Answer:
a prezygotic barrier
Explanation:
Both wild tigers and lions are said to be reproductively isolated.
Reproductive isolation is defined as the existence of barrier between organisms of different species such that they cannot reproduce.
The mechanisms of reproductive isolation varies. While some act to prevent the formation of zygotes (in case of mating) between organisms of different species, some ensures that the resulting zygotes are invalid.
Reproductive isolation mechanisms that act to prevent fertilization and formation of zygotes are referred to as prezygotic mechanisms while those that ensure that invalid zygotes result (in case of successful fertilization) are referred to post zygotic mechanisms.
<em>The natural differences in the ranges of wild tigers and lions ensure that both animals do not mate with each other, let alone results in zygote. This is a form of pre-zygotic reproductive isolation mechanism.</em>
Answer:
It decreases the levels of cAMP in the cell, repressing transcription from the lac operon.
Explanation:
When glucose is absent, cAMP serves as coactivator binds to CRP, the catabolite gene activator protein. The CRP-cAMP complex binds to the site near the lac promoter and stimulates the expression of the operon by RNA polymerase many folds.
Catabolite repression refers to inhibition of the synthesis of enzymes of lactose catabolism when glucose is present as an energy source. In the presence of glucose, synthesis of cAMP is inhibited resulting in its lower cellular concentration. The lower cAMP levels do not allow the binding of cAMP and CRP. The result is reduced expressed of lac operon.
Answer:
a steep temperature gradient in a body of water such as a lake, marked by a layer above and below which the water is at different temperatures.
Explanation:
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Answer:
the first one is plants
the second one is animals
the third one is plants
the fourth one is animals
Answer:
The kidney consists of an inner renal medulla and an outer renal cortex. Between these is a flow of Nephrons. They work together to create urine.
