Fraser Leckie - Assessment Task 2 Revision PDF

Science Revision Basic scientific knowledge and skills (SRP) Scientific Method Aim: The goal of an investigation and is written as a statement Hypothesis: An educated guess/suggestion about the results Method: Procedure/steps taken to conduct the experiment and also includes a risk...

Science Revision Basic scientific knowledge and skills (SRP) Scientific Method Aim: The goal of an investigation and is written as a statement Hypothesis: An educated guess/suggestion about the results Method: Procedure/steps taken to conduct the experiment and also includes a risk assessment Results: Where observations (5 senses) are written and data (quantitative - numbers or qualitative - pictures) is recorded in a table or graph Discussion: Results are discussed, validity and reliability is questioned, any adjustments are mentioned and provides a link to the results Conclusion: Stating whether the data support your hypothesis and if the aim was achieved Reference List: Any sites used Variables Independent Variable: The variable in an experiment that is being changed Dependent Variable: The variable in an experiment that is being measured Controlled Variable: The variables in an experiment that are always kept the same Reliability, Validity and Accuracy Reliability: Are the results consistent and was the experiment repeated/replicated Validity: Was the experiment a fair test and were all the variables considered Accuracy: Was it a fair test and was the correct equipment used, how close are the results to a known value and were the results correct Choosing the right graph Line graphs: Used to compare changes over a period of time, Numbers (x-axis) vs numbers (y-axis) Column graphs: Used to compare things between different groups or to track changes over time, categories (x-axis) vs numbers (y-axis) Physical Word (Physics and Motion) A force is a push, pull or twist that causes or stops motion Contact forces touch something, non-contact forces don’t Balanced forces are equal in size and act in opposite directions causing no movement because of a net force of 0 Unbalanced forces are not equal in size and can act in opposite or the same direction and because the net force is more than 0 one object moves Gravity is dependent on the size and distance between two objects Mass is the amount of matter in an object and is measured in Kg (kilograms Weight is a force and is the pull of gravity acting on a mass and is measured in N (Newtons) W = mg (Weight = Mass x Gravity) To find distance: d = st (distance = speed x time) To find time: t = d/s (time = distance ÷ speed)  To find speed: s = d/t (speed = distance ÷ time) Acceleration is the change in velocity (speed in a given direction) over time and is a vector quantity (magnitude + direction). It can be an increase or decrease (deceleration) in velocity Acceleration measurement units are m/s2 Average acceleration = change in velocity ÷ time taken (a = v - u / t) Another acceleration equation is v = u +at (velocity = initial speed + acceleration x time) A = acceleration, v = final velocity, u = initial velocity and t = time taken Distance is a measure of how far an object moves regardless of its starting or ending position and is a scalar quantity because it only has magnitude (just a number) Displacement is a measure of how far an object goes and in what direction from its starting point so it is a vector quantity Speed is the rate at which distance is covered and is scalar whereas velocity is the speed in a given direction so it is a vector quantity Average velocity = displacement ÷ time taken (v = s/t) Stopping distance is made up of thinking (reaction) distance (1st) and braking distance (2nd) A ticker time is a dive that accurately measures distances travelled and times taken and one tick is equal to 1/50s or 0.02s Newton’s 1st Law of Motion: Law of Inertia states that an object tends to stay at rest unless acted on by an unbalanced force and that an object in motion tends to stay in motion with the same speed and direction until acted on by an unbalanced force Newton’s 2nd Law of Motion: F = ma states that force equals mass x acceleration The acceleration (a) of an object is dependent upon two variables, the net force (F) and the mass of an object (m) A = f/m (acceleration = force ÷ mass) M = f/a (mass = force ÷ acceleration) Newton’s 3rd Law of Motion: Action-Reaction states that for every action force, there is an equal opposite reaction force and that forces must always occur in pairs Chemical World (Chemical Reactions) Periodic table, Groups = Columns, Periods = Rows Atomic number equals the number of protons or electrons (Remember APE - Atomic number = protons = electrons Atomic mass equals