Unit 2: Organisms and evolution KA 2.5: Parasitism

Question 1

define the term ecological niche

Answer 1

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

Question 2

example of a biotic tolerance (2)

Answer 2

-density of predators
-intensity of competition

Question 3

example of biotic requirement (3)

Answer 3

-availability of prey
-availability of pollinators
-other ecological services

Question 4

examples of abiotic tolerances (2)

Answer 4

-range of temperatures
-range of pH

Question 5

example of abiotic requirements (1)

Answer 5

-suitable habitat features, such as flat rock for basking

Question 6

define intraspecific competition

Answer 6

competition between members of the same species for the exact same resources

Question 7

define interspecific competition

Answer 7

competition between members of different species for similar resources

Question 8

what is a fundamental niche

Answer 8

the niche a species occupies in the absence of any interspecific competition

Question 9

what is a realised niche

Answer 9

the niche occupied in response to interspecific competition

Question 10

describe competitive exclusion

Answer 10

where the niches of 2 species are so similar that one species declines to local extinction

Question 11

describe resource partitioning

Answer 11

where the realised niches become sufficiently different, potential competitors can co-exist by resource partitioning

Question 12

what does degenerate mean in terms of parasites

Answer 12

the host provides so many of the parasites needs, many parasites are degenerate, lacking structures and organs found in other organisms

Question 13

define ectoparasite

Answer 13

a parasite that lives on the surface of its host

Question 14

define endoparasite

Answer 14

a parasite that lives within the features of its host

Question 15

define a definitive host

Answer 15

the organism in/on which the parasite reaches sexual maturity, produces gametes or undergoes sexual reproduction

Question 16

describe an intermediate host

Answer 16

intermediate hosts may also be required for the parasite to complete its life cycle

Question 17

what is a vector

Answer 17

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

Question 18

what is the name of the parasite responsible for malaria

Answer 18

plasmodium

Question 19

where does asexual reproduction occur in the lifecycle of the plasmodium parasite

Answer 19

in humans, within the liver then in red blood cells

Question 20

what is released into the bloodstream when red blood cells burst in the lifecycle of the plasmodium parasite

Answer 20

plasmodium gametocytes

Question 21

where does sexual reproduction occur in the lifecycle of the plasmodium parasite and what does that make this host

Answer 21

the mosquito, the definitive host

Question 22

what is the name of the parasitic flatworms

Answer 22

schistosomes

Question 23

where does sexual reproduction occur in the lifecycle of the schistosome parasite and what does this make that host

Answer 23

the human intestine, a definitive host

Question 24

how do the fertilised eggs in the human intestine turn into larvae in the water

Answer 24

the fertilised eggs pass out via faeces into water where they develop into larvae

Question 25

where does asexual reproduction occur in the lifecycle of the schistosome parasite

Answer 25

water snails

Question 26

how do schistosomes get transmitted to humans

Answer 26

motile larvae penetrate the skin of a human that's in the water and enter the bloodstream

Question 27

what is in the centre of a virus

Answer 27

genetic material in the form of dna or rna

Question 28

what surrounds the genetic material in a virus

Answer 28

a protective protein coat

Question 29

what is on the outer surface of a virus

Answer 29

antigens, that a host cell may or may not be able to tell is foreign

Question 30

what are some viruses surrounded by and what is it derived from

Answer 30

a phospholipid membrane, which is derived from host cell material

Question 31

what are the stages of the life cycle of a virus inside a host cell

Answer 31

1) infection of the host with genetic material 2) Host cell enzymes replicate viral genome, transcription of viral genes and translation of viral proteins 3) assembly and release of new viral proteins

Question 32

examples of what the host cell supplies a virus with (4)

