthesis Effect of carbon dioxide concentration on the rate of photosynthesis Effect of temperature on the rate of photosynthesis - Measuring photosynthesis What is energy and why do organisms need it? How does ATP store energy? How is ATP synthesised? What is the role of ATP in biological processes? How is the plant leaf adapted to carry out photosynthesis? What are the main stages of photosynthesis? How is ATP made during the light-dependent reaction? What is the role of photolysis in the light-dependent reaction? How are chloroplasts adapted to carry out the light-dependent reaction? How is the carbon dioxide absorbed by plants incorporated into organic molecules? What are the roles of ATP and reduced NADP in the light-independent reaction? What is the Calvin cycle? What is meant by the concept of limiting factors? How can photosynthesis be measured? 6

7 Glycolysis (pages 50-52) Energy yields from glycolysis: glycolysis takes place in the cytoplasm and involves the oxidation of glucose to pyruvate with a net gain of ATP and reduced NAD Link reaction and Krebs cycle (pages 53-55) pyruvate combines with coenzyme A in the link reaction to produce acetylcoenzyme A The significance of the Krebs cycle - Coenzymes in respiration in a series of oxidation-reduction reactions the Krebs cycle generates reduced coenzymes and ATP by substrate-level phosphorylation, and carbon dioxide is lost acetylcoenzyme A is effectively a two carbon molecule that combines with a four carbon molecule to produce a six carbon molecule which enters the Krebs cycle Electron transport chain (pages 55-57) The electron transport chain and the synthesis of ATP - Sequencing the chain synthesis of ATP by oxidative phosphorylation is associated with the transfer of electrons down the electron transport chain and passage of protons across mitochondrial membranes. Anaerobic respiration (pages 58-60) Glycolysis followed by the production of ethanol or lactate and the regeneration of NAD in anaerobic respiration. Production of ethanol in plants and some microorganisms Energy yields from anaerobic and aerobic respiration - Investigating where certain respiratory pathways take place in cells Where does glycolysis fit into the overall process of respiration? What are the main stages of glycolysis? What are the products of glycolysis? What is the link reaction? What happens during the Krebs cycle? What are hydrogen carrier molecules and what is their role in the Krebs cycle? Where does the electron transport chain take place? How is ATP synthesised in the electron transport chain? What is the role of oxygen in aerobic respiration? How is energy released by respiration in the absence of oxygen? How is ethanol produced by anaerobic respiration? How is lactate produced by anaerobic respiration? 7

8 Food chains and food webs (pages 64-66) Producers / Consumers / Decomposers / Food chains / Food webs Energy transfer between trophic levels (pages 67-69) Energy losses in food chains Calculating the efficiency of energy transfers Ecological pyramids (pages 70-72) Pyramids of number / Pyramids of biomass / Pyramids of energy Agricultural ecosystems (pages 73-75) Comparison of natural and agricultural ecosystems - Energy input - Productivity Chemical and biological control of agricultural pests (pages 76-79) Biological control / Integrated pest-control systems / How controlling pests affects productivity the use of natural and artificial fertilisers the use of chemical pesticides, biological agents and integrated systems in controlling pests on agricultural crops Intensive rearing of domestic livestock (pages 80-83) Features of intensive rearing of livestock - Economic and environmental issues concerned with intensive food production How does energy enter an ecosystem? How is energy transferred between the organisms in the ecosystem? What is meant by the terms: trophic level, food chain, food web, producer, consumer and decomposer? How is energy lost from the ecosystem? What percentage of energy is transferred from one trophic level to the next? How is energy lost along a food chain? Why do most food chains have no more than five trophic levels? How is the percentage efficiency of energy transfers calculated? What are the different types of ecological pyramid? What are the relative merits and disadvantages of each? What is an agricultural ecosystem? How do natural and agricultural ecosystems differ? What is meant by productivity? How is net productivity calculated? What are pests and pesticides? What are the features of an efficient pesticide? How are biological agents used to control pests? What is integrated pest management? How does rearing animals intensively increase the efficiency of energy conversion? 8

