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NB Grade 8 Scientific Literacy study materials
NB Grade 8 Scientific Literacy study resources

NB Grade 8 Scientific Literacy practice questions

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Question 1Scientific Inquiry and Process Skills

A student wants to find out whether adding salt to water changes how fast sugar dissolves. Which is the independent variable in this investigation?

  1. The amount of salt added to the water Correct answer.
  2. The amount of sugar used
  3. The time the sugar takes to dissolve
  4. The temperature of the water

Explanation

The independent variable is the factor the experimenter deliberately changes. Here the student chooses how much salt to add, so that factor is manipulated. Speed of dissolving is the measured response, and temperature and sugar amount must be held constant.

Question 2Scientific Inquiry and Process Skills

A class measures the length of the same leaf five times and gets 12.1 cm, 12.0 cm, 12.2 cm, 12.1 cm, and 12.1 cm. Which statement best describes these measurements?

  1. They are both inaccurate and imprecise
  2. They are accurate but not precise
  3. They are precise but may still be inaccurate Correct answer.
  4. They cannot be judged without more trials

Explanation

Precision refers to how closely repeated measurements agree with one another. These values cluster tightly together, so they are precise. Accuracy requires comparison with a true value, which is not given, so the readings could still be off.

Question 3Scientific Inquiry and Process Skills

Which instrument would be most appropriate for measuring the volume of a liquid to the nearest 0.1 mL?

  1. A metre rule
  2. A thermometer
  3. A graduated cylinder Correct answer.
  4. A stopwatch

Explanation

Volume of a liquid is measured with a graduated cylinder, which has a scale marked in millilitres. Choosing an instrument depends on matching the quantity being measured with the scale it provides. The other instruments measure length, time, and temperature.

Question 4Scientific Inquiry and Process Skills

In an experiment, a student heats a beaker of water and records the temperature every minute. Which type of data has the student collected?

  1. Qualitative data
  2. A conclusion
  3. Quantitative data Correct answer.
  4. A hypothesis

Explanation

Quantitative data are numerical observations that can be measured and compared. Temperature readings are numbers with units, so they are quantitative. Qualitative data would describe qualities such as colour or smell.

Question 5Scientific Inquiry and Process Skills

A student predicts that a plant given more light will grow taller. She places one plant in bright light and one in a dark cupboard. Both plants are the same species and size. What is the main flaw in her experimental design?

  1. The plants are the same size
  2. She is measuring plant height
  3. More than one variable differs between the plants Correct answer.
  4. She has not made a hypothesis

Explanation

A fair test changes only one factor while keeping all others the same. Moving one plant into a dark cupboard changes both light and possibly temperature, so the cause of any difference cannot be identified. Controlled variables must be held constant across trials.

Question 6Scientific Inquiry and Process Skills

Which of the following is the best example of a testable scientific question?

  1. Should students be allowed to choose their own experiments?
  2. Is it wrong to keep plants indoors?
  3. Does the amount of water affect how tall bean plants grow? Correct answer.
  4. Why is nature so beautiful?

Explanation

A testable question can be answered by collecting measurable evidence. Asking whether water amount affects plant height involves variables that can be changed and measured. Questions about beauty, rules, or ethics involve opinions or values rather than measurable data.

Question 7Scientific Inquiry and Process Skills

A student wants to know which paper towel absorbs the most water. Which procedure would give the most reliable results?

  1. Test one brand once using a large sheet
  2. Test three brands using sheets of different sizes
  3. Ask classmates which brand they prefer
  4. Test three brands, repeating each test three times with equal towel sizes Correct answer.

Explanation

Reliability improves when trials are repeated and conditions are controlled. Using equal towel sizes and repeating each test reduces the effect of random variation. Comparing brands under identical conditions makes the comparison fair.

Question 8Scientific Inquiry and Process Skills

A bar graph is best used to display which type of data?

