What Is Biology & Characteristics of Life

Question 1. [4 marks]

• Biology = the scientific study of life and living organisms. [1]
• Any three sub-disciplines (1 mark each, max 3): [3]
  • Zoology — study of animals
  • Botany — study of plants
  • Microbiology — study of microorganisms
  • Genetics — study of heredity and genes
  • Ecology — study of organisms and their environment
  • Physiology — study of how organisms function

Question 2. [4 marks] Seven characteristics (½ mark each = 3.5, rounded scheme: 4 marks for all seven, deduct proportionally):

1. Nutrition, 2. Respiration, 3. Movement, 4. Excretion, 5. Growth, 6. Reproduction, 7. Responsiveness (sensitivity). [4] (Accept MRS GREN mnemonic. Homeostasis/adaptation acceptable variants.)

Question 3. [4 marks] (1 mark each — classification + reason)

• (a) Wooden chair → once-living (made from wood, formerly a living tree). [1]
• (b) Germinating seed → living (shows growth, metabolism, respiration). [1]
• (c) Rock → non-living (never had the characteristics of life). [1]
• (d) Dried leaf → once-living (was part of a living plant, no longer functioning). [1]

Question 4. [4 marks]

• (a) Anabolism = building up of complex molecules from simpler ones, requiring energy. [1] Catabolism = breaking down of complex molecules into simpler ones, releasing energy. [1]
• (b) Anabolism example: photosynthesis / protein synthesis. [1] Catabolism example: respiration / digestion. [1]

Question 5. [5 marks]

• Homeostasis = the maintenance of a stable/constant internal environment despite external changes. [2]
• Temperature: sweating/shivering and blood vessel dilation/constriction keep body temp ~37 °C. [1]
• pH: buffers (e.g. in blood) keep blood pH ~7.4; excess acids removed by lungs/kidneys. [1]
• Glucose: insulin lowers and glucagon raises blood glucose to keep it steady. [1]

Question 6. [5 marks]

• (a) Sexual = involves two parents, fusion of gametes, offspring genetically different. [1½] Asexual = one parent, no gametes, offspring genetically identical (clones). [1½]
• (b) Sexual advantage: genetic variation → better adaptation/survival. [1] Asexual advantage: fast, no mate needed, energy-efficient. [1]

Question 7. [4 marks] Correct order (smallest → largest): [3] atom → molecule → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere (3 marks full; deduct 1 per misplacement, min 0)

• Emergent properties = new characteristics that arise at each higher level of organization that are not present in the individual parts. [1]

Question 8. [5 marks]

• (a) Steps: Observation → Question → Hypothesis → Experiment/Test → Data collection & Analysis → Conclusion. [3] (½ each, accept reasonable variants)
• (b) Independent variable = light intensity. [½] Dependent variable = plant growth (height/mass). [½] Controlled variable = water amount / temperature / soil type / plant species (any one). [1]

Question 9. [5 marks]

• (a) Conversions: (i) $2.5 \text{ mm} \times 1000 = \mathbf{2500 \ \mu m}$ (1 mm = 1000 µm). [1] (ii) $3400 \text{ g} \div 1000 = \mathbf{3.4 \ kg}$ (1000 g = 1 kg). [1] (iii) $0.75 \text{ L} \times 1000 = \mathbf{750 \ mL}$ (1 L = 1000 mL). [1]
• (b) Hypothesis = a testable, tentative explanation/prediction for an observation. [1] Theory = a well-substantiated, broad explanation supported by a large body of repeated evidence. [1]

[
  {"claim":"2.5 mm equals 2500 micrometers","code":"result = (2.5*1000 == 2500)"},
  {"claim":"3400 g equals 3.4 kg","code":"result = (Rational(3400,1000) == Rational(34,10))"},
  {"claim":"0.75 L equals 750 mL","code":"result = (0.75*1000 == 750)"},
  {"claim":"There are seven listed characteristics of life","code":"chars=['Nutrition','Respiration','Movement','Excretion','Growth','Reproduction','Responsiveness']; result = (len(chars)==7)"}
]