exchanging materials

Question 1

for many single celled organisms like plankton, amoeba and bacteria, diffusion,osmosis and active transport are all that is needed to exchange materials with their environment … why?

Answer 1

because they have a relatively large surface area compared to the volume of the cell. (this allows sufficient transport of molecules into and out of the cell to meet the needs of the organism).

Question 2

S. A. to volume ration very important. It makes a big difference to the way animals can exchange substances with their ..

Answer 2

environment.

Question 3

S A is also important when you consider …

Answer 3

1. how energy is transferred by living organisms, and

2. how water evaporates from the surface of plants and animals.

Question 4

the ratio of SA to volume falls as objects get bigger. Bigger organisms (smaller SA to volume ratio) have to transport molecules …

Answer 4

further.

Question 5

In a small object, the surface area to volume ratio is relatively large. this means that …

Answer 5

diffusion distances are short and that simple diffusion is sufficient for the exchange of materials.

Question 6

As organisms get bigger the surface area to volume ratio falls. The distances between the center of the organism and the surface get …

Answer 6

bigger.

Question 7

When the distances between the center of the organism and the surface get bigger happens simple diffusion is no longer enough to …

Answer 7

exchange materials between the cells and the environment.

Question 8

what substances can no longer reach every cell inside the organism by simple diffusion?

Answer 8

Gases and food molecules

Question 9

what cannot be removed fast enough to avoid poisoning the cells?

Answer 9

metabolic waste

Question 10

In many larger organisms there are …

Answer 10

special surfaces where the exchange of materials take place. The surfaces are adapted to be as effective as possible.

Question 11

These special surfaces can be found where?

Answer 11

In humans, in other animals and in plants.

Question 12

To make the process of exchange more efficient ..

Answer 12

there are various adaptations.

Question 13

Name four ways in which the effectiveness of an exchange surface can be increased. (Adaptations)

Answer 13

1. having a large surface area over which exchange can take place.
   2 having a thin membrane or epithelium or being thin to provide a short diffusion path (reduces the travel distance)
2. Exchange surfaces will have an efficient blood supply. this moves the diffusing substances away from the exchange surfaces and maintains a steep concentration (diffusion) gradient.
3. being ventilated makes gas exchange more efficient by maintaining steep concentration gradients.

Question 14

Exchange surfaces usually have a …

Answer 14

large Surface area and thin walls which provide short diffusion pathways.

Question 15

Different organisms have different …

Answer 15

adaptations for the exchange of materials.

Question 16

How does the Australian Fitzroy river turtle ‘breathe’ underwater.

Answer 16

Inside the rear opening are two large sacs lined with finger like folds which provide a large surface area and rich blood supply for gas exchange. Water is pumped in and out, ventilating the folds and maintaining a steep concentration gradient for gas exchange.

Question 17

the human SA to volume ratio is very ..

Answer 17

low

Question 18

The cells inside a human cannot get the ..

Answer 18

food and oxygen the need, or get rid of the waste they produce by simple diffusion.

Question 19

air is moved into and out of your lungs when you breathe. What does this do?

Answer 19

Ventilates the millions of tiny air sacs called alveoli.

Question 20

The alveoli have … (2 things)

Answer 20

1. an enormous SA and 2.a very rich blood supply, for effective gas exchange.

Question 21

The villi of the small intestine also provides …

Answer 21

a large SA, short diffusion paths and a rich blood supply to make exchange of materials more effective.

Question 22

What do fish need to do?

Answer 22

Exchange oxygen and carbon dioxide between their blood and the water in which they swim.

Question 23

How does this happen?

Answer 23

Across the gills.

Question 24

What are the gills made up of?

Answer 24

Stacks of thin filaments, each with a rich blood supply.

Question 25

What do fish need?

Answer 25

A constant flow of water over the gills to maintain the concentration Thneeded for gas exchange.

Question 26

How do they maintain this concentration gradient?

Answer 26

by pumping water over the gills using a flap that covers the gills called the operculum.

Question 27

Plant roots have a large

Answer 27

SA - This makes the uptake of water and mineral ions more efficient.

Question 28

What is this SA made bigger by?

Answer 28

root hair cells

Question 29

Plant leaves are also modified to make …

Answer 29

gas and solute exchange as effective as possible.

Question 30

What helps to provide a big SA and maintain a steep concentration gradient for the diffusion of substances?

Answer 30

Flat, thin leaves, the presence of air spaces in the leaf tissues, and the stomata.

Question 31

What substances are being diffused?

Answer 31

Mineral ions, water and carbon dioxide.

Question 32

What is a cell?

Answer 32

Basic building block of an organism

Question 33

What is a nucleus?

Answer 33

Part of a cell which carries the genetic information.

Question 34

What is a chromosome?

Answer 34

Thread like structure holding genes.

Question 35

What is a gene?

Answer 35

A small packet of information controlling a characteristic.

Question 36

What is DNA?

Answer 36

The chemical from which chromosomes are made.