UNIt 2 - parasitism

Question 1

what is a niche?

Answer 1

a niche is the multi-dimensional summary of tolerances and requirements of a species

Question 2

what is a fundamental niche?

Answer 2

a fundamental niche is the set of resources that a species is capable of using in the absence of interspecific competition

Question 3

what is a realised niche?

Answer 3

a realised niche is the set of resource that a species actually uses in response to interspecific competition

Question 4

what is competitive exclusion?

Answer 4

if the realised niche of two species is very similar, the level of competition can lead to one species losing out to the other

this leads to population decline and local extinction of one species

Question 5

what is resource partitioning?

Answer 5

two or more species can co-exist by exploiting different components of the resource they both require

Question 6

what are endoparasites?

Answer 6

they live within their host

Question 7

what is an ectoparasite?

Answer 7

they live and feed on the surface of the host

Question 8

what type of relationship do parasites and their hosts have?

Answer 8

they have a symbiotic relationship. the parasites gain nutrients at the expense of their host - for growth and reproduction- and the host incurs costs from losing resources and defending its tissues

Question 9

what does the red queen hypothesis state (parasites and hosts)?

Answer 9

The Red Queen Hypothesis states that parasites will co-evolve with their host and develop adaptations in response to their host’s defences.

Question 10

how can parasite niches be described?

Answer 10

we can describe the parasite niche as:​
Narrow​
Host-specific

Question 11

How are parasite/host relationships different from predator/prey?

Answer 11

Parasites have a far greater reproductive potential than their host.

Question 12

what do parasites lack?

Answer 12

Many parasites are also degenerate meaning they lack structures and organs found in other organisms

Question 13

what is an endoparasite and and ectoparasite

Answer 13

An ectoparasite lives on the surface of its host, whereas an endoparasite lives within the tissues of its host.

Question 14

how many hosts can a parasite have?

Answer 14

Some parasites require only one host to complete their life cycle, while others require more than one host to complete their life cycle.

Question 15

what is a definitive host?

Answer 15

The definitive host is the organism on or in which the parasite reaches sexual maturity.

Question 16

what are intermediate hosts and what is their purpose?

Answer 16

A host that is normally used by a parasite in the course of its lifecycle in which it may multiply asexually but not sexually.. Intermediate hosts may also be required for the parasite to complete its life cycle.

Question 17

what is a vector and its purpose?

Answer 17

A vector may also be a host. A vector is an organism which does not cause the disease itself but instead spreads the parasite from one host to another

Question 18

what is malaria caused by?

Answer 18

The human disease malaria is caused by the parasite Plasmodium.

Question 19

how do mosquitoes work as a vector?

Answer 19

An infected mosquito, acting as a vector, bites a human and Plasmodium enters the bloodstream; asexual reproduction occurs in the liver and then in the red blood cells, which burst to release gametocytes into the bloodstream. If a mosquito bites an infected human, gametocytes enter the mosquito, maturing into male and female gametes and allowing sexual reproduction to occur.

Question 20

what are schistosomes and what do they do?

Answer 20

Schistosome parasites cause the human disease schistosomiasis. Schistosomes reproduce sexually in the human intestine and fertilised eggs pass out via faces into water where they develop into larvae that infect water snails, where asexual reproduction occurs producing another type of motile larvae that escape the snail and penetrate the skin of humans, entering the bloodstream.

Question 21

what are viruses an example of and how do they work?

Answer 21

Viruses are parasites that can only replicate inside a host cell. .

Question 22

what’ are viruses made up of?

Answer 22

some viruses are surrounded by a phospholipid membrane derived from host cell materials. The outer surface of a virus contains antigens that a host cell may or may not be able to detect as foreign. Viruses contain genetic material in the form of DNA or RNA, packaged in a protective protein coat

Question 23

what is the viral life cycle?

Answer 23

Viral life cycle stages include:
infection of the host cell with genetic material

then host cell enzymes replicate the viral genome,

which is transcribed and translated into viral proteins

new viral particles are assembled and released from host cells.

Question 24

how do RNA retroviruses work?

Answer 24

RNA retroviruses use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell, allowing new viral particles to be formed,

Question 25

what is transmission?

Answer 25

Transmission is the spread of a parasite to a host.

Question 26

what is virulence?

Answer 26

Virulence is the harm caused to a host species by a parasite.

Question 27

how are ectoparasites and endoparasites transmitted

Answer 27

Ectoparasites are generally transmitted through direct contact or by the consumption of intermediate hosts. Endoparasites of the body tissues are often transmitted by vectors

Question 28

how are endoparasites transferred?

Answer 28

Endoparasites of the body tissues are often transmitted by vectors

Question 29

what are factors that are increase transmission rates?

Answer 29

Factors that increase transmission rates include the overcrowding of hosts when they are at high
density, and mechanisms such as vectors and waterborne dispersal stages, which allow the
parasite to spread even if infected hosts are incapacitated.

Question 30

can behaviour of hosts be modified by parasites?

Answer 30

Host behaviour is often exploited and modified by parasites to maximise transmission. Alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour becomes part of the extended phenotype of the parasite

Question 31

what physical qualities of a host can be modified by a parasite?

Answer 31

Parasites often suppress the host immune system and modify host size and reproductive rate in
ways that benefit parasite growth, reproduction or transmission.

