Unit 2 - section 5

Question 1

What is a parasite?

Answer 1

An organism that forms a symbiotic relationship with a host where it benefits at the expense of the host

Question 2

What is a host?

Answer 2

An organism that harbours a parasite

Question 3

How common are parasites?

Answer 3

At least 50% of all species are parasitic

Question 4

How likely are free living organisms to be hosts?

Answer 4

All free living organisms are thought to be hosts

Question 5

Compare the reproductive potential of host-parasites to predator-prey relationships

Answer 5

When compared to predator-prey relationships the reproductive potential of the parasite is much greater than that of the host

Question 6

What is an ecological niche?

Answer 6

A complex outline of the tolerances and requirements of a species

Question 7

Why do parasites have a narrow niche?

Answer 7

Due to high host specificity

Question 8

Why do parasites have limited structures?

Answer 8

Parasites are degenerate, lacking in structures and organs found in other organisms, because the host provides many of the parasites needs

Question 9

Compare ectoparasites and endoparasites

Answer 9

Ectoparasites live on the surface of their host eg fleas on cats

Endoparasites live inside their hosts eg tapeworms live in hosts intestine

Question 10

Compare definitive and intermediate hosts

Answer 10

Definitive - host the organism reaches sexual maturity in/on

Intermediate - host the organism completes some part of its lifecycle in/on

Question 11

What is a vector?

Answer 11

An organism that plays a role in the transmission of the parasite. Vectors can also be hosts

Question 12

Describe the two types of niche

Answer 12

Fundamental - niche the organism occupies when there is no other species competing for space or resources

Realised - niche the organism occupies when there is competition from other species

Question 13

What is competitive exclusion?

Answer 13

When two different species occupy similar niches and are in intense competition with each other the weaker of the two species may die out

Question 14

What is resource partitioning?

Answer 14

When competing species occupy different realised niches compromising over resources and managing to exist simultaneously

Question 15

What do transmission and virulence mean?

Answer 15

Transmission is the spread of a parasite to a host

Virulence is the deleterious effect the parasite has on the host

Question 16

What are 2 qualities of a successful parasite?

Answer 16

Easily transmitted

Evolve rapidly

Question 17

What factors increase transmission rate of parasites?

Answer 17

Host density is high

Parasite has mechanisms of transmission even when the host is incapacitated

Question 18

What are 5 aspects of host behaviour that can be altered to exploit the parasite phenotype?

Answer 18

Foraging
Movement 
Sexual behaviour 
Habitat choice 
Anti-predator behaviour

Question 19

Why do parasites often suppress the immune system, size and reproductive rate of the host?

Answer 19

For their own benefit

Question 20

Describe the distribution of parasites

Answer 20

Non-uniformly

Question 21

How does parasites having both sexual and asexual phase benefit them in terms of evolution rates?

Answer 21

Allows for rapid evolution and rapid population growth

Question 22

What are the non-specific barriers mammals have to parasites?

Answer 22

Physical barriers 
Chemical secretions 
Inflammatory response 
Phagocytes 
Natural killer cells

Question 23

Describe the process of phagocytosis

Answer 23

Phagocytes are special white blood cells that engulf parasites by enfolding their plasma membrane around the membrane.

The parasite is brought into the phagocyte in a vacuole or vesicle. Phagocytes contain organelles called lysosomes that are filled with digestive enzymes. The lysosomes fuse with the vacuole, releasing the digestive enzymes allowing the enzymes to digest the parasite

Question 24

What is specific cellular defence?

Answer 24

Responses that are triggered when non-specific responses fail. The response will be specific to the foreign antigen present

Question 25

What are the 2 types of lymphocytes and what are their roles?

Answer 25

B lymphocytes - produce specific antibodies in response to foreign antigens T lymphocytes - destroy specific cells or damaged tissue by bringing about cell apoptosis

Question 26

What is clonal selection of lymphocytes?

Answer 26

Where lymphocytes become amplified with some clones being used for immediate defence and other clones acting as memory cells

Question 27

What are immunological memory cells?

Answer 27

Cloned lymphocytes that remain in the body allowing it to respond faster if the individual is exposed to the same antigen a second time

Question 28

What is epidemiology?

Answer 28

The study of the outbreak and spread of infectious diseases

Question 29

What is herd immunity threshold?

Answer 29

The number of resistant members needed to prevent an epidemic

Question 30

What are the possible parasite responses to host responses?

Answer 30

Mimicking host antigens Modifying host-immune response Antigenic variation

Question 31

Why do parasites mimic host antigens?

Answer 31

Allows them to evade detection

Question 32

Why do parasites modify host-immune response?

Answer 32

To suppress the hosts immune system

Question 33

Why do parasites change their outer antigens?

Answer 33

To evade detection as they change quicker than the host immune system can keep up with

Question 34

What are the 6 common types of parasites and give examples of each?

Answer 34

``` Protists - Protozoa, algae, diatoms Plathyhelminthes - flatworms Nematodes - roundworms Arthropods - ectoparasites Bacteria - TB, cholera Viruses - colds, flu ```

Question 35

What are two examples of parasites that require more than one host?

Answer 35

Malaria | Schistosomiasis

Question 36

How are endoparasites and ectoparasites of the main body cavities transited?

Answer 36

Direct contact or by consumption of secondary hosts

Question 37

How are endoparasites of body tissues often transmitted?

Answer 37

By vectors

Question 38

Give examples of parasites that can complete their lifecycle in one host

Answer 38

Ectoparasitic arthropods Endoparasitic protists Bacteria and viruses

Question 39

Give an example of a bacterial human disease

Answer 39

Tuberculosis

Question 40

Give two examples of viral human diseases

Answer 40

Influenza | HIV

Question 41

What is a virus?

Answer 41

A tiny infectious agent that can only replicate inside a host

Question 42

What form is genetic information found in viruses?

Answer 42

DNA or RNA packaged in a protective protein coat

Question 43

Describe the basic structure of a virus

Answer 43

Viruses are composed of a protein coat around some form of nucleus acid (DNA/RNA). Some viruses also have a lipid membrane made out of host resources. The antigens in this protein coat may or may not be recognised by the host immune system

Question 44

What is a rectotransposon?

Answer 44

Segment of DNA that carries off reverse transcription before being inserted into a new site on the genome

Question 45

What is thought to be the origin of retrotransposons in the eukaryotic genome?

Answer 45

Retroviruses

Question 46

What is the role of retrotransposons in host immunity?

Answer 46

??

Question 47

What is a retrovirus?

Answer 47

They are thought to be the origin of retrotransposons in the eukaryotic genome

Question 48

What enzyme is involved in DNA formation in retroviruses?

Answer 48

Reverse transcriptase

Question 49

What are the 3 challenges faced in the treatment and control of parasites?

Answer 49

Some parasites are difficult to culture in the laboratory Rapid antigen change has to be reflected in the design of vaccinations Similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite without negatively affecting the host

Question 50

What are 2 practical control strategies for parasites?

Answer 50

Civil engineering projects to improve sanitation Coordinated vector control

Question 51

Under what conditions do parasites thrive and what impact does this have on certain countries in the world?

Answer 51

Thrive in tropical climates and areas where there is overcrowding. Has the greatest impact on countries where they face the difficulties of war/refugee camps, aftermath of natural disasters or rapidly growing cities in the least developed countries

Question 52

What are 2 advantages of improving parasite control?

Answer 52

Reduce child mortality Allows improvement in child development and intelligence