Nile Egyptian International Schools Grade 8 Science Past Paper PDF

1|P a g e  CONTENTS 01 Unit 7: Pressure and density Study sheet page 2 02 Unit 7: Pressure and density Worksheet Page 21 03 Unit 8: Selection...

1|P a g e  CONTENTS 01 Unit 7: Pressure and density Study sheet page 2 02 Unit 7: Pressure and density Worksheet Page 21 03 Unit 8: Selection Study sheet Page 39 TABLE OF 04 Unit 8: Selection Worksheet Page 59 2|P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 1 Unit 7 1 out of 1 Learning Outcome /Objective: Differentiate between mass and volume Measure mass with a with appropriate units Measure volume with a with appropriate units Identify measuring tools needed to measure mass and volume 1) Mass It is the amount of matter in an object. How to measure mass? By using a balance scale. Measuring unit of mass: The mass of an object is measured in grams (g), kilograms(kg) or tons (t). One ton = 1000 kilograms One kilogram = 1000 grams 2) Volume the amount of space that a substance or an object takes up. Measuring unit of volume Volume is measured in Cubic centimeters cm3 and Cubic meters m3 How to measure volume? Liquid volume is usually measured using either a graduated cylinder or a burette. Regular shaped solid Objects volume is calculated by multiplying the Length x width x height. 3|P a g e  Irregular shaped solid Objects volume is calculated by Water displacement Volume of stone = Final Volume - Initial Volume. Volume of stone = 75 cm3 - 50 cm3 = 25 cm3. Initial Volume after Volume adding object (Final Volume) Other apparatus for measuring of volume irregular objects: Eureka Can A eureka can is filled with water and when you place an object in the water, the water overflows. The eureka can has a spout so that you can capture the overflowing water and measure its volume. The volume of displaced water is the same as the volume of the object. 4|P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 1 Unit 7 1 out of 1 Learning Outcome /Objective: Explain the effect of mass and volume on density Calculate density of different materials using Density = Mass / Volume Rearrange and use formula Density = Mass / Volume to calculate mass or volume Describe that densities of different objects but with the same material are the same Density Is the mass of unit volume of a substance Or it is the mass of one cubic centimeter of substance Calculating Density Density = Mass / Volume or D = M / V Density is usually expressed in grams per cubic centimeters( g/cm3). 5|P a g e  Effect of mass and volume on density From the law of density discussed previously we can conclude that : 1) There is a direct relationship between Density and mass By increasing mass, density increases and vice versa 2) There is an inverse relationship between density and volume By increasing volume, density decreases and vice versa Densities of solids, liquids and gases All matter contains particles. The difference between the different states of matter is how the particles are arranged: 6|P a g e  For most substances, the change from a solid to a liquid state does not mean a big change in volume. This is because the particles stay approximately the same distance apart. This means that the density of a substance, for example iron, does not change by much when it melts. Relative particle density for a solid, liquid and gas When a liquid changes into a gas, the spacing between the particles increases significantly. This means that the gas takes up a lot more space than the liquid, so its volume increases dramatically. When a gas condenses to form a liquid, its volume decreases significantly. Note that: 1) Equal masses of different substances have different volumes. 2) Equal volume of different substances have different masses. (Why?) Because of their different densities. 3) Different materials usually have different densities 4) Substance of density less than water float on water (like cork, ice, oil). 5) Substances of density higher than water sink in it (like iron, copper). 6) Pure freshwater density = 1 g/cm3. if an object have a bigger density it will sink in water and if it have density less than that of water it will float. 7|P a g e Example : 1. What is the density of a material if 450 cm3 of it has a mass of 200 g? Answer mass = 200 g volume = 450 cm3 𝑀𝑎𝑠𝑠 200 Density = Density = 𝑉𝑜𝑙𝑢𝑚𝑒 450 Density = 0.44 g/cm3 The density of the material is 0.44 g/cm. 2. A block of aluminum has dimensions: length = 5cm, width = 5cm, height = 2cm. i. Calculate the volume of the aluminium block. ii. If its mass is 135g, find the density of aluminium. Answer i. volume = length x width x height v = 5 x 5 x 2 v = 50 cm3 The volume of the aluminium block is 50 cm3 ii. mass = 135 g volume = 50 cm3 𝑀𝑎𝑠𝑠 135 Density = Density = 𝑉𝑜𝑙𝑢𝑚𝑒 50 Density = 2.7 g/cm3 The density of aluminium is 2.7 g/cm3 8|P a g e 3. Water has a density of 1 g/cm. Calculate the mass of water in a 250 cm3 measuring cylinder. Answer mass = ? volume = 250 cm3 Density = 1 g/cm mass = volume x density mass = 250x 1 mass = 250 g The mass of water in the measuring cylinder is 250 g 4. Iron has Q density of 7.8 g/cm3 i. What does that mean? ii. Calculate the volume of 300 g of lead. Answer i. It means that 1 cm3 of lead has Q mass of 7.8 g. ii. mass = 300 g Density = 7.8 g/cm3 volume = ? 𝑀𝑎𝑠𝑠 300 Volume = Volume = 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 7.8 Volume = 38.5 cm3 The volume of lead is 38.5 cm3 9|P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 2 Unit 7 1 out of 1 Learning Outcome /Objective: Solve problems related to pressure and density Explain the effect of area and force on pressure Measure force with a with appropriate units Measure area with a with appropriate units Calculate pressure using formula Pressure = Force / Area Pressure Pressure is the amount of force acting per unit area. Or is a measure of how concentrated (or spread out) a force is. The amount of Pressure can be measured in pressure many different units, but exerted on an scientists usually use unit called Pascal’s (Pa). object depends on the force 1 pascal corresponds to applied and the 1 newton per meter squared surface area it ( 1Pa = 1 N/m2 ) is spread over. 10 | P a g e  Enrichment information Other units commonly used to measure pressure include: Reading only bar (bar), standard atmosphere (atm), torr (torr) or millimeters of mercury (mmHg), inches of mercury (inHg), and pounds per square inch (psi). Calculating Pressure 𝑭𝒐𝒓𝒄𝒆 (𝑵𝒆𝒘𝒕𝒐𝒏) Pressure( N/m2 ) = 𝑨𝒓𝒆𝒂 (𝒎𝒆𝒕𝒆𝒓 𝒔𝒒𝒖𝒂𝒓𝒆𝒅) Measuring area of some geometrical shapes 11 | P a g e  Effect of Force and Area on pressure Force have a direct relationship with pressure. by increasing force, pressure increases. Also Area have an inverse relationship with pressure. by increasing Area, pressure Decreases. Application of pressure Example 1: Tractors Tractors have large tyres. This spreads the weight (force) of the tractor over a large area. This reduces the pressure which prevents the heavy tractor from sinking into the mud. 12 | P a g e  Example 2: Drawing pins Drawing pins have sharp pointed ends with a very small area. This concentrates the force, creating a large pressure over a small area. This allows the drawing pin to be pushed into a wall. Large area small pressure small area high pressure Example 3: Knives Knives have a narrow blade edge This concentrates the force, creating a large pressure over a small area. This allows the knife to cut objects easily Narrow knife blade High Pressure 13 | P a g e Example 4: Heels High heels have small, sharp points with a small area This concentrates the weight (force), creating a large pressure over a small area Flat shoes have a larger area which the weight (force) is spread over resulting in a lower pressure This explains why high heels sink into soft surfaces more easily than flat shoes The effect of surface area on pressure 14 | P a g e  1. A balloon is being popped using the blunt end of a pencil. If the area of the end of the pencil is 0.5 cm2 and the force required to pop the balloon is 50 newtons, calculate the pressure. Answer Area = 0.5 cm2 Force = 50 N Pressure = ? 