Grade 8 S1 Final Exam Study Material PDF

INPS School Shakhbout – Middle & High Section Science Department (2024-2025) Grade 8 Final Exam Study Materials Semester 1 Student’s Name: ____________ Grade: ____ Objectives Tracker Lessons...

INPS School Shakhbout – Middle & High Section Science Department (2024-2025) Grade 8 Final Exam Study Materials Semester 1 Student’s Name: ____________ Grade: ____ Objectives Tracker Lessons Standards Objectives Lesson 1: Natural MS-LS4-4 Explain how variations and adaptations in a Selection population support survival, reproduction, and natural selection in changing environments. Lesson 2: Artificial MS-LS4-4 Compare selective breeding and artificial selection, selection understanding their purposes, processes, and effects on future generations. Lesson 3: Genetic MS-LS4-5 Analyze and differentiate artificial selection, natural Engineering selection, and genetic engineering, exploring genetic modification techniques, trait impacts, and ethical considerations. Lesson 4: MS-LS4-6 Explore species diversity, causes of extinction and Speciation and speciation, and the role of conservation efforts in Extinction protecting endangered species. Lesson 5: Using MS-ESS3-4 Analyze how human population growth and Resources resource consumption impact Earth’s systems.  Grade 8 S1 Final Exam - Study Sheet Lesson 1: Natural Selection Natural selection is a process by which a population’s environment determines which traits are beneficial, and which are not. Individuals with traits that are advantageous in an environment, are better able to survive, reproduce, and pass on traits. Principles of natural selection Individuals show variation. Variations are heritable. More offspring are born than can survive. Variations that increase reproductive success will be more common in the next generation. 2 Lesson 2: Artificial selection Artificial selection is the process where humans intentionally choose specific traits in plants and animals for breeding purposes, leading to the development of new varieties or breeds. Dogs – bred for a purpose: Dogs have been selectively bred for a purpose for 15,000 years Starting with some wolves, dogs were initially bred to help with: hunting; producing hounds, terriers, and retrievers farming; producing herding dogs and guard dogs Modern breeding has given us companion dogs and toy dogs – whose purpose is to keep us company… funnily enough The Auroch – where all domesticated cattle were bred from. 3 Artificial selection in plants Wheat Tall wheat plants have a high yield, but are easily damaged in wind and rain Dwarf wheat plants have a low yield, but are robust against bad weather Q: What do you think happened when the two types were cross-bred? A: A dwarf wheat with high yield that was robust! Other types were produced, but they were discarded In Summary Selective breeding = Artificial selection Has been used for animals and plants. The method: o The desired characteristics are identified. o They are bred together. o Only the offspring exhibiting the desired characteristics are bred. o This is repeated over several generations until the desired trait is fully developed. Problems: Traits are chosen to benefit humans, not the animal. o Physical problems often occur in domestic animals eg. Inflammation of the udder (mastisis) in cows due to increased milk production Usually involves inbreeding, which can lead to reduced genetic diversity. Lesson 3: Genetic Engineering What is genetic engineering? A Genetic engineering is the direct modification of an organism’s genome, which is the list of specific traits (genes) stored in the DNA. Changing the genome enables engineers to give desirable properties to different organisms. Organisms created by genetic engineering are called genetically modified organisms (GMOs). History of GMO Development 1973: created first genetically modified bacteria 1974: created GM mice 1982: first commercial development of GMOs (insulin-producing bacteria) 1994: began to sell genetically modified food 2003: began to sell GMOs as pets (Goldfish) 4 What is the GMO process? All genetic changes affect the protein synthesis of the organism. By changing which proteins are produced, genetic engineers can affect the overall traits of the organism. Genetic modification can be completed by a number of different methods: - Inserting new genetic material randomly or in targeted locations - Direct replacement of genes (recombination) - Removal of genes - Mutation of existing genes GMO Bacteria Bacteria are the most common GMOs because their simple structure permits easy manipulation of their DNA. One of the most interesting uses for genetically modified bacteria is the production of hydrocarbons (plastics and fuels) usually only found in fossil fuels. u Cyanobacteria have been modified to produce plastic (polyethylene) and fuel (butanol) as byproducts of photosynthesis. u E. Coli bacteria have been modified to produce diesel fuel. Genetically Modified Crops How might genetic engineering modify plants to solve everyday problems? (Consider world hunger, weather problems, insecticide pollution…) Examples: One common modified crop is Bt-corn. A gene from the Bt bacteria is added so the corn produces a protein that is poisonous to certain insects but not humans. Venomous Cabbage 5 Scorpion genes added to the cabbage prevent insects from eating it. Other Reasons to Genetically Modify Crops - Insect resistant - Herbicide resistant - Drought/freeze resistant. - Disease resistant - Higher yield - Faster growth - Improved nutrition - Longer shelf life Engineering Animals Bioluminescent Animals Uses: u Protein tracking u Disease detection using bioluminescent imaging (BLI) to identify different types of cells. u