Biology paper 2 aqa

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cellulose). Breakdown of glucose in respiration to release energy. Proteins Synthesis of amino acids from glucose and nitrate cons. • Amino acids used to form proteins. Excess proteins broken down to form Urea for excretion.? variation Lipids & Synthesis of lipids from one molecule of glycerol and three molecules of fatty acid. metabolism 0 populations Differences in the characteristics in a are called variation, variation may be due to differences in : The genes they have inherited for example eye colour. The environment in which they have developed. A combination of genes and the ent nment. mutation: There is usually a lot of genetic variation within a population of a species arises from mutations - this Subject A → Subject → A mutation is a change in a DNA sequence mutations occur continuously. • very rarely a mutation will lead to a new phenotype, but some may change an existing phenotype and most have no effect. •If a new phenotype is suited to a environmental change. It can lead to a relatively rapid change in the species. Cloning mature egg adult cell nucleus removed O a cell variation mock B ↑ nucleus removed fused together - ariation A Clone is an individual that has been produced asexually. and is genetically identical to its parent. implanted into Subject ->> clone melosis halves the amount of chromosomes in gametes and fertilisation restores the full number of Chromosomes. mecosis 0 melosis is a type of cell division that makes gametes in the reproductive organs. Parent cell 0 0 DNA Replicates Genetic inheritancer Each daughter cell forms 2 gametes 0 They are all genetically different Reproduction • Gene → part of chron protein. Some a single gene but most are caused by genes interacting. Two daughter cells • Gamete → Specialsed sex cell formed by melosis. Chromosome → long molecule found in the nucleus of cells made from DNA. Allele → Different forms of the same gene. Pominant → Allele that only needs one copy to be expressed (it is always expressed). • Recessive → Allele that needs two copies present to be expressed. con some that codes for a characteristics are controlled by Homozygous → when an individual carries two for trait. Heterozygous when an individual carries two a tract. acnotype combination of aucies an individual Phenotype → Physical expression of the genotype- the characteristic shown. DNA + Genome Genetic material in the nucleus of a cell is composed of DNA. DNA is made up of two Strands forming a double helix. DNA IS Contained in Structures called Chromosomes. A gene is a small section of DNA on a chromosome that codes for a specific Sequence of amino acids, to produce a specific protein. The genome is the entire genetic material. Selective breeding cartificial selection) is the process by which humans breed plants and animals, for paticular characteristics. Benefits: • Disease resistance in food crops" • Animais produce more meat or milk. Domestic dogs with a gentle nature, 0 selective breeding RISKS: • can lead to cloning inbreeding, where some breeds are particularly. prone to inherited defects or diseases. Sexual reproduction O • Two parents, cell division through matosis. JOLning (Fusion) of male and female sex cells (gametes) sperm and egg in animais pollen and ovule in plants. - 。 Produces non-identical offspring that are genetically different to the parents. Reproduction Advantages : • Produces variation in Offspring • If the endironment changes, the Offspring may have a surowal advantage due to their genetic variation. Disadvantages : • finding a mate and reproducing is time consuming and requires lots of energy. Asexual reproduction One parent, cell division through mitosis, no FUSION of gametes, Offspring are clones of the parent. Advantages: • Only one parent needed • Time and energy efficient as do not need to find a mate. • faster than sexual reproduction, identical Off Spring co be produced when Conditions are favourable! Successful traits passed on. many O 0 Disadvantages : Reduced genetic variation - If the environment changes the offspring may have a survival disadvantage. mutations in parent would be passed on to all Offspring. O Darwin's work • Charles Darwin proposed the theory of evolution by natural selection. 。 