2025 Junior Science Olympiad Examination Foundation Study Notes (Years 7 & 8)

2025 Junior Science Olympiad Examination Overview

• Target Audience: Students in Years 7 and 8 (and others up to Year 10).

• Organizing Body: Australian Science Innovations (ABN 81731558309).

• Examination Duration: 120 minutes (with 0 minutes of designated reading time).

• Materials Permitted: Non-programmable, non-graphical calculator; pens; pencils; erasers; and a ruler.

• Structure: Four sections covering Biology, Chemistry, Earth Science, and Physics. Boundaries between disciplines are considered fluid.

• Marks and Scoring: Total of 48 marks. Each question is worth 1 mark unless specified otherwise. No marks are deducted for incorrect answers.

• Integrity: Evidence of collusion or academic dishonesty leads to disqualification; the markers' decisions are final.

Biology: Cell Theory, Evolution, and Ecology

• Louis Pasteur and Cell Theory (mid-1800s):

  • Goal: To demonstrate that germs cause disease and that new cells arise from existing cells, refuting spontaneous generation.

  • Methodology: Heating a growth medium (broth) to kill existing microorganisms. Placing it in different flask setups:

    • Flask I: Open to the air, allowing microorganisms to enter and grow.

    • Flask II: "Swan-neck" flask to test if bacteria present externally can enter and multiply. The neck allows air but traps particles/bacteria in the bend.

    • Purpose of Heat: To ensure the broth is sterile initially. Any subsequent growth must be from external sources.

• Adaptations: The Andean Condor:

  • Lifestyle: Scavenger feeding on decaying carcasses; nests in high-altitude Andes mountains.

  • Adaptation (Baldness): The lack of feathers on the head and upper neck reduces the retention of bacteria and microorganisms during feeding on carrion.

  • Dimorphism: Males often have white feather patches and can be larger than females; both sexes have a white feather ruff at the neck base.

• Evolution of Marsupials:

  • Origins: Evolved in the Americas approximately $125 \times 10^6$ years ago.

  • Historical Spread: Spread to Australia when continents were connected. Evolution led to diverse roles in Australian ecosystems.

  • Phylogeny: A phylogenetic tree reflects genetic differences. Branches (e.g., Potorus, Vombatus, Dromiciops) indicate divergence from common ancestors.

  • Taxonomy Challenges: The extinct Trilobite (evolved $571 \times 10^6$ years ago, extinct $250 \times 10^6$ years ago) illustrates difficulties in applying modern taxonomy to morphological vs. genetic data from fossils.

• Human Taxonomy and Species Interaction:

  • Hierarchical Ranks: Genus and Species (e.g., Homo sapiens, Vulpes vulpes).

  • Wolf/Dog Lineage: Grey Wolves (Canis lupus), Domestic Dogs (Canis lupus familiaris), and Dingoes (Canis lupus dingo). Dogs and dingoes share a more recent common ancestor with each other than with red foxes.

  • Viability: Species closely related (same species/subspecies) can reproduce to produce viable young.

• Aquatic Food Webs and Ecosystem Dynamics:

  • Nutrient Levels: Eutrophic (high nutrient) vs. Oligotrophic (low nutrient).

  • Gulf of Naples Case Study: Increased nutrients lead to higher numbers/types of phytoplankton and picoplankton.

  • Energy Transfer: Typically, only $10\%$ of energy passes between trophic levels (Picoplankton $\rightarrow$ Microzooplankton $\rightarrow$ Mesozooplankton $\rightarrow$ Small Fish $\rightarrow$ Large Fish).

• Cellular Structures and Organelles:

  • Nucleus: Contains genetic material.

  • Mitochondria: Powerhouse; facilitates energy release through cellular respiration.

  • Ribosomes: Synthesize proteins.

  • Cell Membrane: Controls the passage of substances.

  • Cell Specialization Examples:

    • Muscle Cells: Contain high counts of mitochondria for high work capacity.

    • Nerve Cells: Branched dendrites for impulse transmission.

    • Red Blood Cells (RBCs): Lack a nucleus to maximize oxygen-carrying capacity.

    • Fat Cells: Specialized for storage.