  1. Step-by-step instructions for a procedure
  2. Continuous change over a period of time
  3. Counts or measurements in separate categories Correct answer.
  4. The exact location of a single point

Explanation

Bar graphs compare discrete categories, such as the number of students choosing each colour. Continuous change over time is usually shown with a line graph. Instructions and single points are not data displays.

Question 9Scientific Inquiry and Process Skills

A student measures a liquid's mass as 45.0 g and its volume as 50.0 mL. Which calculation gives the density in g/mL?

  1. 45.0 multiplied by 50.0
  2. 50.0 minus 45.0
  3. 50.0 divided by 45.0
  4. 45.0 divided by 50.0 Correct answer.

Explanation

Density is mass per unit volume, so the mass is divided by the volume. Substituting the readings gives 45.0 g divided by 50.0 mL, which is 0.90 g/mL. Multiplying, subtracting, or inverting the ratio does not give density.

Question 10Scientific Inquiry and Process Skills

Why should a scientist repeat an experiment several times before drawing a conclusion?

  1. To avoid recording any data
  2. To make the experiment take longer
  3. To guarantee the hypothesis is correct
  4. To reduce the influence of random variation on the results Correct answer.

Explanation

Repeated trials help average out random errors and show whether results are consistent. Consistent results increase confidence that the pattern is real rather than a chance event. Repetition cannot guarantee a hypothesis is true, since new evidence may still contradict it.

Question 11Scientific Inquiry and Process Skills

A student observes that ice melts faster in a metal tray than in a plastic tray at the same room temperature. Which conclusion is best supported by this observation?

  1. Plastic does not allow ice to melt at all
  2. Metal conducts heat to the ice more quickly than plastic does Correct answer.
  3. Metal is always colder than plastic
  4. The ice in the plastic tray was a different substance

Explanation

The only difference between the two setups is the tray material, so the faster melting is best explained by the metal's greater thermal conductivity. A conclusion should follow from the evidence and stay within what was tested. Claims about temperature or identity are not supported by the observation.

Question 12Scientific Inquiry and Process Skills

Which of these is a qualitative observation?

  1. The solution took 40 seconds to form
  2. The solution had a mass of 25 g
  3. The solution's temperature was 30 degrees Celsius
  4. The solution turned cloudy and blue Correct answer.

Explanation

Qualitative observations describe qualities that are not expressed as numbers, such as colour or cloudiness. Mass, temperature, and time are all numerical measurements. Recognising the type of observation helps decide how data should be recorded and analysed.

Question 13Scientific Inquiry and Process Skills

A student wants to compare how much two different fertilizers affect the number of leaves on tomato plants. Which factor must be kept the same for a fair comparison?

  1. The number of leaves on each plant
  2. The type of fertilizer used
  3. The brand of fertilizer used
  4. The amount of water each plant receives Correct answer.

Explanation

In a fair test, all variables except the independent variable are held constant. Water amount affects plant growth, so it must be identical across groups. Fertilizer type and brand are the manipulated variable, and leaf number is the measured outcome.

Question 14Scientific Inquiry and Process Skills

A graph shows that as the temperature of a solvent increases, the time needed for sugar to dissolve decreases steadily. Which statement best describes this relationship?

  1. There is an inverse relationship between temperature and dissolving time Correct answer.
  2. There is no relationship between the two variables
  3. Dissolving time increases as temperature increases
  4. Temperature has no effect on dissolving time

Explanation

An inverse relationship means one variable decreases as the other increases. The graph shows higher temperatures paired with shorter dissolving times. Describing the trend accurately is a key step in interpreting data.

Question 15Scientific Inquiry and Process Skills

Which step normally comes immediately after a scientist forms a hypothesis?

  1. Designing and carrying out an investigation to test it Correct answer.
  2. Publishing the results as a proven fact
  3. Discarding the hypothesis without testing
  4. Writing a final conclusion

Explanation

A hypothesis is a testable prediction, so the next step is to plan and conduct an investigation that can support or contradict it. Conclusions come only after data have been collected and analysed. A hypothesis is never treated as proven before evidence is gathered.

