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Biology 2 warm up session: Higher tier Remember, you have learnt all the information on the following slides in your lessons. This is just to refresh your memory of the essentials Animal Cells Nucleus - controls cell’s activities Cytoplasm - where chemical reactions take place Cell membrane - controls what enters and leaves cell Mitochondria - where energy is released during aerobic respiration • Ribosomes - where proteins are made • • • • Plant Cells Plant cells also have: • A rigid cell wall - for strength and support • Chloroplasts - absorb light to make energy for photosynthesis • Vacuole filled with cell sap Specialised cells These are cells adapted to carry out different functions Different types of cells • Yeast cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall • A bacterial cell have a cytoplasm, cell membrane and a cell wall • But the genes are not in a distinct nucleus Diffusion and concentration gradients high low concentration concentration • Diffusion is the spreading of the particles… …from a higher concentration to a region of lower concentration... …the greater the difference in concentration, the faster the rate of diffusion. • Diffusion happens in gas exchange in the lungs and in leaves Enzymes and their structure heat pH normal denatured • Enzymes are biological catalysts –they speed up reactions in living things • Enzymes are protein molecules - made up of amino acids •The shape of the enzyme is vital to its function. • Temperature and pH affect enzyme activity 1.) High temperatures can destroy the enzymes ‘special shape’ so it becomes denatured. 2.) Different enzymes work best at different pH values. Enzymes in digestion Enzyme: Produced in Job Where Amylase - Salivary glands - Pancreas - Small intestine - Catalyses the breakdown of starch into sugars Mouth -Small intestine Protease -Stomach - Pancreas - Small intestine Catalyses the breakdown of proteins into amino acids -Stomach - Small intestine Lipase - Pancreas - Small intestine - Catalyses the breakdown of lipids (fats and oils) into fatty acids and glycerol Small intestine Making use of enzymes Enzymes in industry Type of enzyme Use Proteases Carbohydrases To ‘pre-digest’ protein in baby To turn starch into sugar syrup for To turn glucose The baby may Sugar syrup is sweet and makes the food ‘taste Fructose is twice foods Why is it used? not be able to digest all the protein itself making chocolates and cakes nice’ Isomerases syrup into fructose syrup to use in slimming foods as sweet as glucose so it can be used in smaller amounts in slimming foods Body organisation The body is made of cells A group of cells that work together are called a tissue A group of tissues that work together are called an organ A group of organs that work together are called an organ system Types of animal tissue A tissue is a group of cells with similar structure and function. There are 3 examples of tissue: • Muscular tissue, which can contract to bring about movement • Glandular tissue, which can produce substances such as enzymes and hormones • Epithelial tissue, which covers some parts of the body Types of plant tissue include • Palisade layer – where photosynthesis happens • Spongy mesophyll layer – allows gases to reach palisade layer • Xylem – transports water and nutrients • Phloem – transports food (e.g. sugars) The digestive system includes Aerobic respiration can be summarized by this equation: glucose + oxygen carbon dioxide + water + energy Mitochondria are the energy-producing part of the cell. The energy that is released during respiration is used: -For GROWTH - MOVEMENT - MAINTAINING A CONSTANT TEMPERATURE (in mammals and birds) - MAKING PROTEINS Aerobic respiration during exercise During exercise the heart rate increases and the rate and depth of breathing increases... …this increases the supply of sugar and oxygen to cells and increases the rate of removal of carbon dioxide Anaerobic respiration • During exercise, if insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy. • Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid. • As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Inheritance recap – Inside the cell Mitosis • Mitosis is the division • Produces of body cells new identical cells for growth and repair • Before cell division, genetic information on the chromosomes is copied so new cells have the same genes as the parent cells Meiosis (Higher) • Cells in reproductive organs (testes and ovaries) divide to form sex cells (gametes) • Before division a copy of each chromosome is made. •The cell now divides twice to form 4 gametes – each new cell has half a set of chromosomes • Sexual reproduction results in variation as the new individual gets half a set of chromosomes from each parent Alleles ? •Some allele for blue eyes allele for brown eyes characteristics are controlled by a single gene. •Different forms of genes are called alleles Eg, for eye colour, skin colour, hair colour etc Inherited disorders Polydactyly •A disorder causing extra fingers or toes •Caused by dominant allele of a gene •Can be passed on by only one parent who has the disorder •50% chance