𝐹𝑜𝑟𝑐𝑒 50 Pressure = Pressure = 𝐴𝑟𝑒𝑎 0.5 Pressure = 100 pa or 100 N/cm2 If the balloon was popped using the sharp end of the pencil which have a much smaller surface area 0.001 cm2, the force needed to pop the balloon was much lower 0.1 N. Answer Area = 0.001 cm2 Force = 0.1 N Pressure = ? 𝐹𝑜𝑟𝑐𝑒 0.1 Pressure = Pressure = 𝐴𝑟𝑒𝑎 0.001 Pressure = 100 pa or 100 N/cm2 This is why the balloon popped more easily - the pressure required to pop the balloon is the same as before, but the force needed was much lower. A smaller force exerted the same pressure, because the area over which it was spread (the sharpened end of the pencil) was much lower. 15 | P a g e  2. Assuming the pressure required to pop the balloon is the same 100 N/cm2 and the area of your palm is 100 cm2, calculate the force required to pop the balloon. Answer Area = 100 cm2 Force = ? Pressure = 100 N/cm2 𝐹𝑜𝑟𝑐𝑒 Pressure = Force = Pressure x area 𝐴𝑟𝑒𝑎 Force = 100 x 100 Force = 10,000 N 16 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 2 Unit 7 1 out of 1 Learning Outcome /Objective: Investigate that the pressure in a liquid: – increases with depth – is not affected by the shape of the container – acts the same in all directions Liquid pressure Liquids and gases are both fluids. Fluids can flow or be poured, because the particles in them are able to move around freely and can change positions. Liquids and gases exert pressure on any objects immersed in them and on surfaces in contact with them, for example the walls of their containers. This is because the particles in a fluid are free to move around and can therefore expand and ‘bounce’ off surfaces. liquids exert pressure on objects due to collisions between the liquid particles and the object. Factors affecting liquid pressure 1. The pressure beneath the surface of a liquid will increase with the depth of the liquid. o This is because the pressure in a liquid is caused by the force of the weight of the liquid above it. o As the depth increases, there is increasingly more liquid above which causes the pressure to increase. 2. Pressure in a liquid also depends on the density of the liquid. o The more dense the liquid, the greater the pressure it exerts 17 | P a g e  Pressure in a column of water In a column of water, the highest pressure would be at the bottom o If a hole is made at the bottom of the column, the water will pour out with a large force o If a hole was made at the top of the column, the water will pour out with a small force o This is because of the difference in pressure in the column caused by the weight of the water If several holes were made at the same height, the water would spurt out the same distance from each hole o This is because pressure at the same depth acts equally in all directions 18 | P a g e  Characteristics of pressure in liquid 1. The pressure of liquid is always the same regardless the shape as long as the height of the container is the same. In the previous figure the pressure at the points A, B, C, D and E are all the same as Pressure in liquid equals Δ p =ρ g Δ h (Reading only) Where: Δ p = change in pressure, measured in pascals (Pa) Where 1 Pa = 1 N/m2 ρ = density of the liquid, measured in kilograms per meter cubed (kg/m3) g = gravitational field strength on Earth, measured in newtons per kilogram (N/kg) Δh = change in height of the column, measured in meters (m) So in the figure the Density (ρ) of water , gravitational field strength(g) and Height( Δh) are the same at each point, so the pressure exerted by the liquid is the same regardless the shape 19 | P a g e 2. The pressure in water increases with Depth (Discussed in pressure in column of water). 3. The pressure in water acts the same in all directions. 20 | P a g e 21 | P a g e  1. What is density? ………………………………………………………………………………………………………… ………………………………………………..……………………………………………………… ………………………………………………………………………………………………….. 2. What is the equation used to measure density? Write the unit for density. ………………………………………………………………………………………………………… ……………………………………………….............................................................. 3. Calculate the densities of the following objects. Remember to place units after each number. Object A length = 6cm width = 3cm height = 1cm mass = 36g volume = _____ density = _____ Object B Length = 10cm width = 5cm height = 2cm mass = 300g volume = _____ density = _____ 4. Use the data below to calculate the density of each unknown substance.Then use the density chart below to calculate the density to determine the identity of each substance. Volume Density(gm/ Mass (g) D=m/v substance (cm3) cm3) 4725 350 D=4725/350 D= 13.5 Mercury 171 15 148 40 475 240 680 1000 22 | P a g e 5. A student measures the mass of an 8 cm3 block of brown sugar to be 12.9 g. What is the density of the brown sugar? ………………………………………………………………………………………………………… ………………………………………………..……………………………………………………… …………………………………………………………………………………………………......... 6. A machine shop worker records the mass of an aluminum cube as 176 g. If one side of the cube measures 4 cm, what is the density of the aluminum? ………………………………………………………………………………………………………… ………………………………………………..……………………………………………………… …………………………………………………………………………………………………........ 7. A carver begins work on the following block of granite that weighs 2700 g. What is the density of the granite? …………………………………………………………………………………………………………… ……………………………………………..…………………………………………………………… ……………………………………………………………………………………………................ 8. A chef fills a 50 mL container with 43.5 g of cooking oil. What is the density of the oil? ………………………………………………………………………………………………………… ………………………………………....................................................................... 9. Calculate the mass of a liquid with a density of 2.5 g/mL and a volume of 15 ml......................................................................................................................................................................................................................................... 23 | P a g e 10.. 11. A block of an unknown material is shown in the diagram. Its mass is 500 g. 24 | P a g e 12. 13.. 25 | P a g e 14. An elephant weighing 40,000 N stands on one foot of area 1000 cm2 (0.1 m2). What pressure is exerted on the ground? Pressure =........... /........... = …………………………… = …………………………….. 15. What is the pressure exerted by a girl weighing 400 N standing on one ‘stiletto’ heel of area of 1 cm2 (0.00001 m2)? Pressure =........... /........... = …………………………… = …………………………….. 16. A cube-shaped box of mass 10 kg is sitting on a level table. If the length of each edge of the box is 0.2 m, calculate the pressure the box exerts on the table. Pressure =........... /........... = …………………………… = …………………………….. 