Communicable diseases 4.1

Question 1

What is meant by a pathogen

Answer 1

a microorganism that causes a disease

Question 2

How do pathogens live?

Answer 2

They live by finding a good habitat in a host that can produce and fund the nutrition need for the organism to thrive.

Question 3

Describe and explain bacteria

Answer 3

Bacteria belong to the Prokaryote kingdom

• smaller than eukaryote cells and reproduce rapidly
• Their presence in the hosts body cuases damage as the bacteria feeds of teh nutrients in the surrounding tissue and cells
• in plants they often live in the vascular tissues
• tuberculosis and ring rot are examples of this.

Question 4

Describe and explain Fungi

Answer 4

Fungi is common where it lives and grows in the skin of an animals where its hypahe form mycelium which grow under the skin surface. They also send out reproductive hyphae which is used to grow out and produced spores on the skin. In plants they are normally found in the vascular bundles to gain nutrients . The hyphae also release cellulases enzymes that are used to consume the surrounding host tissue. , back sigotota and athletes foot are examples of this.

Question 5

Describe and explain Viruses

Answer 5

Viruses invade and take over the genetic machinery of the cell and begins to to force the cell to produces copies of the virus. Eventually the cell bursts and all the viruses replicated shoot out infecting all surrounding cells also.

Question 6

protoctista

Answer 6

These are organisms that enter the hosts cells and feed off the contents of the cell, such as nutrients and proteins.

Question 7

Name all Bacteria diseases (there are 3 in total that you need to know )

Answer 7

Tuberculosis - bacteria - affecting may parts of the body especially the lungs killing cells and tissue
Bacterial meningitis - the membrane surrounding the spinal cord and brain is swollen and therefore this can affect the fragile nature of the nervous system and the spinal cord it self.
Ring rot - Ring of decay that is found in the plants vascular tissue of a potato tuber or tomato accompanied by leaf wilting.

Question 8

Name all virus diseases ( there are 3 you need to know )

Answer 8

HIV - Attack the cells in the immune system and then compromises the immune response
influenza(flu) - Attacks respritory system and causes sever muscle and head pains.
Tobacco mosaic viurs - causes mottling(marks of spots and colour) and discoloration of leaves

Question 9

Name all fungi diseases ( there are three for you to know

Answer 9

Black sigatoka - causes leaf spots on banana plants reducing yields
Ringworm - growth of fungus in skin with sport cases erupting through skin to cause a rash
Athletes’s foot - growth under skin of feet - particulart between the toes ( moist areas )

Question 10

Name all protoctistan diseases

Answer 10

Blight - attacks young rapidly growing tissue, affecting potato tubers and leaves.
Malaria - parasite in the blood that causes headache and fever and may progress to coma and death.

Question 11

What are the ways in which pathogens can be transmitted between animals

Answer 11

Direct contact, oral , droplet infection(pathogen carried by water droplets in air) , spores that my be on surfaces or carried in the air(wearing masks prevent this).

Question 12

What are the classic ways that disease is spread ( think old school diseases )

Answer 12

Overcrowding , poor ventilation , poor health , poor diet , homelessness , third world to first world migration.

Question 13

What is meant by indirect transmission ( use malaria as an example)

Answer 13

Infected person is bitten , the female mosquito sucks the blood containing the malaria and then bites another host. Then the plasmodium infects the liver of the host, the plasmodium migrates to the red blood cells and the host is now infected.

Question 14

Direct transmission for a plant

Answer 14

This is mainly done by spores being carried in the air and by the soil beneath being infected and the fungi or virus affecting the plant.

Question 15

Indirect transmission for a plant

Answer 15

This is mainly from insect as they may touch a plant that has already been infected and they are carrying the spore or disease that they then spread to all plants they bite or touch depending on if they are spores.

Question 16

What are the optimal conditions for these diseases to grow.

Answer 16

Warm moist environments are the best places for the diseases t thrive in and therefore they are normally found in warm climates. They struggle to survive in very cold environments and therefore are not found in cold climates.

Question 17

What is meant by the term passive defence

Answer 17

These are defences that present in the animal or plant prior to entry of the pathogen.

Question 18

Physical defences

Answer 18

These consist of physical features that help support the plant. A number of these features are
Cellulose cell wall that help to act as a physical barrier as well as the chemical defences that are activated at the presence of a pathogen.
The lignin that has been impregnated into the cell walls is waterproof and almost completely indigestible.
Waxy cuticles - prevent the build up of water collecting on the cell surface and since pathogens collect in moist environments this is a defence.
Tree bark - this contains many chem defences that are triggered by the pathogens
Closing the stomata
Callose can be used to stop the pathogen spreading through the plant.
Tylose - this can balloon in the xylem tissue to prevent flowing of water and therefore this stops the spreadd of the pathogen

Question 19

What is known as a chemical defence

Answer 19

These are chemicals that are produced that are anti pahtogenic, the chemicals are only produced when they are needed as they require alot of energy to produce and it would be a waste to produce them for no reason.

Question 20

Describe and explain the active defences used by a plant, 4 marks

Answer 20

Callose is produced to block up vessels to prevent the spread of the pathogen, extra cellulose is placed in cell walls to thicken them and to add extra protection. Also they can produce oxidative bursts that are used to send highly reactive oxygen particles to react with the cells that are invading to cause damage. Necrosis may also take place this is cell suicide. Canker my take place

Question 21

Primary defences for animals

Answer 21

The skin(keratin) , blood clotting, mucus , stomach acid.

Question 22

Blood clotting (4 marks)

Answer 22

There is a wound due to a cut. Once this has happened clotting factors cause an enzyme cascade to form, this forms the clot. Once this has happened the scab dries and as the drying continues the scab shrinks pulling the wound together. Underneath the scab there is specialised skin tissues that are attaching to the end of the scab to form new skin cells . These cells form tissues that contract and then cause the skin to be pulled together once the edges have met and the skin is healed the scab is removed.

Question 23

Mucous membrane (2 marks)

Answer 23

Goblet cells secrete a mucus that traps pathogens and the cilia wafts them to be sneezed or coughed out or they are swallowed into the stomach to be dissolved by the acid.

Question 24

Inflammation

Answer 24

If there is an antibody detected the body uses histamine to cell signals to white blood cells and to vasodilate the walls to allow for space for the white blood cells. There is a buildup of white blood cells in the tissue fluid and therefore the tissues slew up. The lymph system also comes into contact with the pathogens which will trigger the specific immune response.

Question 25

Antigens and opsonins

Answer 25

Antigens are proteins that are organism specific and are on the exterior of the cell surface. These are recognised by the host body by opsisns that detect any foreign antigens. This then alerts the immune system that a foreign presence has been detected.

Question 26

Phagocytes

Answer 26

First line of defence, these are specialised cells that are used to engulf and digest the pathogens.

Question 27

How are phagocytes used to digest invading pathogens

Answer 27

Firstly an opsonin attaches to the antigen on the pathogen. After this the neutrophils attach to the opsonin Once this happens the neutrophils engulfs the cell by endocytosis , this forms a phagosome inside the cell. The neutrophils has lysosomes inside and these attach to the phagosome injecting digestive lytic enzymes, the harmless parts of the pathogen are reused by the cell the rest are digested.