Amoeba(Complete)

Question 1

What are the general characteristics of the kingdom Protista?

Answer 1

Have a membrane-enclosed nucleus- eukaryotic.

Are mainly unicellular and do not produce tissue.

Question 2

Give examples of protozoans.

Answer 2

Amoeba.
Algae.
Slime moulds.

Question 3

Write a note on amoeba.

Answer 3

Amoeba are single-celled animal-like creatures.
They are found mostly in freshwater ponds- habitats- where mud and water join.
They vary in size.
They are considered advanced- evolved as they can carry out all characteristics of living things in a single cell.

Question 4

What is an amoeba’s habitat?

Answer 4

Freshwater ponds.

Question 5

Describe an amoebas cell membrane.

Answer 5

Cell membrane is selectively permeable to allow some molecules through.
Allows for gas exchange by diffusion.
Retains cell contents.

Question 6

Describe an amoebas nucleus.

Answer 6

The nucleus is enclosed by a nuclear membrane.

It controls the cellular functions of amoeba like growth and reproduction.

Question 7

Describe an amoebas cytoplasm.

Answer 7

The cytoplasm is split into two parts: The ectoplasm and the endoplasm.
The ectoplasm is the stiff clear gel that gives the cell strength and slows the intake of water by osmosis.
The endoplasm is fluid-like and granular as it has fat droplets and food vacuoles. It provides support for the nucleus, contractile vacuole, food vacuoles and mitochondria.
The ectoplasm and endoplasm hold a major role in the formation of pseudopods.

Question 8

Describe an amoebas pseudopods.

Answer 8

Used for movement and feeding-engulf prey.

Question 9

Describe an amoebas food vacuoles.

Answer 9

Used for feeding- secrete acids to kill prey, secrete enzymes to digest prey so that it can be absorbed by the cytoplasm.

Question 10

Describe an amoebas contractile vacuole.

Answer 10

Osmoregulation- maintains the cytoplasm of the amoeba at a correct concentration for efficient metabolism.

Question 11

Suggest one reason why the contractile vacuole is more active in freshwater.

Answer 11

More water is taken in by osmosis as freshwater is more dilute.

Question 12

What is feeding in amoeba called?

Answer 12

Phagocytosis or heterotrophic nutition.

Question 13

Describe the process of feeding in amoeba.

Answer 13

Amoeba engulf prey like small protozoans, bacteria and dead organic matter.
It used pseudopods to move in the direction of food.
The pseudopods engulf the prey and form an internal food vacuole.
The food vacuoles secrete acids which kill the prey and then secrete enzymes to digest the prey.
The products of digestion are then passed into the cytoplasm.
Undigested matter is egested by the food vacuoles and sent to the cell surface.

Question 14

Describe movement in amoeba.

Answer 14

Pseudopods are formed when the fluid-like endoplasm flows towards the gel ectoplasm forming a temporary structure.
This means that pseudopods are formed through streaming of the endoplasm.
The pseudopod is formed in the direction of travel and movement is called ameboid movement.

Question 15

Refer to an ameboid disease:
Name it
State its effect
State symptoms 
State how it is contracted 
State the treatment.

Answer 15

Name- Amoebic dysentery formed by entamoeba
Effect- it digests and penetrates human tissue
Symmptoms- diarrhoea, vomiting, abdominal pain.
Contracted- From faecal contamination in water and food.
Treatment- anti- amoebic drugs.

Question 16

Describe osmoregulation in amoeba.

Answer 16

Water enters cytoplasm through osmosis from lower concentrated freshwater.
Excess water enters the contractile vacuole by active transport.
The contractile vacuole swells and touches the cell membrane.
The vacuole bursts and expels water to the outside.

Question 17

Why do marine species of amoeba often lack a contractile vacuole?

Answer 17

Ads the concentration of their cytoplasm and outside water is isotonic.

Question 18

What does isotonic mean?

Answer 18

Of the same concentration.

Question 19

Why do plant cells lack a contractile vacuole

Answer 19

As they have a cell wall which prevents bursting when water enters by osmosis.