Size and Surface Area

Question 1

Definition of surface area

Answer 1

the total area of the organism that is exposed to the external environment.

Question 2

Definition of volume

Answer 2

the total internal volume of the organism (total amount of space inside the organism)

Question 3

Surface area: volume ratio correlation.

Answer 3

As the surface area and volume of an organism increase (and therefore the overall ‘size’ of the organism increases), the surface area: volume ratio decreases.

Question 4

Smaller animals have a greater SA:V ratio

Answer 4

so they lose more heat, meaning they have to use up more energy to maintain their body temperature.

Question 5

Single-celled organisms have a high SA:V ratio

Answer 5

• The large surface area allows for maximum absorption of nutrients and gases and secretion of waste products.
• The small volume means the diffusion distance to all organelles is short

Question 6

Removal of Carbon Dioxide:

Answer 6

• Carbon dioxide is a toxic waste product of aerobic respiration.

-If it accumulates in cells/tissues it alters the pH.

Question 7

Single-celled organisms

Answer 7

-Substances can diffuse directly into the cell across the cell-surface membrane.

-The diffusion rate is quick because of the small distances the substance must travel.

Question 8

In multicellular organisms, diffusion across the outer membrane is too slow, for two reasons:

Answer 8

1.Some cells are deep within the body – there is a big distance between them and the outside environment.

2.Larger animals have a low surface area to volume ratio – its difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface.

Question 9

What does mass transport refer to?

Answer 9

Normally refers to the circulatory system, which uses blood to carry glucose and oxygen around the body.

Question 10

Mass transport in plants

Answer 10

Involves the transport of water and solutes in the xylem and phloem.

Question 11

Body size

Answer 11

The rate of heat loss from an organism depends on its surface area. If an organism has a large volume.

Question 12

Body shape

Answer 12

Animals with a compact shape have a small surface area relative to their volume – minimising heat lost from their surface.

Question 13

Animals with a high surface area: volume ratio

Answer 13

Tend to lose more water as it evaporates from their surface.

Question 14

What adaptions do animals living in hot regions have?

Answer 14

Small desert mammals have kidney structure adaptions so that they produce less urine to compensate.