Novelty pets (Goldfish are available now). Fast-Growing Salmon Genes from two other fish cause this salmon to continually produce growth hormones. GMO Concerns What are some concerns regarding genetically modified foods and animals? u Risk to human health; unsafe to eat u Harm to the environment and wildlife u Increased pesticide and herbicide use u Farmers’ health 6  u Seed and pollen drift u Creation of herbicide-resistant super weeds u What about genetic engineering in humans? Lesson 4: Speciation and Extinction species — a group of organisms that are closely related and can mate to produce fertile offspring. speciation — the formation of new species as a result of natural selection. Causes of Speciation For speciation to occur, populations must be reproductively isolated. Geographic barriers, such as the formation of mountains or a river, are one cause of reproductive isolation. Isolation between two populations may also occur if individuals begin to specialize in different food sources or habitats, or develop different behaviors related to mating. Extinction Extinction occurs when there are no members of a species left on Earth. Mass Extinctions Scientists have identified at least five major mass extinctions in Earth’s history. During a mass extinction, large numbers of species die on different parts of Earth during a relatively short period of time. Most of all organisms that ever lived on Earth are extinct. Causes of Extinction 1. Genetics and Demographics - Small populations = increased risk - Mutations - Loss of Genetic Diversity - Shallow gene pools promote massive inbreeding 2. Habitat Degradation 3. Climatic Heating and Cooling. 4. Human activities. Human Activity and Extinction Human activity is a relatively new cause of extinctions. For example, red pandas are in danger of extinction due to the spread of agricultural activities, including deforestation. 7  If human induced environmental changes are extreme or rapid, populations may not have time to adapt and survive. The current rate of extinctions is more than 100 times the expected background rate. Endangered species Endangered species are organisms that are at risk of becoming extinct in the near future. Lesson 5: Using Resources Part1: Human Population and Resource Use World Population Over Time A population is a group of individuals of the same species living in the same place at the same time. For most of human history, the human population size was many times smaller than it is today. 8 Population Growth Rates growth rate – whether a population has grown and how fast it has grown. Growth rate depends on the birth rate and death rate ratios, and the migration of people. birth rate ratio= number babies born: total population size If birth rate > death rate, a population will grow. Factors Affecting Population Growth Rates of population change can be used to analyze causes of population change and to predict future changes. Key factors influenced the huge increase in world population in a short time: – Improvements in agriculture created larger, reliable food supply. – Industrial developments increased efficiency of agriculture, industry, transportation. – Improvements in sanitation, diet, and medical care decreased death rates. Natural Resources Renewable natural resources cannot be used up, or can be replaced at about the same rate they are used. Ex: sunlight Nonrenewable resources cannot be replaced as quickly as they are used. Ex: coal, petroleum Use and management can determine whether some resources are renewable or nonrenewable. Ex: Water is renewable, but pollution or overuse deplete it faster than it can be replaced. Renewable Resources Renewable resources can be used for materials. Ex: plant fibers such as cotton; animal fibers such as wool Wind, moving water, and solar panels are used to generate electrical energy. How Are Natural Resources Used? Metals and minerals are nonrenewable resources. Ex: copper, gypsum Fossil fuels: coal, natural gas, and oil Fossil fuels are nonrenewable: they formed from geologic processes acting on the remains of organisms that lived hundreds of millions of years ago. Nonrenewable Resources Use of natural resources varies greatly from region to region. 9  In general, richer, industrialized nations use more natural resources than populations of less industrialized nations do. As societies become more industrialized, they tend to consume more resources. New technologies and more efficient practices can allow consumption to level off or decline. Population Growth and Resource Use Over Time Natural resource use increases as populations grow, but efficient use can also affect overall use. Availability of resources also affects where people live: higher population densities occur along with resources (food, water, shelter). Improved transportation and engineering have made resources available in new places. Human populations tend higher near more available resources. Resource Use and Population Growth Resource Use Over Time Resource use changes over time due to a variety of factors. To compare resource use at different times, data can be measured as units used per time period. Example: oil is generally measured in barrels of oil consumed per day or year. The data can be shown using models, such as graphs, which make comparisons easier. Per Capita Consumption Resource use can be reported for a certain period two ways: overall amount used by a population. average amount used by individuals. Per capita consumption is the amount of a resource that one person consumes in a certain time. (Amount per person per unit of time) 10 Part 2: Resource Use and Earth's Systems Relating Rates of Resource Use to Impacts on Earth’s Systems This area of rain forest near