Biology Gcse Flashcards
What are the parts of an animal (and plant) cell?
Nucleus Cytoplasm Cell membrane Mitochondria
What are parts of a plant cell?
Rigid cell wall Large vacuoleChloroplasts(nucleus, cytoplasm, cell membrane and mitochondria)
What does the nucleus do?
Contains DNA that controls what the cell does
What does the cytoplasm do?
Its a gel-like substance where most of the chemical reactions happpen
What does the cell membrane do?
Holds the cell together and controls what goes in and out
What does the mitochondria do?
This is where most of the reactions for respiration take place. Respiration releases energy that the cell needs to work.
What does the rigid cell wall do?
It is made up of cellulose and it gives support for the cell
What does the large vacuole do?
Contains cell sap, a weak solution of sugar and salts
What do chloroplasts do?
This is where photosynthesis occurs. They contain a green substance called chlorophyll.
What are the features of a bacteria cell?
Chromosomal DNAPlasmidsFlagellumCell wall
What is chromosomal DNA?
Chromosomal DNA controls the cells activities and replication. It floats free in the cytoplasm.
What are plasmids?
Plasmids are small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like drug resistance and can be passed between bacteria.
What is the flagellum?
The flagellum is a long, hair-like structure that rotates to make the bacterium move.
What does the cell wall do?
Support the cell
What is magnification?
How much bigger the image is that the specimen
How do you work out magnification?
length of image / length of specimen
What is the difference between light microscopes and electron microscopes?
Light microscopes let us see things like the nuclei, chloroplasts and mitochondria. Electron microscopes let us see much smaller things in more detail like the internal structure of mitochondria and chloroplasts and even tinier things like plasmids.
What is DNA?
DNA is the complex chemical that carries genetic information. DNA is found in chromosomes which are found in the nucleus of most cells.
What is the structure of DNA? (6marker)
-A DNA molecule has two strands coiled together in the shape of a double helix.-The two strands are hold together by chemicals called bases. The four bases are adenine, thymine, guanine and cytosine. -The bases are paired, and they always pair up in the same way; A-T and C-G. This is called base pairing. -The base pairs are joined together by weak hydrogen bonds.
What is a gene?
A gene is a short piece of DNA that codes for a specific protein. You have genes for hair structure, eye colour enzymes and every other protein in your body.
Who discovered the structure of DNA?
-Rosalind Franklin and Maurice Wilkins worked out DNA had a helical structure by directing beams of X-rays onto crystallised DNA and looking at the patterns of x-rays formed as they bounced off. -James Watson and Francis Crick used these ideas along with the idea the amount of adenine+guanine matched the amount of thymine+cytosine to make a model of the DNA molecule where all the pieces fitted together.
What would be a practical to extract DNA?(6 marker)
-Mash or chop fruit or vegetable (e.g kiwi) and mix with salty water and detergent to break open the cells and help release the DNA from the nuclei.-Add protease enzyme to the filtered mixture to break up proteins in cell membranes and so release more DNA. -Add ice cold ethanol carefully down inside the tube into the mixture. The ethanol makes the DNA separate from the liquid so it is easy to lift out.
How does a cell make proteins?
By stringing amino acids together in a particular order. There's only 20 different amino acids that are used to make up thousands of different proteins. The order of bases in a gene tells cells in what order to put the amino acids together. Each set of three bases (triplet) codes for a particular amino acid.
What can DNA determine?
Which genes are switched on or off and so which proteins the cell produces e.g keratin. That in turn determines what type of cell it is e.g. red blood cell, skin cell.
What are proteins made by?
Proteins are made in the cell by oraganelles called ribosomes.
Why does the cell need mRNA?
Because DNA is found in the nucleus and can't move out of it because its too big. The cell needs to get the information from the DNA to the ribosome in the cell cytoplasm. This is done by using a molecule called mRNA, which is very similar to DNA, but it's shorter and only a single strand. Also, instead of thymine, mRNA has the base uracil (u), which pairs with adenine. mRNA is like a messanger between the DNA in the nucleus and the ribosome. It happens during transcription and translation.
What happens during transcription?
-Transcription takes place in the nucleus. -The weak hydrogen bonds break and a section of DNA is unwound and the two strands separate.-One strand is used as a template. -Complementary bases to this strand link to it. -mRNA is formed. -mRNA stands for messenger RNA-mRNA moves out of the nucleus into the cells cytoplasm
What happens during translation?
