UNIT 2 - KA5 Flashcards
What is an ecological niche
An ecological niche is a multi-dimensional summary of tolerances and requirements of a species
When does a species occupy its fundamental niche
A species has a fundamental niche that it occupies in the absence of any interspecific competition
When is a realised niche occupied
A realised niche is occupied in response to interspecific competition
What can happen as a result of interspecific competition
As a result of interspecific competition competitive exclusion can occur, where the niches of two species are so similar that one declined to local extinction
What happens where the realised niches are sufficiently different
Where the realised niches are sufficiently different, potential competitors can co exist by resource partitioning
What is parasitism
Parasitism is a symbiotic interaction between a parasite and its host (+/-)
Which terms does a parasite gain benefit in
A parasite gains benefit in terms of nutrients at the expense of it’s host
What is the reproductive potential of the parasite compared to the host
Unlike predator - prey relationship the reproductive potential of the parasite is greater than that of the host
What type of niche do most parasites have
Most parasites have a narrow (specialised) niche as they are very host specific
What are many parasites
As the host provides so many of the parasites needs, many parasites are degenerate lacking structures and organs found in other organisms
Where does an ectoparasite live
An ectoparasite lives on the surface of its host
Where does an endo parasite live
An endo parasite lives within the tissues of its host
What do some parasites only require
Some parasites require only one host to complete their life cycle
What do many parasites require
Many parasites require more than one host to complete their life cycle
What is the definitive host
The definitive host is the organism on or in which the parasite reaches sexual maturity
What may be required for the parasite to complete its life cycle
Intermediate hosts may alone be required for the parasite to complete its life cycle
What is the role of a vector
A vector plays an active role in the transmission of the parasite and may also be a host
What are viruses
Viruses are parasites that can only replicate inside a host cell
In what form do viruses contain genetic material
Viruses contain genetic material in the form of DNA or RNA packaged in a protective protein coat
What are some viruses surrounded by
Some viruses are surrounded by a phospholipid membrane derived from host cell materials
What does the outer surface of a virus contain
The outer surface of a virus contains antigens that a host cell may or may not be able to detect as foreign
Viral life cycle stages
1 - infection of host cell with genetic material
2 - host cell enzymes replicate viral genome
3 - transcription of viral genes and translation or viral proteins
4 - assembly and release of new viral proteins
What do RNA retroviruses use
RNA retroviruses use the enzyme reverse transcriptase to form DNA which is then inserted into the genome of the host cell
How can viral genes be expressed
Viral genes can then be expressed to 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 generally transmitted
Ectoparasites are generally transmitted throigh direct contact
How are endoparasites transmitted
Endoparasites of the body tissues are often transmitted by vectors or by consumption of intermediate hosts
Factors that increase transmission rates
the 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 is host behaviour exploited
Host behaviour is often exploited and modified by parasites to maximise transmission
What does the host behaviour become a part of
The host behaviour becomes part of the extended phenotype of the parasite
How do parasites suppress the host immune system in ways that benefit
Parasites often suppress the body immune system and modify. host size and reproductive rate in ways that benefit the parasite growth reproduction or transmission
What type of aspects does immune response in mammals have
Immune response in mammals has both non-specific and specific aspects
Examples of non-specific defences (6)
- physical barriers
- chemical secretions
- inflammatory response
- phagocytes
- natural killer cells destroying cells infected with viruses
What does epithelial tissue block
Epithelial tissue blocks the entry of parasites
What can destroy bacterial cell walls
Hydroloytic enzymes in mucus saliva and tears
What can denature cellular proteins of pathogens
Low pH environments of stomach, vagina and sweat glands denatures cellular proteins of pathogens
What do injured cells release
Injured cells release signalling molecules
What do injured cells releasing signalling molecules result in
This results in enhanced blood flow to the site bringing antimicrobial proteins and phagocytes
How does killing of parasites occur
Killing of parasites using powerful enzymes contained in lysosomes by engulfing them and storing them inside a vacuole in the process of phagocytosis
How can natural killer cells induce apoptosis
Natural killer cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis
Specific cellular defences
A range of white blood cells constantly circulate monitoring the tissues
What happens if tissues become damaged or invaded