9 Nutrient cycles Chemical elements are recycled in ecosystems. Microorganisms play a key role in recycling these elements. The role of microorganisms in the carbon and nitrogen cycles in sufficient detail to illustrate the processes of saprobiotic nutrition, ammonification, nitrification, nitrogen fixation and denitrification The carbon cycle and global warming (pages 88-94) The importance of respiration, photosynthesis and human activity in giving rise to short-term fluctuation and long-term change in global carbon dioxide concentration. The roles of carbon dioxide and methane in enhancing the greenhouse effect and bringing about global warming. analyse, interpret and evaluate data relating to evidence of global warming and its effects on the yield of crop plants the life-cycles and numbers of insect pests the distribution and numbers of wild animals and plants. The nitrogen cycle (pages ) Stages of cycle: Ammonification / Nitrification / Nitrogen fixation / Dentrification The environmental issues arising from the use of fertilisers. Leaching and eutrophication. Where does carbon enter the living component of an ecosystem? Where does carbon enter the non-living component of an ecosystem? What role is played by saprobiotic organisms in the carbon cycle? What is the greenhouse effect? Which are the major greenhouse gases and where do they come from? Why is the production of greenhouse gases increasing? How do greenhouse gases contribute to global warming? What are the consequences of global warming? How is nitrogen recycled in ecosystems? What is the role of saprobiotic microorganisms in this recycling? What do you understand by the terms ammonification, nitrification, nitrogen fixation and denitrification? Where does nitrogen enter the living component of an ecosystem? Where does nitrogen enter the non-living component of an ecosystem? Why are fertilisers needed in agricultural ecosystems? How do natural and artificial fertilisers differ? How do fertilisers increase productivity? What are the main environmental effects of using nitrogen fertilisers? What is meant by leaching and eutrophication? 9

10 Succession and Conservation of habitats (pages ) Succession from pioneer species to climax community. At each stage in succession, certain species may be recognised which change the environment so that it becomes more suitable for other species. The changes in the abiotic environment result in a less hostile environment and changing diversity. Conservation of habitats frequently involves management of succession. Candidates should be able to use their knowledge and understanding to present scientific arguments and ideas relating to the conservation of species and habitats evaluate evidence and data concerning issues relating to the conservation of species and habitats and consider conflicting evidence explain how conservation relies on science to inform decision-making. What changes occur in the variety of species that occupy an area over time? What are meant by the terms succession and climax community? How can managing succession help to conserve habitats? What is conservation? How can managing succession help to conserve habitats? Inheritance and selection Studying inheritance (pages ) Genotype and phenotype Genes and alleles Monohybrid inheritance (pages ) Crosses Inheritance of pod colour in peas - Determining genotypes Sex inheritance and sex linkage (pages ) Co-dominance / Multiple alleles and a dominance hierarchy Allelic frequencies and population genetics (pages ) Species exist as one or more populations. The concepts of gene pool and allele frequency. The Hardy-Weinberg principle. The conditions under which the principle applies. Candidates should be able to calculate allele, genotype and phenotype frequencies from appropriate data and from the Hardy-Weinberg equation, p2 + 2pq + q2 = 1 where p is the frequency of the dominant allele and q is the frequency of the recessive allele. Candidates should understand that the Hardy-Weinberg principle provides a mathematical model which predicts that allele frequencies will not change from generation to generation. Selection (pages ) Differential reproductive success and its effect on the allele frequency within a gene pool. Directional and stabilising selection. 10