-Translation takes place in the cytoplasm when the mRNA attaches to a ribosome.-The ribosome moves along the mRNA in one direction reading a triplet of bases (codon) at a time. -tRNA molecules bring amino acids to thee ribosome. The amino acids attached to each tRNA molecule depends on the order of bases in the tRNA.-Complementary bases of tRNA pair with the bases of the mRNA strand.-Amino acids that are close together are joined to make an amino acid chain (a polypeptide) -Every protein is formed from a specific number of amino acids in a particular order. The order of the bases in the DNA defines the order in which the amino acids are joined together. So one section of DNA codes for one particular protein.
What do mutations do?
A mutation is a change in an organisms DNA base sequence. This may change the amino acid that is added to the chain during translation on the ribosome.
What could a harmful mutation change do?
A harmful mutation could cause a genetic disorder, for example, cystic fibrosis
What can a beneficial mutation do?
A beneficial mutation could produce a new characteristic that is beneficial to an organism e.g. a mutation in genes on bacterial plasmids can make them resistant to antibiotics
What can neutral mutations do?
Some mutations are neither harmful nor beneficial e.g. they don't affect a proteins function
What does the haemoglobin (in blood) do?
Carries oxygen to red blood cells. They have a globular shape
What do hormones do?
Hormones are transported in blood to target cells. They have a globular shape
What does the collagen do?
The collagen is in tendons and ligaments. Ligaments hold bones together and tendons attach muscles to bones.
Why does the shape of a protein matter?
The shape of a protein affects the way it works. The sequence of amino acids gives each protein a particular 3D shape. These shapes may be globular (blobbly) or fibrous (long,strong fibres)
Enzymes have a very specific shape that allows them to work effectively. Why might a gene with a mutation change the activity of an enzyme? Refer to active site in your answer
A gene mutation can change the base sequence in DNA. If this change produces a different amino acid sequence, this may change the shape of the active site. The shape of the active site controls how well an enzyme works. If the shape of the active site matches the shape of the substrate better, then the enzyme will work better. But if the shape of the active site is not as good a match, then the enzyme will not work so well.
What are enzymes?
Enzymes are biological catalysts that control reactions in the body.
What is a catalyst?
A catalyst is a substrate which increases the speed of a reaction without being changed or used up in the reaction.
What is meant by the 'lock and key' hypothesis for enzymes?
Each enzyme has an active site. Some substrates may or may not fit the active site. If the substrate matches the shape of the active site, the substrate molecules hold them close together so bonds can form between them and make a product. If the product molecule doesn't fit the active site, it is released from the enzyme. Enzymes usually only join with one substrate as they have a high specificity for their substrates.
How would someone measure the rate of a reaction by using amylase as the enzyme and starch substrate?
-Amylase catalyses the breakdown of starch. So you time how long it takes for the starch to dissappear -To do this, regularly take a drop of the amylase and starch mixture, and put it into a drop of iodine solution on a spotting tile. Record the colour change - it will true blue-black if starch is present. Note the time when the iodine solution no longer turns blue-black - the starch has then been broken down by the amylase. You can use times to compare reaction rates under different conditions.
What are the variables you may change during an enzyme controlled reaction?
-Changing the temperature = put test tubes into different temperature water baths -Effect of pH = use a range of different pH buffers-Effect of substrate concentration = vary the substance concentrations of the starch solutions
What happens at lower temperatures to molecules and how does this link to the 'lock and key' hypothesis?
At lower temperatures, molecules move more slowly. So substrate molecules take longer to fit into and react in the active site.
What is the optimum temperature?
The temperature where the enzyme is working at the fastest rate
What can higher temperatures cause the active site to do?
Higher temperatures cause the active site to change shape, so it cant hold the substrate as tightly and the reaction goes more slowly.
What happens to the active site at very high temperatures?
At very high temperatures the active site breaks up and the enzyme is denatured.
How does the pH effect an enzyme?
If the pH is too high or too low, it interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.
What is an optimum pH for an enzyme?
The optimum pH for an enzyme is the pH that they work best at. This is often neutral pH 7, but not always.
How does substrate concentration effect an enzyme?
The higher the substrate concentration, the faster the enzyme will react with substrate molecules. However, after adding so many substrate molecules eventually if you add more it will make no difference.
What is the human genome project?
Scientists in 18 different countries collaborated to decode the human genome. This is the order of bases on all the human chromosomes. The project was completed quickly because so many scientists worked on it at the same time. The work was published in 2003.
What are the positives of the human genome project?