17. If a dog weighs 300N and has four legs each 5cm2 in area what is the pressure on one foot? Pressure =........... /........... = …………………………… = …………………………….. 18. If a goat weights 300N and has four legs each 5cm2 in area. What is the pressure on the grass paddock? Pressure =........... /........... = …………………………… = …………………………….. 19. If the force on a submarine porthole at a depth of 100m is 1000N, and the area of the porthole is 1m2. What is the pressure? Pressure =........... /........... = …………………………… = …………………………….. 26 | P a g e 20. What is pressure? Complete the sentences using the words below. Force area pressure.................. is the amount of................... pushing on a certain................. The amount of...................... depends upon the size of the.................... and the size of the....................it is pushing on. 21. How is pressure calculated? This is the formula to calculate pressure. 𝑭𝒐𝒓𝒄𝒆 (𝑵) pressure = 𝒂𝒓𝒆𝒂 (𝒎𝟐) a) Can you rearrange it to work out force? force =................................. b) Complete this formula triangle, use the letters p for pressure, a for area and f for force. c) If the units for force are Newtons and the units for area are Cm2 what do you think the units for pressure will be?...................... d) Use the formula to work out the following pressure problems. i. A stone statue has a weight of 3 000 N and its base has an area of 0.6 m2. What is the pressure exerted by the statue on the floor?............................................................................................................................................................................................................................................................................................................................................. 27 | P a g e  ii. A car weighs 5 000 N the pressure each tyre exerts is 1250 N/m2. What is the area of each tyre in contact with the ground?.................................................................................................................................................................................................................................................................................................................................... 22. Complete the question by circling the correct words. a) Pressure measures the ( mass / force ) applied to a certain ( volume / area ). b) Pressure is calculated using the force applied at ( 900 / 1800 ) to an area. c) The more force there is over a given area, the ( greater / smaller ) the pressure. d) The greater the area over which the force acts, the ( greater / smaller ) the pressure. e) Pressure is worked out from dividing ( force / area ) by ( force / area ) f) Force is measured in ( pascals / newtons ) g) Area is measured in ( cm3/ m2 ) h) Pressure is measured in either ( pascals / newtons ) or (Nm / N/m2 ). 28 | P a g e 23. 29 | P a g e 24. Calculate the pressure for the following situation: 30 | P a g e 25. A student wants to calculate the pressure he exerts on the floor when he stands on one foot. He records these measurements. a. (i) Complete this table by adding the unit for weight. (ii) Which piece of equipment should the student use to measure his weight? ………………………………………………………………………………………… b. Suggest how the student measured the area of the floor in contact with his feet. ………………………………………………………………………………………… ………………………………………………………………………………………… c. state the equation linking pressure force and area. ………………………………………………………………………………………… d. Calculate the pressure that the student’s foot exerts on the floor. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… Pressure= ……………………N/Cm2 31 | P a g e 26. 27. 28.. 32 | P a g e 29. A teacher uses this apparatus to demonstrate pressure difference in water. The apparatus is hollow and has three short tubes at different depths. The teacher completely fills the apparatus with water. Water comes out of the tubes. a. State the relationship between pressure difference, Hight and density. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………….......................................................... b. The diagram shows the path of water coming from the top tube. Complete the diagram by drawing the paths of water you would expect to see from the other two tubes. 33 | P a g e 30. The diagram shows a brick rests on sand. a) Which formula is used to calculate the force exerted by the brick on sand Tick (✓) the correct box. Force=pressure ÷ area. Force=area÷ pressure. Force=pressure + area. Force= pressure  area. b) Which of these boxes produces the largest pressure if placed on floor? 34 | P a g e  c) Which diver experiences less pressure under water? 31. The figure shows a tall cylinder with three holes. Which is the correct order, from highest pressure to lowest pressure? Tick () the correct box. A-B-C C-B-A B-A-C A-C-B 35 | P a g e 32. A, B, C and D are objects with different densities. The diagram shows how they are arranged in water according to their densities to the water. The water density is 1 g /cm3. A B C D a) Match the objects' letters to their densities to complete the table. The student works out the density of object C using its mass and volume. b) Which statement best describes the mass? Tick (✓ ) the correct box. 36 | P a g e  The diagram shows the object C. c) Which tool the student can use to measure the volume of object C? Tick (✓ ) the correct box. d) Describe how the student can use this tool to measure the volume of the object....................................................................................................................................................................................................................................................................................................................................................... 37 | P a g e The lava lamp is a liquid motion lamp that shows how temperature affects density of liquids. The diagram shows the lava lamp when it is turned on and off. The lava lamp contains water and oily substances. The density of oily substances is greater than water. A student uses the lava lamp and then says: e) Use the diagram to describe how the lava lamp works causing the oily substances to move........................................................................................................................................................................................................................................................................................................................................... 38 | P a g e 39 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 3 Unit 8 1 out of 1 Learning Outcome /Objective: Define adaptation Identify the term niche Identify types of adaptation (structural – functional – behavioral) Explain the role of adaptation in survival. Adaptation They are set of features and characteristics that allows an organism to survive and reproduce in its ecosystem. Organisms have features (adaptations) that enable them to survive in the conditions in which they normally live. These adaptations may be structural, behavioral or functional: Types of adaptation to the environment 40 | P a g e Adaptations to the cold regions Animals here often have a small surface area: volume ratio to minimize heat loss to their surroundings (rounded shape of penguins/seals, small ears of the Arctic fox) A thick layer of fat (seal blubber) or fur (polar bears) insulates against the cold; these are examples of structural adaptations. Adaptations to desert regions Some desert animals have specially adapted kidneys which produce very concentrated urine, helping the animal to retain water – this is a functional adaptation. Some are only active in the early mornings, late evenings or at night when it is cooler – this is a behavioural adaptation. Some animals have structures to increase their surface area: volume ratio to aid heat loss (large ears of African elephants) – these are structural adaptations. 