Science Notes Yr 10 PDF

Chemical Reactions Law of Conservation of Mass - The mass of matter is always the same before and after the changes occur. The law of conservation of mass states that matter cannot be created or destroyed. The law of definite proportions states that a given chemical compound always contains the sam...

Chemical Reactions Law of Conservation of Mass - The mass of matter is always the same before and after the changes occur. The law of conservation of mass states that matter cannot be created or destroyed. The law of definite proportions states that a given chemical compound always contains the same elements in the exact same proportions by mass. Periodic Table Groups Groups are numbered 1–18 from left to right. The elements in group 1 are known as the alkali metals; those in group 2 are the alkaline earth metals; th; those in 17 are the halogens; and those in 18 are the noble gases. Alkali metals Alkaline earth metals Halogens ,Noble gases Period - Horizontal ow Group - vertical column Electronic configuration Group 1 - 1 valence electrons - (electrons in the outermost shell of an atom) Group 2 - 2 valence electrons … Group 8 - 8 valence electrons - Stability is achieved when the atom has a full valence shell ( 8 valence electrons) Ion - an atomic molecule with a net electrical charge due to the loss or gain of one or more electrons. Cation - positively charged ion Anion - negatively charged ion Chemical Change - there to tends be in change in appearance and/or physical properties of the new substance formed Eg: Permanent change in colour, the formation of a solid (precipitate), evolution of gad and emission or absorption of light and/or heat. Physical change - mostly involves a change in state of the substance and can be easily reversed Ionic Bonding one atom donates electrons to the other.In the formation of an ionic bond , one or more valence electrons are transferred from one another to another forming ions. Force between ionic bonds is electrostatic force. Non-metals that are missing one or two electrons to complete their outer shell have high electronegativity, such as chlorine and fluorine. On the periodic table, electronegativity increases as you move up in a group and to the right across the periods. In an ionic bond, the more electronegative atom takes an electron from the less electronegative atom, usually form crystal lattices. Covalent Bonding In a covalent bond , one or more valence electrons are shared. Covalent bonds are usually formed between nonmetals. Physical Properties Covalent Ionic Conductivity Non - conductors of electricity Conductors on electricity when liquid or dissolved in water. Melting Pointy Low High Physical State Usually gas Always solid at room temp Hardness The solids are soft and pliable Brittle Solids Structure Naming ionic and molecular compounds Ionic: cation always written before the anion Anion must end in ide , eg: chlorine - chloride Covalent: Assign prefixes to the elements , final element ending is changed to ide, eg: oxygen - oxide. eg: Diphosphorus pentasulfide Polyatomic Ions - covalently bonded groups of atoms and having a positive or negative charge caused by the formation of an ionic bond with another ion. Formula Polyatomic ion name: C2H302 - Acetate NO3 - Nitrate S04 2- Sulfate OH- Hydroxide C03 2- Carbonate PO4 3- Phosphate NH4 + Ammonium Indicators of a chemical reaction: odour production, temperature change, gas production, precipitation, and colour change. Law of Conservation of Mass: The law of conservation of mass states that in a chemical reaction mass is neither created nor destroyed. For example, the carbon atom in coal becomes carbon dioxide when it is burned. The carbon atom changes from a solid structure to a gas but its mass does not change. pH - is a measure of how acidic or basic a substance is. The pH scale serves as a measure of the concentration of hydrogen ions in a solution - The higher the concentration of hydrogen ions , the lower the pH - The lower the concentration of hydrogen ions. The higher the pH Indicators - An indicator is a chemical compound that changes its colour in presence of an acid or base. Acid : covalent compound a substance with particular chemical properties including turning litmus red, neutralising alkalis and tastes sour. - Tastes sour - Corrosive - phoh- When acids dissociate in water , the concentration of hydrogen ions increase Bases: - pH > 7 - Tastes bitter - - Turns red litmus blue - Feels slimy - Eg : bleach , soap, sodium hydroxide  A base is a substance which forms hydroxide ions OH- when dissolved in water A base will always have greater concentration of hydroxide ions than hydrogen ions OH- > H+ When bases dissociate in water, the concentration of hydroxide ions increase Strong Acid Weak Acid Strong Base Weak Base Hydrochloric acid Acetic Acid Lithium hydroxide Ammonia Nitric Acid Nitrous Acid Sodium hydroxide ethylamine Sulfuric Acid Phosphoric Acid Potassium hydroxide Aniline Perchloric acid Oxalic Acid Barium hydroxide Methylamine Neutralisation reaction Acid + Base - Salt and Water Hydrogen ions plus hydroxide ions equals water hence h20 Salt is a combination of the anion from the acid and the cation from the base. Acid + metal - salt + hydrogen gas Hydrogen ions from the acid form the hydrogen gas Salt is formed from the anion of tha cid and the cation of the base. Most metals react with acids. Acid + metal carbonate - salt + water + carbon dioxide When acids react with metal carbonates such as calcium carbonate, using lime water carbon dioxide can be detected ( calcium carbonate is formed when lime water is cloudy.) Combustion reaction A chemical reaction between a fuel and an oxidant to produce carbon dioxide and water. Usually, it's a reaction between a hydrocarbon and oxygen which yields carbon dioxide, water and heat. Product: heat/light + Water + Carbon Dioxide Corrosion: is the oxidation of metals by reactions of substances in the environment. ( type of oxidation reaction.) - Often water is involved - Reacts at different speeds - Effects of corrosion on metals: - Reduces the tensile strength of a ,aterial - Hamper’s its ability to conduct electricity  - Pitting and holes Prevention of corrosion - Protect the surface by applying a layer ( paint/oil) tha prevents air and water coming in contact with the metal. - Sacrificial metal coating - a thin coating of a more reactive metal that oxidises before the main metal - Alloying eg: stainless steel is alloyed in small quantities. Oxidation (gain of oxygen and loss of hydrogen) : Oxidation is a chemical process. It is defined as a process that occurs when atoms or groups of atoms lose electrons. Precipitation: A subset of double displacement reaction When substances in a solution are mixed an insoluble product is made. - Must follow precipitation rules N nitrates A acetates G group 1 S sulfate A ammonium G group 7 single Displacement reaction - - The more reactive substance will replace the less reactive substance in a compound. - Use activity series of metals Decomposition reaction - Opposite to synthesis - Complex substances break into simpler substances - Types : Thermal ( heat) , Electrical (electrolysis) and Light ( photolysis) Role of Acids in Digestion: In the stomach, hydrochloric acid (HCl)  - creates an acidic environment that helps break down food, ( helps break down digestive enzymes like pepsin than can break protein into smaller peptides.) - activates digestive enzymes. ( Pepsinogen , an inactive enzyme is activated to pepsin through the presence of hydrochloric acid. - It also kills harmful bacteria present in the food. - Gastric stomach juice contains