IGCSE Biology Paper-3: Specimen Questions with Answers 284 - 286 of 358

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Question 284

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The lower surface of most leaves has many pores.

The pores allow gases to move into and out of a leaf for photosynthesis.

State the name of the gas that is used for photosynthesis.

Explanation

Carbon Dioxide

Oxygen is released during the process of photosynthesis. Photosynthesis is the process in which green plants produce glucose. It involves the conversion of carbon dioxide gas, water, and minerals the plants take in from their surroundings into sugar and gaseous oxygen. Photosynthesis involves the intake of carbon dioxide and the release of oxygen. The release of oxygen is due to photolysis of water.

Question 285

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Lipase is involved in the breakdown of fats.

State the two products of fat digestion.

Explanation

Fatty Acids and Glycerol

Passage

Improved food production has contributed to the increase in the human population.

Question 286 (1 of 4 Based on Passage)

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As the human population has increased, forests have been cleared for farming.

Outline the effects of deforestation on the environment.

Explanation

  • Soil Erosion: it՚s easy to think of soil as compact and unmoving, but that isn՚t always accurate. Soil can be surprisingly loose, and it doesn՚t always stay in the same place. It can be washed away by rain or blown away by wind if it isn՚t properly anchored. What anchors the soil in place? The roots of plants, mostly.
  • Water Cycle Disruption: The water cycle is the process by which all water on earth is distributed. Water from Earth՚s oceans as well as from the surface of bodies of fresh water evaporates and condenses into clouds. Trees and other plants also extract groundwater and release that water into the atmosphere during photosynthesis.
  • Greenhouse Gas Emissions: Greenhouse gases such as methane and carbon dioxide are gases that trap heat in Earth՚s atmosphere, leading to global climate change. Fortunately, in addition to releasing oxygen and water into the atmosphere, trees also absorb carbon dioxide. While trees are still living, they function as efficient greenhouse gas filters.
  • Biodiversity Losses: Living things have mastered the art of adapting to new environments. This is how life on Earth manages to thrive from the Arctic tundra to burning hot deserts. However, it takes time for life to adapt. Deforestation alters land too quickly for plants and animals to cope, which means that many of them do not survive.

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