Paper 1 Biology 2024 questions and their answers, Exams of Biology

Download Paper 1 Biology 2024 questions and their answers and more Exams Biology in PDF only on Docsity! Paper 1 Biology 2024 questions and their answers Explain how leaves are adapted for gas exchange - Verified Answer 1. Thin = short diffusion distance 2. Many stomata for gas to diffuse through 3. Spongy mesophyll has air spaces = faster diffusion Explain how the lungs are adapted for gas exchange - Verified Answer 1. Many alveoli = large surface area 2. Alveolus wall is one cell thick = short diffusion distance 3. Good blood supply = steep concentration gradient How does breathing help gas exchange? - Verified Answer 1. Inhale air with high oxygen concentration. 2. Exhale air with high CO2 concentration. 3. Maintains concentration gradients Describe the process of inhalation - Verified Answer 1. Diaphragm contracts and moves down. 2. Intercostal contract and ribs move up 3. Increases volume of thorax 4. Decreases pressure in thorax 5. Higher pressure air outside body moves into lungs. Describe the process of exhalation - Verified Answer 1. Diaphragm relaxes and moves up 2. Intercostal relax and ribs move down 3. Volume of thorax decreases 4. Pressure in thorax increases 5. Higher pressure air in thorax leaves lungs Explain how smoking affects gas exchange in the lungs - Verified Answer 1. Damage to alveoli 2. Loss of surface area 3. Slower diffusion 4. Inelastic scar tissue = cannot exhale easily 5. Air with low oxygen concentration not replaced 6. Therefore concentration gradient for oxygen is less steep. Describe what would happen to a piece of potato in a salty solution. - Verified Answer 1. Salty solution has lower water potential than potato cells. 2. Water leaves potato cells 3. by osmosis 4. So potato piece loses mass Describe what would happen to a piece of potato in pure water. - Verified Answer 1. Pure water has higher water potential than potato cells 2. Water enters potato cells 3. by osmosis 4. So potato piece gains mass Explain how a red blood cells is adapted for its function - Verified Answer 1. Biconcave shape = more surface area for diffusion of oxygen 2. No nucleus = more space for haemoglobin 3. Haemoglobin binds to oxygen forming oxyhaemoglobin 4. Streamlined shape = flows easily. Describe how white blood cells respond to pathogens - Verified Answer 1. White blood cells identify pathogens by their antigens which are different in shape to our own. 2. Phagocytes... 3. Engulf pathogen... 4. And digest it with enzymes 5. Lymphocytes... 6. Produce antibodies... 7. Which bind to pathogen's antigens and destroy pathogens. Explain how a vaccine works - Verified Answer 1. Contains dead or weakened version of pathogen 2. Lymphocytes which have specific shaped antibody multiply 3. Produce lots of antibodies 4. Produce memory cells 5. Memory cells can produce same antibodies again if same pathogen infects body again. 6. Secondary immune response will produce more antibodies more quickly and without time delay. Describe how blood clots and explain why it is important. - Verified Answer 1. Fibrinogen converts to Fibrin 2. Forms web of fibres at wound site 3. Platelets stick to it, forming clot. 4. Prevent further blood loss 5. Prevents pathogens getting into body. Explain why the wall of the left ventricle is thicker than the wall of the right ventricle - Verified Answer 1. More muscle in left ventricle wall 2. Because it needs to contract with more force 3. To generate higher pressure Describe how the body regulates its temperature on a hot day. - Verified Answer 1. Sweating.... 2. Allows evaporative cooling. 3. Vasodilation of blood vessels supplying the skin... 4. Allows more hot blood to reach the skin 5. So that more heat can be lost by conduction/radiation. Describe how the body regulates its temperature on a cold day. - Verified Answer 1. Vasodilation of blood vessels supplying the skin... 2. So less hot blood reaches the skin 3. so that less heat is lost by conduction/radiation. 4. Hairs stand on end... 5. Which traps a layer of warm air 6. Which acts as an insulator. Compare the adaptations of insect and wind pollinated plants - Verified Answer 1. Insect pollinated plants have colourful petals, wind pollinated plants do not. 2. Insect pollinated plants have nectar, wind pollinated plants do not. 3. Insect pollinate plants make scents/perfume, wind pollinated plants do not. 4. Wind pollinated plants make more pollen than insect pollinated plants. 5. Wind pollinated plants have stigmas that have a larger surface area. Describe the process of fertilisation in plants. - Verified Answer 1. Pollen grows pollen tube down style to ovary. 2. Two male nuclei travel down pollen tube. 3. One fertilises the egg nucleus to form an embryo 4. One fertilises the polar body which becomes the endosperm. Describe what happens to a flower after it is fertilised. - Verified Answer 1. Fertilised ovule becomes seed, 2. Which contains an embryo 3. And the endosperm which acts as nutrient store for when the seed germinates. 