Grade 12 Earth And Life Science:Why Life On Earth Is Possible PDF

17/09/2024 Grade 12 Learning Objectives explain how the Earth was Why Life on Earth is...

17/09/2024 Grade 12 Learning Objectives explain how the Earth was Why Life on Earth is 1. formed according to the accretion hypothesis; and Possible EARTH AND LIFE SCIENCE differentiate homogenous and 2. heterogenous accretion hypothesis. Directions: Arrange the words and define the following Review IGB GABN HETROY TSEDAY TAEST YOTREH LCILTAGNOSI INUVSERE TREOHY ERNUALBA ROTHEY RETCENUOR HORTRY Accretion Just like carnival cotton candy The Origin of machines spin sugar, causing it to Planet Earth stick together and form a large cotton candy. 1  17/09/2024 Accretion Accretion Planet formation shares similarities with In both cases, the spinning or this process, known as accretion. gravitational attraction plays a role in Accretion involves the accumulation of bringing together smaller components to small dust particles that gradually come form a larger structure. together to create larger masses. Accretion Accretion Accretion is one of the leading theories As the objects grow bigger, it pulls more for the formation of planet Earth. fragments of matter due to stronger It is a process that occurs when gravity gravitational pull. attracts tiny bits of matter towards an object. Steps in Accretion 2  17/09/2024 Accretion Accretion Four (4) key steps: Step 2: Planetesimals continue to Step 1: Dust grains accumulate, clump together eventually evolving through collisions, into protoplanets. giving rise to planetesimals. Accretion Step 3: Protoplanets A protoplanet is an embryonic further grow in size planetary structure composed of as they attract more matter. planetesimals. Accretion Step 4: Over time, protoplanets develop into fully-fledged planets through continued accretion and gravitational interactions. 3  17/09/2024 Homogeneous Accretion Two (2) hypotheses on how It is when Earth accreted from materials of the structure of Earth was the same composition after condensation. formed: (1) Homogeneous; and (2) Heterogeneous Accretion Hypotheses. Homogeneous Accretion Homogeneous Accretion Accretion: Homogeneous Accretion Hypothesis: Particles come together to form a uniform Earth's formation began from fine particles primordial Earth composed of iron, in the primitive nebula around 4.6 billion magnesium, nickel, silicates, and years ago. radioactive elements. Homogeneous Accretion Homogeneous Accretion Heat Increase: Separation: Gravitational contraction and radioactive Iron and nickel, being denser, sank to the decay raised Earth's temperature. center while less dense silicates moved upward. NOTE: Radioactive decay is like tiny particles breaking apart inside some materials, and when they break, they release energy. 4  17/09/2024 Homogeneous Accretion Homogeneous Accretion Turmoil: Core Formation: Surface experienced earthquakes, volcanic Iron and nickel eventually formed Earth's eruptions, and lava flows during the iron core, which cooled down. and nickel accumulation. Crust and Mantle: A thin solid rock layer became the crust (land and ocean), and the mantle is semi-molten silicate rocks between the core and crust. Homogeneous Accretion Summary: (1) Similar elements attached to each other, forming a solid mass. (2) Particles were melted due to the heat produced in the process. (3) Lastly, heavier elements descend to the center due to gravity, forming the solid core of Earth. Heterogeneous Accretion Heterogeneous Accretion It is when Earth accreted during Heterogeneous Accretion Hypothesis: condensation, forming a differentiated planet Core formation occurred simultaneously as it grew in size. with Earth's creation, resulting in an initial layered structure of core, mantle, and crust. 5  17/09/2024 Heterogeneous Accretion Heterogeneous Accretion Particle Condensation: Oxides Condensed First: As the nebula cooled, particles condensed Aluminum and calcium oxides were the based on their condensation points. first to condense, followed by iron and nickel. Heterogeneous Accretion Heterogeneous Accretion Accretion Process: Core Formation: The condensed particles collided and Aluminum and calcium oxides accreted first, followed by iron and nickel, forming accreted, with those formed during the Earth's core. initial condensation stage accreting first. Outer Layer: The outermost layer consisted of silicates and volatile particles, including water. Heterogeneous Accretion Summary: (1) Particles of metal attach with each other Evidence and first, forming Earth’s core. (2) As it cools further, lighter elements Loopholes of the Two attached to this core. Hypotheses 6  17/09/2024 Accretion Accretion After the formation of early Earth, The more commonly accepted postulate collisions with meteorites and comets for the Earth’s formation is the resulted to the presence of volatile homogeneous accretion hypothesis. elements on the surface. Most materials that formed early Earth homogeneously accreted after their NOTE: Volatile elements are like substances that easily turn into complete condensation. gases when they get hot. Some examples are water and gases like carbon dioxide. These elements are important in Earth's air and can be found on other planets and comets too. Accretion Main points Earth is considered as a dynamic Homogeneous planet. It continuously changes ever Earth accreted from materials of the same since its formation 4.6 billion years ago. composition after condensation. Accretion Through time, several changes was followed by differentiation. happened in the geographic Heterogeneous distribution of continents and Earth accreted during condensation, composition of the atmosphere. forming a differentiated planet as it grew in size. Evidences Evidences Homogeneous Heterogeneous The homogeneous accretion hypothesis The heterogeneous accretion hypothesis provides a mechanism that explains the qualitatively explains the density presence of volatile elements in the core. It differences among terrestrial planets also provides an explanation of the heat (Mercury, Venus, Earth, and Mars). Also, it source for early mantle melting and can explain the abundance of elements formation of early continents. such as osmium, iridium, ruthenium, and rhodium in the mantle. 