41 | P a g e  Role of adaptation on survival Adaptation plays a critical role in the survival of organisms by allowing them to better interact with their environment and respond to changes over time. Adaptations help organisms maintain a competitive advantage for resources, reproduction, and protection. Here’s how adaptation contributes to survival: 1. Adjusting to Environmental Conditions Polar bears have thick fur and a layer of fat for insulation in cold climates. Cacti store water and have spines to reduce water loss in deserts. 2. Protection Against Predators Camouflage (like a chameleon’s color-changing ability) helps avoid detection. Mimicry, where harmless species imitate harmful ones, discourages predators (e.g., Viceroy butterfly mimics the toxic Monarch butterfly). 3. Obtaining Resources Long necks of giraffes help them reach leaves on tall trees. Birds like eagles have sharp talons and keen eyesight to hunt prey. 4. Survival During Environmental Changes Bacteria develop resistance to antibiotics as a physiological adaptation. Animals migrate or hibernate to survive harsh seasonal changes. 42 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 3 Unit 8 1 out of 1 Learning Outcome /Objective: Explain natural selection Give examples for natural selection and its effect on passing genes Define Darwin’s theory of natural selection relate adaptation to natural selection mention examples of naturally selected animals such as (Galapagos – dolphin - ….. ) explain the effect of natural selection on populations. describe the steps of natural selection according to Darwin's Evolution through natural selection Evolution is a change in the inherited characteristics of a population over time through the process of natural selection, which may result in the formation of new species. Natural selection Natural selection is a process where organisms that are better adapted to an environment will survive and reproduce. This means that the characteristics of this variant organism are passed on to offspring. Over many generations, the process of natural selection leads to evolution occurring. Charles Darwin was a famous English naturalist. During his life he came up with the theory of natural selection and how this drives evolution of new species. Darwin is associated with the term 'survival of the fittest', which describes how natural selection works. Individual organisms in an environment are ‘selected for’. This means that only the organisms that have the best characteristics for that environment will survive. If they survive then they are the ‘fittest’ for this environment, they reproduce and pass on the characteristics to their offspring. 43 | P a g e  Natural selection illustrated by snail shell colour Within the population of snails there is variation in shell colour Normal varieties of shell colours in this snail species is black or grey (as evidenced by the first picture) Chance mutations lead to a small number of snails / one snail having a white shell This ‘small number’ is shown in the second diagram where there are less white shelled snails than black or grey shelled snails The white shelled snail(s) survive longer This is the ‘survival of the fittest’, a term used to explain why some organisms succeed in the competitive struggle for survival against other members of their population The reason the white shelled snail(s) survive longer is because they are better camouflaged This means that they are less likely to be seen by predators and eaten As they survive longer they get more opportunities to reproduce And so the allele for white shells is passed onto offspring more frequently than the alleles for black or grey shells Over generations, this is repeated until the majority of snails in the population have white shells 44 | P a g e Evolution explains how better adapted organisms have an advantage and are more likely to have offspring with this same adaptation. Over many years this leads to the formation of new species. Evolutionary trees show how different species have evolved over time from common ancestors. Evolution is the process by which small changes in organisms occur over long periods of time and new species are formed. A species is a group of organisms that can interbreed to have Fertile offspring. Natural selection drives evolution. The steps of evolution according to natural selection 1. individuals in a species show variation that is caused by differences in genes 2. Individuals with characteristics that are advantageous in their environment have a higher chance of survival 3. This idea of natural selection became known as ‘survival of the fittest' 4. Surviving individuals are more likely to reproduce and so are more likely to pass on their advantageous alleles 5. Over many generations the advantageous characteristics become more common in the population 45 | P a g e Charles Darwin proposed the theory of evolution by natural selection in a book called On the Origin of Species in 1859. He studied fossils and variation in plants and animals on a five year voyage around the world on a sailing ship called HMS Beagle. During this trip, the ship visited the Galapagos Islands off the coast of Ecuador in the Pacific Ocean. There he saw some small birds called finches on the different islands which looked similar, but had differences in their beak shapes. Darwin saw that these changes allowed the birds to feed on different foods. He suggested that they originally all belonged to one population but had slowly changed over time to suit the different habitats on the islands. Darwin chose not to publish his theory. He correctly thought it would cause a lot of controversy. Twenty years later, Darwin was approached by another scientist called Alfred Wallace who had come up with the same theory. They published their scientific ideas jointly, but Darwin is remembered for devising the theory first. At the time many people were upset by his ideas. Today some religious views about the creation of the world and the organisms in it still conflict with the scientific agreement about evolution. 