• Coral Reproduction:

  • Sexual: Combined gametes ensure high genetic diversity.

  • Asexual (Polyp/Fragmentation): Offspring are clones. Fragmentation (piece breaking off) results in offspring genetically identical to the parent, ensuring beneficial traits are passed but limiting diversity.

Chemistry: Matter, Reactions, and Microstructures

• Classification of Matter:

  • Compound: Molecules made of more than one type of atom (e.g., Water, $H_2O$).

  • Physical Changes vs. Chemical Reactions:

    • Melting: A state change (e.g., ice cream on concrete).

    • Dissolving: A solute dispersing into a solvent (e.g., sugar in coffee, blue dye in water).

• Laboratory Procedures and Measurement:

  • Volume: Measured using graduated cylinders at the bottom of the meniscus (e.g., $12.5\,\text{mL}$).

  • Separation vs. Reaction: Steps recovering Copper ($Cu$) metal involves chemical reactions (creating Copper Nitrate $Cu(NO_3)_2$ or Copper Hydroxide $Cu(OH)_2$) and physical separations (filtering out residues).

  • Suspensions: Cloudiness in liquids (e.g., $Cu(OH)_2$) indicates small solid lumps of material blocking light, not full dissolution.

• Hagfish Slime Properties:

  • Creation: Protein strands in gland thread cells uncoil in water to form a gel.

  • Volume Calculation: Cell volume $V = 0.0002\,\text{mm}^3$. Radius $r = 0.0006\,\text{mm}$.

  • Formula: $V = \pi r^2 L$

  • Length ($L$): $L = \frac{0.0002\,\text{mm}^3}{\pi \times (0.0006\,\text{mm})^2} \approx 177\,\text{mm}$.

• Bond Enthalpy and Reaction Energy:

  • Energy Absorption: Required to break bonds (Endothermic).

  • Energy Release: Occurs when new bonds form (Exothermic).

  • Example Calculations: If bond $A-B = 300$, $A-A = 280$, and $B-B = 140$:

    • Reaction $2AB \rightarrow A_2 + B_2$: Absorb $600$, Release $420$. Net change: Energy absorbed (cools surroundings).

• Solubility Profiles:

  • Salt: Soluble in water; insoluble in ethanol/hexane.

  • Sugar: Soluble in water/ethanol; insoluble in hexane.

  • Naphthalene: Insoluble in water; soluble in ethanol/hexane.

  • Recovery: To recover salt specifically from sugar and naphthalene, add ethanol (dissolves sugar/naphthalene) and filter the salt as residue.

• Kinetics (Reaction Rates):

  • System: Magnesium ($Mg$) + Hydrochloric Acid ($HCl$).

  • Relationship: As concentration of $HCl$ increases, the reaction rate increases (time for $Mg$ to disappear decreases).

  • Concentration: $50\,\text{mL}$ acid in $50\,\text{mL}$ total volume is $2.5\times$ more concentrated than $20\,\text{mL}$ acid in $50\,\text{mL}$ total.

• Crystal Lattices (Iridium):

  • Structure: Face-centered cubic (FCC).

  • Unit Cell: Contains parts of 14 atoms. Total whole atoms in one FCC unit cell = $4$.

  • Atomic Radius Calculation: Based on side length $a = 384\,\text{pm}$. In FCC, $4r = a\sqrt{2}$.

  • Result: Radius $r \approx 136\,\text{pm}$.

Physics: Waves, Energy, and Mechanics

• Light and Photosynthesis:

  • Electromagnetic Waves: Visible light characterized by wavelength.

  • Pigments: Chlorophyll a, Chlorophyll b, and $\beta$-carotene absorb specific wavelengths.

  • Color Perception: An object reflects light it does not absorb. A carrot (with $\beta$-carotene) reflects red/orange. Under red light, it appears red. A leaf (Chlorophyll) absorbs red/blue; under red light, it may appear black/dark if absorption is high.

• Quantum Mechanics and Energy:

  • Formula: $E = hf$, where $E$ is energy, $h$ is Planck's constant, and $f$ is frequency.

  • Units: Planck’s constant has units of Joule-seconds ($Js$).

