💚 3.3 Topic 3 - 3.3.1 Surface to volume ratio Flashcards
Why do cells need to take in oxygen?
For aerobic respiration and nutrients.
What are examples of waste products cells need to excrete?
Carbon dioxide and urea.
True or false? A mouse has a bigger surface area relative to its volume than a hippo
True.
Why do organisms need to supply everyone of its cells with substances like glucose and oxygen?
For respiration.
Why do organisms need to remove waste products from all of its cells?
To avoid damaging itself.
In single-celled organisms, how are substances exchanged?
Through diffusion [directly into or out of the cell across the cell-surface membrane].
In single-celled organisms, is the diffusion rate slow or quick and why?
Quick because of the small distances the substances have to travel.
In multicellular animals, is the diffusion rate slow or quick and why?
The diffusion rate is slow across the outer membrane. This is because some cells are deep within the body meaning there is a big distance between the and the outside environment. Larger animals have a low surface area to volume ratio meaning it is difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface.
What do multicellular animals need to help them absorb and excrete substances?
Specialised exchange organs.
What is mass transport?
An efficient system to carry substances to and from their individual cells.
What does mass transport in mammals normally refer to?
… the circulatory system, which uses blood to carry glucose and oxygen around the body as well as hormones, antibodies and waste such as CO2.
What does mass transport in plants involve?
… the transport of water and solutes in the xylem and phloem.
What are two factors which affect heat exchange?
Body size and shape.
What is an example of something in which metabolic activity inside cells creates?
waste products and heat.
What does the rate of heat loss from an organism depend on?
Its surface area.
If an organism has a large volume, its surface area is relatively small = harder for it to lose heat from its body.
If an organism has a small volume, its surface area is relatively large = heat is lost more easily from its body.
Therefore, smaller organisms need a relatively high metabolic rate in order to generate enough heat to stay warm.
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 area relative to their volume …
… increasing heat loss from their surface.
What does whether or not an animal is compact, depend on?
The temperature of its environment.
What are two types of adaptations organisms have to aid exchange?
Behavioural or physiological adaptations.
Animals with a high surface area : volume ratio tend to lose more water? true or false? + why?
True as it evaporates from their surface.
[some small desert mammals have kidney structure adaptations so that they produce less urine to compensate]
What do small mammals living in cold climates need to eat to support their high metabolic rates?
High energy foods.
[e.g. nuts and seeds]
Why may smaller mammals have thick layers of fur or hibernate?
To protect themselves when the weather gets really cold.
Why do larger organisms living in hot regions find it hard to keep cool?
Their heat loss is relatively slow.
What have elephants developed to increase their surface area, allowing them to lose more heat?
Large flat ears.
What is an adaptation hippos have which has helped them lose heat and what type of adaptation is it?
They spend most of the day in the water and this is a behavioural adaptation.
