Year 8 Science | Victorian Curriculum 2.0
Body systems & organ function
Topic 02 | Biological sciences | Answer key

Year 8 answers

Fluency

Systems and organs

    1. cell →\to tissue →\to organ →\to organ system →\to organism.
    2. (a) Heart; pumps blood to transport oxygen, nutrients and waste. (b) Lungs; take in oxygen and remove carbon dioxide. (c) Kidneys; filter liquid waste out of the blood.
    3. The liver.
    4. The nervous system.
    5. Any two of: mouth, oesophagus, stomach, small intestine, large intestine, liver, pancreas.
Fluency

Structure and function

    1. Thin walls (short diffusion distance), large surface area (many gas molecules cross at once), rich blood supply (keeps a steep concentration gradient so gases move quickly).
    2. Villi greatly increase surface area for absorbing digested nutrients into the blood.
    3. The diaphragm pulls down to enlarge the chest cavity (drawing air in), and relaxes to push air out.
    4. The heart pumps against pressure all around the body; thick muscular walls generate enough force.
    5. Without a nucleus, there is more room for haemoglobin, so the cell can carry more oxygen.
Reasoning

Explain and connect

    1. The digestive system breaks down food in the small intestine, where glucose is absorbed into the blood. The circulatory system then pumps the glucose-rich blood to muscle cells, where it is used for energy.
    2. Two of: build-up of toxic waste in the blood; imbalance of water/salts; high blood pressure; tiredness; changes in urine output.
    3. The brain sends signals through the spinal cord to the legs. If the spinal cord is damaged, those signals cannot reach the leg muscles, so they cannot contract even if the muscles themselves are fine.
    4. Hollow bones are still strong in the directions that matter (long-axis loading), but much lighter. Less mass to move means more efficient movement.
Problem solving

Scenarios

    1. Faster heart rate delivers oxygen and glucose more quickly to muscles. Faster breathing brings more oxygen in and removes CO2_2. Sweating prevents overheating as muscles release heat.
    2. Circulatory system (platelets clot the blood), immune system (white blood cells attack any bacteria entering the wound), skin/integumentary system (skin seals the wound as it heals).
    3. High blood sugar is detected by the pancreas, which releases insulin. Insulin signals cells (especially liver and muscle) to take glucose out of the blood. Blood sugar falls back toward normal.
    4. Muscles need a continuous supply of oxygen during hard running. If the lungs cannot take in enough oxygen, muscles run out of fuel (energy) even if they are strong, so performance drops.
Reasoning

Challenge

    1. Flattened villi reduce surface area. Less nutrient absorption happens per length of intestine, so the person may become malnourished even with a normal diet (this is the case in coeliac disease).
    2. In a single loop, blood goes heart →\to gills →\to body →\to heart — losing pressure at the gills. In a double loop, blood returns to the heart to be re-pumped at high pressure to the body, delivering oxygen more rapidly. This supports higher metabolic and activity levels.
    3. In type 1 diabetes the pancreas cannot produce insulin. After a meal, blood sugar rises but cells do not take it up. High blood glucose damages vessels and organs; cells run short of fuel, causing tiredness. The feedback loop has broken at the “effector” step.
    4. Nervous system: pulling a hand from a hot stove (reflex, milliseconds). Endocrine system: growth during puberty (years). Fast responses are needed for threats; slow hormonal changes coordinate long-term processes like growth and digestion.
Year 8 Science study companion | Answer key