-It helps predict and prevent diseases. (This helps early detection and helps cures to be discovered)-Develop new and better medicines. -Accurate diagnoses -Improved forensic science (DNA fingerprint found on crime scenes)
What are the negatives of the human genome project?
-Increased stress (People could easily panic if they are away the may have a disease)-Gene-ism (People with genetic problems could come under pressure not to have children)-Discrimination by employees and insurers (life insurance could be very expensive if you are likely to get a disease)
What are two possible developments as a result of decoding the human genome?
-Identification of genes that can cause disease -Gene therapy (involves replacing faulty alleles in body cells with healthy ones. This would allow the effected person to live a normal healthy life)
What is genetic engineering?
Scientists can remove a gene from one organism and insert it into the DNA of another organism.
What are the steps of genetic engineering?
1) A gene is cut out of chromosome using restriction enzymes. 2) A DNA plasmid is taken out of a bacterium and cut open using enzymes 3) The gene and the plasmid are mixed together. 4) The Gene and the plasmid are stuck together using lypase enzymes to make a new plasmid 5) The new plasmid with the gene is put into a bacterium. The bacterium has been genetically modified and will now make the ....
How can genetic engineering help reduce vitamin A deficiency?
1)Beta-carotene is used by our bodies to make vitamin A. Vitamin A deficiency is a big problem in parts of south Asia and Africa. It can cause people to go blind. 2) Golden Rice is a variety of GM rice. It contains two genes from other organisms which together enable the rice to produce beta-carotene. So fewer people will suffer from vitamin A deficiency if they eat golden rice.
How can genetic engineering help produce human insulin?
The human insulin gene can be inserted into bacteria to produce human insulin. Lots of human insulin can be produced quickly and cheaply to treat diabetes.
How can genetic engineering increase crop yield?
GM crops have had their genes modified e.g to make them resistant to herbicides. Fields of these crops can be sprayed with a herbicide and all the plants except GM crop are killed. This can increase the yield of the crop making more food.
Why do some people thing genetic engineering is a bad thing?
Some people are worried about the long-term effects of genetic engineering, that it may create some unplanned problems such as: -Some thing GM crops will affect the number of weeds and flowers (therefore wildlife) that usually lives in and around the crops - reducing farmland biodiversity -Not everyone is convinced that GM crops are safe, people worry the may develop allergies to the food -Some worry transplanted genes may get out into the natural environment e.g herbicide resistance may be picked up by weeds creating a superweed.
What are diploid cells?
Cells that have two sets of chromosomes. Human body cells are diploid.
What is mitosis?
How cells divide for growth and repair. This happens when humans, animals and plants want to grow or replace cells that have been damaged.
What are the stages of mitosis?
-The parent cell is a diploid cell (it has two sets of chromosomes). Before the parent cell divides, each chromosome is copied exactly. The parent cell divides to form two daughter cells that are genetically identical to each other and the parent cells (these are also diploid cells)
What are situations where mitosis is used to produce new cells?
-Growth-Repairing damaged parts of the body -Asexual reproduction
What is asexual reproduction?
Asexual reproduction is the production of new organisms without fertilisation. The offspring have exactly the same genes as the parent - so there's no genetic variation.
When might asexual reproduction happen?
-When bacteria split to make more bacteria-When plants make new plantlets that split off from the parent plant to grow on their own.
What are gametes?
Gametes are 'sex cells'. They are called ova (single ovum) and sperm in males. During sexual reproduction, two gametes combine to form a new cell which will grow to become a new organism.
What are haploid cells?
Haploid cells have only one copy of each chromosome. Gametes are haploid.
Why are gametes haploid?
So that when two gametes combine at fertillisation, the resulting cell (zygote) has the right number of chromosomes. Zygotes are diploid - they have two copies of each chromosome.
What is meiosis?
Meiosis is when a cell divides to produce four haploid nuclei whose chromosomes are NOT identical. Meiosis only happens in reproductive organs e.g ovaries
What happens during meiosis?
As with meiosis, before the parent cell begins to divide, each chromosome is copied. The cell divides in two and then in two again. Four daughter cells are produces. Each daughter cell gets a copy of one chromosome from each pair. Each daughter cell has only one set of chromosomes therefore these are haploid cells. The daughter cells are not all identical - meiosis results in variation.
What happens during sexual reproduction?
During sexual reproduction, two gametes for a new cell which will grow to become a new organism. The two gametes combine (sperm and egg) to produce a zygote (fertilised egg). Sexual reproduction produces variation in the offspring.