HCL, which is secreted by glands that line in the walls of the stomach. As well as providing optimal condition for the decomposition of proteins, and responsible for killing bacteria in the stomach Role of Bases in Digestion: - To neutralise the acidity of the chyme, the pancreas releases bicarbonate into to the small intestine, raising the pH , that creates a neutral environment , suitable for all enzymes in the small intestine to function effectively - Activation of the enzymes : - Lipase - Amylase - Trypsin - Bicarbonate ensures that these enzymes can act on food efficiently to complete digestion. Aerobic respiration - A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also called cellular respiration - Energy is used for cellular processes like growth,repair and reproduction of cells - Exergonic processes release energy and will happen simultaneously without the need of continual input of energy. Anaerobic respiration - Anaerobic respiration occurs without oxygen and releases less energy but more quickly than aerobic respiration. ENDOTHERMIC Alcoholic fermentation Cellular respiration vs Photosynthesis Cellular respiration A chemical process that is a series of chemical reactions that produces energy Energy is used for cellular processes like growth,repair and reproduction of cells Exergonic processes release energy and will happen simultaneously without the need of continual input of energy. Break down glucose to produce ATP ( Adenosine triphosphate). EXOTHERMIC Photosynthesis: A reaction pathway ( series of chemical reactions) that produces glucose in the chloroplast on green plants. The glucose is a source of energy used in cellular respiration Aka a metabolic pathway that breaks down water and carbon dioxide and then is turned into glucose, Oxygen is the by - product. Motion Chapter 5 5.1 characteristics of motion Scalar quantity - only magnitude Vector Quantity - magnitude and direction Distance - how far an object travels (scalar) Si unit- metre(m) Displacement - the change in the position of an object (vector) Si unit- metre(m) Position-Time graphs(displacement-time graph)  - Picture of the motion of an object - Position–time graphs are really only useful when the motion is linear, that is, in the same line, such as east–west or up–down. Time is always on the horizontal axis and position is always on the vertical axis Speed and Velocity Speed- measures how fast an object is moving (scalar quantity) - Si unit - metres per second (m/s or ms^-1) Formula: Distance/ Time Average speed - the total distance travelled by the object divided by the elapsed time to cover that distance (scalar) Formula: Speed Time graph Instantaneous speed- the speed of an object in a particular moment in time Ticker timer - t is a device to record an object's movement by taking a spot on a paper tape at regular time intervals. The distance between dots on a ticker tape represents the object's position change during that time interval. A large distance between dots indicates that the object was moving fast during that time interval. A small distance between dots means the object was moving slow during that time interval. Velocity- the rate at what an object changes its position (vector quantity)  - Si Unit (m/s) - Velocity conveys information about the direction of movement while speed does not - instantaneous velocity is a vector quantity that describes the velocity at a specific instant in time during its journey Average velocity - defined as the rate of change of displacement with respect to time. (vector quantity) Formula: ( same as velocity ) Acceleration- the rate of change in velocity of an object with respect to time - Si unit m/s^2 or ms^-2 (vector quantity) - It is a measure of how quickly or slowly the velocity is changing , and in which direction - Acceleration describes a change in magnitude and/or direction of the velocity of an object. CHANGE IN VELOCITY EQUALS ACCELERATION Direction of acceleration -A positive acceleration does not always mean an object is speeding up nor is a negative acceleration not always mean an object is slowing down - An object speeds up when acceleration is in the same direction as velocity Speed/distance/time formula 5.2 Force, Mass and Acceleration Force - a push or a pull acting upon an object as a result of its interaction with another object, measured in Newtons (N). Mass - amount of matter in an object (mass always stays the same) Weight - force of gravity on an object Newton’s first law of motion Also known as the law of inertia, states that An object remains at rest or in constant motion unless acted on by a net unbalanced force. Inertia is the tendency of an object to stay in the same state of motion. For instance when a bus is moving, the person is moving at the same speed as the bus , however when the bus slows down by external forces ( brakes) , person inertia causes the person to keep moving forward at the same speed because there is no direct force acting upon the body. However your external forces such as seatbelts resist the forward motion of the person , preventing you from going forward. It's around the pelvis and chest as it has a rigid bone structure that can handle more force than other delicate parts of the body ( neck etc) also furthermore its a bigger surface area covered by the seat belt , reducing the risk of energy by preventing too much force small part of the body. Net force - sum of all force acting upon an object Force and Vector Diagrams Force ( free body) diagram - represents all the forces acting upon an object. ( bigger or smaller to show the magnitude of the force.) Vector diagram: Shows f net force ( resultant force ) , furthermore it has scale ( 1 cm - 1 N) Newton’s Second law of motion F = mass times acceleration , it states that acceleration of an object is directly related to the magnitude and direction of a force acting on the object, and inversely related to the mass of the object. Acceleration is a change of velocity over time. Velocity has both magnitude and direction. so even if the speed of an object is the same. if an object changes direction its accelerating. Newton’s 3rd law of motion For every action force, there is an equal and opposite reaction force. Only forces acting on the same object can cancel. Action-reaction pairs are forces of equal magnitude and opposite direction that act on a different object. Eg: Gun pushes on bullet( bullet is affected) --- bullet pushes back on gun (gun is affected ) (recoil) Player throws ball forward by exerting a force with hand on ball --- ball pushes back on hand ( action force acts upon ball. Reaction force acts upon hand) ACTS ON DIFFERENT OBJECTS HENCE ( NO CANCEL) IT STILL PROPELS. 