46 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 3 Unit 8 1 out of 1 Learning Outcome /Objective: Identify the term selective breeding Differentiate between natural selection and artificial selection Conclude why humans breed specific parents to create offspring with desirable characteristics model the way in which selective breeding can lead to new varieties using computer simulation explain how selecting breeding is used to produce new benefits describe steps of selecting breeding Selective breeding (Artificial breeding) is a process which is carried out by humans to improve characteristics in plants and animals, usually for human benefit. Organisms can be selectively bred for the following features: Desired characteristics in plants: disease resistance in food crops wheat plants that produce lots of grain large or unusual flowers and fruit Increased nutritional content. Desired characteristics in animals: animals that produce lots of milk or meat chickens that lay large eggs domestic dogs that have a gentle nature Horses with fine features and a very fast pace Sheep with good quality wool 47 | P a g e  Steps of selective breeding Selective breeding takes place over many generations. These are the main steps for both plants and animals involve: 1. Decide which characteristics are important enough to select. 2. Choose parents that show these characteristics from a mixed population. They are bred together. 3. Choose the best offspring with the desired characteristics to produce the next generation. 4. Repeat the process continuously over many generations, until all offspring show the desired characteristics. Farmers selectively breed different types of cows with highly desirable characteristics in order to produce the best meat and dairy. 48 | P a g e 49 | P a g e Selective breeding involves choosing plants and animals with the best traits (e.g. most food producing) and breeding them more. It is also known as artificial selection as you artificially select the organisms that will breed to increase the frequency of the desired characteristic in the population. In this way, we are breeding for genetic characteristics. These characteristics can help the organism in many ways. For example, we can breed plants which are resistant to cold weather to improve production by crops in the winter. 50 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 4 Unit 8 1 out of 1 Learning Outcome /Objective: Define species Deduce the relation between different species and their habitats Define species as A group of similar organisms that can interbreed and produce fertile offspring. A group of similar organisms with similar DNA that occupies the same ecological niche. Mention 2 strengths and 2 limitation in different species definitions Species species can be defined in many ways; we will discuss two of the different definitions which are: Biological Species definition It is a group of similar organisms that can interbreed and produce fertile offspring. Phylogenetic or Ecological Species definition It is a group of similar organisms with similar DNA that occupies the same ecological niche. The biological definition emphasizes reproductive compatibility, making it ideal for understanding speciation but less useful for organisms where interbreeding is irrelevant or unobservable. The phylogenetic/ecological definition provides a more modern, genetic, and ecological approach, offering greater flexibility but requiring significant resources and sometimes leading to over-classification. Both definitions complement each other and are used depending on the context, study focus, and the organism being classified. 51 | P a g e  Biological Species definition Strength Limitation 1. Focuses on whether animals or 1. Doesn’t work for species that don’t plants can reproduce with each reproduce sexually (like bacteria). other. 2. Useful for understanding how 2. Can’t be used for extinct species since new species form. we can’t see them reproduce. 3. Doesn’t explain cases where hybrids (like mules) are born but can’t reproduce 4. does not account for hybrid species that are fertile (e.g., some plants and animals like ligers or zonkeys). Phylogenetic or Ecological Species definition Strength Limitation 1. Uses DNA, making it very 1. Needs genetic testing, which accurate. can be expensive or hard to do. 2. Works for both species that 2. Sometimes separates species reproduce sexually and too much based on small DNA asexually. differences. 3. Considers how the organism 3. Doesn’t focus on whether they fits into its environment. can reproduce together. 52 | P a g e  Ecological niche Niche in ecology describes the role or position of an organism in its particular ecosystem. The role of an organism include the type of food it eats, where it lives, where it reproduces, and its relationships with other species. 53 | P a g e  There are several key terms that we use when referring to the various components of an ecosystem and their levels of organization: Habitat A habitat is the place where an organism lives (E.g. badgers, deer, oak trees and ants are all species that would live in a woodland habitat) 54 | P a g e Subject Grade Date Block week Unit/Lesson/Topic Study sheet Science 8 4 4 Unit 8 1 out of 1 Learning Outcome /Objective: Explain why did viruses survive Identify how does a virus reproduce mention living and non-living features of viruses Viruses Viruses are non-cellular, microscopic infectious agents that can only replicate inside a host cell. From a biological perspective, viruses cannot be classified either a living organism or non- living. - Viruses are not classified as living organisms at all as they do not carry out the seven life processes. The reason they are not alive is simple: 1. They are not made of cells. 2. Viruses are much smaller than any cell, even very small prokaryotic cells such as bacteria. 3. No nucleus, no cytoplasm But they have some living features as 1. They reproduce at a fantastic rate, but only in living host cells. 2. They can mutate. 55 | P a g e  General Viruses structure Viruses are tiny and smaller in its size, ranging between 30-50 nm. Viruses do not contain cells and usually lack a cell wall but are surrounded by a protective protein coating called the capsid. It can be seen as a genetic element and is characterized by the combined evolution of the virus and the host. They contain either RNA or DNA as the genetic material. 56 | P a g e  How does Viruses survive without a host ? Viruses survive outside our bodies because of how they are built. Specifically, they are pieces of genetic material (RNA or DNA) contained in a special coating of proteins called capsids. Once a virus is Outside the body, its capsid starts to degrade, and the more degraded its capsid is, the less likely it is to survive. When outside the body, these capsids degrade faster in cold, dry environments. They also degrade faster on soft, rather than on hard surfaces. That's because they need moisture to survive and soft surfaces absorb that moisture. 57 | P a g e How does a virus reproduce? Viruses do reproduce, but only inside the cells of living organisms, using materials obtained from the host cell. Viruses can survive outside the host cell, but they must penetrate a host in order to reproduce. Enrichment information Steps of infection with a virus Reading only 1. The virus sticks to the cell membrane of a suitable host cell. 2. An ‘injection’ tube ‘injects’ into the host cell. 3. The viral uses the cell’s contents to make new one. 4. New virus particles are formed which escape from the cell 58 | P a g e 59 | P a g e 1. Look at the picture of the camel Camels live in hot dry deserts. They have many adaptations to help them survive. a. Complete the table to explain how a camel's adaptations help it survive. The first one has been done for you. 60 | P a g e  b. Animals that live in the cold have different adaptations. Suggest two adaptations that help animals survive in the cold. 1........................................................................................................ 