Question 16Scientific Inquiry and Process Skills

Two students measure the mass of the same object. Student A records 20.0 g. Student B records 20.0 g, 20.1 g, and 19.9 g on three trials. Whose results show greater precision?

  1. Neither, because neither measured the true mass
  2. Student B, because the repeated values are close together Correct answer.
  3. Both equally, because the values are nearly identical
  4. Student A, because only one value was recorded

Explanation

Precision describes how closely repeated measurements agree with each other. Student B's three values fall within a narrow range, showing good precision. Student A has only one measurement, so no spread can be assessed.

Question 17Scientific Inquiry and Process Skills

A scientist claims a new fertilizer doubles crop yield based on one field trial. What would most strengthen this claim?

  1. Reporting the result in a newspaper
  2. Repeating the trial in several fields with control plots Correct answer.
  3. Increasing the amount of fertilizer used
  4. Testing only in the same field again

Explanation

A claim is strengthened by evidence that is repeatable and compared against a control. Testing across several fields with untreated control plots shows whether the effect is consistent and not due to local conditions. A single repeated site or media coverage adds little scientific support.

Question 18Scientific Inquiry and Process Skills

A student is investigating how the angle of a ramp affects the distance a toy car travels. Which is the dependent variable?

  1. The distance the car travels Correct answer.
  2. The angle of the ramp
  3. The surface the ramp rests on
  4. The type of toy car used

Explanation

The dependent variable is the response that is measured and is expected to change. Here the student measures how far the car travels. The ramp angle is deliberately changed, while car type and surface are held constant.

Question 19Scientific Inquiry and Process Skills

A data table shows that a plant given 2 hours of light grew 1 cm, one given 4 hours grew 3 cm, and one given 6 hours grew 6 cm. Which pattern is shown?

  1. Growth is unrelated to light exposure
  2. Growth is highest at 2 hours of light
  3. Growth increases as light exposure increases Correct answer.
  4. Growth decreases as light exposure increases

Explanation

Comparing the rows shows that longer light exposure is paired with greater growth. Recognising such patterns is the basis for describing trends in data. The values rise from 1 cm to 6 cm as light hours increase.

Question 20Scientific Inquiry and Process Skills

A student notices that a metal spoon left in hot soup becomes warm. Which step of scientific inquiry does this best represent?

  1. Publishing a peer-reviewed report
  2. Calculating a mean from repeated trials
  3. Forming a conclusion from controlled data
  4. Making an observation that could lead to a question Correct answer.

Explanation

Scientific inquiry often begins with careful observation of a phenomenon. The warm spoon is a direct observation that could prompt a testable question about heat transfer. Conclusions, publications, and calculations come later in the process.

Question 21Scientific Inquiry and Process Skills

Why is it important for a scientist to record data during an investigation rather than relying on memory?

  1. Written records replace the need for a hypothesis
  2. Recorded data can be checked, shared, and re-analysed by others Correct answer.
  3. Memory is always more accurate than written records
  4. Recording data makes the experiment shorter

Explanation

Written records preserve exact measurements so results can be verified and repeated by others. Reliable records allow later analysis and comparison. Memory is unreliable and cannot substitute for documented evidence, and records do not replace hypotheses.

Question 22Scientific Inquiry and Process Skills

A student wants to test whether temperature affects the strength of a magnet. Which pair correctly identifies what should be changed and what should be measured?

  1. Change the magnet size; measure temperature
  2. Change temperature; measure the number of paper clips lifted Correct answer.
  3. Change the paper clip size; measure the magnet's colour
  4. Change the number of paper clips; measure temperature

Explanation

The independent variable is deliberately changed, and the dependent variable is measured. To test temperature's effect, temperature must vary while the magnet's lifting ability is measured. The other pairs confuse which factor is manipulated and which is observed.

Question 23Scientific Inquiry and Process Skills

A class collects data on the height of 30 bean plants after two weeks. Most plants are between 8 and 12 cm, but one plant is 25 cm tall. What is the most reasonable first step in handling this value?