5.3 Collisions and Energy Transformations Energy is the ability to do work It can be transformed (converted) or transferred ( from an object to another). Kinetic Energy The energy an object has because of its motion. The larger the mass , the greater the Kinetic Energy. KE is proportional to the square of the speed/velocity of an object. Formula: KE=J (joules) Mass=kg(kilograms) V=m/s² (velocity) Gravitational Potential Energy Energy stored in an object when moving an object to a height. The larger the mass and the height, the greater the GPE. GPE=J(joules) Mass=kg(kilograms) height=m(metres) g=gravtiy Elastic Potential Energy Is the potential energy stored as a result of distorting an elastic object. Eg: A flat ball cannot return energy hence cannot bounce. k=N/m(newtons per metre) e=(extension in metres) EPE=J(Joules) Law of conservation of energy Energy cannot be created or destroyed but merely changes forms. Energy Efficiency the use of less energy to perform the same task or produce the same result. Work-is the transfer of energy by a force acting on an object as it is displaced. Difference between energy transfer and transformation Energy transfer is the movement of energy from one place to another while energy transformation is where energy changes from one type to another. Momentum,Impulse and Collision Momentum means mass in motion ( vector quantity) units: kgm/s More momentum harder to stop ( force needs to be applied over a longer period of time) Change in momentum- a force acting for a given amount of time will change an object’s momentum. An unbalanced force will always accelerate an object ( speeding up or slowing down.) If force opposes motion ( frictional force), the object will slow down. Applied in the same direction, the object will speed up. Impulse - the change of momentum in an object when the object is acted upon by a force of interval of time. IMPULSE = CHANGE IN MOMENTUM Impulse formula Change in Momentum formula: Units: Ns(seconds) F= mass times acceleration F= mass times change in velocity/time MULTIPLY BOTH SIDES BY T F times T = mass times change in velocity Impulse = Change in momentum Conservation of momentum The law of conservation of momentum states that the total momentum in a closed system remains constant unless an external force acts upon it. The total momentum of the 2 objects before the collision is equal to the momentum of the objects after the collision. Collision Collision - is any event in which or two or more bodies exert forces on each other in a relatively short time. Elastic Collision - is a collision where the objects separate after impact and there is no net loss of kinetic energy in the system as the result of the collision. KE CONSERVED , NO HEAT ENERGY IS GENERATED Eg: two similar trolleys are travelling toward each other with equal speed. They collide, bouncing off each other with no loss in speed. This collision is perfectly elastic because no energy has been lost. Inelastic collision - a collision where kinetic energy is not preserved. KE IS NOT CONSERVED AND HEAT ENERGY IS GENERATED. There are two types: Perfect and Partially Perfect Perfectly Inelastic - velocity lost, momentum conserved , stick together - move as one Partially Inelastic - momentum is conserved some velocity is lost, stick together briefly then come apart. Evolution Origin of evolutionary ideas One of the first documented explanations for changes in species over time was Jean Bapistde de Lamark , a French naturalist, who believed in evolutionary change ,that organisms change over time due to changing environmental conditions. His theory of inheritance of acquired characteristics , which was first presented in 1801 , proposed that an organism can develop characteristics during its lifetime in order to adapt to its environment, and those changes are passed onto its offspring. His ideas cannot be replicated or tested hence the scientific world deemed his theory as unreliable. Darwin’s discovery of Galapagos islands. Charles Darwin, an English naturalist, read the works of Lamarck and with the background of scientific thoughts , set sail on a 5 year world cruise as an unpaid naturalist aboard the HMS Beagle. The year was 1831 and Darwin was only 22. Over the 5 years , Darwin kept record of fossils, record keeping of his observations in which his important journey was in the final stages of the voyage where Beagle set sail to the Galapagos Islands. Galapagos Islands - Chain of volcanic islands about 1000 km west of mainland Ecuador - Collected 13 finches , yet each specimen had slight differences in beak size and shape and represented a new species. Most of the species were born on different islands. - It looked desolate as there were only ‘’ wretched - looking weeds.’ - He noticed a change in beak size and shape , for instance the large ground Finch had a larger , more crushing beak to be able to consume large seeds, found in the ground of the arid lowlands. - However the warbler finch had a thin pointed beak, suitable to eat insects , a common food source on the islands. - Species were ell adapted to their environment - Darwin also observed tortoises , for example he noticed that tortoises that ate plants near the ground had rounded shells and shorter necks.  - Tortoises on islands with tall shrubs had longer necks and shells that bent upwards, allowing them to stretch their neck, - Different species lived on islands with different environments. On the Origin of Species by Means of Natural Selection Theory of Evolution by Natural Selection: Darwin argued that species evolve over time due to natural selection. Individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation. Variation Within Populations: Darwin highlighted that individuals within a species exhibit variations, which are critical for natural selection to occur. Struggle for Existence: He described how organisms produce more offspring than can survive, leading to competition for limited resources. This struggle for existence drives natural selection. Descent with Modification: Darwin proposed that all species share a common ancestor and that evolutionary change occurs gradually over generations, resulting in new species. Some species keep diverging, splitting eventually into multiple descendent species - ‘’ common descent.’’ Adaptation: He explained how traits that are beneficial in a particular environment tend to become more common, leading to better adaptation of the population to its surroundings. Evidence for Evolution: Darwin provided evidence for evolution from various fields, including comparative anatomy, embryology, the fossil record, and biogeography, to support his ideas about common descent and natural selection. Natural selection - Natural selection is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time. One mechanism that enabled Darwin’s natural selection was that all organisms that reproduce sexually have some measure of choice over which individual they reproduce with. Evolution of natural selection occurs as a result of competition between individuals in a population with different traits. Natural selection doesn't favour traits that are somehow inherently superior. Instead, it favours traits that are beneficial (that is, help an organism survive and reproduce more effectively than its peers) in a specific environment. Traits He made the following observations - Individuals in a species vary - Much of the variation was heritable ( traits are passed from parents to offsprings.) - Reproductive capacity is greater than needed( many species produce more offspring than are required to maintain population size.) - Resources are limited. Contrast of Lamark and Darwin’s Theory Lamarck’s Theory (Inheritance of Acquired Characteristics): Organisms acquire traits during their lifetime (use and disuse). These acquired traits are passed on to offspring. Example: Giraffes' necks became longer because they stretched to reach higher leaves. Evolution is driven by the organism’s direct response to environmental needs. Lacks understanding of genetics. Darwin’s Theory (Natural Selection): Traits arise randomly, and those better suited to the environment increase survival and reproduction. Organisms with favorable traits are more likely to pass them to offspring. Example: Beak shapes of Galápagos finches adapted over generations due to available food sources. Evolution is driven by natural selection, where advantageous traits become more common over generations. Integrated with genetics in modern evolutionary science. Key Differences: Lamarck focused on acquired traits; Darwin emphasized natural selection. Lamarck's