27. a) State two density dependent factors that affect population growth in an ecosystem. • Competition (for resources like food, water, space) • Predation • Disease • Parasitism 27. b) Name the instrument used in measuring the following parameter in a habitat. Depth of light penetration in a pond. Secchi disk 28. a) State what happens during the light stage of photosynthesis. During the light stage, chlorophyll absorbs light energy. This energy is used to split water molecules (photolysis) into oxygen, protons, and electrons. The energy is also used to generate ATP and NADPH. 28. b) State the aspect of photosynthesis that is tested using a variegated leaf. The aspect tested is that chlorophyll is necessary for photosynthesis. 29. Sophia had a tooth ache, on inspection the mother realized that a hole had developed from above. i) Identify the disease Dental caries (or tooth decay) ii) State two ways the disease would have been avoided. • Brushing teeth regularly (at least twice a day) • Reducing the intake of sugary foods and drinks • Regular dental check-ups • Using fluoride toothpaste