IGCSE Biology Paper-3: Specimen Questions with Answers 341 - 343 of 358

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Passage

Flowers contain the male and female reproductive structures of a plant.

The female reproductive structure is the carpel.

The male reproductive structure is the stamen.

Question 341 (3 of 3 Based on Passage)

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Short Answer▾

State two ways in which meiosis is different from mitosis.

Explanation

Organism՚s Life Cycle

Question 342

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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 these pores.

Explanation

Stomata

Stomata are minute pores in the epidermis. Each pore is surounded by two kidney shaped cells, called as guard cells. Guard cells are dumbbelled shaped. Guard cells contain chloroplasts. Inner wall of guard cell is thickened. Usually there is a large air cavity below each stoma. It is called substomatal cavity.

Question 343

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Define the term photosynthesis and outline one reason why it is important to ecosystems.

Explanation

  • Photosynthesis is the synthesis of carbohydrates by green plants in the presence of light by utilizing and By this process, solar energy (ultimate source of energy for all living beings) is trapped by autotrophic organisms and is stored in the form of chemical energy.
  • Annually, about . of carbon (in the form of ) is fixed through photosynthesis, producing about 1700 million tons of dry matter. About of it is carried out in the oceans (largely by the phytoplankton՚s and algae) .
  • Only of the light energy falling on earth is utilized by photosynthetic organisms. Photosynthesis first appeared in cyanobacteria. Later, plants evolved, having chloroplasts as an organelle in the cells. Chloroplasts are specialized in energy production during light.

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