  1. Delete it because it does not fit the pattern
  2. Change it to match the average
  3. Check whether a recording or measurement error occurred Correct answer.
  4. Ignore all the other data

Explanation

An unusual value may be a genuine result or an error, so it should be checked before any decision is made. Reviewing the measurement and recording process protects against discarding valid data. Removing or altering data without investigation undermines the integrity of the results.

Question 24Scientific Inquiry and Process Skills

Which statement best explains why a control group is included in an experiment?

  1. It replaces the need for repeated trials
  2. It guarantees the hypothesis will be supported
  3. It increases the number of variables changed
  4. It provides a baseline for comparison without the treatment Correct answer.

Explanation

A control group is treated the same as the experimental group except that it does not receive the treatment. Comparing the two groups shows whether the treatment caused the observed effect. Controls do not eliminate the need for repetition or guarantee any outcome.

Question 25Scientific Inquiry and Process Skills

A student's hypothesis states that plants watered with sugar water will grow taller than plants watered with plain water. After four weeks, both groups are the same height. What is the most appropriate response?

  1. Abandon the investigation without reporting
  2. Claim the hypothesis was proven correct
  3. Change the measurements to support the hypothesis
  4. Report that the evidence does not support the hypothesis Correct answer.

Explanation

Scientific conclusions must reflect the evidence collected, even when it contradicts the prediction. A hypothesis that is not supported is a valid result that may lead to revised questions. Altering data or ignoring results would be dishonest.

Question 26Scientific Inquiry and Process Skills

A student heats a liquid in a beaker and records its temperature every 30 seconds, then plots the readings on a line graph. Which process skill is best shown by connecting the plotted points with a smooth line?

  1. Classifying the beaker by its material
  2. Interpreting a trend in the collected data Correct answer.
  3. Predicting the mass of the beaker
  4. Estimating the volume of the liquid

Explanation

Drawing a line through plotted points summarizes how the dependent variable changes with the independent variable, which is trend interpretation. The line describes the pattern in the recorded temperatures rather than measuring a new quantity. Skills such as classifying or estimating are not involved in reading the shape of a graph.

Question 27Scientific Inquiry and Process Skills

A student writes the following for a planned investigation: 'If a bean seed is soaked in water for 12 hours before planting, then it will sprout sooner than a dry seed.' Which part of this statement is the prediction being tested?

  1. Sprouting time is difficult to measure accurately
  2. Bean seeds need water to sprout at all
  3. Seeds should always be planted in moist soil
  4. Soaking seeds for 12 hours causes earlier sprouting Correct answer.

Explanation

A hypothesis pairs a proposed cause with an expected outcome that can be tested by observation. The statement that soaked seeds will sprout sooner is the specific, measurable prediction. The other statements are background facts, advice, or comments on measurement rather than a testable prediction.

Question 28Scientific Inquiry and Process Skills

During a field study, a student records: 'The pond water was cloudy and smelled slightly of decay.' Which type of data has the student collected?

  1. Quantitative data measured with instruments
  2. Qualitative data based on the senses Correct answer.
  3. Calculated data derived from a formula
  4. Numerical data expressed in units

Explanation

Qualitative data describe qualities such as color, clarity, texture, or odor using words rather than numbers. Cloudiness and smell are sensory descriptions, so they are qualitative observations. Quantitative data would require measurements with units, such as turbidity in units or a temperature reading.

Question 29Scientific Inquiry and Process Skills

A student wants to know whether the color of light affects how tall seedlings grow. Which list contains only the materials needed to test this question?

  1. Seedlings, ruler, fertilizer, thermometer
  2. Seedlings, colored light filters, ruler, identical pots and soil Correct answer.
  3. Seedlings, colored light filters, microscope, stopwatch
  4. Colored light filters, thermometer, graph paper, calculator

Explanation

A valid test needs the organism, a way to vary the independent variable, and a tool to measure the dependent variable. Colored filters vary light color, and a ruler measures height, with identical pots and soil keeping other conditions constant. Materials unrelated to light color or height measurement add nothing to the test.