What is cloning?
Cloning is a type of asexual reproduction. It produces cells that are genetically identical to an original cell.
What are clones?
Clones are organisms that have identical genes.
How is cloning done?
1) The nucleus is removed from an egg cell 2) The diploid nucleus is removed from an adult body cell.3) The diploid nucleus from the body cell is placed inside the empty egg cell. The cell is then stimulated with an electric pulse to start mitotic division. 4) The cell divides and grows as an embryo 5) The embryo is placed in the uterus of a surrogate mother until it is ready to be born.
What are the advantages of cloning?
- If the animal that is cloned has good features, all of its offspring will have the same good features. - Cloning mammals can help with the shortage of organs for transplants- Cloning can be used to help preserve endangered species
What are the disadvantages of cloning and some issues surrounding cloning?
- Any genetic defect in the parent will be passed on to the offspring- Clones mammals may suffer more health problems than usual, which may cause them to die early - It is more difficult to clone a mammal than a plant; it may take a few attempts- Cloning mammals leads to a reduced gene pool (fewer alleles in the population). This may mean if there is a new disease all the species could become extinct
What are stem cells?
Stem cells are cells that can divide to produce many types of cell. There are two kinds of stem cell; embryonic and adult stem cells.
What are embryonic stem cells?
Embryonic stem cells are taken from embryos that contain only a few cells. The cells in the embryo are all the same (undifferentiated). Stem cells are easy to extract from an embryo. They can also produce any type of cell.
What are adult stem cells?
Adult stem cells are found in differentiated tissue, such as bone or skin - they divide to replace damaged cells. No embryo is destroyed so there's no ethical issue. If adult stem cells are taken from the person to be treated, it will not cause rejection to the body.
What are disadvantages to using embryonic stem cells?
-The embryo is destroyed when the cells are removed and some people think embryos have a right to life- The body recognises the cells are different and will reject them without the use of drugs.
What are the disadvantages of adult stem cells?
-They are difficult to find and extract from tissue-They produce only a few types of cell
What is a risk of using stem cells?
They may produce cancer cells instead of healthy cells
What is respiration?
Respiration is the process used by all living organisms to release energy from organic molecules. Respiration is how all living things get energy from food.
What is the energy from respiration used for?
- Growth and movement - Build up larger molecules (like proteins)- Contract muscles - Maintain a steady body temperature
What is aerobic respiration?
Aerobic respiration uses oxygen from the air to release energy from glucose.
What is the word equation for aerobic respiration?
Glucose + Oxygen = Carbon dioxide + water (+energy)
What is anaerobic respiration?
Anaerobic respiration is the release of energy from glucose without using oxygen. This produces lactic acid.
What is the word equation for anaerobic respiration?
Glucose = lactic acid (+energy)
When is anaerobic respiration used?
Anaerobic respiration happens when there's not enough oxygen available. Anaerobic respiration does not release as much energy as aerobic respiration. It also produces build up of lactic acid in the muscles which gets painful and can give you cramp.
What is the advantage to using anaerobic respiration?
You can keep on using your muscles for longer. Anaerobic respiration is useful for muscle cells because it can release energy to allow muscles to contract when the heart and lungs cannot deliver oxygen and glucose fast enough for aerobic respiration.
What is the disadvantage to using anaerobic respiration?
-Anaerobic respiration releases much less energy from each molecule of glucose than aerobic respiration. -Lactic acid is not removed from the body. It builds up in muscle and blood, and must be broken down after exercise.
What is EPOC?
EPOC (excess post-exercise oxygen consumption) is the amount of oxygen needed after exercise has ended compared with the resting rate.
What is diffusion?
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
When is diffusion used?
Many substances enter and leave the body by diffusion. These substances include gases such as oxygen and carbon dioxide, and small digested food molecules such as glucose.
Why is diffusion needed?
-When cells respire they use up oxygen and glucose, so the concentration of these inside the cells is low. The concentration of these substances in the blood is higher, so they diffuse from the capillaries into the cells. -When cells respire they produce carbon dioxide therefore the concentration is high. The carbon dioxide diffuses from the cells into the blood where the concentration is lower.
Why do you respire more during exercise?
Muscles need energy from respiration to contract. When you exercise some of your muscles contract more frequently than normal so you need more energy. This energy comes from increased respiration. The increase in respiration means you get more oxygen to the cells.
Why is it important that you breathing rate increases during exercise?