theory didn’t account for genetics; Darwin’s theory is foundational in modern biology. Tree of Life Alfred Russel Wallace - Wallace was a naturalist collecting specimens in the Malay Archipelago. During his eight years there , Wallace collected thousands of insects, shells and bird skins, as well as mammal and reptile specimens. - When he became ill , he realised that species evolve by adapting to their environment. - He sent ‘’ An Essay by Mr. Wallace, entitled "On the Tendency of Varieties to depart indefinitely from the Original Type."’’ to suggest his own theory of evolution, which gave confidence to Darwin to publish his book. Wallace Line - Wallace found that fauna ( animal species) of Asia and Australia, divided through a line that runs through Bali and Borneo. It has since been discovered that this line is approximately the collision zone between the Asian and Australian continental plates. - The Australian side were characterised by marsupial species while the Asian side was populated by placental animals - Biogeography is the distribution of fossils of extinct plants and animals, supported by the theory of plate tectonics. - Plate tectonics provide a well supported explanation for the geographical isolation of species that eventually result in speciation - the evolution of new species. - Population - a group of interacting individual of a species living in a particular area Species - a set of organisms in which its members have similar characteristics and can reproduce with each other that produce viable and fertile offspring. Natural selection is the principle mechanism of evolution. Darwin proposed 4 requirements for natural selection: Variation exists between individuals in a population Many differences between individuals in a population are inherited. Not all individuals in a population survive to produce offspring Those individuals in a population that are fitter ( better adapted to the environment) contribute more to the next generation than those who are less fit. This is known as the survival of the fittest. Variation - the difference between individuals of the same species, caused by genetic and environmental factors. - Despite the unifying traits , no two people look the same ( except for identical twins). - Individuals of the same population generally have the same number and type of genes, but different alleles, ( variation of genes.) How do environmental conditions of a species put pressure on individual Environmental conditions exert pressure on individuals of a species through factors like temperature, availability of food, predation, and competition for resources. These pressures influence an individual's chances of survival and reproduction, a concept known as natural selection. For example, in the Arctic, where temperatures are extremely cold, animals like polar bears have evolved thick layers of fat and dense fur to insulate them from the cold. Those polar bears without these traits would be less likely to survive and reproduce, resulting in the survival of individuals better adapted to the harsh conditions. Natural selection - Natural selection is a process of adaptation by an organism to the changing environment by bringing selective changes to its genotype or genetic composition. ( caused by natural causes,guided by environmental factors) - Eg. During the Industrial Revolution , tree become darkened because of soot. Peppered moths with darker colouration had better camouflage against predators compared to the light-coloured pepper moth. Hence this population grew more and were more prominent in polluted forest areas Artificial selection - Artificial selection, also called selective breeding, is the process where humans identify desirable traits in animals and plants and use these traits to develop desirable phenotypic traits by breeding. Eg: A specific example of dog breeding is the breeding of Golden Retrievers. Golden Retrievers were selectively bred in Scotland during the 19th century by crossing the Yellow Retriever with the now-extinct Tweed Water Spaniel, along with other breeds such as Bloodhounds and Irish Setters. The goal was to create a breed that excelled in retrieving game from both water and land, with a gentle mouth for carrying game and a friendly, obedient temperament. Today, Golden Retrievers are known for their intelligence, gentle nature, and ability to be trained as service dogs, which makes them popular as family pets and working dogs. Allele Frequencies - refers to how common an allele is in a population. Gene Flow - is the transfer of genetic material from one population to another. Isolating mechanism- a mechanism that prevents two populations from interbreeding and thus enables the populations to diverge enough to allow separate species to evolve. Speciation - is the evolutionary process by which populations evolve to become distinct species Genetic drift - is the change in frequency of an existing gene variant in the population due to random chance When populations become reproductively isolated, they can evolve into two separate species. Reproductive isolation can develop in a variety of ways, including behavioural isolation, geographic isolation, and temporal isolation.  3 Types of isolating mechanism Temporal Isolation Occurs when individuals of different populations reproduce at different times Behavioural Isolation prevents gene flow between related species living in the same territory through difference in behaviour Mechanical isolation Occurs when there is a physical incompatibility between the body parts of potential mates. For instance flowers have a spiny barrier as a reproductive body , ( spiny barrier), thus excluding certain pollinators. Allopatric speciation ( aka geographic isolation ) - speciation that occurs when biological populations of the same species become isolated due to geographical changes. ( mountain ranges). Each population begins to experience very different environmental selective pressures. In their separate habitat, the different groups accumulate different gene mutations and are subjected to various selective pressures, hence favours different adaptations. Eg: The distance between the islands and the mainland ( South America) is too far for the little birds to fly and so gene flow between the mainland and the island species stopped. The environment of the Galapagos islands was different from the mainland. Hence the finches evolved from the ancestral mainland species by allopatric speciation. Sympatric Speciation - is when new species arise within an existing species that share the same geographical isolation. This form of speciation is much more common in plants than in animals. It may occur as a result of chromosome failure of chromosome separation during meiosis, the resulting new species cannot breed with parent species, but may be able to reproduce asexually. This is most common in animals when some individuals take advantage of a different niche ( small area within habitat with highly specific and limited conditions.) within the same environment. Sympatric speciation is less common than allopatric speciation because gene flow is not disrupted within the original population. Fossils - remains of an organism from a past geological age, embedded in rock or other substances by natural processes. Fossils provide important evidence for evolution and the adaptation of plants and animals to their environments. Fossil evidence provides a record of how creatures evolved and how this process can be represented by a 'tree of life', showing that all species are related to each other. The evolution of antibiotic resistant bacteria such as penicillin which was first