4. The ovary turns into a fruit around the seeds. Describe and explain the conditions required for a seed to germinate. - Verified Answer 1. Warm - to provide enzymes with enough kinetic energy for reactions to happen quickly (e.g. respiration) 2. Water - so that new cells of root and shoot can swell with water and become turgid. 3. Oxygen - for respiration Explain the purpose of the endosperm in a seed. - Verified Answer 1. The endosperm is a nutrient store in a seed, typically it contains starch. 2 During germination the starch is broken down to glucose by amylase. 3. The glucose can then be used for respiration 4. To release energy for growth. Compare sexual and asexual reproduction - Verified Answer 1. Sexual reproduction involves two parents, asexual only involves one. 2. Sexual reproduction produces genetically unique individuals, asexual produces genetically identical individuals 3. Sexual reproduction involves meiosis, asexual reproduction only involves mitosis. Describe the roles of oestrogen in the body - Verified Answer 1. Triggers development of uterus lining during menstrual cycle 2. Controls secondary sexual characteristics during puberty 3. e.g. breast development, pubic hair, wider pelvis, start of menstrual cycle, growth spurt Explain how the placenta is an effective exchange surface. - Verified Answer 1. Many capillaries = large surface area 2. Mothers and foetus' capillaries very close together = short diffusion distance 3. Capillaries have one cell thick walls = short diffusion distance Compare meiosis and mitosis - Verified Answer 1. Meiosis produces 4 daughter cells, mitosis produces 2. 2. Meiosis produces haploid cells, mitosis produces diploid cells. 3. Meiosis produces genetically unique cells, mitosis produces genetically identical cells. 4. Meiosis produces gametes, mitosis produces body cells. Explain why individuals in a population are genetically unique. - Verified Answer 1. Mutations create new alleles 2. Meiosis creates genetically unique gametes 2. Sexual fertilisation combines the DNA of two parents into a new unique combination. Explain how an organism evolves by natural selection - Verified Answer 1. There is genetic variation in a population due to mutations. 2. Some individuals are better adapted than others (in the exam you must explain which individuals are best adapted in that specific question) 3. These individuals are more likely to reproduce 4. Therefore they pass on their alleles more often 5. So these alleles become more common in the population. Explain how antibiotic resistance can develop in bacteria - Verified Answer 1. There is genetic variation in bacterial population due to mutations. 2. So some bacteria are more resistant to the antibiotic than others. 3. If they are exposed to antibiotics the ones that are more resistant are more likely to survive and reproduce. 4. These ones pass on their alleles for resistance 5. So the alleles for resistance become more common. 6. This is natural selection. Describe how a plant or animal can be bred to have a particular characteristic. - Verified Answer you must tailor this to the example in the exam question: 1. Mate male and female with the desired characteristic 2. Take the offspring with the best characteristics and breed them together. 3. Repeat for many generations. Describe the test for sugars - Verified Answer 1. Add Benedict's solution to liquid sample of food 2. Heat at 85 degrees in water bath 3. Check for orange/red colour Describe test for starch - Verified Answer 1. Add iodine 2. goes black Describe test for proteins - Verified Answer 1. Add Biuret solution 2. goes purple/lilac Describe test for lipids - Verified Answer 1. Dissolve food in ethanol 2. Then mix with water 3. Check for white emulsion Define the term 'osmosis' - Verified Answer 1. Osmosis is the movement of water 2. from an area of higher water potential to an area of lower water potential 3. across a semi-permeable membrane Describe the process of active transport - Verified Answer 1. Movement of molecules up a concentration gradient 2. Using energy 3. and a protein carrier. Explain the concept of herd immunity - Verified Answer 1. Vaccinate lots of people 2. Therefore fewer people can become infected 3. Therefore fewer people can transmit the pathogen 4. Therefore vulnerable people who cannot have a vaccine are less likely to get infected. Describe how a synapse works. - Verified Answer 1. Electrical impulse arrives at synapse 2. Triggers release of neurotransmitter chemicals 3. They diffuse across synapse 4. And bind to receptors on the next neuron 5. Triggering a new electrical impulse. Explain how gender is determined in humans - Verified Answer 1. Mother has two X chromosomes 2. So egg always carries X