Science Yearly Notes PDF

Reproduction and Genetics – What you need to know Advances in scientific understanding often rely on developments in technology, and technological advances are often linked to scientific discoveries. 1. Relate the organs involved in human reproductive systems to their function a. identify the p...

Reproduction and Genetics – What you need to know Advances in scientific understanding often rely on developments in technology, and technological advances are often linked to scientific discoveries. 1. Relate the organs involved in human reproductive systems to their function a. identify the parts and describe the function of the reproductive system: - female: ovaries, fallopian tubes, uterus, cervix, vagina Ovaries - produce eggs for fertilisation producing the reproductive hormones, estrogen and progesterone that regulate the menstrual cycle Fallopian tubes - Transport the ova (eggs) from the ovary to the uterus Uterus - the fertilized ovum that develops into the fetus and holding it till the body is mature enough for birth. Cervix - Allow the flow of menstrual blood from the uterus into the vagina, and direct the sperms into the uterus during intercourse. Vagina - receives the penis during sexual intercourse and serves as a conduit for menstrual flow from the uterus. - male: testes, scrotum, vas deferens, prostate gland, seminal vesicle, urethra, penis. Testes - They are the primary reproductive organ. They produce and store sperm (male gamete) and they secrete hormones, primarily testosterone. Scrotum - Contains the testicles (also called testes). The scrotum acts as a climate control system for the testes (for normal sperm development, the testes must be at a temperature slightly cooler than the body temperature) Vas deferens - Transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body. Prostate gland - Secrete prostate fluid, one of the components of semen. the muscles of the prostate gland also help propel this seminal fluid into the urethra during ejaculation. Seminal vesicle - Store and produce the majority of the fluid that makes up semen.The fluid produced by seminal vesicles contains several key components e.g. sugar to provide energy for swimming sperm cells. Urethra - The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of ejaculating semen when the man reaches orgasm. Penis - The male genital organ of higher vertebrates, which transfers the sperm during copulation. 2. Identify that during reproduction the transmission of heritable characteristics from one generation to the next involves DNA and genes a. outline the process of meiosis and the importance of halving the number of chromosomes before fertilisation. Feature Mitosis Meiosis Role To form new cells for growth, To form sex cells (gametes) repair and replacement. Creates everything other than sex cells Number of daughter cells Two Four produced Number of chromosomes Diploid (two copies of each Haploid (one copy of each in daughter cells chromosome) chromosome) This means that when an egg and sperm cell join together, the zygote formed has the correct number of chromosomes Genetically identical or Genetically identical Genetically different different to parent cell Meiosis 1. DNA replicates to form two copies of DNA 2. The chromosomes migrate to opposite sides of the cell 3. The cell divides, forming two new cells 4. Steps 2 and 3 repeat in order to form four haploid (one copy of each chromosome) daughter cells b. explain the relationship between dominant and recessive genes and phenotype using examples. There are normally at least two versions (alleles) of a gene. Dominant alleles mask recessive alleles - this means that two recessive alleles are required for the recessive phenotype to be visible. Only one copy of a dominant allele is required to see the dominant phenotype. E.g. Purple pea flower colour is dominant over white. If P represents purple flower colour and p represents white flower colour, this means that both PP and Pp plants will have purple flowers, while only pp plants will have white flowers. c. use the terms genotype, phenotype, homozygous and heterozygous. Genotype - combination of alleles in an organism (e.g. Bb, BB, or bb) Phenotype - physical appearance of a trait (e.g. brown eye colour, blue eye colour Homozygous - two identical alleles (e.g. BB or bb) Heterozygous - two different alleles (e.g. Bb) d. solve problems involving Punnett squares 1. Write a key! Say what the phenotypes are and what the big and little letters represent 2. Write the male parent genotype (two alleles) up the top 3. Write the female parent genotype (two alleles) on the left 4. Fill in the Punnett squares 5. Identify the probability of each genotype (each box is 25%) 6. Identify the probability of each phenotype (each box is 25%) e. interpret pedigrees Pedigrees are used to track the inheritance of traits and diseases. - They help geneticists to determine whether traits are dominant or recessive and can be used by genetic counsellors to advise couples who are planning to have a baby. - Provide clues as to whether certain traits are genetically inherited and the mode of inheritance they follow. - Specific symbols are used to represent the individuals in a family. → Circles represent females → Squares represent males. → Affected Individuals are coloured in. ★ Modes of Inheritance - Autosomal dominant: An affected individual ALWAYS has at least one affected parent. Two affected parents can have an unaffected child. - Autosomal recessive: An affected individual may have unaffected parents. Two affected parents only have affected children. - X-linked recessive: Occurs more often in males. Males inheritance can skip a generation. All sons on an affected female are also affected. - Dominant trait: Parents are affected but the child is not. - Recessive trait: Both parents are unaffected but the child is affected. 