8th Grade Science Study Notes
Natural Hazards
Flood: an overflow of water onto land that is normally dry.
Drought: prolonged period of very low precipitation leading to water shortage.
Tsunami: series of ocean waves caused by underwater earthquakes or landslides.
Tornado: violently rotating column of air extending from a thunderstorm to the ground; intensity measured by the Fujita scale.
Hurricane: large tropical cyclone with strong winds and heavy rain; intensity measured by a regional scale (often Saffir–Simpson).
Meteorite: fragment from space that reaches Earth’s surface.
Landslide: movement of rock/soil down a slope due to gravity; triggered by rain, earthquakes, or destabilization.
Earthquake: sudden release of energy causing ground shaking; magnitude scales include the Richter scale and newer moment magnitude scales.
Wildfire: uncontrolled fire spreading through vegetation.
1) Catastrophic event vs natural disaster
Catastrophic event: a large-scale event with widespread damage and disruption.
Natural disaster: a natural hazard that causes significant damage, disruption, or loss of life to humans.
2) Fujita scale and Richter scale
Fujita scale: measures tornado intensity based on damage, from F0 to F5.
Richter scale (magnitude): historically used to describe the size of an earthquake; now often replaced by moment magnitude (Mw) but still referenced.
3) Graph interpretation (natural hazard data)
Be able to read trends, peaks, and compare frequencies/severities across time or regions.
Interactions among Organisms and Ecosystems
Biodiversity: the variety of life in an ecosystem, including species richness and evenness.
Effects of disturbances on populations and communities
Forest after a fire: pioneer species increase; some species decline; overall biodiversity may decrease temporarily.
Golf course after a flood: habitat change toward open water/turf; native plants replaced by flood-tlood-tolerant species; potential invasives increase.
Hilly terrain after a flood: erosion and sediment deposition; altered plant communities; changes in habitat structure.
Forest after a tornado: tree loss creates openings; increased light; shifts toward pioneer species; temporarily reduced habitat complexity.
Pasture after flash flooding: soil deposition/erosion; changes in plant composition; potential invasion by flood-tossed species.
Biodiversity comparison (corn field vs native wildflowers/shrubs/trees): monoculture corn field has lower biodiversity and typically less ecosystem health; native area supports more species and interactions.
Acidic rain impact after two years: lower pH in soil/water affects sensitive aquatic and soil organisms; altered nutrient availability; potential declines in sensitive species.
Invasive species and ecosystem management
Invasive species example: identify potential nonnative plants/weeds; they often outcompete natives and reduce biodiversity.
Biologist’s proposed biocontrol (nonnative herbivorous insects): potential reduction of invasive plants but risks to native plants and food webs; outcomes are uncertain and require risk assessment.
Bee colony introduction for native plant support: can enhance pollination, support native plant diversity, but may compete with native pollinators if not managed.
How invasive species reduce biodiversity: outcompete natives, reduce habitat heterogeneity, and alter food webs.
Human Impacts
Greenhouse effect and human contribution: increased greenhouse gases (CO₂, CH₄, N₂O) trap heat; burning fossil fuels, deforestation, and industrial processes raise concentrations.
Ocean pollution impact on sea life: plastics and chemicals harm marine organisms; bioaccumulation, disrupted food webs, and habitat degradation.
Positive vs negative human impacts on Earth
Positive: conservation, sustainable practices, renewable energy adoption, pollution reduction.
Negative: pollution, overexploitation of resources, habitat destruction, climate change.
Biodegradable vs nonbiodegradable: biodegradable materials break down naturally; nonbiodegradable persist in the environment.
Fossil fuels: coal, oil, natural gas; nonrenewable energy sources formed from ancient organic matter.
Natural resources: materials or substances used by humans; can be renewable or nonrenewable.
Action contributing directly to ocean acidification: increased CO₂ emissions dissolving in seawater.
Surface pollution: pollutants on land surfaces that contaminate soils and surface water.
Groundwater pollution: contaminants seeping into and polluting underground water supplies.
Sustainability: meeting present needs without compromising the ability of future generations to meet theirs.
Degradation times: items that degrade quickly vs. those that take long to degrade (examples below).
Short degradation: paper, fruit/vegetable scraps, some yard waste.
Long degradation: plastic bottles, plastic bags, glass, certain synthetic materials.
Synthetic materials examples: plastics (polyethylene, polypropylene), nylon, polyester, synthetic rubber.
Natural Selection / Adaptations / Fossils
Variation in populations: genetic and phenotypic differences among individuals.
Why variation is needed: natural selection acts on variation; without it, adaptation cannot occur.
First theories of evolution: proposed by Charles Darwin and Alfred Russel Wallace.
Dating fossils by layers: relative dating using rock layers; principle of superposition and index fossils.
Concept of evolution: organisms change over time and pass on traits through generations (Darwin's theory of natural selection).
Geological processes exposing fossils: erosion and uplift reveal fossils at the surface.
Index fossils and trace fossils: index fossils help determine age; trace fossils record activity (burrows, footprints).
Survivors in a population: tend to survive and reproduce more successfully.
Evidence birds evolved from dinosaurs: features like feathers and other bird-like traits in theropod dinosaurs.
Vestigial structure: a body part that serves little or no current function but existed in ancestors.
Homologous structure: similar bone structures with different functions indicating common ancestry.
Why these organisms are homologous: share a common bone pattern from a common ancestor; similar structure indicates ancestry.
Analogous structures: similar in function but different underlying anatomy due to convergent evolution.
Identical rock types, fossils, and similar mountain ranges across continents: evidence for plate tectonics and past connections (continental drift).
Embryo development in common ancestry: similar early developmental stages suggest relatedness among species.
If two species descend from the same common ancestor, they will share: common ancestry and similar traits/structures by virtue of that origin.
Conservation biology focus: preserving biodiversity, protecting ecosystems, and maintaining ecosystem services.
Earth Systems
Primary natural resource used in production of synthetic materials (plastics): (petroleum).
Synthetic vs natural materials: natural materials come from nature; synthetic materials are human-made, often from petrochemicals.
Geoscience process influencing resource locations: plate tectonics and related geological processes shape mineral and energy resource distribution.
Human activities raising Earth’s temperature: burning fossil fuels, deforestation, industrial processes, agriculture.
Fixing environmental pollution: reduce emissions, cleanup and remediation, waste management, sustainable practices, technology.
Ecosystem resilience: the capacity of an ecosystem to recover after disturbance.
Interconnection of Earth’s spheres: lithosphere, hydrosphere, biosphere, and atmosphere interact through energy and matter cycles.
Practices protecting soil and preventing erosion: cover crops, contour farming, reduced tillage, terracing, vegetation buffers.
Weather event linked to El Niño: El Niño correlates with altered global weather patterns, including increased rainfall in some regions and drought in others.
Gas that makes up most of Earth’s atmosphere: (nitrogen).
Purpose of Earth Overshoot Day: marks when humanity’s yearly demand on nature exceeds what Earth can regenerate in that year; indicates sustainability gap.