of inheriting disease Inherited disorders Cystic fibrosis • A disorder which affects cell membranes in many organs of the body particularly the lungs and the pancreas • Caused by recessive allele so must be inherited by both parents Embryo screening Unborn embryos can be checked for the alleles that cause these and other genetic disorders… …some people think this leads to more abortions and so they think it’s unethical Photosynthesis Carbon dioxide + water (+ light energy) Glucose + Oxygen • Photosynthesis is when green plants use light energy to make their own food • The rate of photosynthesis may be limited by 3 things: 1) carbon dioxide 2) light intensity 3) temperature Limiting carbon dioxide levels • Increasing carbon dioxide levels increases the rate of photosynthesis up to a point. • Eventually one of the other factors (temperature and light) becomes limiting • If there is too little carbon dioxide the rate will slow down. • Carbon dioxide maybe limited in an enclosed space eg, a greenhouse on a sunny day or in a rapidly photosynthesising rain forest Limiting light intensity • Increasing light intensity increases the rate of photosynthesis up to a point • When a certain light intensity is reached the rate of photosynthesis stays constant • Eventually one of the other factors becomes limiting Limiting temperature • If it is cold then enzymes do not work effectively slowing down the rate. • The rate of photosynthesis increases steadily with a rise in temperature up to a certain point (35-40ºC = optimum temp) • After this the enzymes are destroyed and the reaction stops completely. Healthy plant growth Plant roots absorb mineral ions needed for healthy growth For healthy growth plants need mineral ions including - Nitrates and - Magnesium Mineral ions: Needed for: Symptoms shown by plants if deficient in mineral Nitrates Magnesium Nitrates used to make proteins for growth Needed for Stunted growth Yellow leaves chlorophyll production Populations The factors that effect population size are: - Temperature - Availability of nutrients - Amount of light - Availability of water - Availability of oxygen and carbon dioxide There are 2 methods for collecting environmental data To sample randomly: - Choose area to sample Place quadrat randomly onto area Count number of species within quadrat Repeat 5 times To sample along a transect: - Choose area to sample Choose a straight line through the area Place quadrat at one end of the line Count number of species within quadrat Repeat at 5 set intervals along the line Fossils and exctinction • Fossils are the remains of dead plants and animals which lived millions of years ago. • Fossils show us how much or how little different organisms have changed as life developed on Earth. • Many early life forms were soft-bodied... which means that they have left few traces behind....what traces there were have been mainly destroyed by geological activity. Fossils and exctinction Extinction may be caused by: - changes to the environment - new predators, diseases or more successful competitors - a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids Fossils and exctinction New species arise as a result of: isolation – two populations of a species become separated, eg geographically HT only: genetic variation – each population has a wide range of alleles that control their characteristics natural selection – in each population, the alleles that control the characteristics which help the organism to survive are selected speciation – the populations become so different that successful interbreeding is no longer possible. Some scientific terms... Reproducible Would another scientist be able to repeat it and get the same results? Valid Keep everything the same except the independent & dependent variables Precision Smaller scale division on equipment Range From the smallest to biggest Interval What the values go up by Claims You decide if it is true or false by looking at evidence, independent organisations avoid bias What is the questions asking you to do? Describe a graph Refer to the pattern e.g. as……...increases………increases etc Explain Describe & give a reason “because…….” Evaluate For & against Compare What is the same & what is different Calculate Show calculations & give units Suggest a reason This should be scientific Things to think about when evaluating a situation... • Economical aspect - money • Environmental – pollution/ greenhouse gases/ global warming/ acid rain/ carbon dioxide/ habitat destruction • Health risks – body rejection/damage • Availability/accessibility • Ethical – suffering/human rights • Religious Some final tips... • Read the whole Q – 33% of the Qs can be answered from information given to you in text, diagrams, graphs & tables • Follow instructions – “tick a box” “tick two boxes” “use info from the table” • Don’t write “it” – “the concentration increases” NOT “it increases” And remember... • 1 mark per minute – you have 60 minutes to answer 60 marks • Use bullet points for short questions – e.g. 3 marks should mean 3 bullet points • Write in ‘good English’ for the 6 mark question • Check your answers – read over your answers at the end Good luck