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before we proceed to discuss kin selection we should define the term altruism it refers to the behaviour pattern of an individual in the population
while explaining the concept of natural selection we have stressed the fact that natural selection is synonymous with differential or non-random
in this section you will be introduced to a variant of darwinian concept of natural selection which he termed sexual selection you may have observed
tonicity and the plant cell table 3 amount of water displaced by potato samples before and after
coevolutionary relationships between parasites and their hosts can be more complicated than between predators and their prey as in the case of
there has been a perfect coevolution between plants and herbivorous animals this has often developed into a mutually beneficial relationship whereas
predation is a process by which one organism predator eats another organism prey if the prey population is abundant the predator population also
you now know that natural seleqtion aims at evolving adaptations of organisms in response to environmental changes in the inanimate world also many
consider two species of organisms species a and species b species a has a population in a community another population species b arrives into the
from your studies in ecology you must be aware that most ecosystems are quite complex consisting of several habitats and that habitats in turn are
in the preceding block you learnt the darwinian premise of natural selection based on certain facts and deductions thereof you would have noticed
darwin while evolving the concept of natural selection laid emphasis on competition among individuals belonging to a species that is intraspecific
in this section we shall discuss a classic example of natulal selection in action in the preceding unit it was stated that natural selection always
it is generally believed that genetic drift occurs as a result of sampling error as we said earlier it occurs in small populations such as peripheral
hybrid sterility can be regarded as yet another form of interspecific sterility the offspring of the interspecific crosses are mainly sterile
in interspecific sterility the failure in mating occurs because of inability of the sperm to reach the egg in animals and the pollen to reach ovules
the second category of isolating mechanism that may permit interspecific mating but ensures reduced viability is called post-mating isolating
in certain instances differences in the morphology of genitalia between species make it impossible for normal mating to occur and sympatric species
members belonging to different species refrain from mating because of the behavioural differences between them such behavioural differences usually
ecological isolation is based on the fact that population shows preference to one habitat over the other this extensive forests become barriers to
we mentioned earlier that pre-mating mechanisms are concerned with the prevention of occurrence of interspecific crosses in such casesa the potential
in this section we are to discuss the means by which populations get separated or isolated from each other first gain the status ofsub-species and
an island may be colonised by just a few individuals or just a pair or even a single gravid female when a new population develops from these early
according to the current concept of speciation a widely distributed species should break up into partially isolated rule species the different
peripatric speciationspeciation by small populations isolated on the periphery of the distribution of the parent population can be described as