Altamira, Brazil, was clear-cut to provide resources, including land on which grow crops. Both the size of the population and the per capita consumption affect the amount of Earth’s resources that humans use. Earth’s Systems The Earth system is made up of four interconnected subsystems: hydrosphere – all the water on Earth. geosphere – solid part of Earth. atmosphere – the mixture of gases that surrounds the planet. biosphere – all the living things on Earth. Because the four different subsystems are interconnected, changes in one subsystem affect all the others. The Rate at Which We Use Resources More than 7 billion people use Earth’s resources to meet needs (food, water, shelter, clothing, etc.) Everything people use comes from Earth’s natural resources. Consumption of natural resources commonly increases as population increases. If per capita consumption increases, resource use also increases even if the population stays the same. 11 Impacts of Resource Use on Earth’s Systems Clear-cutting is the cutting down and removal of all the trees in an area to obtain timber or to clear land. Clear-cutting in the rain forest causes changes to the biosphere and the geosphere. Many living things lose habitats. Over a longer time, water or wind may remove soil from the land. As more trees are cut, the impact increases. The Impact of Resource Use When humans use too much of a resource or use a resource too quickly, Earth’s systems can be negatively affected. Human impact can be reduced by effective resource management, including reducing per capita consumption, engineering technologies to reduce environmental impact, and finding ways to replenish renewable resources. The Impact of Obtaining and Using Resources from the Hydrosphere About 71% of Earth’s surface is water (mostly salt water), but fresh water is not always where people need it. People build dams, make reservoirs, build canals and drill wells to get water. These activities may result in habitat destruction. Habitat destruction happens when land inhabited by an organism is destroyed or changed. As demand increases, impacts also increase. 12 The Impact of Obtaining and Using Resources from the Geosphere Removing resources from the land can affect all Earth’s systems. Humans can change the geosphere, limiting nutrients available for plants. Plants: - affect the atmosphere, adding oxygen and removing carbon dioxide - affect the geosphere by preventing erosion - provide habitats for other organisms in the biosphere - help the hydrosphere by filtering water Fossil fuels and minerals must be mined from beneath Earth’s surface. Tunnels or holes dug to mine resources cause immediate changes to the geosphere. Mining can add harmful materials to the air, water, and land and can harm living things. Resource Use and Pollution A negative effect of the Industrial Revolution was increased pollution. Pollution is an undesired change in air, water, or soil that negatively affects the health and survival of organisms. Burning coal and other fossil fuels causes air pollution. The gasses given off can: – cause smog – combine with water to form acids and cause acid rain – increase greenhouse gases in the atmosphere Greenhouse gases absorb and radiate energy in the atmosphere, raising Earth's average global temperature. Pollution changes the chemical and physical makeup of the atmosphere and hydrosphere. Ex: acid rain can alter the makeup of the biosphere through habitat destruction and the death of organisms. Although mining and using mineral and energy resources cause pollution, people will not necessarily stop using those resources. Society must balance the needs of people with the protection of the environment. 13 Case Study: Pollution in the Atmosphere When fossil fuels are burned, carbon dioxide, a greenhouse gas, is produced. Increasing amounts of greenhouse gases warm the atmosphere, leading to changes in Earth’s climate. A warmer atmosphere also affects the hydrosphere. Increasing amounts of carbon dioxide: – warming ocean – more acidic ocean These changes can have negative effects on living things. The concentration of greenhouse gases in the atmosphere has increased as populations around the world increase. More people drive cars that burn fossil fuels. More people use more electrical energy and consume more products produced using fossil fuels. As human populations and per capita consumption of natural resources increase, so do the negative effects on Earth's systems. People can engineer processes, behaviors, or technologies to minimize the effects of human actions on the environment. Since the Industrial Revolution, the use of energy resources has increased. Most of this energy is generated by burning fossil fuels and biomass, which releases carbon dioxide and other greenhouse gases. 14 The Harvesting of Living Resources Humans harvest plants, animals, and other organisms from the biosphere. Harvesting living things can affect the land, water, and air. Overharvesting – a species used so much that the population becomes very small. It sometimes puts the survival of a species at risk. Ex: overfishing Any change in a species’ population will affect all of Earths systems that the organism interacts with. Many plants and animals that were once common for people to eat are now endangered or extinct, such as the passenger pigeon. (1914) The last passenger pigeon died. The passenger pigeon was officially declared extinct. 15 The Harvesting of Living Resources Plant Resources Sometimes, trees are harvested by cutting down or burning large forest areas, destroying forest habitats. Soil may erode and nearby water sources may become polluted. The atmosphere is affected: trees take in carbon dioxide from the air and give off oxygen. 16