Feature Placenta Lungs Total surface area / m 2 16 55 The thickness of the barrier across which substances must diffuse / um 3.5 0.5 Approximate rate of blood flow/cm 3 per minute 500 5000 Use the data in the table and your knowledge of the features of gas exchange surfaces, to explain why more oxygen can be absorbed per minute across the lungs than across the placenta.

The lungs are the main respiratory organ of the body engaged in the gaseous exchange in and out of the body. It has a 55 m 2 surface area which provides a platform for more gaseous exchange. The placenta is a temporary organ that develops in the uterus during pregnancy. It provides oxygen and nutrients to your growing baby. Placenta has only 16 m 2 total area which is much less than the lungs. So more oxygen is absorbed by the lungs per minute than cross the placenta and more carbon dioxide is removed from the lungs compared to the placenta. Due to this the blood flow per minute in the lungs is more nearly 5000 cm 3 and the blood flow in the placenta is only 500 cm 3 .

The table shows the percentage of people in Asia and the Pacific region who are infected with HIV, who knew that they had the virus. Year Percentage of people living with HIV who knew they had the virus 2015 59 2016 62 2017 65 2018 65 On the grid below, draw a bar chart to display these data.

This bar graph shows the percentage of people living with HIV who knew they had the virus. The percentage is increasing each year and the people infected with this virus also increases. HIV (human immunodeficiency virus) is a virus that attacks the body's immune system. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). You can get HIV from contact with infected blood, semen, or vaginal fluids.

Year Percentage of people living with HIV who knew they had the virus 2015 59 2016 62 2017 65 2018 65 Suggest how the data in the above table have been estimated.

The data in the table has been estimated by calculating the number of people with HIV who knew they had the virus each year. The estimation was done by visiting hospitals and laboratories that have records of people who are suffering from HIV infection in a particular area or city. In 2015, only 59% of those surveyed were aware that they had HIV. This percentage increased in 2016 and 2017 by 3 per cent, reaching 62 and 65 per cent, respectively. But it is stable in 2018 as compared to the previous year. This estimation is based on the calculation of each person suffering from HIV infection.

The table shows data relating to the other two components of the United Nations’ target. Year Percentage of people diagnosed with HIV who are receiving antiretroviral drugs Percentage of people receiving antiretroviral drugs in whom the virus is suppressed 2015 62 89 2016 68 89 2017 74 90 2018 79 90 Use all the data to discuss the progress made by the United Nations in achieving its target in the Asia and Pacific region. Use the data to evaluate the likelihood that the target will be achieved by 2020.

In 2015 and 16, 62 per cent and 68 per cent of people diagnosed with HIV who receives antiretroviral drug respectively. Out of the 89 per cent of people, who receive the antiretroviral drug in whom the virus is suppressed. The percentage of people diagnosed with HIV who receive antiretroviral drug is increased to 74 and 79 per cent in the year 2017 and 18 respectively but the people in which virus is suppressed is increased only one per cent in both the year. The possibility of per cent of people who receive the antiretroviral drugs and those receiving antiretroviral drugs in whom the virus is suppressed will be the same until 2020 and it is 91 per cent.

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Earn 100

Oxygen moves by diffusion across the exchange surface in both the placenta and the lungs.

Explain fully why the net movement of oxygen is in this direction in the lungs.

Important Questions on Reproduction in Humans

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Biology for Cambridge IGCSE Workbook 4 th Edition Digital Access>Chapter 15 - Reproduction in Humans>Exercise 15.1>Q 5

Feature	Placenta	Lungs
Total surface area / m²	16	55
The thickness of the barrier across which substances must diffuse / um	3.5	0.5
Approximate rate of blood flow/cm³ per minute	500	5000

Use the data in the table and your knowledge of the features of gas exchange surfaces, to explain why more oxygen can be absorbed per minute across the lungs than across the placenta.

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Biology for Cambridge IGCSE Workbook 4 th Edition Digital Access>Chapter 15 - Reproduction in Humans>Exercise 15.1>Q 6

Oxygen is not only a substance that crosses the placenta from the mother's blood to the foetus's blood.

Amino acid moves across the membranes of the cells in the placenta by active transport.

Explain how active transport differs from diffusion.

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Biology for Cambridge IGCSE Workbook 4 th Edition Digital Access>Chapter 15 - Reproduction in Humans>Exercise 15.2>Q 7

The table shows the percentage of people in Asia and the Pacific region who are infected with HIV, who knew that they had the virus.

Year	Percentage of people living with HIV who knew they had the virus
2015	59
2016	62
2017	65
2018	65

On the grid below, draw a bar chart to display these data.

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Biology for Cambridge IGCSE Workbook 4 th Edition Digital Access>Chapter 15 - Reproduction in Humans>Exercise 15.2>Q 8

Year	Percentage of people living with HIV who knew they had the virus
2015	59
2016	62
2017	65
2018	65

Suggest how the data in the above table have been estimated.

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Biology for Cambridge IGCSE Workbook 4 th Edition Digital Access>Chapter 15 - Reproduction in Humans>Exercise 15.2>Q 9

The table shows data relating to the other two components of the United Nations’ target.

Year	Percentage of people diagnosed with HIV who are receiving antiretroviral drugs	Percentage of people receiving antiretroviral drugs in whom the virus is suppressed
2015	62	89
2016	68	89
2017	74	90
2018	79	90

Use all the data to discuss the progress made by the United Nations in achieving its target in the Asia and Pacific region. Use the data to evaluate the likelihood that the target will be achieved by 2020.

Oxygen moves by diffusion across the exchange surface in both the placenta and the lungs. Explain fully why the net movement of oxygen is in this direction in the lungs.

Important Questions on Reproduction in Humans

Learn and Prepare for any exam you want !

Oxygen moves by diffusion across the exchange surface in both the placenta and the lungs.

Explain fully why the net movement of oxygen is in this direction in the lungs.