Human Defence/Plant Defence

Question 1

How does skin help prevent diseases?

Answer 1

• Acts as a physical barrier so that pathogens cannot enter.
• Secretes oils and antimicrobial substances that kill pathogens.

Question 2

How does the nose and mouth protect itself against pathogens?

Answer 2

• Little hairs
• Mucus
• Both to trap Pathogens

Question 3

How does the trachea protect itself against pathogens and defend the liver?

Answer 3

• The trachea, bronchi and bronchioles are all covered in a layer of mucus.
• The mucus traps the pathogens.
• To prevent mucus build up, they are also lined with cilia (tiny finger like structures that protrude from cells).
• The cilia slowly move the mucus and trapped particles up to the back of our throat so that we can swallow it into the stomach.

Question 4

What does the stomach do with the mucus and pathogens?

Answer 4

It produces hydrochloric acid. This acid is so strong that it brings the PH of the stomach contents to 2, which is so acidic that it kills mostly all the pathogens.

Question 5

List 3 functions of the white blood cells.

Answer 5

1. Phagocytosis
2. Producing Antitoxins
3. Producing Antibodies

Question 6

What is phagocytosis?

Answer 6

Phagocytosis is the process by which a white blood cell tracks a pathogen that has entered our body and binds to it, before engulfing it. The white blood cell then uses enzymes to break down and digest the pathogen. The bits of the pathogen that are no longer harmful, are released into the blood stream.

Question 7

What are antitoxins and how do they work?

Answer 7

Antitoxins are the response to the toxins that are found on pathogens. They are small molecules that can bind and counteract these toxins so that they cannot do any damage to us.

Question 8

What are antigens?

Answer 8

Antigens are what our body detects to be foreign. For example, the cell wall of bacteria or a virus protein.

Question 9

What are antibodies?

Answer 9

They are small proteins made by white blood cells that can lock onto antigens and then act as signals to the white blood cells so that they can destroy them.
Each antibody is specific to a particular antigen. They can only bind once.

Question 10

Where can plants catch diseases?

Answer 10

• Microorganisms (fungi, viruses, bacteria)
• Larger organisms (insects)
• Deficiency diseases (lack of essential minerals)

Question 11

What are nitrate ions used for in the plant?

Answer 11

They produce proteins and so are needed for growth.

Question 12

What are magnesium ions used for in the plant?

Answer 12

The are used to make chlorophyll, which is needed for photosynthesis.

Question 13

What symptoms might a plant with aphids and spider mites have?

Answer 13

• Abnormal grows/lumps
• Patches of decay
• Discolouration on leaves
• Malformed stem/leaves

Question 14

Physical barriers of plant cells:

Answer 14

• Waxy cuticle
• Cell wall
• tree bark
• leaves falling

Question 15

Chemical barriers of plants:

Answer 15

• Plants that create poison
• Thorns
• Hairy stems or leaves
• drooping or curling up when touched (movement)
• mimicry (droop to mimic unhealthy plants)