the number of protons + neutrons together and round up or down Ions are atoms with an electrical charge Neutrons are found by subtracting the atomic number from the atomic mass Elements are made up of only one type of atoms Compounds are made up of 2 or more different atoms chemically combined Molecules are 2 or more atoms chemically bonded and can be elements and/or compounds All compounds are molecules but not all molecules are compounds Mixtures are 2 or more different atoms physically combined and not chemically bonded Chemical Change / Reactions: New substances formed  Physical Change: No new substances are formed Endothermic reactions absorb energy = colder Exothermic reactions produce energy = hotter Evidence of a chemical reaction include a permanent colour change, a gas is given off, energy (heat) is produced or absorbed, a precipitate (solid) forms from a solution (liquid) or a one metal deposits or forms on another Factors affecting rates of reaction include concentration, temperature, pressure, surface area, catalysts and inhibitors A catalyst is a small substance that changes the rate of a chemical reaction, but is chemically unchanged at the end of the reaction and there is only a small amount needed. Corrosion is the gradual decay of a metal to a more stable form by chemical and/or electrochemical reaction with its environment like rusting of iron because of oxidation Word equation: iron + oxygen → iron (III) oxide Chemical equation: 4Fe + 3O2 → 2Fe2O3 Precipitation reactions result in an insoluble solid (called a precipitate) being formed when two clear solutions (liquids) are mixed. Like the formation of silver chloride Word equation: silver nitrate + sodium chloride → silver chloride + sodium nitrate Chemical equation: AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq) Composition are two substances that combine to form a new substance e.g. A + B = AB Decomposition is when one substance breaks down to form two or more new substances e.g. AB → A + B Single displacement is when one molecule switches with another to form a new substance e.g. AB + C = AC + B Double displacement is when two molecules switch to form 2 new substances e.g. AB + CD → AD + CB Balancing chemical equations is ensuring that when combining molecules that there are the same number of atoms that you started with before you combined This can be achieved by adding a coefficient in front of a formula like H2O → 2H2O The little number in a formula is called the subscript Big Bang Theory (Not the show) A Nebula is a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. A supernova is a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass. A black hole A region of space having a gravitational field so intense that no matter or radiation can escape. Stars are bodies of gas that radiate heat. Planets are large spherical bodies made up of gases, solids and/or liquids that orbit around the sun and have their own gravity. The larger and hotter a star is, the bluer it appears in the night sky. Smaller, cooler stars appear more reddish.  Our cosmic address is Earth, Solar system, Milky Way, Virgo Supercluster and Observable Universe The types of galaxies are spiral, elliptical and irregular Dark Nebulae are nebulas formed by the dust of an exploded star Quasars are massive and extremely remote celestial objects emitting exceptionally large amounts of energy Pulsars are a celestial object thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation A neutron star is a celestial object of very small radius and very high density composed predominately of closely packed neutrons Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star A light year is the distance light travels in one year A light year is 9.46 trillion kilometres The Big Bang Theory states that the universe started about 13.7 billion years ago when the singularity was caused because of a sudden expansion since all matter, energy and space was squeezed into a very small volume Evidence for the Big Bang Theory are ○ Movements of objects in the universe - Red Shift ○ Cosmic Microwave Background ○ Composition of the Universe - elements, quasars, and stellar distances If a star is moving away from us, the light gets stretched out making it appear more red and if a star is moving toward us, it appears more blue Cosmic Microwave Background Radiation are remnants of energy left out in the far reaches of the universe in the form of microwaves coming at us from every point in the universe The abundance of hydrogen and helium throughout the universe supports the Big Bang Theory Open “Big Chill” Theory states the universe will keep expanding forever at a decreasing rate and eventually all the stars and galaxies will die resulting in a