3. Identify that genetic information is transferred as genes in the DNA of chromosomes a. describe the structure of DNA, including nucleotides b. describe the relationship between DNA, genes and chromosomes. c. discuss the benefits and limitations of different models of DNA DNA has a double helix (twisted ladder) shape with nucleotides made from 1 deoxyribose sugar, 1 phosphate group and 1 nitrogenous base. The sugar and phosphate groups form 2 backbones either side of the bases similar to a ladder. There are four different nitrogenous bases (A, T, C and G) that make up the steps of the ladder. These nitrogenous bases are complementary: - Adenine joins with Thymine - Cytosine joins with Guanine Chromosomes - long strands of DNA that have been wrapped up tightly (like cotton on a cotton reel) around proteins (histones). Genes - Sections of the DNA strand (or chromosome) that provide instructions to the cell to produce proteins (e.g. eye colour, hair, cell structures, enzymes). 4. Outline how the Watson-Crick model of DNA explains - the exact replication of DNA - changes in genes (mutation) a. describe the process of DNA replication DNA replication is the copying of chromosomes in order to produce new cells via mitosis and meiosis. It is required before cell division (e.g. mitosis) can take place. This ensures that both cells have a complete set of chromosomes. The steps of DNA replication are: 1. The DNA double helix unwinds and untwists. 2. The untwisted DNA then unzips via the enzyme helicase. 3. Single-strand binding proteins called DNA polymerase coat the DNA on both forks to prevent the DNA from rewinding. 4. Complementary nucleotides are added to exposed bases (i.e. A-T, C-G) by DNA polymerase. 5. Two identical DNA strands are formed  b. define mutation A mutation is a permanent change in the sequence of DNA that can be caused by bases being swapped, inserted, or deleted. It can be caused by radiation, chemicals, or spontaneous changes during replication. It can result in incorrect amino acids being joined together to make a protein, which can have a positive, negative, or no effect on the organism. Some examples of mutation in humans are blue eyes (a mutation of brown eyes) and sickle cell anaemia. Mutations can also occur when one base is swapped for another (substitution) OR a new base is inserted (insertion), OR a base is removed (deletion). This can change the base that pairs with it on the other DNA strand and causes a permanent change in the DNA sequence (order of DNA bases). If a base is deleted, this can lead to a ‘frameshift’ mutation, which changes all of the amino acids downstream from the mutation. Frameshift mutations are serious and usually lead to the production of non-functional proteins. An example of DNA base substitution that changes the amino acids that are coded What You Need to Know - Evolution The theory of evolution by natural selection explains the diversity of living things and is supported by a range of scientific evidence 1. Describe scientific evidence that present-day organisms have evolved from organisms in the past. a. Describe evidence that present-day organisms have evolved from organisms in the past, including evidence from: - Paleontology / Fossil record e.g. Archaeopteryx (reptile to bird) Paleontology is used in the investigation of evolution and natural selection to compare fossilised body structure and fossilised tracks of movement. Paleontology is used to compare similarities in fossil and bone structure to demonstrate the relation of different species through a common ancestor. The fossil record shows gradual changes in organisms, moving from very simple to quite complex forms of life. Transitional fossils show the way in which the evolutionary process has occurred (e.g. Whale fossils with five phalanges suggest a transition from land to sea). This allows scientists to determine when species began differentiating from their common ancestor (e.g. transitional reptile fossils with mammal-like jawbones allows scientists to date the emergence of early mammals to approximately 245 million years ago). Paleontology allows scientists to estimate when species began appearing, find common ancestors between species and use transitional fossils to approximately date the divergence of species with common ancestors. - Comparative anatomy e.g. pentadactyl limb Comparative Anatomy compares the structural features of