2.4.1-2 parasitism - niche and lifecycle

Question 1

what is an ecological niche

Answer 1

a multi dimensional summary of tolerances and requirements of a species

Question 2

what is a fundamental niche

Answer 2

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

Question 3

when is a realised niche occupied

Answer 3

in response to interspecific competition

Question 4

what happens as a result of interspecific competition

Answer 4

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

Question 5

what happens once the realised niches are sufficiently different

Answer 5

potential competitors can co exist by resource partitioning

Question 6

what is parasitism

Answer 6

a symbiotic interaction between a parasite and its host

Question 7

who benefits in parasitism

Answer 7

a parasite gains benefit in terms of nutrients at the expense of its host

Question 8

which organism has the greater reproductive potential - parasite or host

Answer 8

parasite

Question 9

what does it mean that parasites are degenerate

Answer 9

they lack structures and organisms found in other organisms

Question 10

what does it mean if a parasite is an endoparasite

Answer 10

lives within the tissues of its host

Question 11

what does it mean if a parasite is an ectoparasite

Answer 11

lives on the surface of the host

Question 12

do most parasites require one or many hosts to complete their lifecycle

Answer 12

many

Question 13

what is the definitive host

Answer 13

the organism on or in which the parasite reaches sexual maturity

Question 14

what role do vectors play

Answer 14

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

Question 15

what does plasmodium cause

Answer 15

malaria

Question 16

how does plasmodium cause malaria in humans

Answer 16

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

Question 17

what causes the human disease schistosomiasis

Answer 17

schistosomes

Question 18

how do schistosomes cause schistosomiasis in humans

Answer 18

they reproduce sexually in the human intestine.
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

Question 19

what are viruses

Answer 19

parasites that can only replicate inside a host cell

Question 20

what do viruses contain

Answer 20

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

Question 21

what are some viruses surrounded by

Answer 21

a phospholipid membrane derived from host cell materials

Question 22

what does the outer surface of a virus contain

Answer 22

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

Question 23

what are the stages of viral life cycle

Answer 23

infection of host cell with genetic material
host cell enzymes replicate viral genome
transcription of viral genes
translation of viral proteins
assembly and release of new viral particles

Question 24

what do the RNA retroviruses use to form DNA

Answer 24

the enzyme reverse transcriptase

Question 25

what happens once the RNA forms DNA

Answer 25

it is inserted into the genome of the host cell. viral genes can then be expressed to form new viral particles