very dark and cold universe Closed “Big Crunch” Theory states that as the universe keeps on expanding the gravitational forces will cause the universe to eventually collapse on itself Flat “Critical” Universe Theory states the universe will eventually stop expanding but never reverse Accelerating “Big Rip” Universe Theory states that the universe’s expansion is not slowing down and is expanding more rapidly eventually going to cause a big rip in the universe Evolution Fossils are most commonly found in sedimentary rocks It is a basic principle that the younger fossils are above the older ones in the sedimentary layers. Fossils are formed by  ○ Quick burial of dead organisms ○ Layers of sediments building up over the organism ○ Left for a long period of time ○ Erosions and uplifting exposes them to the Earth’s surface The Law of Superposition states the older the rock layers the closer it is to the Earth’s core The fossil record tells us when organisms lived and how they changed over time The main types of fossils are ○ Petrification - replacement and permineralisation ○ Molds and Casts ○ Carbonisation (Carbon Films) ○ Fossil Resin (Amber) ○ Preserved Remains (Tar and Ice) ○ Trace Fossils Petrification happens when water dissolves the original solid material and replaces them with mineral matter such as calcite, silica, pyrite and hematite Permineralisation is the preservation of bone, wood or shells Mold leaves an imprint after the hard parts of the organism have completely dissolved Cast forms as the result of a cavity like a shell filled with minerals over time A carbon film is a fossil left on sedimentary rock after all the substances except carbon have decayed Amber is a sticky resin that captures organisms and preserves them in resin Whole animals can be trapped and preserved in tar or ice Trace fossils are objects left behind by an organism like faeces Relative dating allows for the age of fossils to be found and determine if one fossil is older than another Correlating fossils gives relative ages Actual ages can be determined by measuring the amount of radioactivity remaining in some rocks Transitional fossils record and show the overall pattern of change in organisms through evolution  The geological time scale Time is broken into different time chunks or divisions from Eon, Era, Period and Epoch Stromatolites are rock-like structures built by blue-green algae and are some of the first forms of life on Earth Mass extinctions are periods in Earth’s history when abnormally large numbers of species (approximately 75%) die out simultaneously or within a limited time frame Lamark’s Theory of Evolution is the Theory of Inheritance of Acquired Characteristics This theory states that if an organism changes during life in order to adapt to its environment, those changes are passed on to its offspring Lamark said that change is made by what the organisms want or need Darwin’s Theory of Evolution is the Theory of Natural Selection Natural selection is the process where an environmental factor acts on a population and results in some organisms having more offspring than others The favoured individuals pass on their features/genetic traits/adaptations to the next generation This is also known as ‘survival of the fittest’. Variations are caused by difference in genes which result in different characteristics Selective breeding is the act of choosing organisms to mate and produce offspring based on favourable physical characteristics or traits Selection pressures are factors that cause organisms to adapt to try and survive natural selection The age of the Earth has been found through dating using radioactive dating techniques Comparative anatomy compares the anatomy and skeletons of different animals/organisms to show if they have evolved from a common ancestor The Pentadactyl Limb is the structure of limbs that some fish, all the amphibians, reptiles, mammals and birds have and is the same basic bone structure in their limbs  These fundamentally similar structures are called homologous structures (individual variations on a common anatomical theme) their similarity strongly suggests a common ancestor Embryology is the study of embryos Biogeography is the study of the distribution of species over geographical areas, both now and in the past Isolation and migration of species cause divergent evolution Common genetics and biochemistry support the idea that all living things are related and have evolved from common ancestors Comparisons of DNA are used to provide evidence of how closely different species are related The longer ago two species had a common ancestor, the more likely it is for gene mutations to have occurred to produce small changes in their protein structure Members