Biology > EXAM > IGCSE BIOLOGY EXAM 2024-25 QUESTIONS AND ANSWERS (All)

IGCSE BIOLOGY EXAM 2024-25 QUESTIONS AND ANSWERS

Document Content and Description Below

IGCSE BIOLOGY EXAM 2024-25 QUESTIONS AND ANSWERS The results for oxygen and carbon dioxide in the samples of breathed out air taken before and after exercise are different. Describe and explain th... ese differences. In breathed out air, after exercise there is less oxygen and more carbon dioxide. As a higher amount of energy is required during exercise for muscle contractions. The muscle cell's respire at a faster rate. Therefore, rate of gas exchange increases. Hence, more oxygen is absorbed into the blood and more carbon dioxide is produced (and released into the lungs.) Moreover, the body must also "repay" the oxygen to oxidise the lactic acid build up during excercise, thus oxygen levels exhaled still remain lower also due to oxygen debt. Describe what happens when an egg is fertilised by a sperm. Sperm cell uses enzymes (from acrosome) to digest through the zona pellucida (jelly coat.) Fusion of gametes occurs as the ehad of the sperm enters the ova's cytoplasm, during this stage the cell membrane of the ova changes so that no other sperm may enter. The two haploid nuclei then fuse to form a diplod zygote. Explain why substances are transported in the phloem upwards at one time of the year and downwards at another. During growing season (when photosynthesising or when food is made i.e spring and summer.) Substances are transported down, to the roots for storage or transported up to the flowers, fruits, seeds and new leaves. The time of year when no photosynthesis occurs (winter.)Substances are transported upwards from the roots, storage organ , (or downwards) seed to the other parts of the plant like the leaves to provide them with nutrients and cellular energy. [Show More]

Last updated: 4 months ago

Preview 1 out of 20 pages

Buy Now

Instant download

We Accept: