Exchanging materials + SA/V ratio

Question 1

How does surface area to volume ratio get smaller?

Answer 1

As an object gets bigger, surfaces area to volume ratio gets smaller

Question 2

Why can’t larger and more complex organisms easily exchange materials with the environment?

Answer 2

Their size means materials cannot reach the cells in the middle of the organism just by diffusion, unlike smaller organisms.

Question 3

What materials need to be exchanged with the environment for an organism to survive?

Answer 3

-Gases

-Food molecules

-Metabolic waste

Question 4

How do larger organisms meet their needs for material exchange?

Answer 4

-Special surfaces where the exchange of materials takes place

Question 5

What are examples of special adaptations for material exchange in humans?

Answer 5

-Lungs (millions of tiny alveoli have an enormous surface area and a rich blood supply for effective gas exchange)

-Small intestine (millions of tiny villi have an enormous surface area and a rich blood supply to absorb nutrients)

Question 6

What are some special adaptations for material exchange in other large organisms?

Answer 6

-Fish have gills which are made up of stacks of thin filaments, each with a rich blood supply to absorb oxygen from water.

-Plant roots have a large surface area to make the uptake of water and minerals more efficient.

-Leaves are as flat and thin as possible to maintain a high surface area to volume ratio for gas exchange.

Question 7

Why don’t single celled organisms have specialised exchange surfaces?

Answer 7

-They have such a large surface area to volume ratio because of their small size that all the exchanges can happen through their cell membrane by diffusion.