introduced in the 1940’s and due to its widespread use in the 1950’s to treat bacterial infections , bacteria have developed antibiotic resistance. After an animal dies, the soft parts of its body decompose leaving the hard parts, like the skeleton, behind. This becomes buried by small particles of rock called sediment. As more layers of sediment build up on top, the sediment around the skeleton begins to compact and turn to rock. - Relative dating places fossils in a temporal sequence by noting their positions in layers of rocks, known as strata. As shown in the diagram, fossils found in lower strata were deposited earlier and thus must be older than fossils in higher strata (this principle is known as superposition). Absolute dating - (aka known as radiometric dating ) , relies on the radioactivity detected in rocks containing radioisotopes. Transitional fossils are fossils that show features of both an ancestral species and its descendants, providing evidence of evolutionary change between groups. They represent "in-between" forms that help illustrate how a species evolved over time. For example, Archaeopteryx is a transitional fossil that shows features of both dinosaurs (like teeth and a long bony tail) and modern birds (like feathers and wings), suggesting a link between dinosaurs and birds. Living fossils are organisms that have remained relatively unchanged for millions of years and closely resemble their ancient ancestors found in the fossil record. They provide insight into species that have survived with little evolutionary change. An example is the coelacanth, a type of fish that was thought to have gone extinct millions of years ago until it was found alive in the 20th century, showing little difference from its ancient fossilised relatives. Divergent evolution and convergent evolution are two evolutionary processes that describe how species evolve over time, but they occur in different contexts: Definition: This process occurs when two or more species share a common ancestor but evolve in different directions, leading to increasing differences over time. Result: Divergent evolution often results in homologous structures—similar structures with different functions due to adaptations to different environments. For example, the forelimbs of bats (wings) and whales (flippers) are homologous structures adapted for flight and swimming, respectively. Cause: Divergent evolution is typically driven by different environmental pressures and the need to adapt to diverse ecological niches Convergent Evolution: Definition: This occurs when species that do not share a recent common ancestor evolve similar traits independently due to similar selective pressures. Result: Convergent evolution leads to analogous structures—different structures with similar functions. For example, the wings of birds and insects are analogous because they evolved independently for flight but have different anatomical origins. Cause: This process occurs when unrelated species face similar environmental challenges or opportunities, leading to similar adaptations despite different evolutionary backgrounds. Homologous structures: Similar structures in different species that come from a shared ancestor, even if they have different functions (e.g., human arm and bat wing). Analogous structures: Different structures in unrelated species that have similar functions, but did not come from a shared ancestor (e.g., bird wings and insect wings). Vestigial structure - Structures that have no apparent function and appear to be residual parts from a past ancestor ( eg: wings of flightless birds and human appendix.) Comparative Anatomy: The similar bone structure of a human arm, a bat's wing, and a whale's flipper shows that they share a common ancestor, suggesting evolution through homologous structures. Embryology: Embryos of different species, like fish, birds, and humans, have similar early stages (e.g., gill slits and tails), indicating shared ancestry and evolutionary relationships. Comparative Biochemistry: The similarity in DNA sequences and proteins, such as the cytochrome c protein in humans and chimpanzees, suggests that these species share a common evolutionary path. Genetics Interphase is the phase of the cell cycle in which a typical cell spends most of its life. Interphase is the "daily living" or metabolic phase of the cell, in which the cell obtains nutrients and metabolises them, grows, replicates its DNA in preparation for mitosis, and conducts other "normal" cell functions. Mitosis: cell division for somatic cells. produce body and identical cells , essential for cell regeneration PMAT Prophase - the nuclear envelope where 92 sister chromatids are contained , centrioles go to the opposite sides of the cell. Spindle fibres from one side attach to one of their sister chromatids. Metaphase - all 46 chromosomes line up in the equator of the cells along the metaphase plate Anaphase - The centromere splits, allowing the sister chromatids to separate. At the conclusion of anaphase , each end of the cell has an a complete set of 46 chromosomes or 23 pairs of homologous chromosomes, they are still diploid (SEPARATED SISTER CHROMATIDS , NOW CALLED CHROMOSOMES.) Telophase: Remains of the network if spindle fibres are dismantled. A nuclear envelope begins to form around each complete set of chromosomes and the daughter chromosomes begin to decondense. Cytokinesis - The cytoplasm begins to split, these two have identical copies of one another , hence two identical daughter cells. Meiosis Interphase : 46 chromosomes ( 92 chromatids) Prophase 1 : homologous chromosomes line up side by side. Synapsis happens, which is crossing over. Crossing over is when DNA is exchanged between two non sister chromatids of a homologous chromosome. The section in one non-sister chromatid is swapped for the same section in the other sister chromatid. Overall, it produces a mixture of maternal and paternal DNA , tightly held together. Metaphase:The spindle apparatus forms from opposite ends of the cell, The spindle sets out spindle fibres send out spindle fibres to attach to the chromosomes, which makes contact with the kinetochore Anaphase 1 - the attachment of the spindle fibre is complete. The homologous chromosomes are pulled apart, ( not chromatids ) where 23 chromosomes are at opposite sides of the cell. Telophase - nuclear division occurs, each daughter cell will have 23 chromosomes with each chromosome having 2 chromatids. Hence 2 haploid cells. Prophase II - the chromosomes begin to condense and spindle fibres begin to from once again, attaching to the sister chromatids. Metaphase 11 - each of the 23 chromosomes line up at the centre of the cell Anaphase II - the centromere splits , freeing the sister chromatids, pulled to the opposite cells ( chromatids are not genetically identical due to crossing over.) Telophase II - cell division creates 4 daughter cells., each of the 4 daughter cells contain 23 chromosomes making them haploid. Male gamete production - - Meiosis occurs in the testes ( inside seminiferous tubules) - Spermatogonia are the starting cells of the process of sperm production , and are found in the linings of the seminiferous tubules. - They divide once by mitosis to produce 2 daughter cells , one remains a spermatogonium to repeat the process, and the other becomes a primary spermatocyte. - Primary spermatocyte undergoes meiosis to produce 4 haploid spermatids - Spermatids grow tails, develop into sperm cells are are released into the seminiferous tubule. - Immature sperm are moved to the epididymis, stored until mature, when they leave the testes and move into the vas deferens , the