Unit 2: KA5 - Parasitism Flashcards
Define the term: ecological niche
A multi-dimensional summary of tolerances and requirements of a species
Define the term: fundamental niche
The niche occupied in the absence of any interspecific competition
Define the term: Realised niche
The niche occupied in response to interspecific competition
Describe competitive exclusion
If the realised niches of two species are very similar, then one species will lose out in the competition and decline to local extinction
Describe resource partitioning.
This involves species exploiting different components of the resource.
Why is resource partitioning important?
If the realised niche is sufficiently different, then potential competitors can co-exist.
Define the term: parasitism
The symbiotic interaction between a parasite and a host.
The parasite gains energy and nutrients at the expense of the host.
Describe the interaction between a host and a parasite.
The parasite gains energy and nutrients at the expense of the host.
Describe the reproductive potential in parasitism.
The reproductive potential of the parasite is much greater than the host.
Describe the reproductive potential in a predator-prey relationship.
Similar reproductive potential
Describe a parasite’s niche.
Most parasites have a narrow (specialised) niche as they are host-specific
Describe why parasites are ‘degenerate’.
As they lack structures and organs found in other organisms, since the host provides so many of the parasite’s needs.
Define the term: Ectoparasite
A parasite which lives on the surface of their host
Define the term: endoparasite.
A parasite which lives inside their host.
Define the term: Definitive host
The organism in/on which the parasite reaches sexual maturity
Define the term: Intermediate host
An organism in/on which the parasite may complete part of its life cycle.
Define the term: vector.
A vector plays an active role in the transmission of a parasite and may also be a host
What causes the human disease malaria?
plasmodium
What causes the human disease schistosomiasis?
Schistosomes
Describe the hosts of plasmodium.
- Mosquitos are the definitive host and act as a vector
- Humans are the intermediate host
Describe the hosts of Schistosomes
- Humans are the definitive host
- Water snails are the intermediate host
Describe viruses.
Viruses are parasites that can only replicate inside a host cell.
They contain genetic material in the form of DNA or RNA
How is a virus’ genetic material packaged?
In a protective protein coat
Describe the surface of viruses
It contains antigens, which the host cell may be able to detect as foreign.
Explain the Viral lifecycle
- 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
What enzyme do RNA retroviruses make use of?
Reverse Transcriptase
Describe RNA Retroviruses
- Virus antigens attach to host surface
- Virus RNA inserted into host cell
- An enzyme converts RNA to DNA in cytoplasm
- Viral DNA inserted into host cell genome
- Viral proteins expressed and form new viral particles to be released
How are new viral particles produced?
The expression of viral genes
Define the term: transmission
The spread of a parasite to a new host
Define the term: virulence
The harm that a parasite causes to a host species
What two ways may ectoparasites be transmitted?
- Direct contact
- Consumption of intermediate host
How are endoparasites transmitted?
Vectors
What two factors can increase transmission rates?
- Overcrowding of hosts in high density
- A parasite’s mechanisms of transmission, even when the host is incapacitated (vectors, waterborne dispersion etc.)
Define the term: extended phenotype.
A parasite’s ability to exploit and change host behaviour in order to increase transmission rates.
What behaviours of a host may parasites alter?
- Alteration of host foraging
- Movement
- Habitat choice
- Sexual behaviour
- Anti-predator behaviour
How may parasites benefit from altering a host’s body?
increased:
- Growth
- Reproduction
- Transmission
What 3 things may parasites do to a host’s body to gain benefits?
- Suppress immune system
- Modify host size
- Modify reproduction rate.