different species or groups of animals. It is the study of similarities and differences in the anatomy of different species. The similarity in characteristics found that are a result from common ancestry is known as homology. Anatomical signs of evolution are called homologous structures. In the diagram shown it is visible that each limb has a similar number of bones that are arranged in the same basic pattern. Their functions may be different, but the similarities still exist. - Comparative embryology Comparative embryology is used to investigate the similarities in structure among distantly related species and they also provide evidence for natural selection. An example of comparative embryology which supports common ancestry is the tail and gill slits present in all early vertebrate embryos. - Biogeography Biogeography refers to the study of the variation of species and ecosystems in geographic space and geological time. This study of living things was used by Darwin and Wallace to propose theories about evolution. They had observed that organisms and biological communities had often varied across geographic gradients of latitude, elevation, isolation and habitat area. The Galapagos finches is a bird that is known for its various shapes of beaks. Wallace and Darwin had used this to show that species living in one area had similar features compared to a species living in an environment much the same although further apart. The flightless birds (ratites) show how birds such as emus and kiwis and kakapos have evolved from a common ancestor to suit their environment. E.g. kiwis are small with thick down to allow them to hide from predators and stay warm in the cold forest environment of New Zealand. The long legs and lack of feathers on the Australian Emu help it to run fast to avoid predators and keep cool in the desert. - Biochemistry Biochemistry is used to investigate if species have similarities in essential proteins which means that species also have a very similar DNA/amino acid sequence. An example of this is Cytochrome C, a protein essential for the production of ATP which can be found in most living organisms. Scientists can look at the Cytochrome C sequence of different species and compare them to humans' Cytochrome C sequence, with species who have less differences in the DNA sequence, being more closely related. eg. Chimps and Humans have a 100% similar Cytochrome C sequence, insinuating that they have a very close relationship and therefore recent common ancestor. 2. Relate the fossil record to the age of the Earth and the time over which life has been evolving. a. Recall the definition of a fossil and how they are formed A fossil is any remains or traces of once living things. Fossils are formed in a number of ways but are mostly formed when a plant or animal dies in a watery environment. Once they die, these radioactive atoms slowly decay. In order for a fossil to form: 1. body parts need to be quickly covered by sediment so that the dead organism is not eaten by scavengers or lost via erosion 2. oxygen must be excluded to prevent decay of the organism 3. hard body parts are often present (e.g. bones, teeth, shells) b. Explain how the age of fossils can be determined by sequencing and by radioactive dating. There are two main ways of determining an age of a fossil : 1. Relative dating by comparing a fossil to similar rocks and fossils or know age The age of fossils are determined using the law of superposition. The law of superposition states that the older fossils are found in lower layers of rock and younger fossils are found in higher layers of rock in undisturbed layers of rock. - Index Fossils: An organism that existed within a very short span of time, which can be used for a marker for archaeologists to determine the age of fossils surrounding it. 2. Absolute dating by using radiometric dating methods (radioactivity) Absolute dating is more accurate than relative dating. The age of a fossil is determined by measuring the remaining proportion of radioactive atoms in the remains using radiometric dating techniques. Carbon-14 dates fossils of plants and animals younger than 50,000 years old Uranium-238 dates rocks older than 50,000 years old (since carbon’s half life is too short)  In this graph, the half life of carbon can be found by finding the number of years it takes for 50% of the radioactive atoms to decay. We find 50% on the y-axis, come across to the trendline and then read down to 5700 years on the x-axis 3. Explain, using examples, how natural selection relates to changes in a population, eg in the development of resistance of bacteria to antibiotics and insects to pesticides. a. Describe natural selection as the process through which evolution occurs Natural selection is a mechanism for evolution in which the favourable alleles become more prevalent. This occurs since nature favours the survival of organisms with favourable characteristics or traits for that particular environment (“survival of the fittest”). Isolation can speed up natural selection/evolution ````` b. Outline the requirements for natural selection to occur 1. Overproduction (Each