Question

Radioactive isotopes have____. excess electrons insufficient neutrons insufficient protons excess neutrons excess protons What can result in speciation within a few generations? change in environmental conditions the introduction of a new predator into an area postzygotic isolating mechanisms development of a physical barrier polyploidy an sing in a plant species Which characteristic of a chloroplast makes it appear green? The outer membrance The stroma The chlorophyll The inner membrane The plastid Which interval below is classified as a "period" in the geologic time scale rather than an "era''? Carboniferozoic Cenozoic Paleozoic Mesozoic Proterozoic

Answer 1

Question 68

d. excess neutrons

(The stability of nucleus is dependent on the ratio of protons and neutron. In radioactive isotopes, the number of neutrons is more than protons and as a result the nucleus becomes unstable which is reflected as emission of alpha, beta and gamma rays)

Question 69

e. polyploidy arising in a plant species

(There are two kinds of polyploidy namely autopolyploidy and allopolyploidy which cause reproductive isolation and rapid change in speciation. It is estimated that around 30 - 70 % of angiosperms and 95 % of ferns have arisen as a result of polyploidy)

Question 70

c. the chlorophll

(Chlorophyll molecules in chloroplast are responsible for imparting green color. These molecules are also called as photoreceptors and exist as chlorophyll a or chlorophyll b. The different side groups and delocalised polyenes in these molecules absorbs most of energy in the blue / red parts of the spectrum whereas green region of spectrum is reflected back which imparts green color to chloroplasts)

Question 71

a. carboniferozoic