7  17/09/2024 Loopholes Loopholes Homogeneous Heterogeneous The hypothesis cannot explain the Accretion must be very fast (103 to 104 abundance of elements such as osmium, years for completion). But, this rate does not iridium, ruthenium, and rhodium in the coincide with the occurrence of large mantle. impact craters. Also, the abundances of iron, calcium, titanium, and aluminum do not coincide with what was predicted by the theory. Lesson Objectives Water: The Medium of Life - Earth is often called the "blue planet" due to its water-covered surface. Water: The - Despite its abundance, EARTH Medium of Life conserving water resources is crucial. 8  17/09/2024 - The hydrosphere encompasses - Water is vital for all life forms, Earth's water environment. serving various purposes like - It includes water drinking, irrigation, and hygiene. in all its forms: - Human development and life on vapor, liquid, and EARTH ice. Earth have always relied on water. The Hydrosphere - Bodies of water like oceans, lakes, rivers, and marshes are part of the hydrosphere. - Clouds, snow, glaciers, and rain also belong Bodies of water are classified into either saltwater or freshwater, based to the hydrosphere. on salinity. - The hydrosphere consists of 97.5% saltwater and 2.5% freshwater. The Hydrosphere The Hydrosphere Saltwater Saltwater contains salt and is found in oceans and seas. Oceans and seas are home to various marine life and mineral resources. Many marine organisms, including fish and invertebrates, depend on saltwater. 9  17/09/2024 Saltwater Freshwater People interested in keeping saltwater Freshwater contains small amounts of salt organisms in aquariums must take special in very low concentrations (It has zero to care due to the sensitivity of marine very little salt content) animals to water quality. It can be found in various forms, including rain, snow, and frozen soil (permafrost). Freshwater sources include rivers, streams, ponds, lakes, marshes, glaciers, and polar caps. Freshwater Freshwater Despite Earth's abundant water, only a This percentage will be constant since water small fraction (2.5%) is freshwater. is continually recycled through the Of the freshwater, only 1% is potable atmosphere. (suitable for drinking). Growing populations create competition for clean freshwater resources. Global Freshwater 10  17/09/2024 Properties of Water Properties of Water Density Water has the (1) right density, (2) ○ Density is measured as mass per unit of transition temperatures, and (3) heat volume (in g/cm3). capacity that enable existence and ○ The density of water changes with perpetuation of life in the planet. several factors such as temperature and salinity. ○ Water is at maximum density at 3.98°C and is least dense at freezing temperature. Properties of Water Properties of Water Density ○ Lower Density- Ice has lower density than liquid water, causing it to float on the surface. ○ Insulation- Floating ice acts as insulation, preventing the underlying liquid from freezing completely. ○ Preservation of Life- Ice's ability to float is crucial for the survival of organisms in lakes during winter, as it maintains a liquid environment beneath the ice. Properties of Water Transition Temperatures ○ Cell Membrane The cell membrane is a vital component of all life forms, separating them from their environment. It functions as a selective barrier, allowing essential substances to enter the cell while blocking harmful ones. 11  17/09/2024 Properties of Water Properties of Water Transition Temperatures Transition Temperatures ○ Substance Transfer ○ Selective Permeability Water's ability to remain in liquid form at The consistency of water in maintaining room temperatures facilitates the flow and liquid form at room temperatures enables transfer of substances across the cell cell membranes to maintain their selective membrane, ensuring the exchange of permeability, ensuring that only necessary nutrients and waste products between the substances are transported, thus cell and its surroundings. safeguarding the cell's internal environment. Properties of Water Properties of Water Heat Capacity ○ Water has a relatively high heat capacity, which allows it to resist temperature changes. Properties of Water Properties of Water Heat Capacity Heat Capacity - Water has a high heat capacity, meaning it - High heat capacity is vital for maintaining needs a lot of heat to change its temperature. stable temperatures within our body cells. - This property keeps the Earth's atmosphere - Without it, our body temperature could from extreme temperature swings in winter quickly become dangerously high. and summer. - It's crucial for the survival of aquatic life, as rapid temperature changes would harm fish. 12  17/09/2024 Origin of Water on Earth Theory 1: These properties make aquatic ○ Earth's water came from comets colliding habitats a stable place for organisms with it. to live in, since aquatic habitats can ○ In 2000, scientists found a comet that somewhat resist temperature contained water and had the same isotopic changes. composition as Earth's seas. This comet was named LINEAR S-4. Origin of Water on Earth Uses of Water in Modern Civilizations Theory 2: - Agriculture: 70% of global freshwater is used Water was trapped in Earth's magma and for crop irrigation. emerged as liquid water during - Industry: 20% of global water usage is for degassing. industrial processes, including manufacturing The actual origin of Earth's water may and cooling. involve a combination of both theories. - Domestic: 10% of freshwater is used for drinking, household chores, and personal hygiene in homes. Uses of Water in Modern Civilizations - Water plays a crucial role in various stages of product manufacturing, transportation, and facility sanitation in industries. Any Question? 13  17/09/2024 THANK YOU! 14