Your breathing rate increases to get more oxygen into the blood around the body so your heart rate increases. This removes CO2 more quickly at the same time.
How do you calculate cardiac output?
Cardiac output = heart rate * stroke volume
How could you investigate the effect of exercise on breathing and heart rate?
-You can measure breathing rate by counting breaths and heart rate by taking a pulse. -You could exercise for 5 minutes doing three different exercises of different intensities. After each exercise take your pulse and heart rate. -Your pulse rate will increase the more intense the exercise is as your body needs to get more oxygen to the muscles ad take away the carbon dioxide.
What is photosynthesis?
Photosynthesis is the process that plants use to make glucose.
Where does photosynthesis happen?
In the leaves of all green plants. It happens inside the chloroplasts. They contain chlorophyll which absorbs energy in sunlight and uses it to convert carbon dioxide and water into glucose.
What is the equation for photosynthesis?
SUNLIGHTcarbon dioxide + water = glucose + oxygen CHLOROPHYLL
How are leaves adapted for photosynthesis?
-Leaves are BROAD so theres are large surface area exposed to light -Leaves contain lots of CHLOROPHYLL in chloroplasts to absorb sunlight-Leaves have little holes called STOMATA. That open and close to let gases like CO2 and 02 in and out. They also allow water vapour to escape which is known as transpiration.
What is the stomata in in leafs for?
The stomata in the leaf surface allow carbon dioxide needed for photosynthesis to diffuse into the leaf. They also allow oxygen and water vapour produced by photosynthesis to diffuse out of the leaf.
What might affect the rate of photosynthesis (limiting factors)?
-Light intensity (night = no light)-Concentration of CO2 -Temperature (winter = cold, in an experiment you could use different temperature water baths)
What might be an experiment to work out the ideal condition for photosynthesis in a plant?
-Place a plant e.g Pondweed in a flask.-Add some water-Change the thing you testing -Place a bung on top-Measure how much oxygen is produced by counting the bubbles given off, or if you wanted to be more precise, use a gas syringe. -To keep it a fair test, make sure the light if used isn't getting blocked by anything and keep the flask in a water bath to keep it a contant temperature (..that is if your not testing the temperature effectiveness).
How does light effect photosynthesis?
-Light provides energy needed for photosynthesis -As the light level is raised, the rate of photosynthesis increases steadily - but only up to a certain point-Beyond this point, light intensity wont make any different, it will either be the amount of CO2 or temperature that is the limiting factor. -You could change light intensity by moving a lamp -
How does carbon dioxide effect photosynthesis?
-CO2 is one of the raw materials needed for photosynthesis -CO2 concentration will only increase up to a certain point, after it is other limiting factors which effects the rate of photosynthesis -When a graph flattens out, it shows carbon dioxide is no longer a limiting factor-A way to control the concentration of CO2 may be by dissolving different amounts of sodium hydrocarbonate in the water of the plant.
How does temperature effect photosynthesis?
-If the temperature is too low, the enzymes needed for photosynthesis work more slowly-If the plant gets too hot, the enzymes needed for photosynthesis will become denatured this happens at around 45 degrees
What is osmosis?
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of lower water concentration
What is a partially permeable membrane?
A membrane that has very small holes that only small molecules such as water can pass through them and bigger molecules such as sugar molecules cant.
How does osmosis work in a solution of sugar molecules and diluted sugar molecules? (4 marks)
Definition of osmosis. Water molecules are small enough to pass through the membrane while sugar molecules are too large.
how can potato strips be used to investigate osmosis?
-Cut potatoes into identical cylinders and get some beakers with different sugar solutions in them. Measure the lengths of the potato cylinders. -Using same size beakers, place an even amount of potato cylinders in a beaker with pure water and a beaker of concentrated sugar solution. -After half an hour or so, take out the potato cylinders and measure them. IF water has moved into the cylinders by osmosis they'll be longer. If they have shrunk, water has moved out.
What is a dependent variable?
Things you keep the same
What is an independent variable?
One that chnges.
How are root hair cells adapted to take in water by osmosis?
-The cells on plant roots grow into long 'hairs' which stick out into the soil. -Root hairs are covered in millions of microscopic hairs which give them a large surface area for absorbing water from the soil. -There's usually a higher concentration of water in the soil than there is inside the plant so the water enters the root hair cell by osmosis.
How do root hairs take in minerals?
-Using active transport. Define active transport -Root hairs also absorb minerals from the soil-The concentration of minerals in soil is low. It is usually higher in the root hair cell than in the soil around it
What is active transport?