species produces more offspring that can survive) 2. Variation (Each individual has a unique combination of inherited traits) 3. Competition (Compete for limited resources) 4. Selection (The best/favourable traits will survive and are passed onto the next generation) 5. Isolation occurs in many examples of speciation (this prevents interbreeding) 1. Genetic Variation present within population (different alleles) 2. Change in selection pressure eg. natural disaster, change in environment, new predator 3. Those with favourable traits survive, reproduce and pass on the favourable trait 4. Over time, change of allele frequency in population c. Investigate a model of natural selection, describing its benefits and limitations The jelly bean model had benefits which included showing variation within the population (jelly beans) by including the different colours. The model also showed a change in environment when we ate some of the jelly beans which was selection pressure,the organisms with favourable traits which were the jelly beans that didn’t get eaten (pink, red, yellow) are passed on and their population became bigger over time. The only limitation with this model is that the process happens much slower in real life than it did with the model. Toothpicks Model: The toothpicks model used two colours (green, light brown) toothpicks to represent the genetic variation within a population, the model also showed a change in selection pressure when the light brown toothpicks were being picked up more than the green ones, showing the green toothpicks had the favourable trait. The model used the process of doubling the remaining toothpicks at the end of each trial to represent the process of reproduction, each generation survived and passed on their traits to the next generation, over time, the number of green toothpicks much outweighed the number of light brown toothpicks, demonstrating a change in allele frequency and population proportion. The only limitation with this model is that the process happens much slower in real life than it did with the model. d. Use an example to explain how an environmental change caused the evolution of a named species A species is a group of organisms that can breed to form infertile offspring. Peppered Moths 1. Colour - light and dark variants of the Peppered moth are present in the population 2. Industrial revolution - tree trunks became dark as they were covered in soot 3. Dark moths are more camouflaged compared to the light moths and therefore eaten less often by birds and therefore more likely to reproduce 4. The dark colour allele is passed on to the offspring 5. The population has a higher proportion of dark pepper moths which are better adapted to blend in with the trees and therefore not as easily preyed upon by birds Antibiotic resistance 1. Some bacteria within a population have a mutation that provides resistance against certain antibiotics 2. When people, or animals, are treated with antibiotics, some bacteria survive as they possess resistance genes against the antibiotic 3. The resistant bacteria reproduce and pass on their resistance genes to their offspring 4. The population of bacteria changes to become better adapted to the antibiotic environment Koala 1. Koalas have a few variants in the total population, some of them have lighter, shorter fur whilst the others have longer and darker fur. 2. The weather in Southern Australia is usually colder and wetter than the weather in Northern Australia (Queensland) since the Northern part is much closer to the equator. 3. The koalas living in Queensland have longer and darker fur and can’t bear the heat therefore the other koalas who have shorter and lighter fur survive and keep reproducing. 4. Similarly, the koalas in the Southern parts that have shorter and lighter fur are not able to adapt to the freezing environment therefore the other koalas who have longer and darker fur are more likely to subsist. 5. Accordingly, the Queensland koalas generally have lighter and shorter fur whereas the koalas in Southern Australia have darker and longer fur. Horses - Deforestation has been a major factor contributing to the evolution of the horse. This is evident as their size became bigger and their bones fused to form hooves which allowed them to run away from their predators quicker as deforestation transformed the environment from dense bushes to open grasslands. They also developed new teeth due to the spread of grasslands and this allowed them to chew tough plants and grasses. What You Need to Know - Forces and Motion The motion of objects can be described and predicted using the laws of physics. 1. describe qualitatively the relationship between force, mass and acceleration a. solve problems using F = m x a Force is determined by multiplying the mass by acceleration. Heavier masses require greater force to accelerate at the same rate as lighter masses. Lighter objects will accelerate more quickly than heavier masses. Example: Brandon pushes a 400 kg rock until it accelerates at the rate of 8 m/s2. What is the force required to produce this acceleration? m = 400 kg, a = 8 m/s2 F=mxa F = 400 kg x 8 m/s2 F = 3200 N 2. explain qualitatively the relationship between distance, speed and time. a. distinguish between distance and displacement Distance is the length between two points. Displacement is the distance and direction from the starting point to the final position. Distance is a scalar and displacement is a vector. Displacement can decrease in magnitude, distance cannot. 