In a growing population of a country, [2018]
pre-reproductive individuals are more than the reproductive individuals
reproductive individuals are less than the post-reproductive individuals
reproductive and pre-reproductive individuals are equal in number
pre-reproductive individuals are less than the reproductive individuals
(1)
In a population where the number of pre-reproductive individuals or the younger individual is larger than the reproductive individuals, the population will increase.
Which one of the following population interactions is widely used in medical science for the production of antibiotics? [2018]
Commensalism
Mutualism
Parasitism
Amensalism
(4)
Amensalism is a relationship between organisms of different species in which an organism does not allow other organism to grow or live near it. Inhibition is achieved through the secretion of chemicals called allelochemics. Antibiotics are a kind of allelochemics produced by some microbes which in small concentration can kill or retard growth of harmful microbes without adversely affecting the host.
Asymptote in a logistic growth curve is obtained when [2017]
K = N
K > N
K < N
the value of ‘r’ approaches zero
(1)
Asymptote in a logistic growth curve is obtained when carrying capacity (K) reaches the population density (N), i.e., K = N.
Mycorrhizae are the example of [2017]
amensalism
antibiosis
mutualism
fungistasis
(3)
Mycorrhiza is a mutualistic interaction between a fungus and roots of higher plants.
Which of the following is correct for r-selected species? [2016]
Large number of progeny with small size
Large number of progeny with large size
Small number of progeny with small size
Small number of progeny with large size
(1)
Organisms that are r-selected (r-strategists) able to colonise a habitat rapidly, utilising the food and other resources before other organisms are established and begin to compete. The r-strategists tend to be relatively small organisms with short life spans (e.g., bacteria) and often live in temporary or unstable environments; characteristically their survival depends on their ability to produce large numbers of offspring rather than on their ability to compete.
If ‘+’ sign is assigned to beneficial interaction, ‘–’ sign to detrimental and ‘O’ sign to neutral interaction, then the population interaction represented by ‘+’ ‘–’ refers to [2016]
mutualism
amensalism
commensalism
parasitism
(4)
Parasitism is an association in which one organism (the parasite) lives on (ectoparasitism) or in (endoparasitism) the body of another organism (host), from which it obtains its nutrients. This association is beneficial for the parasites as they get continuous supply of nutrients from their host and are able to rapidly multiply their numbers. But it is detrimental for the host organism as parasitic infection leads to various complications and diseases in the host body may also be fatal to the host under certain circumstances.
The principle of competitive exclusion was stated by [2016]
C. Darwin
G.F. Gause
Mac Arthur
Verhulst and Pearl
When does the growth rate of a population following the logistic model equal zero? The logistic model is given as dN/dt = rN(1–N/K) [2016]
when N/K equals zero
when death rate is greater than birth rate
when N/K is exactly one
when N nears the carrying capacity of the habitat
Gause’s principle of competitive exclusion states that [2016]
no two species can occupy the same niche indefinitely for the same limiting resources
larger organisms exclude smaller ones through competition
more abundant species will exclude the less abundant species through competition
competition for the same resources exclude species having different food preferences
(1)
Two or more species with closely similar niche requirements cannot exist indefinitely in the same area as sooner or later they come into competition for possession of it. This is called as Gause’s principle of competitive exclusion, which states that an ecological niche cannot be simultaneously and completely occupied by established populations of more than one species. Two species can live in same habitat but not in the same niche. More similar the two niches are, severe the competition is.
In which of the following interactions both partners are adversely affected? [2015]
Parasitism
Mutualism
Competition
Predation
(3)
Competition is the rivalry between two or more organisms for obtaining the same resources such as food, light, water, space, shelter, mate, etc. Competitors adversely affect each other.