  • Wavelength Relationship: Blue light (high frequency) carries more energy per photon than red light (low frequency).

• Energy Efficiency (Sankey Diagrams):

  • Leaf Model: Net glucose storage efficiency is calculated by dividing stored energy by total solar input. Example: $5\%$ efficiency.

• Solar Irradiance:

  • Solar Input: Varies due to Earth's spherical shape and tilt ($23^{\circ}$).

  • Tropic Lines: Cancer ($23^{\circ}$ N) and Capricorn ($23^{\circ}$ S).

  • Geometry: High irradiance occurs where the surface is perpendicular to sunlight (equatorial regions).

  • Calculations (Rockhampton): Irradiance $1100\,\text{W/m}^2$. Solar panel ($1.7\,\text{m} \times 1.0\,\text{m}$) at $22\%$ efficiency generates $1100 \times 1.7 \times 0.22 \approx 411\,\text{W}$.

  • Power Devices: A $411\,\text{W}$ panel can power approximately $29$ LED bulbs of $14\,\text{W}$ each ($411 / 14 \approx 29.4$).

• Electricity and Work:

  • kWh to Joules: $1\,\text{kWh} = 3.6 \times 10^6\,\text{J}$.

  • Daily Usage: $25\,\text{kWh} = 25 \times 3,600,000 = 90 \times 10^6\,\text{J}$ (90 million Joules).

  • Incandescent Bulbs: Waste electrical energy as heat. Heat rises due to air flow, making the top of the bulb hotter than the base.

  • Circuit Logic: A bulb lights only if the terminal and the side casing complete a path with the battery and wire.

• Motion and Forces:

  • Speed: $\text{speed} = \frac{\text{distance}}{\text{time}}$.

  • Motion Diagrams: Equally spaced dots = constant speed (balanced forces). Increasing spacing = acceleration (unbalanced forces).

  • Weight Force: A non-contact force acting downwards. Only force on an object in free air.

  • Normal Force: Upward force from ground contact.

  • Athlete Scenario (200m): World record $21.34\,\text{s}$. Athlete with 11 dots @ $2.00\,\text{s}$ intervals = $22.00\,\text{s}$. Difference = $0.66\,\text{s}$ ($66$ hundredths of a second).

Earth Science: Geology and Geochronology

• Rock Classification:

  • Igneous:

    • Extrusive (Volcanic): Cool quickly; small/no crystals; gas bubbles (vesicles) common.

    • Intrusive (Plutonic): Cool slowly; large visible crystals (e.g., Granite); no bubbles due to high pressure.

    • Mineral Composition: Felsic (light), Mafic (dark), Ultramafic (green, e.g., Olivine), Intermediate (grey).

  • Metamorphic: High pressure/temperature; includes Schist, Gneiss, Marble (from Limestone), Slate (from Shale).

  • Sedimentary: Conglomerate (fast water), Sandstone (river/beach), Siltstone/Mudstone (still water/deep marine), Limestone (coral/shells).

• Stratigraphy and Law of Superposition:

  • A sequence of fossils (e.g., Silurian coral $\rightarrow$ Permian shells $\rightarrow$ Jurassic ferns) illustrates changing environments (shallow marine to swamp) over millions of years.

  • Dykes: Igneous intrusions cutting through older sedimentary "country rock." They can cause small zones of contact metamorphism (e.g., limestone turning into marble).

• Topography and Landforms:

  • Contour Lines: Join points of equal elevation. Close lines indicate steep gradients.

  • Billabongs (Oxbow Lakes): Form from river meanders. Sediments include mud, silt, pollen, and historical human artifacts.

• Chronostratigraphic Chart:

  • Eras: Paleozoic, Mesozoic (Triassic, Jurassic, Cretaceous), Cenozoic.

  • Ages: Measured in Ma (Mega-annum, million years before present).

• Astronomy: Moon Phases:

  • New Moon: Rises at sunrise, sets at sunset.

  • Full Moon: Rises at sunset, sets at sunrise.

  • First Quarter: Rises at noon, sets at midnight (moonlit first half of night).

  • Last Quarter: Rises at midnight, sets at noon (moonlit second half of night).