sperm are fully motile and are capable of fertilisation. - Mitosis of spermatogonia ensures there are always new sperm cells. Ova Production - Gametes begin the development in the ovaries. Females possess their potential ova at birth ( 1-2 million). The primordial follicle is made up of an oocyte ( undeveloped ovum) and a protective layer of granulosa cells. - Because the oocyte cannot repair itself, most die during puberty , 300k - 400k left. - Triggered by hormones, the primordial follicle grows in size and creates a protective layer of cells. - When matured, the first stage of meiosis occurs, where vast majority of the cytoplasm ends up in the oocyte, hence the smaller cell dies. - During ovulation , the mature follicle ruptures and releases the oocyte and its protective layer into the fallopian tube. - Second stage of meiosis only occurs after the sperm combines with the oocyte. Wehn it occurs , it produces a haploid ovum which accepts DNA from the sperm, fertilisation is achieved and a diploid zygote is formed Advantage of meiosis in genetic diversity of species meiosis creates new combinations of genetic material in each of the four daughter cells. These new combinations result from the exchange of DNA between paired chromosomes. Such exchange means that the gametes produced through meiosis exhibit an amazing range of genetic variation. Why Mendel was highly appreciated Mendel's study produced astonishing results and found very similar patterns of inheritance for all seven features he studied. He also identified a consistent mathematical formula that explained the frequency with which each trait appeared and observed dominant and recessive traits. He founded the basics of genetics , with no microscope. 4 basic principles of genetics - The mere must be factors inside a cell that controls characteristics ( factor - gene) - Two copies of each gene are present in every cell and control each characteristic, one from each parent.. - Each gene separates from each other before fertilisation and recombines during it but the two genes do not blend. - The genes that control different characteristics are passed onto the next generation , independent of each other. Law of segregation - there are two copies of every gene in all sexually reproducing organisms that control each characteristic and the same genes are grouped together on the homologous pairs of chromosomes. During meiosis , these homologous chromosomes separate , with easy copy on every gamete, which recombine at fertilisation. They do not blend, instead from a homologous pair again. Law of independent assortment - When the homologous pair of chromosomes segregate. They do so independently of other pairs of chromosomes. When chromosomes line up in ther homologous pairs, the sides of each chromosome takes is completely random. The mother chromosome may be left on one pair but right on the pair. Gene - basic unit of heredity Allele - one of a pair of genes that appear at a particular location on a particular chromosome and control the same characteristic Genotype - the genetic makeup of an organism Phenotype - an observable physical trait Autosomal chromosome - aving to do with any of the 22 numbered pairs of chromosomes found in most human cells. Autosomal chromosomes are numbered 1-22 Sex chromosomes - a chromosome concerning the sex of an organism  Traits influenced by a combination of genotype and the environment - - Skin colour - Muscle strength / endurance - Intelligence - Personality Since there are no 2wo X chromosomes in a male , its either he has haemophilia or doesnt , unlike females who have 2 x chromosomes, and only need 1 dominant allele to not have haemophilia ( a recessive x linked trait.) Watson and Crick model of DNA - Deoxyribonucleic Acid (DNA) is a blueprint for the structure and function within an organism - Large molecule composed of basic units called nucleotides containing nitrogenous bases adenine (Adenine), guanine (G), cytosine(c), Thymine (T) - They made the double helix model DNA is a type of nucleic acid - There are two main types : DNA and RNA ( ribonucleic acid). - A nucleotide is the basic unit of a nucleic acid - Nucleotides are complex molecules made up of three components - a nitrogenous base , a five carbon sugar and a phosphate group. Dna contains the sugar deoxyribose and the 4 bases , A,C,T,G. - Nucleotides are joined by their sugar and phosphate groups. This forms a sugar - phosphate backbone, The bases are attached to the sugars and are at right angles to the sugar - phosphate backbone, like the rungs of a ladder. - Any number of nucleotides can join together to form a polymer , or polynucleotide chain - Watson found out that A nst always pair and c and g always pair, nature of complementary bases. It makes it easier to unzip during dna replication as a large base ( a or g) id always bonded to a small base ( t or c ), hence giving a consistent amount of space between strands, Dna is located at the nucleus of an organism , in which polynucleotide strands from specific lengths are called chromosomes ( a thread-like structure that carries genetic information ). Chromosomes exist in homologous pairs. A gene - basic unit of heredity. Single chromosome might contain hundreds or thousands of genes. Karyotype - an individual’s complete set of chromosomes Dna Replication - - Done before a cell divides so the daughter cells can have a. before mitosis and meiosis ( during interphase ). - Starts at the origin - Original strand goes from 3 ‘ to 5’ - Helicase is the enzyme that breaks down the hydrogen bond the DNA holds together, - DNA polymerase replicates DNA molecules to build a new strand of DNA. ( can only build to 5 to 3 ‘ direction , hence called leading strand), lagging strand ( 3 ‘ to 5 ‘) will create Okazaki fragments. ligase glues the fragments together - The enzyme that duplicates genetic information stored in the DNA (Deoxyribonucleic acid) is called DNA polymerase. Primase whole produces primer ( contains RNA) as they can only add nucleotides to the growing polypeptide chains. - Ligase glues the DNA fragments together. - At the end two identical double helix dna molecules, semi conservative - because two copies each contain one original strand and one newly formed gene. DNA to Mrna to Trna to amino acids - ATG CCT CTA GTA - TAC GGA CAT CAT - In mrna instead of thymine , you get uracil - AUG CCU CUA GUA - codon - Trna - anticodon hence complementary pairing - UAC GGA GAU CAU - Hence amino acids Mutations - any change in the DNA sequence of a cell Mutagens ( environmental factors) like chemicals , radiation and UV light can increase the frequency of mutations. - Somatic mutations occur during the mitosis of body cells - Germ - line mutation occur during meiosis and the formation of gametes, dont affect individuals but are passed onto offspring - heritable Genetic mutations only affect individuals' genes. 