Question 30Scientific Inquiry and Process Skills

A student claims that a certain battery lasts longer than another brand. To compare the two brands fairly, which procedure is most appropriate?

  1. Compare the prices of the two brands and choose the cheaper one
  2. Ask several friends which brand they think lasts longer
  3. Use each brand in identical devices under the same conditions and record run time Correct answer.
  4. Use each brand in a different device and compare how long each device runs

Explanation

A fair comparison changes only the variable under test, which is the battery brand, while holding device, load, and conditions constant. Recording run time in identical devices gives a measurable dependent variable. Differences in devices or reliance on opinions would confound or fail to measure the claim.

Question 31Scientific Inquiry and Process Skills

A class grows radishes in four identical trays placed at different distances from a window. All trays receive the same soil, water volume, and number of seeds. Which variable is being changed on purpose?

  1. The distance of each tray from the window Correct answer.
  2. The amount of water given to each tray
  3. The number of seeds planted in each tray
  4. The type of soil used in each tray

Explanation

The independent variable is the one the experimenter deliberately manipulates to observe its effect. Here the distance from the window, which changes light exposure, is intentionally varied among trays. Water, seed number, and soil are held constant so they cannot explain differences in growth.

Question 32Scientific Inquiry and Process Skills

A student measures the length of a leaf three times and gets 6.2 cm, 6.3 cm, and 6.2 cm. A classmate measures the same leaf once and gets 7.8 cm. Which statement best describes the two sets of measurements?

  1. The student's measurements are accurate but not precise
  2. Both sets of measurements show the same level of precision
  3. The classmate's measurement is both precise and accurate
  4. The student's measurements are precise but may not be accurate Correct answer.

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to closeness to the true value. The three readings cluster tightly together, showing high precision, but they may still differ from the actual length. A single reading cannot demonstrate precision, and its distance from the cluster suggests it may be inaccurate.

Question 33Scientific Inquiry and Process Skills

A scientist tests a new plant food on 10 plants and gives 10 similar plants plain water. Both groups are kept in the same greenhouse with equal light and water. What is the main purpose of the group receiving plain water?

  1. To test whether plain water can harm plants
  2. To make the experiment finish more quickly
  3. To provide a baseline for comparing the effect of the plant food Correct answer.
  4. To increase the total number of plants in the study

Explanation

A comparison group that does not receive the treatment shows what would happen without it, giving a baseline. Measuring the treated group against this baseline reveals whether the plant food caused any change. Without such a comparison, natural growth could be mistaken for an effect of the treatment.

Question 34Scientific Inquiry and Process Skills

A student measures the mass of a sample on a balance and records 12.4 g. The balance display shows two decimal places, and the same sample is measured again as 12.40 g. Which statement about the recorded values is most accurate?

  1. The two values describe different masses of the sample
  2. The second value shows the instrument's smallest readable unit Correct answer.
  3. The first value should be discarded as a mistake
  4. The second value is more precise because it has more digits

Explanation

The number of decimal places recorded reflects the smallest division the instrument can read. Writing 12.40 g indicates the balance reads to the hundredth of a gram, not that the mass changed. Both records describe the same sample, and extra digits do not by themselves create greater precision.

Question 35Scientific Inquiry and Process Skills

A student tests how the length of a pendulum string affects the number of swings in 30 seconds. The results are 10 cm: 22 swings, 20 cm: 16 swings, 30 cm: 12 swings. Which conclusion is best supported by these data?

  1. Shorter strings make the pendulum swing more slowly
  2. Longer strings always produce more swings in 30 seconds
  3. The string length has no effect on the number of swings
  4. The number of swings decreases as the string gets longer Correct answer.

Explanation

The data show a steady decrease in swing count as string length increases from 10 cm to 30 cm. A conclusion should describe the pattern the data actually display without overgeneralizing beyond the tested range. Statements about no effect or reversed direction contradict the recorded numbers.