2........................................................................................................ 2. The diagram shows a black scabbard fish from the Atlantic Ocean. This fish is adapted to live in very deep water where there is very little light. a. Describe how this fish is adapted to live where there is very little light......................................................................................................... b. The black scabbard fish is a fast-moving predator. 1. Suggest how the colour of this fish helps to make it a successful predator............................................................................................................ 2. Describe two other adaptations that suggest that this fish is a fast-moving predator. 1........................................................................................................ 2........................................................................................................ 61 | P a g e 3. The owl has caught a mouse to feed its young. The owl has good hearing for finding prey at night. Look at the picture. How else is the owl suited to catching its prey?..................................................................................................................................................................................................................................................................................... 4. This picture shows a cactus. a) What kind of environment do cacti live in?.......................................................................................................................... b) Explain how the shape of the cactus helps it cope with the environment it lives in................................................................................................................................. c) The cactus's root system is adapted to its environment. Describe how the root system helps the cactus survive in its environment....................................................................................................................................................................................................................................................................................................................................................................................................... 5. Animals have to cope with changes in their environment between summer and winter. a. Write down three things that are less plentiful in winter than in summer............................................................................................................................... b. European swallows are able to fly very long distances. How might they cope with winter conditions?.............................................................................................................................. 62 | P a g e 6. The concentration of carbon dioxide in the Earth’s atmosphere is rising. The rise in carbon dioxide concentration may cause more of the Earth’s surface to become desert. The drawing shows a plant that is adapted to life in a hot, dry desert Suggest two ways in which the structure of the plant helps it to survive in a hot, dry desert. 1).......................................................................................................................................................................................................................................................................................................................................................................................... 2).......................................................................................................................................................................................................................................................................................................................................................................................... 63 | P a g e 7. The photograph shows a musk ox The musk ox lives in the Arctic. An adult musk ox is 2.5 m long and 1.4 m high at the shoulder. Adults usually have a mass of about 400 kg. Use this information and information from the photograph to explain two ways in which a musk ox is adapted for survival in the Arctic. (a) (i) Adaptation 1 ____________________________________________________ (ii) How this adaptation helps the musk ox to survive in the Arctic..................................................................................................................................................................................................................... (b) (ii) Adaptation 2 ____________________________________________________ (ii) How this adaptation helps the musk ox to survive in the Arctic..................................................................................................................................................................................................................... 64 | P a g e  8. Wild camels often live in desert areas which are hot during the day and cold at night. They may have to manage without a supply of food or water for several days and travel great distances over soft sand to find some. Match labels, A, B, C and D, with the numbers 1—4 in the table 1 stops camel sinking into the sand 2 enables survival without food or water for several days 3 helps protect the body from temperature changes at night and during the day 4 keeps out sand that is being blown about 9. Which line1,2,3 or 4, in the table is correct. Circle the correct number 65 | P a g e 10. image below shows Phiomia (an ancestor of elephants) and a modern African elephant. Phiomia lived about 35 million years ago. Both Phiomia and the African elephant reach up into trees to get leaves. a) Use Darwin’s theory of natural selection to explain how the elephant’s trunk evolved.......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... b) Describe the causes of variation in a population.............................................................................................................................................................................................................................................................................................................................................. 