Paper 1 biology

• The nucleus contains the cell's genetic material and controls the cell's activities.
• The basic structure unit of all living organisms is the cell, which is the smallest unit of life.
• Cells contain cytoplasm, nucleus, ribosome, mitochondria, and cell membrane.
• Plant cells contain chloroplasts, vacuole, and a cell wall.
• Specialized cells are cells adapted for a specific role with features that are called adaptations.
• Sperm cells have a long tail to help them swim, packed with mitochondria for energy, a haploid nucleus with only half the normal amount of DNA, and an acrosome to help them digest their way into the egg.
• Egg cells have a thick jelly coat that hardens when the first sperm cell penetrates it, lots of mitochondria and nutrients to give it energy to grow, and a haploid nucleus with only half the normal amount of DNA.
• Silated cells, red blood cells, nerve cells, xylem cells, and root hair cells are other types of specialized cells.
• Bacterial cells have a cell membrane, cytoplasm, ribosomes, and a cell wall, but they don't have a nucleus.
• Tuberculosis is a lung disease that causes inflamed and broken down lungs, causing coughing up blood and other horrible symptoms, caused by bacteria, and is airborne, spreading through coughing and sneezing.
• Colds and flu are caused by a virus, are airborne, and spread through coughing and sneezing.
• Food poisoning is caused by bacteria and is spread through contaminated food, not cooked properly.
• Hemorrhagic fevers, such as Ebola, are caused by viruses and are spread predominantly through direct contact and bodily fluids.
• HIV/AIDS is a virus which is spread through sexual contact and bodily fluids, and can also be spread through blood.
• Chalara ash dieback, a disease in trees, causes the leaves of ash trees to wilt and kill the tree within about a year and a half, spread by a fungus, and is airborne, making it difficult to control.
• Malaria is caused by a protozoan, causing severe fevers and chills, and kills a few million people every year, spread by a vector, a mosquito carrying the malaria virus.
• Our body has evolved physical barriers and chemical defenses to keep us safe from pathogens, including mucus in the nose, cilia, hydrochloric acid in the stomach, and an enzyme called lysozyme.
• The immune response works by matching antigens on the surface of pathogens with antibodies produced by the body, coordinated by a type of white blood cell called a lymphocyte.
• A lymphocyte produces antibodies and when first infected, there might only be one lymphocyte that produces the right antibodies for the pathogen, but these antibodies are stuck to the surface of the lymphocyte, activating it and causing it to produce hundreds of thousands of copies of itself, flooding the body with antibodies and destroying all pathogens.
• Most of the lymphocytes produced in the immune response will die, but a few will remain in the body as memory lymphocytes, ready to quickly produce enough antibodies to destroy the pathogen if it is encountered again.
• DNA has a sugar phosphate backbone with alternating sequences of sugar phosphate, sugar phosphate, sugar phosphate, and the bases are attached to the sugar, not the phosphate.
• Genes come in different versions called alleles, and an allele can be dominant or recessive.
• A dominant allele means we only need one copy of it to show that feature, while a recessive one needs two copies of it to show the feature.
• Our genes are inherited from our parents, each parent giving us one allele of each gene.
• Punnett square is used to predict the likelihood of different offspring based on knowing the genotype of the parents.
• Discontinuous variation is variation that can only be one thing or another, caused by your genes, and cannot be changed.
• Continuous variation is caused by a combination of genes and the environment, and can be any number within a range.
• Variation is important as it affects your chances of survival, with no two people being the same.
• There are two types of variation discontinuous and continuous.
• Discontinuous variation can only be one thing or another, for example, blood group, and is caused by your genes.
• Continuous variation can be any number within a range, for example, height, and is caused by a combination of genes and the environment.
• Microscopes produce magnified images and use two lenses, the objective lenses and the eyepiece length, to determine the overall magnification.
• Micrographs are pictures produced by microscopes.
• Concentration is the number of particles in a given volume.
• The first way that substances move in and out of cells is diffusion, which is the movement of substances from high concentration to low concentration, described as being down a concentration gradient.
• Carbon dioxide enters a leaf from the air where there's a high concentration into the leaf where there's low concentration and oxygen leaves the leaf by the same process of diffusion.
• Osmosis is how water moves in and out of cells and it is the diffusion of water across a partially permeable membrane, such as a cell membrane.
• The concentration of water can be determined by the amount of solute that is dissolved in it, with a higher concentration of solute leading to a lower water concentration.
• Active transport moves substances from low concentration to high concentration, described as being up a concentration gradient.
• Cells that do a lot of active transport will have a lot of mitochondria to provide them the energy to do so.