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Advanced Higher Biology 🧬🔬 > Parasitism 2.5 > Flashcards

Parasitism 2.5 Flashcards

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1
Q

what is an ecological niche?

A

a multi-dimensional summary of tolerances and requirements of a species

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2
Q

a species has a fundamental niche that it occupies in what?

A

in the absence of any interspecific competition

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3
Q

a realised niche is occupied in response to what?

A

interspecific competition

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4
Q

what can occur as a result of interspecific competition?

A

competitive exclusion - where the niches of two species are so similar that one declines to local extinction

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5
Q

what happens where the realised niches are sufficiently different?

A

potential competitors can co-exist by resource partitioning

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6
Q

what is parasitism?

A

a symbiotic interaction between a parasite and its host in which the parasite benefits (+) in terms of nutrients at the expense of its host, which loses these (-)

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7
Q

a parasite gains benefit in terms of what?

A

nutrients at the expense of its host

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8
Q

the reproductive potential of the parasite is greater than that of the host unlike in what relationship?

A

in a predator–prey relationship

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9
Q

most parasites have a narrow (specialised) niche because?

A

they are very host-specific

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10
Q

what is symbiosis?

A

an intimate co-evolved relationship between two species that can be notated:
- + for benefits
- - for detriment
- 0 for neutral

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11
Q

many parasites are degenerate, what does this mean?

A

they have lacking structures and organs such as digestive systems found in other organisms

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12
Q

where does an ectoparasite live?

A

it lives on the surface of the host

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13
Q

where does an endoparasite live?

A

it lives within the tissues of it host

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14
Q

what is the definitive host?

A

the organism on or in which the parasite reaches sexual maturity

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15
Q

what is the intermediate host?

A

the organism which may be required for the parasite to complete its life cycle

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16
Q

what is a vector?

A

it plays an active role in the transmission of the parasite and may also be the host

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17
Q

what is malaria caused by?

A

the parasite Plasmodium

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18
Q

describe how plasmodium enters humans

A
  • infected mosquito (acts as a vector) bites human and plasmodium enters bloodstream
  • asexual reproduction occurs in the liver and then in the red blood cells - burst to release gametocytes into bloodstream
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19
Q

what happens if a mosquito bites a human infected with malaria?

A

gametocytes enter mosquito - maturing into male and female gametes and allowing sexual reproduction to occur

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20
Q

what do schistosome parasites cause?

A

schistosomiasis

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21
Q

describe the life cycle of schistosomes

A
  • schistosomes reproduce sexually in the human intestine
  • fertilised eggs pass out via faeces into water where they develop into larvae that infect snails
  • once they infect the snails, they reproduce asexually which produces another type of motile larvae
  • motile larvae escape the snail and penetrates the skin of humans - enters blood stream
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22
Q

what are viruses?

A

parasites that can only replicate inside a host cell

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23
Q

what do viruses contain?

A

genetic material in the form of DNA or RNA - packaged in a protective protein coat

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24
Q

what are some viruses surrounded by?

A

phospholipid membrane derived from host cell materials

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25
Q

what does the outer surface of a virus contain?

A

antigens that a host cell may or may not be able to detect as foreign

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26
Q

describe the life cycle stages of a virus

A
  • infection of the host cell with genetic material
  • host cell enzymes replicate viral genome
  • viral genome is then transcribed and translated into viral proteins
  • new viral particles are assembled and released from host cells
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27
Q

how do retroviruses work?

A

they use the enzyme reverse transcriptase to form DNA
- the DNA is then inserted into the genome of the host cell - allowing new viral particles to be formed

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28
Q

what is transmission?

A

the spread of a parasite to a host

29
Q

what is virulence?

A

the harm caused to a host species by a parasite

30
Q

how are ectoparasites transmitted?

A

through direct contact or by consumption of intermediate hosts

31
Q

how are endoparasites of the body tissues transmitted?

A

by vectors

32
Q

what are some factors that increase transmission rates?

A
  • overcrowding of hosts when at a high density
  • mechanisms such as vectors and waterborne dispersal stages - allows parasite to spread even if infected hosts are incapacitated
33
Q

how do parasites maximise transmission?

A

by exploiting and modifying its hosts behaviour

34
Q

what becomes part of the extended phenotype of the parasite?

A

the alteration of:
- host foraging
- movement
- sexual behaviour
- habitat choice
- anti-predator behaviour

35
Q

in what ways do parasites often suppress the host immune system and modify host size and reproductive rate?