66 | P a g e 11. Complete the gaps in the paragraph using the words in the box below: Natural selection can also be called ‘ of the ’. The ‘fittest’ organisms are the ones that are most well for the environment that they are in. The organisms that survive will be able to and pass on the that gave them the advantage to their. Over time, the characteristics of a particular species will change to allow in their environment. This is called. evolution adapted genes survival fittest offspring reproduce survival 12. Bacteria a) Why are the bacteria in Stage 1 different colours?.............................................................................. Stage 1........................................................................................................................................................................................................................................................................................................................ Stage 2 b) why is there a reduction in bacteria between Stage 1 and Stage 2?................................................................................................................................................................................................................................................ Stage 3 c) Explain what happens between Stage 2 and Stage 3.......................................................................................................................................................................................................................................................................................................................................................... d) Why is genetic variation so important to a population of organisms?......................................................................................................................................................................................................................................................................................................................................................... 67 | P a g e 13. Elephants with long trunks have evolved from ancestral population of elephants with shorter trunks. Write the name of each step of natural selection under its description. One has been done for you Choose from the word list. 68 | P a g e 14. match up the key words then put them in the correct order of natural selection. 15. The diagram shows two different species of beetles live in the desert. The green and brown species can be eaten by birds. I. Explain why brown beetles become the most common species over time. ………………………………………………………………………….........................................……………………………………………………………………………………................................................................................................................................................................................................................................ II. Name the process through which species with desirable traits survive and pass on their genes to be the next generation...................................................................................................... 69 | P a g e 16. use the following diagram to answer the questions: I. Describe what is happening in figures 1-3......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... II. Is the population of mice different in figure 3 than in figure 1? Explain............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ 70 | P a g e 17. The islands of Hawaii are home to around 40 species of birds called honeycreepers. They have descended from an original species of honeycreeper which is now extinct. Look at the diagram. It shows five species of honeycreeper. a) (i) Which process causes the gradual change from one species to another?............................................................................................................... (ii) Name the scientist who developed the theory to explain how this process could happen............................................................................................................... 71 | P a g e  b) This key can be used to identify four species of honeycreeper. use the key to identify species A and species D. Species A........................................................................................... Species D........................................................................................... 18. The diagrams show the modem horse and three of its ancestors. a) What evidence has been used to find out the appearance of the ancestors of the modern horse?.................................................................................................................. 72 | P a g e b) The appearance of the horse has changed over the last 55 million years. i. Use the diagrams to describe two ways the appearance of the horse has changed. 1)............................................................................................................ 2)............................................................................................................ ii. A scientist developed the theory of natural selection to explain this gradual change in appearance. What is the name of this scientist?......................................................................................... 19. Complete the gaps in the paragraph using the words in the box below: Selective breeding can also be called selection and is a process of creating organisms with characteristics. For example, with a lot of muscle, with a calm nature, that can lay big eggs… Selective breeding is different to natural selection because it is humans controlling the selection and of organisms. Organisms that are naturally selected have characteristics involved in their. Organisms that are selectively bred have desirable characteristics that are not necessarily involved in their survival. dogs cows reproduction survival desirable artificial chickens advantageous 73 | P a g e 20. The picture below shows the increase in size of chickens breed for meat between 1957 and 2005. a) Read the statements below and order them 1-4 to explain how selective breeding of chickens occur. b) What is a ‘desirable characteristic’?............................................................................................................................................................................................................................................................................................................................................. 21. Explain how natural selection is different to selective breeding.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. 74 | P a g e 22. Many different types of animals are produced using selective breeding. Some cats are selectively bred so that they do not cause allergies in people. a) Suggest two other reasons why people might selectively breed cats 1....................................................................................................................................................................................................................................... 2....................................................................................................................................................................................................................................... b) Selective breeding could cause problems of inbreeding in cats. Describe one problem inbreeding causes..................................................................................................................................................................................................................................................................... c) Many people have breathing problems because they are allergic to cats. The allergy is caused by a chemical called FelD1. Different cats produce different amounts of FelD1. A cat has been bred so that it does not produce an allergic reaction. This cat does not cause an allergic reaction. Explain how the cat has been produced using selective breeding......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... 