Size And Surface Area UNIT 2 Flashcards
Do smaller animals have a higher or lower surface area to volume ratio
Higher
What substances do cells exchange with the environment
Cells need to take in oxygen (for aerobic respiration) and nutrients, need to excrete waste products like carbon dioxide and urea. Most organisms need to roughly stay at same temp, so heat needs to be exchanged to
How easy the exchange of substances is depends on the organisms….
Surface area to volume ratio
In single cell organisms how are substances exchanged
Substances (glucose, oxygen) diffuse directly into or out of the cells across the cell surface membrane. The diffusion rate is quick because of the small distances the substances have to travel
In multicellular animals, how are substances exchanged
Diffusion across the outer membrane is too slow, for two reasons…
Some cells are deep within the body, there’s a big distance between them and the outside enviro.
Larger animals have a low surface area to volume ratio, it’s difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface
What is mass transport
When multicellular organisms need specialised exchange organs. They also need an efficient system to carry substances to and from their individual cells
Example of mass transport in mammals
The circulatory system, which uses blood to carry glucose and oxygen around the body. It also carries hormones, antibodies and waste like carbon dioxide
What 2 factors affect heat exchange
Body size and shape
How is heat exchange affected by the body size
The rate of heat loss from an organism depends on its surface area. If an organism has a large volume, it’s surface area is small. Makes it harder for it to lose heat from its body. If an organism is small, it’s surface area is large so heat is lost more easily.
How is heat exchange affected by body shape
Animals with a compact shape have a small surface area relative to their volume, minimising heat loss from their surface. Animals with a less compact shape have a larger surface sera relative to their volume, increase heat loss from their surface. Whether or not an animal is compact or not depends on the temp and enviro
How does an arctic fox minimise heat loss
Has small ears and a round head to reduce its surface area to volume ratio and heat loss
How does the African bat eared fox maximise heat loss
Large ears and pointed nose to increase surface area to volume ratio and heat loss
How does a European fox minimise and maximise heat loss
It matches the temperature of its environment
Examples of behavioural and physiological adaptations to aid exchange
Animals with a high surface area to volume ratio tend to lose more water as it evaporates from their surface. Some small desert mammals have kidney structure adaptations so that they produce less urine to compensate
Smaller animals living in colder regions often have much higher metabolic rate to compensate for their high surface area to volume ratio, helps to keep them warm by creating more heat. To do this they eat large amounts of high energy foods such as seeds and nuts
Larger organisms living in hot regions find it hard to keep cool as their heat loss is slow. Elephants have developed large flat ears which increase their surface area allowing them to lose more heat. Hippos spend much of the day in water, a behavioural adaptation to help them lose heat
