2.5 Parasitism

Question 1

What is meant by the term niche?

Answer 1

An ecological niche is a multi-dimensional summary of tolerances and requirements of a species

Question 2

What are biotic tolerances?

Answer 2

Density of predators and intensity of competition

Question 3

What are abiotic tolerances?

Answer 3

Range of temperatures and pH

Question 4

What are biotic requirements?

Answer 4

Availability of prey, pollinators or other ecological services

Question 5

What are abiotic requirments

Answer 5

Suitable habitat features, such as flat rock for basking

Question 6

What is interspecific competition?

Answer 6

Competition between members of different species for similar resources
e.g food

Question 7

What is intraspecific competition?

Answer 7

Competition between members of the same species for the exact same recourses
e.g food, space and mates

Question 8

What is a species fundamental niche?

Answer 8

A species occupies it in the absence of any interspecific competition

Question 9

What is a realised niche?

Answer 9

What a species occupies in response to interspecific competition

Question 10

What is competitive exclusion?

Answer 10

As a result of interspecific competition, competitive exclusion can occur when the niches of two species are so similar that one species declines to local extinction

Question 11

What is resource partitioning?

Answer 11

Where the realised niche become sufficiently different, potent competitors can co-exist by resource partitioning. (if they have atleast one significant difference in their niches)

Question 12

What is parasitism?

Answer 12

This is a symbiotic interaction between a parasite and its host (+/-). A parastite gains benefit in terms of nutrients at the expense of its host

Question 13

Why do many parasites have narrow (specialized) niches?

Answer 13

They are very host specific, some may even been restricted to living on a certain area of a host

Question 14

What does it mean if a parasite is degenerate?

Answer 14

As the host provides so many of the parasites needs, many parasites are degenerate, lacking structure and organs found in other organims

Question 15

Where does an ectoparasite and endoparasite live?

Answer 15

Ecto- lives on the surface of its host
Endo- lives within the tissue of its host

Question 16

What is a definitive host?

Answer 16

The organisism on or in which the parasite reaches sexual maturity, produces gamates or undergoes sexual reproduction

Question 17

What is a intermediate host?

Answer 17

These may also be required for the parasite to complete its life cycle

Question 18

What is a vector?

Answer 18

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

Question 19

What parasite causes malaria?

Answer 19

Plasmodium, and is an endoparasite

Question 20

How does a plasmodium cause malaria

Answer 20

An plasmodium infected mosquito acting as a vector bites a human, this causes the parasite to enter the bloodstream and asexual reproduction occurs in the liver and then in the red blood cells. When these red blood cells burst gameocytes are released into the bloodstream. If another mosquito bites an infected human the gameocyte enters the mosquito maturing into male and female gamates allowing sexual reproduction to occur

Question 21

What parasite causes schistosomiasis?

Answer 21

Schistosomes - parasitic flatworms, endoparasites that rely on vectors to reach their definitive hosts - humans

Question 22

Where can parasites replicate?

Answer 22

Only inside a host cell

Question 23

Describe the structure of a virus

Answer 23

-Genetic material in the form of DNA or RNA
-This is packaged in a protective protein coat
-The outer surface of a virus contains antigens
-Some viruses are surrounded by a phospholipid membrane

Question 24

What are the stages involved in a viruses life cycle in a host cell?

Answer 24

-Penetration
-Synthesis + new components
-Assembly
-Release

Question 25

What do host cells supply viruses with?

Answer 25

-Nucleotides -Amino acids -ATP -Enzymes

Question 26

What enzyme is used to form DNA?

Answer 26

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

Question 27

What is transmission?

Answer 27

How much parasites spreads to hosts

Question 28

What is virulence?

Answer 28

How much harm parasites cause their host and the affect on the hosts fitness

Question 29

What factors increase transmission rates?

Answer 29

-Overcrowding of hosts at high density -Mechanisms that allow the parasite to spread even when infected hosts are incapacitated, such as: vectors or waterbone dispersal -Host behaviour

Question 30

How can host behavior be altered by parasites?

Answer 30

Host foraging, movement, sexual behaviour, habitat choice, or anti-predator behaviour

Question 31

What other changes to hosts can be caused by parasites excluding host behavior?

Answer 31

Supress the hosts immune system, modify host size, modify reproductive rate in ways that benefit growth, reproduction or transmission

Question 32

What is a pathogen?

Answer 32

A disease causing microbe such as; bacteria, virus or fungi

Question 33

What is an example of a nonspecific physical defence?

Answer 33

Epithelial tissue blocks the entry of parasites

Question 34

What is an example of a nonspecific chemical defence?

Answer 34

Hydrolytic enzyes in musuc, saliva and tears destroy bacterial cell walls.

Question 35

What is an example of a nonspecific cellular defence?

Answer 35

Inflammatory response, phagocytosis, natural killer cells

Question 36

Describe the inflammatory response

Answer 36

Injured cells release signalling molecules (cytokines). This results in enhanced blood flow to the site, bringing antimicrobacterial proteins and phagocytes to deal with any pathogens

Question 37

Describe the process of phagocytosis

Answer 37

Killing of parasite using powerful hydrolytic enzymes contained in lysosomes, by engulfing the parasite and enclosing them inside a vacule. The lysosome then fuses with the vacule and the enzymes destroy the parasite

Question 38

Describe the actions of natural killer cells

Answer 38

(a type of lymphocyte) conidentify and attach to cells infected with viruses, releasing chemicals that lead to cell dealth by inducing aptosis

Question 39

Why are memory lymphocytes important for secondary immune response?

Answer 39

Inital antigen exposure produces memory lymphocyte cells specfic for that antigen that can produce a secondary response when the same antigen enters the body in the future when this occurs antibodie production is enhanced

Question 40

What is the red queen hypothesis?

Answer 40

Co-evolved organisms evolve adaptations as a response to selection pressures applied to the other species

Question 41

What is antigen mimicry?

Answer 41

Endoparasites mimics the antigens of the self cells to evade detection by the antibodies

Question 42

What is antigenic variation?

Answer 42

This occurs in some parasites and allows them to change between different antigens during the course of infection of a host. It may also allow reinfection of the same host with the new varient

Question 43

What is latency?

Answer 43

There but not actively dividing

Question 44

What is epidemiology?

Answer 44

This is the study of the outbreak of infectious diseases

Question 45

What is herd immunity?

Answer 45

This occurs when a large percentage of a population is immunized

Question 46

What 3 factors does herd immunity threshold depend on?

Answer 46

-type of disease -the effectiveness of the vaccine -the density of the population

Question 47

What is a herd immunity threshold?

Answer 47

This is the density of resistant hosts in the population required to prevent an epidemic

Question 48

Why must vaccines reflect antigenic variation?

Answer 48

Vaccines that reflect antigenic variation produce a range of antibodies so remain effective

Question 49

Why is it difficult to develop effective vaccines and treatment for parasitic infections?

Answer 49

-The similarities between host and a parasite metabolism makes it difficult to find drug compounds that only target the parasite -Some parasites are difficult to culture in the laboratory making it difficult to design vaccines

Question 50

What are some possible control measures for parasites?

Answer 50

-co-ordinated vector control -civil engineering products to improve sanitation