2.5 parasitism Flashcards
Ecological niche
A summary of the tolerances and requirements of a species.
Fundamental niche
The niche that an organism will occupy with no interspecific competition.
Realised niche
The niche that an organism occupies when there is interspecific competition present.
Competitive exclusion principle
Where when two species are in intense competition with each other and have extremely similar fundamental and realised niches one will decline to local extinction.
Resource partitioning
Where two different species with different realised niche coexist with each other by compromising which each other over resources.
Parasite definition
An organism which forms a symbiotic relationship with a host and benefits by gaining nutrients and energy at the expense of a host.
Benefits of parasitism to the parasites
Gain nutrients and energy from host.
Reproductive potential do parasites
Parasites have high reproductive potential compared to host since many parasites can survive on one host.
Degenerate meaning
When a parasite lacks vital organs to survive without host, such as a digestive system.
Fasciola acaris
Flatworm
Endoparasite
A parasite which remains inside a host.
Ectoparasite
A parasite which remains on the outside of the host.
Vector definition
An organism which allows for transmission of parasites from one host to another.
Schistosomes lifecycle
Schistosomes sexually reproduce inside the human (definite host).
Fertilised eggs pass out human faeces and into water.
They develop into larvae and infect water snails. (Intermediate host)
Asexual reproduction occurs inside the water snail.
Exit the snail and penetrate human entering the bloodstream.
Definite (primary) host
The host that a parasite will reach sexual maturity by detrimentally effecting
Intermediate host
The host which a parasite requires to complete its lifecycle, such as carrying out asexual reproduction to increase transmission.
Schistosomes
A form of flatworm which causes the disease schistosomiasis.
Schistosomes intermediate host
Water snails
Schistosomes definite hosts
Humans
Malaria pathogen
Plasmodium
Why is plasmodium so difficult to treat
It can hide in the liver or on inner walls of blood vessels in a dormant state, remaining undetected by the immune system
Malaria lifecycle
Plasmodium enters the human bloodstream by being bitten by an infected mosquito.
Humans are the intermediate host and therefore plasmodium undergoes asexual reproduction in the liver and red blood cells.
Red blood cells burst and gametocytes are released into the bloodstream.
Mosquito bites infected human and plasmodium enters the definite host.
Gametocytes mature into gametes allowing for sexual reproduction inside the mosquito.
Plasmodium reaches sexual maturity.
Mosquito infects another human.
Plasmodium definite host
Mosquito
Plasmodium intermediate host
Human
Structure of viruses
Has a viral head with DNA surrounded by protein coat.
Has a tail which is a hollow tube made of protein
Has tail fibre which is made of protein
Viral replication process
Virus binds to the membrane of a host cell.
Virus gains using lipid membrane on the surface of the protein coat and injects DNA into the host.
Viral DNA enters the nucleus and is replicated using host enzymes and nucleotides.
Viral DNA is translated into viral protein coats by host organelles
Viruses are assembled by protein coats surrounding the virus DNA
host is broken open by virus and virus repeats the cycle.
Viruses lipid membrane function
Viruses have a lipid membrane on their surface allowing the viruses to gain access to a cell and avoid detection from the immune system.
Retrovirus structure
Glycoprotein on membrane envelope
Protein coating
Capsid containing two single stranded RNA molecules
Retrovirus viral replication
Glycoprotein on protein coat
allows for the retrovirus to enter the host cell and removes membrane envelop
Viral reverse transcriptase catalyses the synthesis of DNA from RNA
DNA is incorporated into the hosts genome.
Viral DNA is then transcribed and translated into viral RNA and viral organelles.
New viral particles assemble
Each viral cell will be enveloped in a glycoprotein membrane and leave the cell.
Viral reverse transcriptase
The enzyme in viruses which transfers information on RNA into host DNA.
Transmission
The spread of a parasite to a host
Virulence
The harm a parasite causes a host.
Factors increasing transmission rate
High population and overcrowding
Presence of vectors or other means of transmission
Extended phenotype definition
Where the presence of parasitism will alter a hosts behaviours to benefit the parasite.
Extended phenotype examples
Foraging
Movement
Sexual behaviour
Habitat choice
Anti predator behaviour
Reasons for extended phenotype
Increase parasite transmission and reproductive rate
Types of defence against parasites
Non specific immune response
Specific immune response
Non specific immune response examples
Skin
Chemical responses such as mucus, tears and stomach acid
Inflammatory response
Natural killer cells
Skin defence
The skin prevents pathogens and parasites entering the body
Localised Inflammatory response defence
When skin is broken parasites enter and this signals to the body to increase blood flow to the site and transport white blood cells and antimicrobial proteins to the site of security breach .
Chemical secretions defence
Can kill parasites and pathogens by denaturing their proteins and breaking down the parasites.
Localised inflammation process
Skin breaks
Histamine and prostaglandins released
Capillaries dilate and clotting begins
Phagocytes are attracted to parasites and pathogens
Phagocytes in gulf and consume cell debris and parasite.
Phagocytes definition
Non specific white blood cells which engulf a parasites and then break them down with lysosomes.
Phagocytosis process
Phagocytes is attracted to chemical signals by pathogen
Vacuole forms around the pathogen
Lysosomes fuse with vacuole and pathogen is digested
Vacuole breaks down and the digested products are released into the phagocyte cytoplasm
Natural killer cells definition
A type of lymphocyte which targets virus infected and cancer cells and triggers apoptosis.
How do natural killer cells identify targets
By identifying proteins inside the cell which show normal cell behaviour.
Specific defence examples
B lymphocytes
T lymphocytes
Immunology surveillance
Clonal selection
Memory cells.
Antigen
A molecule which binds to an antibody or receptor
Antibody
A molecule which binds to a pathogen and prevents the pathogen from entering other cells
B lymphocytes
White blood cells which produce specific antibodies to bind to pathogen antigens and deactivates pathogens by preventing them from entering cells.
T lymphocytes
White blood cells which Target specific infected damaged cells and begin apoptosis.
Clonal selection
Where lymphocytes undergo mitosis, with one daughter cell becoming a plasma cell, and the other becoming a memory cell to prevent further infections.
Plasma cells
A lymphocyte which produces antibodies to combat infection
Memory cells
Cells which prevent further infections of a pathogen by producing antibodies
Methods of immune evasion
Antigenic variation
Latency
Antigenic variation definition
Where a pathogens antigens change over time preventing memory cells from identifying the pathogen. Meaning the pathogen can reinfect the same host again.
Latency definition
Where a pathogen enters an inactive state by integrating their genome into the host cells and waiting for favourable conditions to arise.
Antigenic variation benefits
Can allow for reinfection of the same host
Can provide sufficient evasion for a pathogen to remain inside a host.
Epidemiology definition
The study of outbreak and spread of infectious diseases
Herd immunity
Where a large percentage of a population are immune to a disease and therefore protect non immune members of the public by preventing the spread of the disease.
Herd immunity threshold definition
The population percentage needed to achieve herd immunity for a specific disease.
Methods of increasing herd immunity
Vaccinations
Challenges in treating a controlling parasites and pathogens
Some parasites are difficult to culture in a lab
Parasites rapidly evolve
Host and parasite metabolisms are similar and connected - meaning drugs can harm the host.
Methods of controlling parasites and pathogens
vector control (killing vectors)
High sanitation
Benefits of parasite control
Reduced child mortality
Improved intelligence of population