This states that all Living species evowed from a common ancestor that first developed more than three bilion years ago. It has been Shown that Characteristics are passed onto offspring ingenes. Evidence from the FOSSII record. Natural selection Evolution of Antibiotic resistant bacteria. •The theory of natural selection States that : →Organisms within a species show a wide range of variation in phenotype. Individuals with characteristics Suited to the environment are more likely to survive. →These characteristics are then passed onto their Offspring. Evidence for evolution JOLELO Speciation • Evolution occurs throw the process of natural Selection and may result in a new Species. O Theory of evolution Evolution: The gradual Change in the inherited Characteristis of a population. Alfred Russel wallace, Independently proposed the theory of natural selection and évolution. He published joint writings with Darwin in 1858 on the subject. Wallace worked worldwide gathering evidence for evolutionary theory. •Speciation The gradual formation of a new Species as a result of evolution. Process → 1. TWO populations of one species are isolated (e.g. by a river or a mountain range). 2. Natural selection occurs so that the better adapted individuals reproduce and pass on these Characteristis. 3. The populations have an increasing number of genetic mutations as they adapt to their different environments. 4. Eventually the two populations are so genetically different they cannot breed to produce fertile Offspring. Extinction Extinction is when there are no more living individuals of a species Still alve. Structure OF DUA DNA is made Of repeating nucleotide units 0 O Alternating Sugar+ phosphate backbone DNA IS a polymer made from four different nucleotides. A nucleotide is a molecule made of a phosphate, a Sugar and one of four Organic bases (A.C. G and T). x 2 A Sequence of three bases codes for a particular amino acid. The order of the bases determines the Order in which aming acids are assembled to produce a specific protein. In complimentary, DNA Strands cand a are united and Tand A. Reproduction Protein synthesis on the ribosomes using a template of DNA Carrier molecules bring amino acids to add to the protein chain in the correct order when the Protein is complete it folds up to form a specific Shape which allows proteins to do specific jobs. Non-coding parts of DNA can control the expression of genes by switching them on and off. M father mutations occur continuosly and change the the base code of DNA. In coding DNA they may alter the activity of a protein. mother B B bBb Bb bBb Bb Proteins are Synthesised most do not alter the appearance or function of the protein the DNA produces. • A change in DNA structure may change the amino acid order, causing a gene to Synthesise a different protein, some mutations alter the shape of a protein, so the protein may no Longer fit the substrate binding site. or lose its strength if it is structual. Polydacty!. → Extra fingers / toes. Dominant allele. Cystic fibrosis (Disorder of cell membranesi recessive. Genetic crosses A genetic cross is when you Consider the Offspring that might result from two known parents. Punnett squares can be used to predict the outcome of a genetic cross, for both pheno + Genotypes. e.g : 1 Genotype: 100% Bb phenotype: All black for Structure of the eye. retina O Sclera Sopric OU nerve is the Accommodation Process Of Changing the Shape of a lens to focus on near or distant Objects. Treatments of eye defects a D Tens cornea Suspensory ligament Ciliary muscle TO FOCUS On a near object Clary muscles contract Suspensory ligaments slacken solens is thicker and more curved and refraces light rays more strongly. TO FOCUS On distant objects ciliary muscles relax so Suspensory ligaments are pulled taught. Lens: Sits behind the Pupil and focuses light onto the reting Cornea: Transparent + Changes lights direction Retina: contains light sensitive cells (conest rods) Sclera & Protects eye Accommodation Nervou System + Homeostasis Homeostasis is the regulation Homeostasis Of internal conditions in a Spectade lenses to refract light Hard+ Soft contact lenses, lasereye surgery, replacement lenses. response to internal and external change to constantly maintaihoptimum conditions to function. Control of body If temperature is too high : dilation) 0 temperature Blood vessels dilate cuasodilation) this means more heat energy is Cost to the surroundings. Sweat is produced from the sweat glands. Energy transferred from Skin to envir body temperature falls. ment so If temperature is too low O Blood vessels constrict cuasoconstriction) so less heat energy is lost to the surroundings. • Skeletal muscles contract 0 Body temperature frises. Body temperature is monitored and controlled by the thermoregulatory centre in the brain. The Centre contains receptors sensitive to the blood temperature. The nervous system Stimulus: Change in the environment (stimulus) is detected by receptors. Receptors: Information from receptors travers along neurones to the CNS as electrical impulses. 