11 Speciation (pages ) Geographic separation of populations of a species can result in the accumulation of difference in the gene pools. The importance of geographic isolation in the formation of new species. What are meant by the terms genotype and phenotype? What are dominant, recessive and co-dominant alleles? What are multiple alleles? How are genetic crosses represented? How is a single gene inherited? How is sex determined genetically? What is sex linkage? How are sex linked diseases such as haemophilia inherited? How does co-dominance affect the inheritance of characteristics? How do multiple alleles affect inheritance? How are blood groups in humans inherited? What are meant by the terms gene pool and allelic frequency? What is the Hardy Weinberg principle? How does reproductive success affect allele frequency within a gene pool? What is selection? What environmental factors exert selection pressure? What are stabilising and directional selection? What is speciation? What is geographical isolation? How can geographical isolation lead to the formation of new species? 11

12 Unit 5 Control in cells and in organisms Coordination Sensory reception (pages ) Stimulus and response / Taxes / Kineses / Tropisms Nervous control (pages ) Nervous organisation The spinal cord - Importance of reflex arcs Control of heart rate (pages ) The autonomic nervous system e.g. Control of heart rate - Control by chemoreceptors - Control by pressure receptors Role of receptors (pages ) Structure and function of a Pacinian corpuscle Receptors working together in the eye - Rod cells - Cone cells What are a stimulus and a response? What is the advantage to organisms of being able to respond to stimuli? What are taxes, kineses and tropisms? How does each type of response increase an organism s chances of survival? How does a simple reflex arc work? What roles do sensory, intermediate and motor neurones play in a reflex arc? How do reflex arcs prevent damage to the body? What is the autonomic nervous system? How does the autonomic nervous system control heart rate? What role do chemical and pressure receptors play in the process? What are the main features of sensory reception? What is a Pacinian corpuscle and how does it work? How do receptors work together in the eye? 12

13 Coordination (pages ) Chemical mediators / Plant growth factors / Control of tropisms by IAA - Discovering the role of IAA in tropisms Neurones (pages ) The structure of neurones / The structure of a myelinated motor neurone. The nerve impulse (pages ) The establishment of a resting potential in terms of differential membrane permeability, electrochemical gradients and the movement of sodium and potassium ions. Passage of an action potential and its speed (pages ) Changes in membrane permeability lead to depolarisation and the generation of an action potential. The all-or-nothing principle. The nature and importance of the refractory period in producing discrete impulses Factors affecting the speed of conductance: myelination and saltatory conduction; axon diameter; temperature. Synaptic transmission (pages ) The detailed structure of a synapse and of a neuromuscular junction. Explain: unidirectionality / temporal and spatial summation / inhibition. The sequence of events involved in transmission across a cholinergic synapse and across a neuromuscular junction. Predict and explain the effects of specific drugs on a synapse. (Recall of the names and mode of action of individual drugs will not be required) What is a neurone? What is the structure of a myelinated motor neurone? What are the different types of neurone? What is resting potential? How is resting potential established in a neurone? What is an action potential? How does an action potential pass along an unmyelinated axon? How does an action potential pass along a myelinated axon? What factors affect the speed of conductance of an action potential? What is the refractory period? What is its role in separating one impulse from the next? What is meant by the all-or-nothing principle? What is a synapse? What functions do synapses perform? How is information transmitted across a synapse? 13

14 Muscle contraction (pages ) Gross and microscopic structure of skeletal muscle. The ultrastructure of a myofibril. The roles of actin, myosin, calcium ions and ATP in myofibril contraction. The roles of calcium ions and tropomyosin in the cycle of actinomyosin bridge formation. (The sliding filament theory of muscle contraction) The role of ATP and phosphocreatine in providing the energy supply during muscle contraction. The structure, location and general properties of slow and fast skeletal muscle fibres. What are the gross and microscopic structure of a skeletal muscle? What is the ultrastructure of a myofibril? How are actin and myosin arranged within a myofibril? What evidence supports the sliding filament mechanism of muscle contraction? How does the sliding filament mechanism cause a muscle to contract and relax? Where does the energy for muscle contraction come from? Principles of homeostasis (pages ) The importance of homeostasis Control mechanisms / Coordination of control mechanisms Regulation of body temperature (pages ) Mechanisms of heat loss and gain Regulation of body temperature in ectotherms Regulation of body temperature in endotherms - Conserving and gaining heat in response to a cold environment - Losing heat in response to a warm environment - Comparing heat gain and loss in ectotherms and endotherms - Role of the hypothalamus in temperature regulation Hormones and the regulation of blood glucose (pages ) The role of the pancreas in regulating blood glucose Regulation of blood glucose - Blood glucose and variations in its level - Insulin and the β cells of the pancreas - Glucagon and the α cells of the pancreas - Role of adrenaline in regulating the blood glucose level - Hormone interaction in regulating blood glucose Diabetes and its control (pages ) Types of sugar diabetes - Control of diabetes - Effects of diabetes on substance levels in the blood 14

