Botany MCQs for NEET — Practice Questions with Answers

A 'steeper slope' (higher Z value) means that for a given increase in area, there is a proportionally larger increase in species richness. The question asks for the significance of steeper slopes mentioned in the context for specific examples.

While not explicitly stated as 'conservation planning', the underlying implication of understanding how species richness changes with area is vital for ecological studies and conservation efforts, especially in the context of biodiversity conservation. The question (4) given in the first excerpt 'What is the significance of the slope of regression in a species – area relationship?' points to its importance.

The NCERT text states: 'Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar).'

Mendel's studies mainly described those traits that have distinct alternate forms such as flower colour which are either purple or white. Human skin color, however, is an example of polygenic inheritance, which is not distinct and is spread across a gradient, unlike the traits Mendel studied.

According to the NCERT text, 'Such traits are generally controlled by three or more genes and are thus called as polygenic traits. Besides the involvement of multiple genes, polygenic inheritance also takes into account the influence of environment. ... In a polygenic trait the phenotype reflects the contribution of each allele, i.e., the effect of each allele is additive.'

The NCERT text states: 'The genotype with all the dominant alleles (AABBCC) will have the darkest skin colour and that with all the recessive alleles (aabbcc) will have the lightest skin colour.'

The NCERT text defines this: 'There are however instances where a single gene can exhibit multiple phenotypic expression. Such a gene is called a pleiotropic gene.'

The NCERT text explains: 'The underlying mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways which contribute towards different phenotypes.'

The text states: 'For example, in humans we don’t just have tall or short people as two distinct alternatives but a whole range of possible heights. Such traits are generally controlled by three or more genes and are thus called as polygenic traits.'

The NCERT text says: 'As expected the genotype with three dominant alleles and three recessive alleles would have an intermediate skin colour.' An individual with three dominant alleles (e.g., AaBbCc) would have an intermediate phenotype.