Exchange

Question 1

Small objects have a relatively ______ _______ ______.

Answer 1

Large surface area

Question 2

Cells or organisms need to exchange materials and heat with their _______.

Answer 2

Environment

Question 3

More or less: chemical reactions happen every second in organisms with a larger volume than ones with smaller volumes.

Answer 3

More

Question 4

Which as the bigger surface area to volume ratio, a small organism or a large organism?

Answer 4

A small organism

Question 5

An animal has a surface area of 7.5 cm2 and a volume of 1 cm3. What is its surface area to volume ratio?

Answer 5

7.5:1

Question 6

Which animal has the greatest surface area to volume ratio: Animal A (9.8:1) or animal B (0.98:1)?

Answer 6

Animal A

Question 7

Give three materials that need to be exchanged across the membranes of organisms’ cells.

Answer 7

Oxygen, nutrients, waste products

Question 8

What are the millions of tiny air sacs in the lungs called?

Answer 8

Alveoli

Question 9

What are the 4 adaptations to the Alveoli that increase the diffusion rate?

Answer 9

1) The walls of the alveoli consist of a single layer of thin, flattened, epithelial cells. Diffusion happens faster when molecules only have to travel shorter distances.
2) Diffusion is faster when there’s a bigger difference in concentration between two regions. The blood flowing through the rich network of capillaries around the alveoli carries away the oxygen that has diffused through the alveolar walls.
3) This ensures that there is always a higher concentration of oxygen inside the alveoli than in the blood. The reverse is true for carbon dioxide.
4) The alveolar walls are fully permeable to dissolved gasses. Oxygen and carbon dioxide can easily pass through the cell membranes of the epithelial cells.

Question 10

Why have large mammals evolved complex blood systems and lungs?

Answer 10

To provide a large surface area for the efficient diffusion of carbon dioxide and oxygen.

Question 11

In which part of the lungs does gas exchange take place?

Answer 11

The alveoli

Question 11

Describe the shape of the cells that make up the walls of the alveoli and explain how their shape suits their function.

Answer 11

The cells are tin and flattened. The gases can diffuse across the cells quickly because the distance is small.

Question 11

Name another gas that can easily pass through the walls of the alveoli.

Answer 11

Carbon dioxide

Question 12

What type of cell are the alveoli walls made of?

Answer 12

Epithelial cells

Question 12

If volume increases, air pressure _____

Answer 12

Decreases

Question 13

Why does oxygen diffuse from inside the alveoli into the blood?

Answer 13

There is a higher concentration of oxygen inside the alveoli than in the blood.

Question 14

The lungs are suspended in the ______ ______.

Answer 14

Airtight thorax

Question 14

Breathing in

Answer 14

1) Intercostal muscles and diaphragm contract
2) Thorax volume increases
3) This decreases the pressure, so air flows in.

Question 15

Breathing out

Answer 15

1) Intercostal muscles and diaphragm relax
2) Thorax volume decreases.
3) This increases the pressure, so air flows out.

Question 16

*Which two sets of muscles contract when we breathe in?

Answer 16

The intercostal muscles and diaphragm *

Question 16

Does the volume of the thorax increase or decrease when you breathe out?

Answer 16

Decrease

Question 16

Describe the relationship between volume and pressure in an enclosed space.

Answer 16

When the volume increases, the pressure decreases (and when the volume decreases, the pressure increases)