of the same species produce fertile offspring Genetics Discovery of DNA ○ In the early 1950s Rosalind Franklin and Maurice Wilkins studied DNA using x-rays ○ Franklin produced an x-ray crystallography photograph ○ In 1953, James Watson and Francis Crick successfully described DNA’s 3D structure as a double helix ○ The DNA molecule model used today s called the Watson-Crick Model ○ Rosalind Franklin’s pivotal contribution was only acknowledged years after she died DNA = Deoxyribonucleic Acid It is a complex molecule that contains the instructions or ‘blueprint’ a living organism needs to develop, live and reproduce DNA determines an organism’s characteristics and contributes to the diversity of living things DNA is found inside every cell (in the nucleus) inside chromosomes and determines how the cells in a body will function DNA is passed down from parents to children (offspring) DNA is made up of molecules called nucleotides ○ Nucleotide molecules have three parts ○ Phosphate group ○ Deoxyribose sugar ○ A nitrogen-rich base The nucleotides are organised in a way that makes DNA a double helix DNA consists of two strans or “backbones” that twist around each other, held together by hydrogen bonds. The strands are made of alternation sugar (deoxyribose) and phosphate molecules Each “rung” of the ladder is made up of two smaller molecules, known as nitrogenous bases  There are four types of bases The four bases are ○ Guanine (G) ○ Cytosine (C) ○ Adenine (A) ○ Thymine (T) Each base can only join with one other type of base to form a ‘rung’ of the ladder ○ Guanine and cytosine join together (G - C) ○ Adenine and thymine join together (A - T) Each G-C or A-T combination is know as a base pair. When a cell grows and divides into two, it first has to make a duplicate copy of each DNA molecule Steps of DNA Replication ○ In the nucleus, weak hydrogen bonds break between the bases of DNA ○ This causes the DNA to unzip like a zipper ○ Enzymes in the nucleus direct free floating nuecleotides in the nucleus to attach to each strand ○ This results in two identical strands of DNA (transcription) ○ This happens at the end of interphase (a stage of mitosis) To carry the gentic message from the nucleus into the cytoplasm we have messenger RNA (mRNA) In the single-stranded RNA, the sugar is ribose (and not deoxyribose) The bases in RNA are: ○ Guanine to cytosine ○ Adenine to Uracil ○ Thymine is not found in RNA, Thymine is substituted with Uracil Chromosomes are found in the nucleus of a cell and carry genes Genes are segments of DNA on a chromosome and are responsible for inherited traits. They contain the instructions to form functional proteins from amino acids The genetic code is the sequence of the nitrogen bases along a DNA molecule that forms the genetic code There are 20 different kinds of amino acids in cells Amino acids are the building blocks of proteins, which determine traits The groups of three bases (3 letter code) in mRNA are called codons or triplets Each codon codes for a particular amino acid There are 64 possible 3 letter code words Different combinations of amino acids (codes) make different proteins Genes don’t actually make proteins - they just contain the instructions on how to make them DNA stays in the nucleus but proteins are built in the cell’s cytoplasm Each gene contains a different sequence of bases DNA goes through transcription to form RNA, RNA goes through translation to form an amino acid chain and an amino acid chain goes through folding to form a protein  A mutation is a change in the DNA sequence often during the replication process, this causes changes in an organism A mutagen is any agent that can cause a change in DNA Types of mutations ○ Point mutation - a single base is changed ○ Deletion - removes a base and causes a frameshift ○ Insertion - adds a base and causes a frameshift Cell division is used for growth, repair and reproduction Mitosis for growth and repair and meiosis for reproduction Chromosomes are thread-like molecules that carry heredity information made of protein and one molecule of DNA Humans have 46 chromosomes organised into 23 pairs in the nucleus in normal cells However, sex cells have 23 chromosomes Each person has one pair of sex chromosomes in each cell, females have two X chromosomes and males have an X and a Y chromosome The Y chromosome contains a gene, which triggers embryonic development to become a male Mitosis results in cells identical as the parent cell with 1 set of division stages and Meiosis results in a variety of geneticall different offspring with 2 sets of division stages Chromatin is unwound DNA Chromatids each of 2 thread -like strands into which a chromosome divides during mitosis Sister chromatids are 2 