3 possible outcomes - Sequence still codes for the same amino acid so there is no change to the polypeptide. - Sequence codes for one at least different amino acid  - Sequence is changed to an earlier stop codon, shortening the peptide , altering its structure and function. Chromosomal mutations - are classified to whether they change the structure of chromosomes or alter the number of chromosomes in the cell. Often identified in the karyotype. Example of mutation - cystic fibrosis, haemophilia Protein synthesis - - RNA is a nucleic acid - Transcription: occurs in the nucleus, rna polymerase will connect complementary rna bases to the dna , these rna bases bonded together form a single stranded mRNA, it goes out of the nucleus and attaches to a ribosome ( made of rrna). The ribosome will build the protein - Translation” In the cytoplasm ,there is trna which carries an amino acid - monomer for a protein. Trna reads in triplets of the mrna ( codon). Trna contains an anticodon that will be carrying an amino acid called methionine It will leave behind the amino acid. Amino acids are held by a peptide bond. Stop codons don't contain amino acids. Just notify that the protein building is finished. Genetics DNA - Deoxyribonucleic Acid (DNA) is a blueprint for structure and function within an organism - DNA molecules of all organisms have the same structure, however each different species has unique DNA - Each individual has unique DNA which can be passed onto offspring - Individuals within a species have slight differences in DNA Double Helix - DNA is nucleic Acid, these are specific types of chemicals that include proteins, lipids and carbs - Two main types of nucleic acids are RNA and DNA - Nucleic acids are polymers, which are chemical structures made of repeating units - Watson Crick model is that DNA is a double helix, like a ladder that can be twisted Nucleotides - Basic unit of nucleic acids - Complex molecules made from - Nitrogenous base - 5 carbon sugar  - Phosphate group - DNA contains sugar deoxyribose and four bases - Adenine (A) - Guanine (G) - Thymine (T) - Cytosine (C ) - Nucleotides join together with their sugar and phosphate groups to form a sugar-phosphate backbone - The bases are attached to sugars and are at right angles to the sugar-phosphate backbone - Any number of nucleotides can join together to form the nucleic acid polymer or polynucleotide chain Genes and Chromosomes - DNA is located in nucleus of cells - Chromosomes are polynucleotide chains that are specific lengths - The number of chromosomes for a species is always even because Chromosomes exist in homologous pairs - During sexual reproduction each parent provides one set of chromosomes, chromosomes are then paired according to their length Genes - A gene is a length of DNA that has a specific sequence of base pairs and code for a particular characteristic - One single chromosome has hundreds and even thousands of genes Karyotypes - Chromosomes can be extracted from a cell, stained and photographed through a microscope - The image is known as a karyotype and can be used to see abnormalities in chromosomes James Watson - Chemist - Studied DNA with Francis Crick and established the structure of DNA - the Double Helix Francis Crick - Physicist - Studied DNA with James Watson and established the structure of DNA - the Double Helix Rosalind Franklin - X Ray Crystallographer - Rosalind Franklin's Photo 51 led to the discovery of the double helix structure of DNA DNA Replication - Watson and Crick determined because of the double-stranded structure of DNA and complementary base pairing, DNA could make copies of itself in a process called replication 1. With the aid of specific enzymes and hydrogen bonds between bases are broken in sections so that strands separate and expose the bases 2. Spare nucleotides that are floating around in the nucleus are added in a complementary sequence to the exposed strands of DNA until 2 new strands have been completed 3. After replication chromosomes are attached at a spot called the centromere and the chromosomes look like an X, each strand of the doubled chromosome is called a chromatid - DNA replication happens before cell division (meiosis and mitosis) RNA - Ribonucleic acid - Four bases are adenine, guanine, uracil, cytosine Cell Division Mitosis + Stages Mitosis is the process used in cell division, it is meant for growth, repair and asexual reproduction. Mitosis results in 2 daughter cells (which are somatic) each of which are diploid (46 chromosomes/23 pairs) and genetically identical to the parent cell. Mitosis contains 5 main steps: interphase; prophase; metaphase, anaphase and telophase. Interphase Normal cell where all functions are carried out normally, chromosomes become visible as long threads in the nucleus Prophase Chromosomes become shorter and thicker and replicate to form ‘X’ shaped pairs Metaphase The chromosomes line up at the equator of the cell, mitotic spindles come out and grab each sister chromatid Anaphase The mitotic spindles pull the sister chromatids apart and brings them to each side of the cell Telophase and Cytokinesis The cell pinches in the middle and divides into 2 identical daughter cells Meiosis + Steps Meiosis is the process used in the production of gametes (sex cells), sperm for men and eggs for females. Meiosis results in 4 daughter cells each of which are haploid (23 chromosomes/ 0 pairs) and genetically different to one another. Meiosis contains 9 steps: interphase; prophase 1; metaphase 1; anaphase 1; telophase 1; prophase 2; metaphase 2; anaphase 2 and telophase 2. Each of these processes are nearly identical to those in mitosis Gametes Gametes are the sex cells responsible for reproduction. They are sperm cells in males and egg cells in females. Male (Sperm Production) Males create sperm from the testes, specifically in the seminiferous tubules. The seminiferous tubules are very fine tubes that in adult males are 300-500 metres long per testis. Spermatogonia are the starting cells of sperm production and are found in the lining of the seminiferous tubules. They divide by mitosis and form two diploid cells. One of these cells remains a spermatogonium (singular: Spermatogonia) whilst the other becomes a primary spermatocyte. This primary spermatocyte then undergoes meiosis to become 4 haploid spermatids, these spermatids grow tails and become sperm cells, and are released into the seminiferous tubules. The immature sperm then move to the epididymis where they are stored till they are mature. By the time they leave the testis and move into the Vas deferens the sperms are fully motile (able to move by themselves) and fertilise an ovum. This process of sperm production is constant so new sperm is always produced. Testis Female (Ova Production) Female gametes begin development as primordial follicles in the ovaries. Unlike males constant sperm production, Females are born with their potential ova at birth (1-2 million). The primordial follicles are made up of oocytes (undeveloped ovum) and protective layer of granulosa cells. Most primordial follicles never develop or mature. Because the oocyte is unable to repair itself, most die before puberty, leaving around 300000-400000 potential ova with around 1000 every month dying after that. If hormones trigger the primordial follicles to develop, it increases in size and grows protective layers of cells through mitosis. When the follicle is matured. The first division of meiosis occurs. However cytokinesis, divides the cell so that the vast majority of the cytoplasm ends up in the oocyte. During ovulation the mature follicle ruptures and releases the oocyte and its protective layer of cells into the fallopian tube. The second division of meiosis does not take place unless a sperm cell penetrates the protective layer and combines with the oocyte. The second division separates the chromatids of the doubled chromosomes and cytokinesis forms a tiny cell and large ovum. The haploid ovum accepts the DNA from the sperm, fertilisation is achieved and a diploid zygote is formed. Identical twins This when egg (ovum) divides after fertilisation Fraternal Twins When 2 eggs (ovum) are fertilised Mutations - Mistakes during cell division and replication are known as mutations, they can happen in the genes or entire chromosomes Genetic - A genetic mutation affects individual genes - Three possible outcomes for genetic mutations - Sequence