Biology
This key characteristic of living things is defined as the ability to detect or sense changes in the internal or external environment and make appropriate responses, such as phytoplankton responding to light intensity at varying water depths
Sensitivity
Question: Define exothermic and endothermic reactions in terms of thermal energy transfer between the reaction system and its surroundings, and state what happens to the temperature of the surroundings in each case.
Exothermic Reaction: Thermal energy is transferred from the reaction to the surroundings, causing the temperature of the surroundings to increase.
Endothermic Reaction: Thermal energy is taken in from the surroundings into the reaction, causing the temperature of the surroundings to decrease
A raindrop falls vertically through the air at a constant speed. What is the resultant force acting on the raindrop?
The resultant force is 0 N (zero). According to Newton's First Law, an object moving at a constant speed in a straight line has no net balanced force acting on it.
A student observes a bacterial cell under a microscope with a magnification of 12 X. If the actual size of the bacterial cell is 6 cm, what is the calculated image size
72 cm
Complete the relative mass and relative charge for each subatomic particle found within an atom: proton, neutron, and electron.
Proton: Relative mass = 1, Relative charge = +1
Neutron: Relative mass = 1, Relative charge = 0
Electron: Relative mass = 0 (or negligible), Relative charge = -1
Found in the roots of plants, this specialized cell features an elongated projection designed to maximize its surface area for the absorption of water and mineral ions.
Root Hair Cell
Complete and balance the word and symbol equation for the reaction of sodium metal with oxygen gas to form sodium oxide.
Soidum + Oxygen --> Sodium oxide
4Na + O2 --> 2Na2O
State the equation for calculating orbital speed (v), defining each symbol in the formula.
v = 2(pie)(r) / T
Name two distinct adaptations of a palisade mesophyll cell that make it specialized for maximum rates of photosynthesis.
They contain a high density of chloroplasts to absorb light energy and are positioned near the upper surface of the leaf to receive maximum sunlight exposure.
Define diffusion and osmosis, and explain the key structural requirement a cell membrane must have for osmosis to take place.
Diffusion: The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient as a result of their random motion.
Osmosis: The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) across a partially permeable membrane.
Key Requirement: The cell membrane must be partially permeable (selectively permeable), allowing small water molecules to pass through while blocking larger solute particles.
Explain how energy flow differs from nutrient cycling within an ecosystem, using a 4-trophic-level food chain (Producer --> Primary Consumer -->Secondary Consumer --> Tertiary Consumer) and the carbon cycle to illustrate your answer.
Energy Flow in Food Chains: Energy flows unidirectionally (one way) through a food chain and cannot be recycled. Solar energy captured by producers is passed along trophic levels, but approximately 90% of energy is lost at each level as heat from respiration, movement, and waste. As a result, energy decreases up the chain, limiting the number of trophic levels.
Nutrient Cycling in the Carbon Cycle: Unlike energy, carbon is recycled continuously within a closed system. Carbon dioxide CO2 absorbed by producers during photosynthesis passes through consumers via feeding. When organisms at any trophic level die or produce waste, decomposers (fungi and bacteria) break them down and release carbon back into the atmosphere as CO2 through cellular respiration, making it available for producers to use again.
Identify the oxidizing agent and the reducing agent in the following reaction:
CuO + H2 --> Cu + H2O
oxidizing agent: copper
Reducing Agent: hydrogen
A gas is trapped in a sealed container of fixed volume. Explain in terms of particles why increasing the temperature of the gas increases its pressure
Increasing temperature increases the average kinetic energy and speed of the gas particles.
The particles collide with the walls of the container more frequently and with greater force per collision, resulting in a higher overall pressure.
A wooden block has a mass of 240g and a volume of 300 cm3. Calculate its density in g/cm3. Will this block float or sink in pure water? (Density of water = 1.0 g/cm3)
density = 0.8 g/cm3
it will float (less dense)
Compare physical (mechanical) digestion and chemical digestion by defining both processes and stating where physical digestion primarily begins in the human digestive system.
Physical Digestion: The mechanical breakdown of food into smaller pieces without altering its chemical structure, which increases the surface area for enzyme action.
Chemical Digestion: The enzymatic breakdown of large, insoluble food molecules into small, soluble molecules that can be absorbed across the intestinal wall into the bloodstream.
Primary Location: Physical digestion begins primarily in the mouth (buccal cavity) through chewing (mastication).