Active transport uses energy from respiration to help the plant pull minerals into the root hair against the concentration gradient. This is essential for growth. Minerals cannot enter the root cells from soil water by diffusion as the concentration is too high.
What are the types of transport?
-Diffusion = Substances move down their concentration gradient. There is no energy needed-Active transport = Substances move up (or against) their concentration gradient. There is no energy needed-Osmosis = Diffusion of water molecules
What is transpiration?
Transpiration is the evaporation of water from inside leaves out into the air. It causes water to move up the plant from the roots. (Transpiration is the loss of water from the plant)
What do xylem tubes do?
Xylem tubes transport water and minerals from the root to the rest of the plant e.g the leaves.
What are phloem tubes?
Phloem tubes transport sugars from the leaves (where their made) to growing and storing tissues.
What happens during transpiration?
-Water evaporates and diffuses from inside the leaves creating a water shortage and so more water is drawn up from the xylem vessels to replace it.-This means more water is drawn up from the roots and so there's a constant transpiration stream of water through the plant. The water enters the roots by osmosis
How do minerals and water travel through a plant?
-Water and dissolved minerals enter plants through their roots from the soil water -Water and dissolved minerals from the roots travel in xylem to the rest of the plant-Glucose, produced by photosynthesis in leaves is converted to sucrose, which is transported in phloem to the rest of the plant.
What is a habitat?
A habitat is the place where an organism lives
What are things you can use to measure the distribution of organisms?
-Pooters -Pitfall traps-Sweep nets-Pond nets
What are pooters?
-Pooters are for collecting ground insects-Pooters are jars that have rubber bungs sealing the top, and two tubes stuck through the book-If you suck the shorter tube and put the end of the longer tube over an insect, it'll be sucked into the jar-Fine mesh strips stop the insect from being breathed in
What are pitfall traps?
-Pitfall traps are for collecting small ground living animals-They are steep-sided containers that are sunk in a hole in the ground. The top is partly open-Leave the trap overnight in the first sample area. Insects fall into the container and cant get out again so you can count them.
What are sweep nets/pond nets?
-Sweep nets are used for collecting animals in long grass-Pond nets are used for collecting animals from ponds. -The net is lined with strong cloth for collecting insects from long grass.-Sweep the nets through long grass or a pond and count how many insects are in the net.
What is a quadrat?
-A quadrat is a square frame enclosing a known area. A quadrat can be used to sample plants or animals that don't move much.
How would you use a quadrat?
-Place each quadrat randomly in a sample area -Count the number of organisms, or estimate the are covered by the organism in each quadrat.-Repeat in different areas-Calculate an average measurement from all of your results
How would you calculate total population using quadrats?
Total polpulation = Average * total area
What are environmental factors that might effect the distribution of organisms and how would you measure them?
-Temperature = Use a thermometer-Light intensity = Use light probes or a light meter -pH of soil = Mix a sample of soil with distilled water, then measure the pH using universal indicator or a pH probe
What are fossils?
Fossils are the preserved traces or remains of organisms that lived thousands or millions of years ago
Why is the fossil record not complete?
-Fossils do not always form (fossils only form if the ground is suitable e.g not too acidic)-Soft tissue decays (hard tissue e.g bones may fossilise but soft tissue e.g muscles usually decay too quick-Many fossils are yet to be found (we only find fossils whee we can dig them up, many are deep underground)
What are the three ways fossils can be formed?
-From gradual replacement by minerals = things like teeth and bones don't decay easily -From casts and impression = Fossils can form when an organisms buried in soft material causing a cast to form e.g footprints-From preservation = In places where no decay happens, this could be because the conditions aren't suitable for microbes e.g too cold
What do fossils found in rock layers show?
-What creatures and plants look like-How long ago they existed-How they've evolved
How does the pentadactyl limb provide evidence for evolution?
-A pentadactyl limb is a limb with five digits-The pentadactyl limb is in many species-In each of these species the pentadactly limb has similar bone structure, but usually a different funtion e.g a human hand and a bat wing-The similarity in bone structure provides evidence that species with a pentadactyl limb have all evolved from a common ancestor.
How can you measure an organisms growth?
-Size (height, weight, width and circumference)-Wet mass (the wet mass of the organism is the mass including all the water in its body, it can vary each day)-Dry mass (the mass of an organism with no water in its body)
Why do plants and animals grow and develop?