15 What is homeostasis? What is the importance of homeostasis? How do control mechanisms work? How are control mechanisms coordinated? What are the main ways in which heat is gained and lost in organisms? How is body temperature regulated in ectotherms? How is body temperature regulated in endotherms? How is body temperature regulated in mammals? How do hormones work? What is the role of thepancreas in regulating blood glucose? What factors infl uence blood glucose concentration? What are the roles of insulin, glucagon and adrenaline in regulating blood glucose? What are the two main types of diabetes and how do they differ? How can each type of diabetes be controlled? The principles of feedback mechanisms (pages ) Negative feedback Positive feedback - Control of blood water potential Control of the oestrous cycle (pages ) Hormonal control of the menstrual cycle - The oestrous cycle in pigs What is negative feedback? How does it help to control homeostatic processes? How does it differ from positive feedback? Which hormones are involved in the control of oestrous cycles? How do these hormones interact in the control of the human menstrual cycle? How are different forms of feedback loop involved in this control? 15

16 Genetic control of protein structure and function (pages ) The genetic code as base triplets in mrna which code for specific amino acids. The genetic code is universal, non-overlapping and degenerate. The structure of molecules of messenger RNA (mrna) and transfer RNA (trna). Compare the structure and composition of DNA, mrna and trna. Polypeptide synthesis transcription and splicing / translation (pages ) Transcription as the production of mrna from DNA. The role of RNA polymerase. The splicing of pre-mrna to form mrna in eukaryotic cells. Translation as the production of polypeptides from the sequence of codons carried by mrna. The role of ribosomes and trna. Gene mutation (pages ) Gene mutations might arise during DNA replication. The deletion and substitution of bases. Gene mutations occur spontaneously. The mutation rate is increased by mutagenic agents. Some mutations result in a different amino acid sequence in the encoded polypeptide. Due to the degenerate nature of the genetic code, not all mutations result in a change to the amino acid sequence of the encoded polypeptide. The rate of cell division is controlled by proto-oncogenes that stimulate cell division and tumour suppressor genes that slow cell division. A mutated proto-oncogene, called an oncogene, stimulates cells to divide too quickly. A mutated tumour suppressor gene is inactivated, allowing the rate of cell division to increase. What is the genetic code and what are its main features? What is the structure of ribonucleic acid (RNA)? What are the structure and the role of messenger RNA (mrna)? What are the structure and the role of transfer RNA (trna)? How is pre-messenger RNA produced from DNA in the process called transcription? How is pre-messenger RNA modified to form messenger RNA? How is a polypeptide synthesised during the process of translation? What are the roles of messenger RNA and transfer RNA in translation? What is a gene mutation? How do deletion and substitution of bases result in different amino acid sequences in polypeptides? Why do some mutations not result in a changed amino acid sequence? What are the causes of gene mutations? How is cell division genetically controlled? 16