Complete the details for the major digestive enzymes below by providing the substrate, end-products, and primary site of action for each:
Amylase:
Substrate: Starch
Products: Maltose / simple sugars
Primary Site of Action: Mouth and Duodenum (small intestine)
Protease:
Substrate: Proteins
Products: Peptides / Amino acids
Primary Site of Action: Stomach (Pepsin) and Duodenum (Trypsin)
Lipase:
Substrate: Lipids (fats and oils)
Products: Fatty acids and glycerol
Primary Site of Action: Duodenum (small intestine)
Solid calcium oxide CaO reacts with dilute hydrochloric acid HCl to form aqueous calcium chloride (CaCl) and water (H2O) in an exothermic process.
Write the balanced chemical equation for this reaction.
Describe what happens to the temperature of the surroundings during this reaction and explain why this temperature change occurs in terms of bond breaking and bond making.
1. CaO + 2HCl --> CaCl2 + H2O
2. The temperature of the surroundings increases.
A rocket with a total weight of 440,000 N produces an upward engine thrust of 510,000 N at launch. If its acceleration is 1.25 m/s2, calculate the total mass of the rocket.
first find resultant force (70,000 N)
then rearrange F formula for mass (56,000 kg)
Red blood cells and root hair cells are both specialized for absorption or transport. Contrast how their structural adaptations relate directly to their specific functions.
Red blood cells have a biconcave disc shape (and lack a nucleus) to maximize surface area and internal volume for carrying oxygen via hemoglobin during transport. In contrast, root hair cells have a long, narrow elongated projection extending outward to maximize surface area specifically for absorbing water and mineral ions from the surrounding soil
A bus travels a total distance of 180 km in 3 hours. Calculate its average speed in km/h, and then convert that speed to m/s.
speed = 60 km/h, 16.67 m/s
During a growth period, a population of phytoplankton increases both its cell number and total dry mass through photosynthesis. Explain how the biological processes of sensitivity, growth, and photosynthesis interact at the cellular level to achieve this, making sure to identify the organelle responsible for energy conversion.
Sensitivity: Phytoplankton detect changes in light intensity at different depths and adjust their location to stay in the photic zone.
Photosynthesis: Inside the chloroplasts, chlorophyll captures light energy to convert carbon dioxide and water into glucose and oxygen.
Growth: The synthesized glucose and nutrients are used to produce structural biomolecules, leading to a permanent increase in cell size, dry mass, and cell division (growth).
Iron reacts with oxygen to form iron(III) oxide (Fe2O3).
Write the balanced chemical equation for this synthesis reaction.
Identify the oxidizing agent and state the change in oxidation state of iron.
1. 4Fe + 3O2 --> 2Fe2O3
2. oxidizing agent: oxygen gas
3. iron is +3
A cylindrical rocket chamber has a circular radius of 6.5m. Gas exerts an inward force of 14.2 N on the end face of the cylinder. Calculate the pressure exerted on this surface in Pascals (Pa), giving your answer in scientific notation to 3 significant figures.
calculate area of circle: 132.73 m2
Calculate pressure: 0.107 Pa
Convet to scientific notation: 1.07 x 10-1 Pa
Explain why chlorine gas Cl2 can displace bromide ions Br- from an aqueous solution of potassium bromide KBr, but iodine I2 cannot. Write the balanced ionic equation for the displacement reaction that occurs.
Explanation: Chlorine is higher up in Group VII (halogens) than bromine, making chlorine more reactive than bromine. A more reactive halogen will displace a less reactive halogen from its salt solution. Iodine is lower in Group VII than bromine and is less reactive, so no reaction occurs.
Balanced Ionic Equation:
Red blood cells (animal cells) and plant root cells are placed into separate beaker treatments containing hypotonic, isotonic, and hypertonic solutions. Predict and explain the physical changes that occur in both cell types when placed in a hypotonic solution.
Hypotonic Solution: Has a higher water potential (lower solute concentration) than the inside of the cell.
Red Blood Cell: Water moves into the cell by osmosis down a water potential gradient. Because animal cells lack a cell wall, water intake causes the cell membrane to stretch and eventually burst (lysis).
Plant Cell: Water enters the cell by osmosis into the cytoplasm and central vacuole. The rigid cellulose cell wall prevents the cell from bursting, causing internal hydrostatic pressure to build up until the cell becomes turgid.