0 Coordinator the stimulus. The CNS coordinates the body's response to C O Effector Effectors bring about a response such as glands Secretung hormones or musdes contracting. Refiesc actions of the nervous System are automatic and rapid - they brain. Stimulus Receptor coordin Effector Response. do not involve the conscious part of the Stimulus> Sensory receptor → Sensory neurone → relay neurone → Synapse → CNS → motor neurone → Effector Reflex Arc Structures Nervous System + Homeostasis myelin Sheath dendates lens 4881 +Crminais The Brain Cerebral cortex : important for consciousness, intelligence, memory and language. cerebellum : coordinates muscle activity! medulla : Contrais unconscious activities eg breathing. common defects of the eye Reflex arcs cs Research on • Research on the brain is conducted the brain in three ways Studying patients with brain damage ↳ Electrically Stimulating parts of the brain 8 myopia (short- Sightedness) Synapses are gaps between neurones which allow electrical impulses from the nervous system to cross between neurones. rays of light. image produced infront of the retina. rays of light image produced behind the retina Hyperopia clong-sightedness) corrected using convex lenses. Corrected using concave lenses. Y concave lenses correctly focus light 0 convexienses refract light before it hits the lens. Human endocryne system The blood carries hormones to a target hormone where an effect is released. compared to the nervous system effects are slower burlast longer. The pituitary gland Secretes several hormones into the blood. If blood glucose is too high O Pancreas responds O The endocrine system is composed Of glands that secrete hormones into the bloodstream. • Insulin released 0 Glucose converted into glycogen. If blood glucose is too low 9 Pancreas responds Glucagon released Glycogen converted into glucose 0 a Type 2 diabetes •Body cloesn't respond to insulin Treated by Controlled clieb. Hormonal O control of blood glucose levels M. Coordination water concentration too high Pituitary gland • Less ADH 0 O RICiney tubules reabsorb less water. Blood Type one diabetes • Pancreas stops producing insulin treated by insulin injections and monitoring diet. maintaining water 0 water leaves the body through the lungs On exchalation, and water, ions + urea are lost from the skin in sweat. 2 balance water too low. • Pituitary gland • more APH kidney tubules reabsorb more water. Femporarily removed from patients body and filtered through a dialysis kidney dialysis machine. • Patients blood passes over dialysis fluid, which has no urea. Urea and waste products diffuse into dialysis fivid as there is a concentration gradient. waste products The digestion of proteins from food results in excess amino acids, which need to be excreted safely. These amino acids are deaminated in the liver to form ammonia. Ammonia is toxic solt is immediately converted into Urea for safe excretion. Hormones in the menstral cycle FSH & Released by the pituitary gland. causes egg to mature. Stimulates production Of oestrogen. Oestrogen: Released by the Ovaries. Causes lining Of uterus wall to thicken. Inhibits release of FSH, Stimulates release of LH. LH Released by the pituitary gland. Stimulates ovulation. Progesterone : Released by the Quares. maintains thick uterus lining. Inhibits release of FSH and LH. Contraception Oral contraceptives → contain hormones to inhibit FSH production so no eggs mature. Injection, implant Or Skin patch → Slow release of Progesterone to inhibit maturation and release of eggs. Disadvantages of IVF & 0 O Emotionally+ physically Stressful Tower success rate O D O O Stimulate the maturation of several eggs. Eggs collected from mother and fertilised in a lab. fertilised eggs developinto embryos Embryos inserted into mother's uterus. Hormones in plants Hormona Coordination O Fossils Treating. Infertility IVF treatments mother given Ethene: controls cell division. used to control ripening of fruit during Storage + transport. FSH and LH TO Gibberellins : Regulates developmental processes used to end seed dormancy, promote flowering. increase fruit size. Auxins Plant growth regulator used as a weed killer, rooting powder + promoting growth what are fossils + FOSSIIS are the remains Of Organisms from millions of years ago which are found in rocks. Fossils can be formed from : Parts of an organism that did not decay because one or more of the conditions needed for decay are absent. Hard parts of an Organism ce g. bones) when replaced by minerals. Preservation of the traces of organisms ce g burrows, footprints).