codes same amino acid no change in polypeptide - Sequence codes for different amino acid, which alters structure and function of polypeptide - Sequence changed to earlier, altering structure and function of polypeptide Chromosomal - Where structure or number of chromosomes is altered - This number being altered is usually a result of homologous pair of chromosomes failing to separate during meiosis Mutagens - Sometimes changes in the base sequence of DNA can cause mutations, which if it changes the amino acid chain it can be fatal - These do not happen naturally but can happen due to environmental factors known as mutagens, such as chemicals, radiation and UV light - Somatic Mutations happen during mitosis, and could lead to issues such as cancer - GermLine Mutations (or heritable mutations) occur during meiosis and the formation of gametes, these will not affect the individual however it will affect their offspring, The Genetic Code - A gene mutation is a change to the sequence of bases within a gene and usually happens during replication - Most of these mutations are detected and fixed by enzymes - Impact of these mutations varies depending on the nature of the change to the genetic code - Genetic Code is the sequence of bases in a gene and provides specific instructions for synthesis of proteins - Some proteins are building materials for organelles within a cell whereas some are enzymes - Proteins are polymers made up of polypeptide, which are chains of amino acids  - There are 20 amino acids that occur naturally in human proteins - Each amino acid requires specific code, which is made up of DNA bases (A,C,T,G) Protein Synthesis - Process where gene (section of DNA) is turned into RNA - These short strands of RNA leave the nucleus and go to a ribosome where they form a template for an amino acid chain - Individual amino acids are coded by a triplet of bases known as a codon, there are 64 possible codons, since there are 20 amino acids there are more than one codon for each amino acid - All proteins start with AUG as this is methionine which is the start codon Gregor Mendel By experimenting with pea plant breeding, Mendel developed three principles of inheritance that described the transmission of genetic traits, before anyone knew genes existed. Mendel's insight greatly expanded the understanding of genetic inheritance, and led to the development of new experimental methods. - In this famous experiment, Mendel purposefully cross pollinated pea plants based on their different features to make important discoveries on how traits are inherited between generations. Seven traits were used by Mendel, including smooth or wrinkled ripe seeds, yellow or green seed albumen, purple or white flower, tall or dwarf stem length, and others. 1. The Law of Segregation offspring acquire one hereditary factor from each parent 2. The Law of Independent Assortment different traits have an equal opportunity of occurring together (this was later shown to not entirely be true) 3. The Law of Dominance offspring will inherit the dominant trait, and can only inherit the recessive trait if they inherit both recessive factors Four Basic Principles of Genetics - There must be factors inside cells that control characteristics - genes  - Two copies of each gene are present in every cell: One from the male parent and one from the female parent - Each gene separates from the other before fertilisation (meiosis and gamete formation) and recombines at fertilisation, but the genes do not blend - Genes that control different characteristics are passed onto the next generation independently of each other Genotypes and Phenotypes - Allele is a different form or variation of a particular gene - Sometimes a gene will have more than one allele, and a specific combination of alleles is known as a genotype - The genotype helps determine the appearance of the individual known as the phenotype Homozygous - Having two identical alleles for a gene Heterozygous - Having two different alleles for a gene Dominant allele - Dominant alleles show even if there is only one copy of dominant allele Recessive allele - Only show if there are two copies of allele Autosomal Chromosomes - Not sex linked (X or Y), don’t affect gender Monohybrid Cross - Genetic cross between two individuals with heterozygous for a particular gene. Punnett Squares - Used to predict genotype of offspring Test Cross - An experimental cross of an individual organism of dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype (and phenotype) Sex Linked Inheritance - X chromosome is significantly longer than Y chromosome - X chromosome also carries genes for blood clotting and red green vision - Traits (phenotypes) that are carried on sex chromosomes are sex linked - Most genes are connected to X chromosome as it much larger, so these genes are called X-Linked X Linked traits vs Males X Linked traits are much more common in boys as males only carry one X chromosome, so they will be affected. However in girls, since females have two X chromosomes, if they have only one copy of the trait they will be unaffected. Pedigrees Males = squares Females = circles Generations = roman numerals Individuals are represented by arabic numerals Example: : To determine whether an allele is dominant or recessive you must follow these rules:  - If neither parent has the trait and the child does, it is recessive - If both parents have the trait and some offspring have it, then it must be dominant - If both parents have the characteristic and no offspring has it, it is dominant Biotechnology Describe specific examples of where improvements in technology has lead to genetic understanding: 1. Next generation sequencing has revolutionised genetic understanding by enabling rapid and cost effective sequencing of genomes 2. CRISPR-Cas9 gene editing technology allows precise modifications of DNA sequences, enhancing the study of gene function and potential correction of disease causing mutations 3. Single cell sequencing has unveiled cellular heterogeneity and dynamics, advancing our understanding of development, tumours, and the immune system 4. Advanced imaging technologies have visualised gene expression, cellular processes, and genetic interactions, providing insights into genome organisation, cellular behaviour, and molecular dynamics. Describe some applications of biotechnology including: - Transgenic organisms Transgenic organisms: Biotechnology allows for the creation of transgenic organisms by transferring genes between species, benefiting fields like agriculture, research, and biomedical production. - DNA fingerprinting/profiling DNA fingerprinting/profiling: Biotechnology enables the identification of individuals through their unique DNA patterns, serving applications in forensic science, paternity testing, and genetic relationship analysis. - Cloning Cloning: Biotechnology facilitates the production of genetically identical copies of organisms, aiding fields like agriculture, medicine, and conservation in replicating superior traits, creating animal models, and preserving endangered species. Describe how computers and advancing technology is critical in genetic sequencing and coding: Computers and advancing technology are essential in genetic sequencing and coding. They process and analyse vast amounts of data, enable bioinformatics analysis, assist in genome assembly and variant calling, store and analyse genomic data, and utilise machine learning and artificial intelligence techniques. These advancements have accelerated genetic research, improved our understanding of genetics, and facilitated practical applications in medicine and other fields.