Parasitism

Question 1

What is an ecological niche

Answer 1

An ecological niche is a multidimensional summary of tolerance and requirements of a species

Question 2

What is a fundamental niche

Answer 2

A species has a fundamental niche that it occupies in the absence of any interspecific competition

Question 3

What is a realised niche

Answer 3

A realised niche is occupied in response to interspecific competition

Question 4

What is the result of interspecific competition

Answer 4

competitive exclusion

Question 5

What is competitive exclusion

Answer 5

Where the niches of two species are so similar that one declines to local extinction

Question 6

What is resource partitioning

Answer 6

Where the realised niches are sufficiently different that potential competitors can co-exist by resource partitioning

Question 7

What is parasitism

Answer 7

A symbiotic interaction between a parasite and its host

Question 8

What is a benefit a parasite can gain from host

Answer 8

Gains benefit in terms of nutrients at expense of its host

Question 9

Why are parasites referred to as degenerate

Answer 9

As host provides many of the parasites needs as the parasite lack the organs and structures found in other organisms

Question 10

Why do some parasites have a narrow (specialised) niche

Answer 10

As they are very host specific

Question 11

Ectoparasite

Answer 11

Lives on the surface if its host

Question 12

Endoparasite

Answer 12

Lives within the tissues of its host

Question 13

Parasitic life cycles

Answer 13

Some parasites need only one host to complete their life cycle whereas some need more than one

Question 14

What is a vector and give eg

Answer 14

A vector plays an active role in the transmission of the parasite and may also be a host

-mosquito

Question 15

How is the human disease malaria caused

Answer 15

By Plasmodium

Question 16

What does schistosomes cause

Answer 16

The human disease schistosomiasis

Question 17

What is a virus

Answer 17

Viruses are parasites that can only replicate inside a host cell

Question 18

What do viruses contain

Answer 18

Viruses contain genetic material in form of DNA or RNA, packaged in a protective protein coat

Question 19

Describe the structure of a virus

Answer 19

• Nucleic acid (DNA or RNA)
• Protective protein coat - Capsid
• Phosphide membrane
• attachment proteins - antigens

Question 20

Phosphoric membrane

Answer 20

derived from host cell materials which surrounds some viruses

Question 21

Viral life cycle stages

Answer 21

• Infection of host cell with genetic material
• host cell enzymes replicate viral genome
• transcription of viral genes and translation of viral proteins
• assembly and release of new viral particles

Question 22

RNA retroviruses

Answer 22

Use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell

Question 23

What happens if viral genes can be expressed

Answer 23

They form new viral particles

Question 24

What is transmission

Answer 24

Transmission is the spread of a parasite to a host

Question 25

What is virulence

Answer 25

Virulence is the harm caused to a host species by a parasite

Question 26

How are ectoparasites transmitted

Answer 26

Through direct contact or by consumption of intermediate hosts

Question 27

How are endoparasites often transmitted

Answer 27

Often transmitted by vectors

Question 28

What are factors that increase transmission rates

Answer 28

- Overcrowding of hosts when they are at high density - mechanisms such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacitated

Question 29

How do parasites maximise transmission

Answer 29

-host behaviour is exploited and modified by parasite

Question 30

What can parasites alter within a host

Answer 30

- Parasites can suppress the host immune system - Modify host size and reproductive rates that benefit parasite growth - reproduction or transmission

Question 31

Defence against parasitic attack

Answer 31

Immune response in mammals has both non-specific and specific aspects

Question 32

State the 5 non-specific defences

Answer 32

- Physical barriers - Chemical secretions - inflammatory response - phagocytes - natural killer cells

Question 33

What happens if tissue becomes damaged

Answer 33

Cells release histamine which causes vasodilation making blood capillaries more permeable increasing blood flow and cytokines which are signalling molecules that signal non-specific and specific white blood cells to site of infection

Question 34

What do lymphocytes posses

Answer 34

Each posses a receptor on its surface which can potentially recognise a parasite antigen

Question 35

Roles of lymphocytes

Answer 35

Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells

Question 36

How do endoparasites evade detection

Answer 36

Endoparasites mimic host antigens to evade detection and modify host immune response to reduce their chances of destruction

Question 37

Antigenic variation in parasites

Answer 37

Antigenic variation in parasites allows them to change between different antigens during the course of infection of a host -allows re-infection of same host with new variant

Question 38

What is latency

Answer 38

Some viruses escape immune surveillance by intergrating their genome into host genomes existing in an inactive state know as latency

Question 39

How does a virus become active again

Answer 39

when favourable conditions arise

Question 40

What is epidemiology

Answer 40

Epidemiology is the study of the outbreak and spread of infectious disease

Question 41

What is the herd immunity threshold

Answer 41

The density of resistant hosts in the population required to prevent epidemic

Question 42

What do vaccines contain

Answer 42

Contain antigens which will elicit an immune response

Question 43

Why is it difficult to find drug compounds/coordinated treatment to target parasite

Answer 43

- Due to the similarities between host and parasite metabolism - Antigenic variation has to be reflected - Some parasites are difficult to culture in the laboratory - rapidly spreading due to overcrowding or tropical climates

Question 44

What are results of improving parasite control

Answer 44

- Reduces child mortality - improvement in child development and intelligence - More resources for growth and development

Question 45

What is a definite host

Answer 45

Where the parasite reaches sexual maturity

Question 46

What is an intermediate host

Answer 46

Hosts for a part Of a parasites life and reproduces asexually

Question 47

Plasmodium life cycle

Answer 47

- mosquito is the definite host and vector - gametocytes develop into gametes - within human who is intermediate host within their liver - blood cells burst - releases gametes in bloodstream

Question 48

Schistosama life cycle

Answer 48

- Human is the definite host - fertilised eggs are passed in faeces - the eggs then hatch and infect snails - larvae then penetrates human skin