Answer 32

-nucleotides -amino acids -ATP -enzymes

Question 33

example of a retro virus

Answer 33

HIV

Question 34

what does RNA retrovirus use to from DNA

Answer 34

reverse transcriptase

Question 35

define the term transmission

Answer 35

how parasites spread to the host

Question 36

define the term virulence

Answer 36

how much harm parasites cause their host and the affect on the hosts fitness

Question 37

factors that increase transmission rate (3)

Answer 37

-overcrowding of hosts -mechanisms that allow the parasite to spread (vectors and waterborne dispersal) -changes in host behavior

Question 38

examples on how host behavior can be altered by parasites (5)

Answer 38

-foraging -movement -sexual behaviour -habitat choice -anti predator behaviour

Question 39

examples of non behavioural changes parasites can cause in their host (3)

Answer 39

-suppress hosts immune system -modify host size -modify reproduction rate (in ways that benefit growth, reproduction and transmission)

Question 40

state the term that describes how host behaviour becomes part of the parasite

Answer 40

extended phenotype

Question 41

how are ectoparasites generally transmitted

Answer 41

direct contact

Question 42

how are endoparasites generally transmitted

Answer 42

by vectors or consumption of intermediate hosts

Question 43

example of a non specific physical defense against parasites (1)

Answer 43

-epithelial tissue-blocks the entry of parasites

Question 44

example of a non specific chemical defense against parasites (2)

Answer 44

-hydrolytic enzymes in mucus, saliva and tears which destroy the cell wall -low pH enviorments of the secretions of the stomach, vagina and sweat glands, which denatures the cellular proteins of pathogens

Question 45

example of a non specific cellular defense against parasites

Answer 45

-inflammatory response -phagocytosis -natural killer cells

Question 46

what happens in the inflammatory response when cells are damaged

Answer 46

-injured cells released signalling molecules (cytokines) -this results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes to deal with any pathogens

Question 47

describe the process of phagocytosis

Answer 47

killing of parasites using powerful hydrolytic enzymes contained in lysosomes, by engulfing them and enclosing them inside a vacuole

Question 48

what do natural killer cells do

Answer 48

identify and attach to cells infected with a virus, releasing chemicals that lead to apoptosis

Question 49

define lymphocytes

Answer 49

white blood cells produced from stem cells in the bone marrow

Question 50

how is a clonal population of identical lymphocytes produced

Answer 50

antigen binding leads to repeated lymphocyte division, resulting in a clonal population of identical lymphocytes

Question 51

what produces memory lymphocytes

Answer 51

initial antigen exposure

Question 52

why are memory lymphocytes important for the secondary responce

Answer 52

antibody production is enhanced in terms of speed of production, concentration in blood and duration when the second response occurs

Question 53

what is antigen mimicry

Answer 53

when an endoparasite copies the antigens of a self cell to evade detection from antibodies

Question 54

what is antigenic variation

Answer 54

it allows the parasite to change between antigens over the course of infection of a host

Question 55

what is latency in terms of viruses

Answer 55

when a virus integrates their genome into the genome of a host the parasite will then become active again when the conditions are favourable

Question 56

define the term epidemiology

Answer 56

the study of the outbreak of infectious disease

Question 57

3 factors the the herd immunity threshold depends on

Answer 57

-type of disease -the effectiveness of the vaccine -the density of the population

Question 58

why must vaccines reflect the antigenic variation found in parasites

Answer 58

vaccines that reflect the antigenic variation produce a range on antibodies, so remain effective

Question 59

describe 2 reasons why it can be difficult to develop vaccines and treatments for parasitic infections

Answer 59

-the similarities between the host and the parasite can make it difficult to find drug components that only target the parasite -some parasites are difficult to culture therefore its difficult to design vaccines

Question 60

examples of possible parasite control strategies

Answer 60

- co-ordinated vector control - civil engineering projects to improve sanitation

Question 61

give two benefits to children when the spread of parasites is controlled

Answer 61

-reduced child mortality -improved child development and intelligence

Question 62

define the term herd immunity threshold

Answer 62

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