Question 36Scientific Inquiry and Process Skills

A student wants to find out whether the temperature of water affects how quickly a sugar cube dissolves. Which is the best operational definition of the dependent variable?

  1. The time in seconds from placing the cube in water until it is no longer visible Correct answer.
  2. The temperature of the water measured in degrees Celsius
  3. The amount of water used in each cup
  4. The size of the sugar cube as measured with a ruler

Explanation

An operational definition states exactly how a variable will be measured in the investigation. Dissolving speed is defined here as the time until the cube disappears, a quantity that can be timed. Temperature is the independent variable, while cube size and water amount are conditions to control.

Question 37Scientific Inquiry and Process Skills

A student's data table shows that a reaction took 40 s at 20 degrees C, 25 s at 30 degrees C, and 15 s at 40 degrees C. Which additional step would most improve the strength of the conclusion drawn from these results?

  1. Recording only the fastest time at each temperature
  2. Adding a trial at a temperature far outside the tested range without repeating others
  3. Repeating each temperature trial several times and averaging the times Correct answer.
  4. Changing the amount of reactants for each temperature

Explanation

Repeated trials reduce the influence of random error and make the averages more dependable. Averaging several runs at each temperature gives a more trustworthy basis for the conclusion. Changing reactant amounts or selecting only the fastest result would introduce bias rather than strengthen the evidence.

Question 38Scientific Inquiry and Process Skills

A student reads that a certain fertilizer is 'best for tomatoes' but the article does not describe how the claim was tested. Which action would best help the student evaluate the reliability of this claim?

  1. Choose the fertilizer with the most attractive packaging
  2. Find the original study and check its sample size and controls Correct answer.
  3. Ask a friend who grows tomatoes which fertilizer they prefer
  4. Accept the claim because it appears in print

Explanation

Evaluating a scientific claim requires examining the evidence behind it, including sample size, controls, and whether the results were repeated. Locating the original study allows the student to judge whether the conclusion is supported. Personal preference or packaging says nothing about the strength of the evidence.

Question 39Scientific Inquiry and Process Skills

Two students investigate whether music affects plant growth. Student A plays music for 4 hours daily, and Student B plays music for 1 hour daily. Their plants differ in height after three weeks. Which flaw most limits this investigation?

  1. The investigation used plants rather than animals
  2. The two students did not use the same music duration Correct answer.
  3. The plants were grown in a classroom
  4. The plants were measured after only three weeks

Explanation

To test whether music affects growth, the treatment must differ from a no-music baseline while other factors stay equal. Here both students played music but for different durations, so the comparison confounds music exposure with duration. A valid design would include a silent control and matched conditions.

Question 40Scientific Inquiry and Process Skills

A student's results do not support the original hypothesis. What is the most scientifically appropriate response?

  1. Revise the data so they match the hypothesis
  2. Conclude that the experiment was meaningless
  3. Report the results honestly and consider a revised explanation Correct answer.
  4. Repeat the experiment until the expected result appears

Explanation

Scientific inquiry treats a hypothesis as a testable proposal that may be rejected by evidence. Honest reporting of unexpected results allows the explanation to be revised and further tested. Altering data or repeating until a desired outcome appears violates the integrity of the process.

Question 41Life Science: Cells, Body Systems, and Reproduction

Which structure controls what enters and leaves a cell?

  1. Vacuole
  2. Cell membrane Correct answer.
  3. Mitochondrion
  4. Nucleus

Explanation

The cell membrane is a thin outer boundary that is selectively permeable, meaning it lets some substances pass through while blocking others. This control keeps the internal conditions of the cell stable. Other organelles sit inside the cell and carry out specific jobs rather than guarding the border.

Question 42Life Science: Cells, Body Systems, and Reproduction

A student views a leaf cell and sees many small green structures. Which organelle are these?

  1. Nuclei
  2. Ribosomes
  3. Chloroplasts Correct answer.
  4. Cell walls

Explanation

Chloroplasts contain the green pigment chlorophyll, which captures light energy for photosynthesis. Their green color is what makes most plant tissues look green under a microscope. The other listed structures are not green and do not carry out photosynthesis.

