biology - 5b - parasitic life cycles Flashcards
What do some hosts require?
Only one host to complete their life cycle.
What do many parasites require?
More than one host to complete their life cycle.
What is the definitive host?
The organism on or in
which the parasite reaches sexual maturity.
What may intermediate hosts also be required for?
The parasite to complete its life cycle.
What does a vector play an active role in?
The transmission of the parasite and may also be a host.
What is the human disease malaria caused by?
Plasmodium.
What does an infected mosquito, acting as a vector do?
Bites a human.
What does plasmodium do?
Enters the human bloodstream.
Where does asexual reproduction occur?
In the liver and then in the red blood cells.
What happens when the red blood cells burst?
Gametocytes are released into the bloodstream.
What does another mosquito do?
It bites an infected human and the gametocytes enter the mosquito, maturing into male and female gametes, allowing sexual reproduction to now occur.
What can the mosquito now do?
Infect another human host.
What do schistosomes cause?
The human disease schistosomiasis.
How do schistosomes reproduce?
Sexually in the human intestine.
What do the fertilised eggs do?
They pass out via faeces into water where they develop into larvae.
What do the larvae then do?
They then infect water snails , where asexual reproduction occurs.
What does larvae infecting water snails produce?
Another type of motile larvae, which escape the snail and penetrate the skin of a human, entering the bloodstream.
What are viruses?
Parasites that can only replicate
inside a host cell.
What do viruses contain?
Genetic material in the form
of DNA or RNA, packaged in a protective protein coat.
What are some viruses surrounded by?
A phospholipid membrane derived from host cell materials.
What does the outer surface of a virus contain?
Antigens that a host cell may or may not be able to detect as foreign.
What are viral life cycle stages?
Infection of host cell with genetic material, host cell enzyme replicate viral genome, transcription of viral
genes and translation of viral proteins,
assembly and release of new viral particles.
What do RNA retroviruses use?
The enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell.
What can viral genes then be expressed to form?
New viral particles.