Due to these processes: -Cell differentiation (where a cell changes to become specialised)-Cell division (by mitosis)-Cell elongation (where a plant cell expands, making it bigger)
How does growth in animals happen?
-Cell division. -Animals tend to grow while their young and then they reach their full growth and stop growing.
How do plants grow?
Continuously. Plants continue to differntiate to develop new parts e.g leaves and roots.
How do people use percentile charts?
Percentile charts can help show if somebody or something is growing faster or slower than its normal rate.
How does growth and development in plants happen?
-Plant growth include CELL DIVISION just behind the shoot tip and CELL ELONGATION further away from the tip of the shoot. Cells at the tip of the shoot are the same and they can develop into any kind of cell in a plant.
How is the growth and differentiation in plants and animals compare?
-Plants produce new cells at their shoot and root tips and continue growing all their lives. Differentiation of plant cells happens behind the shoot or root tips.-Growth by cell division in animals is rapid in the embryo but gets slower as the animal gets older. Cells differentiate as the animal gets older until only a few stem cells are left.
What is tissue?
Tissue is a group of similar cells that work together to carry out a particular function.
What are organs?
An organ is a group of different tissues that work together to perform a particular function e.g heart
What is an organ system?
An organ system e.g the circulatory system is a group of organs working together to perform a particular function
What is the heart?
The heart is an organ that contains tissues such as heart muscle and tendons. Heart muscle is formed from heart muscle cells.
What is the structure and function of the heart?
-The heart has FOUR CHAMBERS and FOUR MAJOR BLOOD VESSELS -The RIGHT ATRIUM of the heart receives deoxygenated blood from the body (through the vena cava)-The deoxygenated blood moves through to the RIGHT VENTRICLE, which pumps it to the lungs (via the pulmonary artery)-The LEFT ARTRIUM receives oxygenated blood from the lungs (through the pulmonary vein)-The oxygenated blood then moves through to the LEFT VENTRICLE, which pumps it out round the whole body (via the aorta)-The LEFT VENTRICLE has a much thicker wall than the right ventricle because it needs more muscle because it has to pump blood around the whole body, whereas the right ventricle only has to pump it to the lungs-VALVES prevent backflow of the blood.
What does the pulmonary artery do?
Carries deoxygenated blood from the heart to the lungs
What does the vena cava do?
Brings deoxygenated blood from the body to the heart
What does the left artrium do?
Recieves oxygenated blood from the lungs (through pulmonary vein)
What do the valves do?
Prevent blood flowing the wrong way through the heart (backflow)
What does the left ventricle do?
Pump blood around the whole body via the aorta. The left ventricle has a much thicker wall than the right because it needs to pump blood around the whole body whereas the right ventricle only has to pump it to the lungs
What does the aorta do?
Carries oxygenated blood from the heart to the body
What does the pulmonary vein do?
Brings oxygenated blood from the heart to lungs
What is the circulatory system?
The circulatory system is an organ system that consists of the heart, the blood vessels and the blood. It's function is to transport materials around the body.
What do red blood cells do?
-Carry oxygen from the lungs to all the cells in thee body-They have a biconcave disc shape which give it a large surface area for absorbing oxygen -They contain substances of haemoglobin (contain iron)-Red blood cells don't have a nucleus
What happens in the lungs to haemoglobin?
-In the lungs, haemoglobin combines with oxygen to become oxyhaemoglobin. In body tissues the reverse happens to release oxygen to the cells.
What do which blood cells do?
-White blood cells defend against disease -They produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by microorganisms. -
What might happen if somebody has a low white blood cell count?
A low white blood cell count could increase the risk of infection, whereas a high count could mean you have an infection, or even leukaemia (cancer of the blood)
What a platelets?
-Platelets are fragments of larger cells. -They help blood clot-Their function is to cause blood to clot when a blood vessel has been damaged-The clot blocks the wound and prevents pathogens getting into the blood
What does the plasma do?
-Plasma is the liquid part of the blood-It carries the blood cells through the blood vessels-It contains many dissolved substances, such as carbon dioxide and glucose
What is urea?
A waste product formed in the liver. The blood transports it to the kidneys where it is removed.
What are the three different types of blood cell?
-Arteries = These carry the blood away from the heart-Capillaries = These are involved in the exchange of raw materials with the tissues -Veins = Carry the blood to the heart
What do arteries do?
-Arteries carry blood under pressure. -The heart pumps the blood out at high pressure so the artery walls are strong and elastic -The walls are thick compared to the size of the hole down the middle (the 'lumen). They contain thick layers of muscle to make them strong
What do capillaries do?