Question 43Life Science: Cells, Body Systems, and Reproduction

Which statement best describes the main function of red blood cells?

  1. They carry oxygen around the body. Correct answer.
  2. They digest worn-out cells.
  3. They produce antibodies against germs.
  4. They clot blood at wound sites.

Explanation

Red blood cells are packed with hemoglobin, an iron-containing protein that binds oxygen in the lungs and releases it in body tissues. Their flattened shape and lack of a nucleus give more room for hemoglobin. Clotting, immunity, and cleanup are handled by other blood components.

Question 44Life Science: Cells, Body Systems, and Reproduction

Which organ system includes the stomach, small intestine, and esophagus?

  1. Nervous system
  2. Skeletal system
  3. Respiratory system
  4. Digestive system Correct answer.

Explanation

The digestive system is the group of organs that breaks food into nutrients and absorbs them. The esophagus, stomach, and small intestine are all parts of this tube-like pathway. The other systems listed involve gas exchange, signaling, or support and movement.

Question 45Life Science: Cells, Body Systems, and Reproduction

During which process does one parent cell divide to form two identical daughter cells?

  1. Meiosis
  2. Fertilization
  3. Pollination
  4. Mitosis Correct answer.

Explanation

Mitosis is division that produces two daughter cells with the same chromosome number and genetic information as the parent. It is used for growth, repair, and replacing worn-out cells. Meiosis and fertilization involve changes in chromosome number, and pollination is a plant reproductive step.

Question 46Life Science: Cells, Body Systems, and Reproduction

Which part of a flower produces pollen?

  1. Anther Correct answer.
  2. Sepal
  3. Ovary
  4. Stigma

Explanation

The anther is the tip of the stamen and contains pollen grains, which hold the male sex cells of the plant. Pollen must reach the stigma for fertilization to occur. The ovary and stigma are female parts, and sepals protect the developing bud.

Question 47Life Science: Cells, Body Systems, and Reproduction

Which gas do green plants release during photosynthesis?

  1. Oxygen Correct answer.
  2. Nitrogen
  3. Carbon dioxide
  4. Hydrogen

Explanation

In photosynthesis, plants use light energy to combine carbon dioxide and water into sugar, and oxygen is released as a by-product. This oxygen comes from splitting water molecules. Carbon dioxide is taken in rather than released during this process.

Question 48Life Science: Cells, Body Systems, and Reproduction

Which human body system carries messages quickly between the brain and other organs?

  1. Nervous system Correct answer.
  2. Muscular system
  3. Lymphatic system
  4. Endocrine system

Explanation

The nervous system uses electrical signals traveling along nerve cells to send fast messages between the brain, spinal cord, and body. This allows rapid responses such as pulling a hand away from heat. Hormones move more slowly through the blood.

Question 49Life Science: Cells, Body Systems, and Reproduction

A cell is placed in pure water and swells. Which explanation fits this observation?

  1. The nucleus absorbed the water.
  2. Water entered the cell by osmosis. Correct answer.
  3. Salt moved into the cell by diffusion.
  4. The cell wall dissolved in the water.

Explanation

Osmosis is the movement of water across a membrane from a region of higher water concentration to lower water concentration. Pure water outside has a higher water concentration than the cell contents, so water enters and the cell swells. This movement is passive and needs no energy.

Question 50Life Science: Cells, Body Systems, and Reproduction

Which sequence correctly shows the path of air into the body?

  1. Nose, bronchi, trachea, lungs
  2. Trachea, nose, bronchi, lungs
  3. Bronchi, nose, trachea, lungs
  4. Nose, trachea, bronchi, lungs Correct answer.

Explanation

Inhaled air passes through the nose, which warms and filters it, then down the trachea, then into the bronchi that branch into each lung. The lungs contain tiny air sacs where gas exchange occurs. Any order that reverses these structures would not match the actual airflow.