identical copies of a chromatid Centromere is a structure in a chromosome that holds the two chromatids Spindle Fibres control the movement and separation of chromosomes during mitosis Centriole helps in the formation of spindle fibres Nuclear envelope is a membrane that separates the nucelus from the cytoplasm in eukaryotic cells Mitosis is a form of asexual reproduction resulting in two daughter cells having the same number and kind of chromosmes as the parent cell Offspring inherit the genes of only one parent cell and are therefore genetically identical to the parent cell Stages of Mitosis ○ Prophase - The cell prepares for division - the chromosomes condense and the nucleus starts to break down ○ Metaphase - The chromosomes line up along the middle of the cell ○ Anaphase - The chromosomes separate and are dragged away frome ach other ○ Telephase - Two nuclei form, eahc with its own set of identical DNA Interphase is the growth and copying of DNA prior to cell division / mitosis Meiosis is a from of sexual reproduction reuslting in four (haploid) genetically ifferent gametes (sex cells), which have half the number of chromosomes (23 instead of 46) Offspring inherit genes from two parent cells The two gametes fuse together to form a zygote with 46 chromosomes The zygote then divides by mitosis  It passes through different developmental phases to transform into multicellular individual Homologous Chromosomes - During meiosis, there is one paternal and one maternal chrome pair inside a cell Crossing over is the process where homologous chromosomes pair up and exchange genetic material to form new chromosomes Haploid cells - Four cells as a result of meiosis, which are genetically different from each other and the parent cells In Meiosis PMAT happens twice resulting in four haploid daughter cells Genetics is the study of heredity, which is a biological process where a parent passes certain genes onto their offspring Genes are inherited from both parents through sexual reproduction Genes express specific traits or characteristics Heredity is the transfer of traits from one generation to another generation Gregor Mendel born in 1822 in Austria discovered the basic principles of heredity He discovered this by experimenting on pea plants and showed that their traits follow a particular pattern He decided that the differences must be inherited, and that the parent plants must be passing on genes for height, flower and colour Inherited traits are genetically determined characteristics coming from both parents so offspring has a combination of both parents’ genes Dominant traits are traits that hide other traits when passed on to offspring and is shown even if only one parent passed the gene to the child Recessive traits are traits that get hidden by dominant traits and is only shown when both parents pass the gene to the child Genotype is the genetic makeup of an organism Phenotype is the physical appearance of an organism based on it genotype, plus environmental factors Alleles are variants in a gene occurring on a fixed spot on a chromosome In humans, an allele might indicate blood type, colourblindness, eye and hair colour, tallness, etc. Homozygous Domonant carries two copies of the same dominant allele (BB) Homozygous Recessive carries two copies of the recessive allele (bb) Heterozygous carries two different alleles (Bb), The dominant allele will mask the recessive allele Codominance is where both alleles are equally strong and both alleles are visible in the hybrid genotype and phenotype Known as blend genes, the genes are neither dominant or recessive of each other Punnett Squares are a diagram used by geneticists to determine the probability of an offspring having a particular phenotype Biotechnology It is the practical use of new procedures and devices based on discoveries about living things (biology)  Energy An electrical circuit consists of a continuous flow of charged particles called electrons. The energy source (battery/cell) gives energy to electrons and pushes them around a circuit from the negative (-) terminal to the positive (+) terminal of the cell. The electrons will only flow through the circuit if it is complete (closed circuit). A switch is used to control the flow of electrons. Direct current (D.C.): Electrons flow in the same direction. Alternating current (A.C.): Electrons change their direction regularly. Scientists draw circuits in 2D and use special circuit symbols to represent each component in the circuit. Every circuit must have the following parts: Energy source: Battery, electric generator, etc. Load or resistance: Device that uses the electric energy (e.g. light globe). Wires: Connect components together. Switch: Opens and closes the circuit.