Unit 2 - Topic 5 - Parasitism - Section B - Parasitic Life Cycles Flashcards
How many hosts do parasites require to complete their life cycle
Some parasites only require on host, many require more than one
What is a definitive host and what else may also be required
The organism on or in which the parasite reaches sexual maturity. Intermediate hosts may also be required for the parasite to complete its life cycle
What is a vector
A vector plays an active role in the transmission of the parasite and may also be a host
Malaria is caused by what
Plasmodium
Describe the life cycle of plasmodium
An infected mosquito, acting as a vector, bites a human. Plasmodium enters the human bloodstream. Asexual reproduction occurs in the liver and then in the red blood cells. When the red blood cells burst gametocytes are released into the bloodstream. Another mosquito bites an infected human and the gametocytes enter the mosquito, maturing into male and female gametes, allowing sexual reproduction to now occur. The mosquito can then infect another human host.
What does schistosomes cause
Schistosomiasis
Describe the life cycle of schistosomes
Schistosomes reproduce sexually in the human intestine. The fertilised eggs pass out via faeces into water where they develop into larvae. The larvae then infect water snails, where asexual reproduction occurs. This produces 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 viruses contain
Antigens that a host cell may or may not be able to detect as foreign
Describe the 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
How do RNA retroviruses work
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 be expressed to form
New viral particles
