Parasitism Flashcards
What is an ecological niche
An ecological niche is a multidimensional summary of tolerance and requirements of a species
What is a fundamental niche
A species has a fundamental niche that it occupies in the absence of any interspecific competition
What is a realised niche
A realised niche is occupied in response to interspecific competition
What is the result of interspecific competition
competitive exclusion
What is competitive exclusion
Where the niches of two species are so similar that one declines to local extinction
What is resource partitioning
Where the realised niches are sufficiently different that potential competitors can co-exist by resource partitioning
What is parasitism
A symbiotic interaction between a parasite and its host
What is a benefit a parasite can gain from host
Gains benefit in terms of nutrients at expense of its host
Why are parasites referred to as degenerate
As host provides many of the parasites needs as the parasite lack the organs and structures found in other organisms
Why do some parasites have a narrow (specialised) niche
As they are very host specific
Ectoparasite
Lives on the surface if its host
Endoparasite
Lives within the tissues of its host
Parasitic life cycles
Some parasites need only one host to complete their life cycle whereas some need more than one
What is a vector and give eg
A vector plays an active role in the transmission of the parasite and may also be a host
-mosquito
How is the human disease malaria caused
By Plasmodium
What does schistosomes cause
The human disease schistosomiasis
What is a virus
Viruses are parasites that can only replicate inside a host cell
What do viruses contain
Viruses contain genetic material in form of DNA or RNA, packaged in a protective protein coat
Describe the structure of a virus
- Nucleic acid (DNA or RNA)
- Protective protein coat - Capsid
- Phosphide membrane
- attachment proteins - antigens
Phosphoric membrane
derived from host cell materials which surrounds some viruses
Viral life cycle stages
- 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
RNA retroviruses
Use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell
What happens if viral genes can be expressed
They form new viral particles
What is transmission
Transmission is the spread of a parasite to a host
What is virulence
Virulence is the harm caused to a host species by a parasite
How are ectoparasites transmitted
Through direct contact or by consumption of intermediate hosts
How are endoparasites often transmitted
Often transmitted by vectors
What are factors that increase transmission rates
- 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
How do parasites maximise transmission
-host behaviour is exploited and modified by parasite
What can parasites alter within a host
- Parasites can suppress the host immune system
- Modify host size and reproductive rates that benefit parasite growth
- reproduction or transmission
Defence against parasitic attack
Immune response in mammals has both non-specific and specific aspects
State the 5 non-specific defences
- Physical barriers
- Chemical secretions
- inflammatory response
- phagocytes
- natural killer cells
What happens if tissue becomes damaged
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
What do lymphocytes posses
Each posses a receptor on its surface which can potentially recognise a parasite antigen
Roles of lymphocytes
Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells
How do endoparasites evade detection
Endoparasites mimic host antigens to evade detection and modify host immune response to reduce their chances of destruction
Antigenic variation in parasites
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
What is latency
Some viruses escape immune surveillance by intergrating their genome into host genomes existing in an inactive state know as latency
How does a virus become active again
when favourable conditions arise
What is epidemiology
Epidemiology is the study of the outbreak and spread of infectious disease
What is the herd immunity threshold
The density of resistant hosts in the population required to prevent epidemic
What do vaccines contain
Contain antigens which will elicit an immune response
Why is it difficult to find drug compounds/coordinated treatment to target parasite
- 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
What are results of improving parasite control
- Reduces child mortality
- improvement in child development and intelligence
- More resources for growth and development
What is a definite host
Where the parasite reaches sexual maturity
What is an intermediate host
Hosts for a part Of a parasites life and reproduces asexually
Plasmodium life cycle
- 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
Schistosama life cycle
- Human is the definite host
- fertilised eggs are passed in faeces
- the eggs then hatch and infect snails
- larvae then penetrates human skin
