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Science B2 Topic 3

GCSE edexcel additional science biology: common systems

QuestionAnswer
What are fossils? Preserved traces or remains of organisms that lived thousands/ millions of years ago
What is the fossil record? The history of life on earth as shown by the fossils from different time periods
Where does evidence for evolution come from? The fossil record (shows organisms have gradually changed over time). the pentadactyl limb structure is found in fossil vertebrates + fossil ancestors of limbless living vertebrates -> all vertebrates evolved from one ancestor h/millions of years ago
Why are there gaps in the fossil record? * Soft tissues decay so do not form fossils, so soft-bodied organisms leave little fossil evidence * Some organisms did not form fossils because the hard parts were destroyed * Some fossils are buried deep in the earth and have not yet been found
Why are gaps in the fossil record an issue? It means that the same sets of fossil data can be interpreted in different ways- the more evidence we collect, the better conclusions we draw
What is growth and how can it be measured? An increase in cell number and size. Measured by size, length or mass.
What is a percentile? A comparison of a person's growth to a certain percentage of the population
What is growth in plants? Cell division, cell elongation, and differentiation
What are meristems? Areas at the tops of plant shoots and roots where there is cell division and elongation. When shoots and roots grow, older meristematic tissue differentiates to form different types of specialised cells e.g. palisade or root hair cells
What is growth in animals? Cell division and differentiation
What are the four main components in blood? Plasma, red blood cells, white blood cells, platelets
What is plasma? A yellow liquid that transports dissolved substances such as carbon dioxide, food substances and hormones around the body
What is the function of red blood cells? Red blood cells contain the red pigment haemoglobin, which can combine reversibly with oxygen in the lungs (haemoglobin + oxygen <-> oxyhaemoglobin). This reaction is reversed at tissues, so that cells get oxygen for aerobic respiration.
How are red blood cells adapted to their function? They have no nucleus to make as much room for haemoglobin as possible. They have a biconcave disc shape (dimple on each side) to create a large surface area to volume ratio for oxygen to diffuse into and out of the cell.
What is the structure function of white blood cells? They all have nuclei. They are part of the body's defenses against disease. Some make antibodies, which are proteins that bind to the microorganisms that cause disease and destroy them. Others surround and destroy foreign cells.
What is the structure and function of platelets? Platelets are tiny fragments of cells (so don't have nuclei) - they are important in making blood clot if a blood vessel is damaged. The clot dries out and forms a scab which stops microorganisms entering the body.
What is a tissue? A group of the same type of specialised cells
What is an organ? Several different tissues that work together to carry out a particular function
What are the four major blood vessels associated with the heart? * pulmonary artery carries deoxygenated blood to the lungs. * pulmonary vein carries oxygenated blood from the lungs to the left atrium. * aorta carries blood to the rest of the body. * vena carva brings blood from the body to the right atrium
What are valves and what is their function? They are flaps of tissue that stop the blood flowing backwards
What is the function of tendons? They stop valves turning inside out
What is the septum? The muscle that separates the two sides of the heart
Why is the muscle wall of the left ventricle thicker than that of the right? Because it has to pump blood around the whole body
Describe the direction of blood flow through the heart Right atrium -> right ventricle -> left atrium -> left ventricle
What is the circulatory system made up of? Heart and blood vessels (capillaries, arteries, veins)
What are the features of arteries? They carry blood away from the heart- they have strong, thick walls as the blood has to be under high pressure so that it can reach all parts of the body.
What are the features of veins? They carry blood to the heart - they have wide passages for blood to flow, and have a thin muscle layer because blood flows relatively slowly under low pressure
What are the features of capillaries? They have thin walls (one cell thick) to allow substances to diffuse in and out of the blood, and into cells and tissues
What is the purpose of digestion? The process of digestion turns large, insoluble molecules into smaller, soluble ones which can be absorbed into the blood stream
What is the digestive system made up of? Alimentary canal, mouth, oesophagus, stomach, small intestine, pancreas, large intestine, anus, liver, gall bladder
What is the alimentary canal? a muscular tube running through the body from the mouth to the anus
What occurs in the mouth? Teeth grind up food into smaller pieces to increase the surface area for enzymes (mechanical digestion), tongue forms the chewed food into a bolus, saliva coats the bolus to lubricate it for swallowing and amylase (enzyme)starts to break down starch
What is peristalsis + where does it occur? The muscle above the bolus contracts to squeeze the food down. occurs in the oesophagus, stomach and the alimentary canal
What occurs in the stomach? The stomach is a muscular bag that makes hydrochloric acid and enzymes, and churns the food by peristalsis
What is the small intestine and what occurs in it? It is a long, coiled, muscular tube which uses its own enzymes and enzymes made by the pancreas to break down larger, insoluble molecules into smaller, soluble ones which are absorbed into the blood stream by villi
What is the function of the pancreas? An organ that makes digestive enzymes and releases them into the small intestine
What is the function of the liver? It builds digested food molecules back into larger molecules and produces bile which helps in the digestion of fats
What is the function of the gall bladder? It stores bile and releases it into the small intestine when needed
What is the large intestine and what occurs in it? It is a wide, thin-walled, muscular tube that undigested food passes through and where water diffuses into blood stream
What is the rectum? Where faeces are stored
What is the anus? Where faeces are egested out of the body
What are carbohydrases + examples? Digestive enzymes that break down carbohydrates. Amylase is a carbohydrase that breaks down starch into sugars- one amylase is found in saliva and another in the small intestine
What are proteases + examples? Digestive enzymes that break down proteins into shorter chains and then into amino acids. Pepsin is a protease made in the stomach that works best in acidic conditions
What are lipases? Digestive enzymes that chemically break down fat molecules into fatty acids and glycerol
What is bile? Bile emulsifies fat by physically breaking down large globules of fats in watery digestive juices into tiny droplets, forming an emulsion. Bile is alkaline, neutralises stomach acid + makes small intestine alkaline (protease)
What is the function of villi? They increase the surface area of the small intestine so that soluble food molecules can diffuse through the walls of the small intestine and into the blood stream quicker
How are villi adapted to their function? They are only 1 cell thick so the molecules don't have to diffuse far. Each villus has a good network of capillaries so that the substances diffuse into the blood stream straight away. Steep concentration gradient.
What is an advantage of the blood stream quickly absorbing food molecules and carrying them away? There is always a lower concentration inside the blood than in the small intestine, so there is a steep concentration gradient that means diffusion takes place rapidly
What is an effect of coeliac disease? Villi may be lost, so a sufferer can’t absorb the products of digestion properly
What are functional foods? Foods that aren’t eaten for nutritional value but which claim to make you healthier
What are probiotics and in which food products are they found? Foods that contain beneficial bacteria (usually lactobacillus and bifidobacteria) which produce lactic acid in the gut. Found in yoghurts and dairy products
What are prebiotics and in which food products are they found? They are substances that the body can’t digest but act as food for the beneficial bacteria in the gut and encourage their growth. Oligosaccharides are a form of prebiotics found in tomatoes, bananas, onions and asparagus
What are plant stanol esters and in which food products are they found? Oil substances found in plants that can stop the small intestine absorbing cholesterol, lowering cholesterol levels in the blood. They can be found in yoghurts and spreads.
What is cholesterol? Cholesterol is a fat which is made in the liver and is carried in the blood, and high levels are associated with an increased risk of heart disease
Created by: 11043