Question 32

what does the immune response in mammals involve?

Answer 32

`immune response in mammals involves both non-specific defences and specific cellular defences.

Question 33

what are some examples of nonspecific defences?

Answer 33

Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected with viruses are examples of nonspecific defences.

Skin and epithelial tissue act as physical barriers by blocking the entry of parasites.

Chemical secretions include hydrolytic enzymes in mucus, saliva and tears, which destroy bacterial cell walls; secretions of the stomach, vagina and sweat glands create low pH environments that denature cellular proteins of pathogens.

Question 34

what do injured cells release?

Answer 34

Injured cells release cytokines that enhance blood flow to the site, bringing antimicrobial proteins and phagocytes.

Question 35

what are natural killer cells?

Answer 35

Natural killer cells can identify and attach to cells infected with viruses, releasing chemicals that
lead to cell death by inducing apoptosis.

Question 36

what type of cell constantly circulates the blood?

Answer 36

A range of white blood cells constantly circulates in the blood, monitoring the tissues.

Question 37

what are phagocytes?

Answer 37

Phagocytes are white blood cells that can kill parasites using powerful enzymes contained in lysosomes, by engulfing them and storing them inside a vacuole in the process of phagocytosis.

Question 38

what do lymphocytes have on their surface?

Answer 38

Mammals contain many different lymphocytes, each possessing a receptor on its surface that can potentially recognise a parasite antigen.

Question 39

what does binding of an antigen to a lymphocyte receptor do?

Answer 39

Binding of an antigen to a lymphocyte’s receptor selects that lymphocyte to divide and produce a The clonal population of this lymphocyte.

Question 40

what is the difference between T lymphocytes and B lymphocytes?

Answer 40

B lymphocytes produce antibodies while T lymphocytes can induce apoptosis in parasite- infected cells.

Question 41

how do antibodies work?

Answer 41

Antibodies possess regions where the amino acid sequence varies greatly between different antibodies; this variable region gives the antibody its specificity for binding antigen.

Question 42

what is the antigen-antibody complex?

Answer 42

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 it can stimulate a response that results in cell lysis.

Question 43

what happens after a lymphocyte is exposed to an antigen?

Answer 43

Initial antigen exposure produces memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future. In a secondary response, antibody production is enhanced in terms of speed of production, concentration in the blood and duration,

Question 44

what have parasites done to avoid the immune system?

Answer 44

Parasites have evolved ways of evading the immune system.

Question 45

what can endoparasites do to survive against the immune response?

Answer 45

Endoparasites mimic host antigens to evade detection and modify the host immune response to reduce their chances of destruction.

Question 46

what affect does antigenic variation have on parasites?

Answer 46

Antigenic variation in some parasites allows them to change between different antigens during the course of infection of a host, and may also allow reinfection of the same host with the new variant.

Question 47

what is latency? (parasites)

Answer 47

Some viruses escape immune surveillance by integrating their genome into host genomes, existing in an inactive state known as latency. A virus emerges from latency when favourable conditions arise.

Question 48

what is epidemiology?

Answer 48

Epidemiology is the study of the outbreak and spread of infectious disease

Question 49

what is the herd immunity threshold?

Answer 49

The herd immunity threshold is the density of resistant hosts in the population required to prevent an epidemic.

Question 50

what do vaccines contain?

Answer 50

Vaccines contain antigens that will elicit an immune response.

Question 51

what can affect can the effectiveness of vaccines?

Answer 51

The similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite.

Antigenic variation has to be reflected in the design of vaccines.

Some parasites are difficult to culture in the laboratory, making it difficult to design vaccines.

Question 52

what can overcrowding cause?

Answer 52

Challenges arise where parasites spread most rapidly as a result of overcrowding or tropical climates.

Overcrowding can occur in refugee camps that result from war or natural disasters, or rapidly growing cities in less economically developed countries (LEDCs).

Overcrowded conditions make coordinated treatment and control programmes difficult to achieve.

Question 53

what can be used to improve sanitation?

Answer 53

Civil engineering projects to improve sanitation, combined with coordinated vector control, may often be the only practical parasite control strategies.

Question 54

what does improved parasite control lead to?

Answer 54

Improvements in parasite control reduces child mortality and result in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development.

Question 55

what does antigenic variation mean?

Answer 55

change between different antigens during the course of infection of a host

Question 56

what are B lymphocytes?

Answer 56

white blood cells that produce specific antibodies in response to specific antigens

Question 57

what is an extended phenotype?

Answer 57

the expression of a parasites genotype into the phenotype of its host by manipulating the hosts phenotype to facilitate its transmission

Question 58

what are gametocytes?

Answer 58

the precursors of male and female gametes

Question 59

what are hydrolytic enzymes?

Answer 59

any enzyme that catalyses the hydrolysis of a chemical bond

Question 60

what is the inflammatory response?

Answer 60

injured or wounded areas become warm and red due to increased blood flow to bring white blood cells to defend

Question 61

LEDC meaning?

Answer 61

less economically developed country

Question 62

what are memory lymphocytes?

Answer 62

lymphocyte-specific for a specific antigen; they are retained in the body following infection and can produce a secondary response to the same antigen

Question 63

what are RNA retrovirsues?

Answer 63

viruses that use the enzyme reverse transcriptase to form DNA