75 | P a g e 23. Look at the diagram of four different varieties of the same species of chicken. A farmer uses selective breeding to produce a new variety of chicken. This new variety of chicken must be black with white spots and have a large tail. Describe two stages in the production of this new variety of chicken. 1.......................................................................................................................................................................................................................................................................................................................................................................................................... 2.......................................................................................................................................................................................................................................................................................................................................................................................................... 76 | P a g e 24. A farmer breeds goats for their milk. 77 | P a g e 78 | P a g e 25. Selective breeding is the process of breeding two parents with beneficial traits to produce offspring with those desired traits. Read the description of every horse, and then answer the following questions. 1. Name two horses which can breed to produce the best racing offspring................................................................................................................ 2. Explain your answer............................................................................................................................................................................................................................................................................................................................................................................................................................................................. 3. State one advantage of selective breeding............................................................................................................................................................................................................................... 79 | P a g e 26. Look at the diagram below then answer the question: 1. Name the type of breeding................................................................................................................ 2. Why would scientist use this type of breeding............................................................................................................................................................................................................................... 3. There is a type of corn that is drought resistant and another type that has a great taste. What would you hope to get by crossing them?............................................................................................................................................................................................................................................................................................................................................. 80 | P a g e 27. Modern wheat plants are developed from wild wheat by selective breeding. Wild wheat has only a small number of small grains. Modern wheat plants have a large number of large grains. Read these sentences about selective breeding. Write the letters of the sentences in order so that they describe the process of selective breeding. 81 | P a g e 28. complete these sentences about evolution. 82 | P a g e 29. The diagram shows the development of maize cobs over the last 1000 years of cultivation. Describe how scientists can use plant breeding programs to produce maize plants with larger cobs................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. 30. Define species in two different ways. 1....................................................................................................................................................................................................................................... 2....................................................................................................................................................................................................................................... 83 | P a g e 31. Friesian and Jersey cows can both be used for meat or to produce milk. The information shows features of Friesian and Jersey cows. In your answers you must make comparisons between the two breeds of cow. a- (i) Give two advantages of a farmer keeping Friesian cows and not Jersey 1....................................................................................................................................................................................................................................... 2....................................................................................................................................................................................................................................... 84 | P a g e  (ii) Give two advantages of a farmer keeping Jersey cows and not Friesian cows. 1.................................................................................................................................................................................................................................................. 2.................................................................................................................................................................................................................................................. 32. The diagram shows four giraffes. They have different patterns on their bodies. 85 | P a g e  33. Are viruses alive? In the chart below, list evidence that viruses are alive and evidence that viruses are not alive. 34. Identify the following labels accordingly 86 | P a g e 35. Place the appropriate word or phrase into the correct section of the Ven diagram. DNA/RNA Organelles Able to reproduce on its own Visible with a light microscope Too small to be seen with a light microscope Living Non-living 87 | P a g e 36. label and write the function of the parts of the virus 1............................................................................................................................................................................................................................................................................... 2............................................................................................................................................................................................................................................................................... 3.............................................................................................................................................................................................................................................................................. 88 | P a g e 37. The following diagram shows viral replication steps. Complete the following table by writing a description for each stage. Description Stage 1 2 3 4 5 6 89 | P a g e 38. The diagram below shows the reproduction between Carrion crow and Hooded crow. 90 | P a g e