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 b. use 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑒𝑒𝑑 = 𝑡𝑖𝑚𝑒 to calculate: - average speed (v) = distance/time - distance (d) = average speed x time - time (t) = distance/average speed speed is measured in m/s or km/h distance is measured in m or km time is measured in seconds, minutes or hours Example: If a car drives 400 km in 2 hours, what is its speed in m/s? Speed = distance / time = 400 km / 2 h = 200 km/h convert to m/s by dividing by 3.6  = 200 km/h ➗3.6 = 55.6 m/s c. distinguish between speed, velocity and acceleration Speed is the rate at which an object travels over a given period of time. Acceleration is the rate at which an object changes its velocity (speed or direction). Speed is a scalar, acceleration is a vector. Velocity is the object's speed and direction e.g. wind speed. D. distinguish between average speed and instantaneous speed. Instantaneous speed is the exact speed that a body is moving at, at a given instant in time. It is a true measure of the object's motion for that point in time. Average speed is a distance an object covers during a certain time span. It does not tell you much about the actual motion that occurred during the period of time. e. analyse graphs involving motion Motion Distance vs. time graph Speed vs. time graph Stationary (no net force) (e.g. forces are balanced) Constant motion (also called ‘constant speed’ or ‘uniform motion’) (no net force) Accelerating (speeding up) Decelerating (slowing down) f. Calculate acceleration using: Example: If a car reaches 100 km/h in 8 seconds from a stationary position (travelling north) what is its acceleration? acceleration = final velocity - initial velocity / time taken = 100 km/h - 0 km/h / 8 s = 100 km/h / 8s convert km/h to m/s by dividing 100 km/h by 3.6 (27.8 m/s) = 3.5 m/s 3. relate acceleration qualitatively to a change in speed and/or direction as a result of a net force a. describe inertia, providing examples Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed or direction of motion. Examples: 1. A person on a train continues to move forward when the train stops suddenly (until an unbalanced force e.g. grabbing hold of a railing is applied) 2. When a car turns left into a corner the passengers get pressed against the right side of the car as they continue to move straight ahead. 4. analyse qualitatively everyday situations involving motion in terms of Newton's laws. a. describe Newton’s Laws 1st law: Inertia - objects will maintain a constant state of motion (or remain stationary) unless an unbalanced force acts on them. eg. a car is travelling 80km/hr and suddenly brakes. The person is still travelling 80km/hr however, the seatbelt is a force that acts upon the person causing them to stop and not go into the windscreen. 2nd law: F=ma - the mass of an object and the force applied to it will determine the object’s acceleration. e.g. heavier objects require more force to accelerate at the same rate as lighter objects. Lighter objects will accelerate more quickly than heavier objects when the same force is applied. 3rd law: Action reaction - every action has an equal and opposite reaction e.g. when a person pushes on a wall, the wall pushes back on the person with the same force. b. analyse situations involving motion using Newton’s Laws. This diagram shows a person moving forward in a car seat after the car stops suddenly. This can be explained by Newton’s First Law (Inertia) which states that objects will maintain a constant state of motion unless an unbalanced force acts on them. The unbalanced force acting on this person is from the seat belt, which stops the person moving forward and crashing into the windscreen. This diagram shows a person stepping off a boat into the water. Newton’s Third Law (Action-Reaction) can be used to explain this. As the person pushes off the boat, they move forward and the boat moves backward. The force applied by the person on the boat AND the boat on the person are equal and opposite.  This diagram shows an object with unbalanced forces acting on it. The net force is calculated by finding the difference between the paired forces and the direction that the net force is acting. This example shows a net force of 1 N to the right. We can then use F = ma to determine an acceleration of 1 m/s2 right. This is an example of Newton’s 2nd Law of motion. Glossary Term Definition acceleration the rate at which an object changes its velocity (speed or direction) force a push, pull or a twist that is capable of changing an object’s motion or shape inertia the tendency of an object to maintain its state of motion speed the rate at which an object moves velocity a vector quantity that indicates distance per time and direction