If tissues become damaged or invaded cells release cytokines that increase blood flow resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage
What do mammals contain
Mammals contain many different lymphocytes each possessing a receptor on its surface which can potentially recognise a parasite antigen
What is the effect of binding of an antigen to a lymphocyte receptor
Binding of an antigen to a lymphocytes receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte
What may some selected lymphocytes
Some selected lymphocytes will produce antibodies other can induce apoptosis in parasite - infected cells
What regions do antibodies posses
Antibodies possess regions where the amino acid sequence varies greatly between different antibodies
What does the variable region give the antibody
This variable region gives the antibody its specificity for binding antigen
What happens as a result of the antigen binding to the binding site
When the antigen binds to this binding site the antigen-antibody complex formed can result in inactivation of the parasite, rendering it susceptible to a phagocyte or can stimulate a response that results in cell lysis
What is also formed
Memory lymphocyte cells are also formed
What can initial antigen exposure produce
Initial antigen exposure produces memory lymphocyte cells specific for that antigen that can proficiency a secondary response when the same antigen enters the body in the future
What happens when memory lymphocyte cells are produced
When this occurs antibody production is enhances in terms of speed of production concentration in blood and duration
What have parasites evolved
Parasites have evolved ways of evading the immune system
How do endoparasites reduce chances of destruction
Endoparasites mimic host antigens to evade detection and modify host immune response to reduce their chances of destruction.
What does antigenic variation in some parasites allow
Antigenic variation in some parasites allows them to change between different antigens during the course of infection of a host
What May antigenic variation also allow
It may also allow re infection of the same host with the new variant
How do some viruses escape immune surveillance
Some viruses escape immune surveillance by integrating their genome into host genomes existing in an inactive state known as latency
When does the virus become active again
The virus becomes active again when favourable conditions arise
What is epidemiology
Epidemiology is the study of the outbreak and spread of infectious diseases
What is the herd immunity threshold
The herd immunity threshold is the density of resistant hosts in the population required to prevent an epidemic
What do vaccines contain
Vaccines contain antigens that will elicit an immune response
What do similarities between host and parasite make difficult
The similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite
What does antigenic variation need to be reflected in
Antigenic variation has to be reflected in design of vaccines
Why is it difficult to design vaccines
Some parasites are difficult to culture in the laboratory making it difficult to design vaccines
Where do challenges arise
Challenges arise where parasites spread most rapidly as a result of overcrowding or topical climates
Where can overcrowding occur
Overcrowding can occur in refugee camps that result from war or natural disaster or rapidly growing cities in LEDCs
What do these conditions make difficult
These conditions make co-ordinated treatment and control programs difficult to achieve
What may often be the only practical control strategy
Civil engineering projects to improve sanitation combined with co-ordinated vector control may often be the only practical control strategies
What do improvements in parasite control reduce
Improvements in parasite control reduce child mortality and result in population wide improvements in child development and intelligence as individuals have more resources for growth and development
What is the human disease malaria caused by
The human disease malaria is caused by plasmodium
How does plasmodium enter the bloodstream (malaria 1)
An infected mosquito, acting as a vector bites a human, plasmodium enters the human bloodstream
Where does asexual reproduction (malaria 2)
Asexual reproduction occurs in the liver and then in the red blood cells
Where are gametocytes released (malaria 3)
When the red blood cells burst gametocytes are released into the
bloodstream.
What happens when gametocytes enter the mosquito (malaria 4)
Another mosquito bites an infected human and the gametocyte enter the mosquito, maturing into male and female gametes allowing sexual reproduction to now occur
What can the mosquito infect (malaria 5)
The mosquito can then infect another human host
What causes the human disease schistosomiasis
Schistosomes cause the human disease schistosomiasis
How do schistosomes reproduce (schistosomiasis 1)
Schistosomes reproduce sexually in the human intestine
How do fertilised eggs pass into water (schistosomiasis 2)
The fertilised eggs pass out via faeces into water where they develop into larvae
When does asexual reproduction occur (schistosomiasis 3)
The larvae then infect water snails where asexual reproduction occurs
What does the asexual reproduction in schistosomiasis produce (schistosomiasis 4)
This produces another type of motile larvae which escape the snail and penetrate the skin of a human entering the bloodstream