A

in ways that benefit parasite growth, reproduction or transmission

36
Q

what do immune responses in mammals involve?

A
  • non-specific defences
  • specific cellular defences
37
Q

what are examples of non-specific defences?

A
  • physical barriers
  • chemical secretions
  • inflammatory response
  • phagocytes
  • natural killer cells destroying cells infected with viruses
38
Q

how do skin and epithelial tissue act as physical barriers?

A

by blocking the entry of parasites

39
Q

what do chemical secretions include and how do they work?

A
  • include hydrolytic enzymes in mucus, saliva and tears
  • they destroy bacterial cell walls
40
Q

how do secretions of the stomach, vagina and sweat glands work?

A

they create low pH environments that denature cellular proteins of pathogens

41
Q

what happens when cells become injured?

A
  • they release signalling molecules that enhance blood flow to the site
  • brings antimicrobial proteins and phagocytes
42
Q

how can phagocytes kill parasites?

A

by using powerful enzymes contained in lysosomes by engulfing them and storing them inside a vacuole in the process of phagocytosis

43
Q

how do natural killer cells work?

A

by identifying and attaching to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis

44
Q

what do a range of white blood cells do?

A

they constantly circulate in the blood, monitoring the tissues

45
Q

what happens if tissues become damaged or invaded?

A

cells release cytokines that increase blood flow - results in non-specific and specific white blood cells accumulating at the site of infection or tissue damage

46
Q

what do mammals contain many different types of and what are its properties?

A

lymphocytes
- each of them possess a receptor on its surface that can potentially recognise a parasite antigen

47
Q

what happens when an antigen binds to a lymphocytes receptor?

A

it selects that lymphocyte to divide and produce a clonal population of this lymphocyte

48
Q

what can selected lymphocytes do?

A
  • some produce antibodies
  • some induce apoptosis in parasite-infected cells
49
Q

what do antibodies possess and what does it do to them?

A
  • regions where the amino acid sequence varies greatly between different antibodies
  • this variable region gives the antibody its specificity for binding antigen
50
Q

what happens when an antigen binds to a binding site and what does it result in?

A

the antigen-antibody complex formed can result in
- the inactivation of the parasite
- rendering it susceptible to a phagocyte
- stimulate a response that results in cell lysis

51
Q

what do initial antigen exposure produce?

A

memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future

52
Q

what happens in a secondary response?

A

antibody production is enhanced in terms of speed of production, concentration in the blood and duration

53
Q

how have parasites evolved?

A

in ways of evading the immune system

54
Q

how do endoparasites reduce their chances of destruction?

A

by mimicking host antigens to evade detection and modify the host immune response

55
Q

what does antigenic variation in some parasites allow?

A

allows them to change between different antigens during the course of infection of a host - may also allow reinfection of the same host with the new variant

56
Q

how do some viruses escape immune surveillance?

A

by integrating their genome into host genomes - existing in an active state known as latency

57
Q

when do viruses emerge from latency (their inactive state)?

A

when favourable conditions arise

58
Q

what is epidemiology?

A

the study of the outbreak and spread of infectious disease

59
Q

what is the herd immunity threshold?

A

the density of resistant hosts in the population required to prevent an epidemic

60
Q

what do vaccines contain?

A

antigens that will elicit an immune response

61
Q

why is it difficult to find drug compounds that only target the parasite?

A

because of the similarities between the host and parasite metabolism

62
Q

what has to be reflected on in the design of vaccines?

A

antigenic variation

63
Q

how do parasites make it difficult to design vaccines?

A

because they are difficult to culture in a laboratory

64
Q

what happens as a result of overcrowding or tropical climates?

A

the arise of challenges where parasites spread most rapidly

65
Q

where can overcrowding occur?

A
  • in refugee camps that result from war or natural disasters
  • rapidly growing cities in less economically developed countries (LEDCs)
66
Q

what do overcrowded conditions make it difficult to achieve?

A

co-ordinated treatment and control programmes

67
Q

what may often be the only practical parasite control strategies?

A

civil engineering projects to improve sanitation, combined with co-ordinated vector control

68
Q

what do improvements in parasite control and what can it result in?

A
  • controls the reduce of child mortality
  • results in population-wide improvements in child developments and intelligence as individuals have more resources for growth and development

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