17 Totipotency and cell specialisation (pages ) Totipotent cells are cells that can mature into any body cell. During development, totipotent cells translate only part of their DNA, resulting in cell specialisation. In mature plants, many cells remain totipotent. They have the ability to develop in vitro into whole plants or into plant organs when given the correct conditions. Totipotent cells occur only for a limited time in mammalian embryos. Multipotent cells are found in mature mammals. They can divide to form only a limited number of different cell types. Totipotent and multipotent stem cells can be used in treating some genetic disorders. Regulation of transcription and translation (pages ) Transcription of target genes is stimulated only when specific transcriptional factors move from the cytoplasm into the nucleus. The effect of oestrogen on gene transcription Small interfering RNA (sirna) as a short, double-strand of RNA that interferes with the expression of a specific gene. What are totipotent cells? Which types of cells are totipotent in plants and animals? How do cells lose their totipotency and become specialised? How can totipotent stem cells be used to treat human disorders? How does oestrogen affect gene transcription? What is small interfering RNA? How does it affect gene expression? 17

18 Producing DNA fragments (pages ) Fragments of DNA can be produced by conversion of mrna to cdna, using reverse transcriptase cutting DNA at specific, palindromic recognition sequences using restriction endonucleases the polymerse chain reaction (PCR). In vivo gene cloning the use of vectors (pages ) In vivo cloning. The use of restriction endonucleases and ligases to insert a gene into vectors, which are then transferred into host cells. The identification and growth of transformed host cells to clone the desired DNA fragments. The importance of sticky ends. Gene markers - Antibiotic-resistance markers - Fluorescent markers - Enzyme markers In vitro gene cloning the polymerase chain reaction (pages ) In vitro cloning. The use of the polymerase chain reaction (PCR) to clone directly. The relative advantages of in vivo and in vitro cloning. The use of recombinant DNA technology to produce transformed organisms that benefit humans. Use of recombinant DNA technology (pages ) Genetic modification how and why it s done. - Examples of genetically modified microorganisms - Examples of genetically modified plants - Examples of genetically modified animals Gene therapy (pages The use of gene therapy to supplement defective genes. Treatment of cystic fibrosis using gene therapy - Delivering cloned CFTR genes Treatment of severe combined immunodeficiency using gene therapy - Effectiveness of gene therapy - Risks and benefits of gene therapy Locating and sequencing genes (pages ) The use of labelled DNA probes and DNA hybridisation to locate specific genes. - Gel electrophoresis Once located, the base sequence of a gene can be determined by: restriction mapping and DNA sequencing. Screening for clinically important genes (pages ) Many human diseases result from mutated genes or from genes that are useful in one context but not in another, e.g. sickle cell anaemia. DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes. The use of this information in genetic counselling, e.g. for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment for cancers. 18

19 Genetic fingerprinting (pages ) An organism s genome contains many repetitive, non-coding base sequences. The probability of two individuals having the same repetitive sequences is very low. The technique of genetic fingerprinting in analysing DNA fragments, that have been cloned by PCR, and its use in determining genetic relationships and in determining the genetic variability within a population. Genetic fingerprinting - Extraction Digestion Separation Hybridisation Development Uses of genetic fingerprinting: Forensic science / Medical diagnosis / Plant and animal breeding How is complementary DNA made using reverse transcriptase? How are restriction endonucleases used to cut DNA into fragments? What is the importance of sticky ends? How can a DNA fragment be inserted into a vector? How is the DNA of the vector introduced into host cells? What are gene markers and how do they work? What is the polymerase chain reaction? How does the process work? How has genetic modification of organisms benefited humans? What roles have genetically modified microorganisms, plants and animals played in the beneficial use of recombinant DNA technology? What is cystic fibrosis? What is the cause of cystic fibrosis? How can gene therapy be used in the treatment of cystic fibrosis? What is the difference between germ-line and somatic-cell gene therapy? How are DNA probes and DNA hybridisation used to locate specifi c genes? How can the exact order of nucleotides on a strand of DNA be determined? What is restriction mapping, how does it help to determine the sequence of nucleotides in a gene? How can DNA probes be used to screen patients for gene mutations? What role does genetic counselling play in the process? What is genetic fingerprinting? How is genetic fingerprinting carried out? How are the results interpreted? For what purposes is it used? 19