-Capillaries are really small-Artries branch into capilaaries-They carry the blood really close to every cell in the body to exchange substances with them -They have a permeable walls, so substances can diffuse in and out -They supply food and oxygen and take away waste such as CO2 -Their walls are usually one cell thick which increases the rate of diffusion by decreasing the distance over which it occurs.
What do veins do?
-Veins take blood back to the heart-Capillaries eventually join up to form veins-The blood is at lower pressure in the veins so the walls don't need to be as thick as the artery walls -They have a bigger lumen than arteries to help the blood flow despite the lower pressure-They also have valves to help keep the blood flowing in the right direction
What is the role of arteries, veins and capillaries in the human circulatory system?
-Arteries carry blood away from the heart - all arteries except the pulmonary arteries carry oxygenated blood to the body. Veins carry blood towards the heart - all veins except pulmonary veins carry deoxygenated blood from the body back to the heart. Capillaries exchange materials, such as oxygen, glucose and carbon dioxide with body tissues.
What is the breakdown of food caused by?
Breakdown of food is catalysed by enzymes
What does the digestive system do?
The digestive enzymes break down the big molecules into the smaller ones: -Carbohydrates e.g amylase digest starch to sugars-Proteases e.g pepsin digest proteins to amino acids -Lipase digests fat to fatty acids and glycerol
How does the digestive system work?
-In the mouth food is moistened with saliva from the salivary glands-The salivary glands produce amylase enzyme in the saliva which breaks down starch-Food is chewed to form a ball of food (bolus before being swallowed)-The oesophagus is a tube that takes food from the mouth to the stomach. It's lined with muscles that contract to help the ball of food move along, by peristalis-The liver is where bile is produced. Bile neutralises stomach acid and emulsifies fats. -The stomach pummels the food with its muscular walls. It produces the protease enzyme pepsin. It produces hydrochloric acid to kill bacteria to give the right pH for the protease enzyme too work-The gall bladder is where bile is stored before its released into the small intestine -The pancreas produces protease, amylase and lipase enzymes. It releases these into the small intestine -The small intestine produces portease, amylase and lipase enzymes to complete digestion. This is also where the food is absorbed out of the digestive system -The large intestine is where excess water is absorbed from the food
What do carbohydrases do?
Digest carbohydrates
What do proteases do?
Digest proteins into amino acids
What do lipases do?
Digest fats to fatty acid and glycerol
What is the role of bile in the digestion of food molecules?
Bile is added in the small intestine to neutralise stomach acid. This means that the enzymes in the small intestine can work at their optimum pH. Bile also emulsifies fats, so there's a greater surface area for lipases to work on
What is visking tubing?
-Visking tubing is a good model for the gut because, like the gut, it only lets small molecules through and not big molecules. However, visking tubing isn't exactly the same as you gut is alot longer and has a large surface area so the speed of digestion and absorbtion will be slightly different
How does the structure of the gut help digestion?
-Theres longitudional muscles down the length of the gut and circular muscles running in circles around the gut-The muscles squeeze the food along. This squeezing action is called peristalsis-Waves of circular muscle contraction push the food along the gut-Waves of longitudional muscle contractions run slightly ahead t help keep the food in a ball
What is villi?
-The inside of the small intestine is covered in million of villi. Villi have three features that make absorbing digested food into the bloodstream very efficient:-The have a large surface area so that digested food is absorbed more quickly into the blood -They have a single layer of surface cells so that digested food diffuses quickly over a short distance-They have a very good blood supply via a capillary network to assist quick absorbtion of digested food.
What are functional foods?
Functional foods are ones that have some kind of health benefit beyond basic nutrition. For example it might prevent some kind of disease
What are probiotics?
Probiotics are live bacteria. These are 'good bacteria' and are similar to those in the gut. Probiotics are added to foods such a yogurt. It's thought they may help keep your digestive system healthier by replacing gut bacteria that are lost during antibiotic treatment.
What are prebiotics?
Prebiotics promote the growth of 'good' bacteria. Prebiotics are carbohydrates that we can't digest. The occur naturally in foods like leeks but some people take supplements for significant effect. They could help improve your digestive system.
What are plant stanol esters?
Plant stanol esters reduce cholesterol. They are chemicals that can lower blood cholesterol and reduce the risk of heart disease. They occur naturally in plants but in very small amounts. They are produced commercially in bacteria.