Mutation can cause instant adaptation while natural selection is the process by which adaptation occurs over a series of generations.
I would guess that the answer would be :'<span>These organisms dig more shallow burrows than they used to.</span>' If the crabs actively dig burrows, as many crab species do, and a layer of oil has persisted in the lower soil strata, it makes sense that the crabs would be reducing the depths of their burrows to avoid contact with the oil. The other possibility is that the crabs might might migrate to deeper waters, but this is less likely because the crabs would be evolved to utilise the intertidal zone.
Answer:
Over 95% of incoming ultraviolet radiation is absorbed in :
A. The Stratosphere.
Explanation:
- Stratosphere is the second layer of the earth's atmosphere that lies next to the troposphere.
- This layer experiences very little turbulence of air and is very significant because of the presence of Ozone layer in it.
- The UV rays entering the Earth's atmosphere, photo dissociates ozone into O₂ and O. But these molecules quickly recombine to form ozone.Thus, stabilizing the concentration of ozone in the atmosphere.
- During this photo dissociation UV radiations loses much of its energy. Thus, 95% of incoming Ultraviolet radiation gets absorbed in the Stratosphere.
- Absorption of ozone UV radiation increases exponentially with the thickness of ozone layer.
Answer:
c. ¼ heavy, ¾ light
Explanation:
DNA replication follows semi conservative model which means that both the strands separate during replication and the newly formed DNA molecule has one old and one new strand. If instead of semi conservative, conservative mechanism is used, old strands will not separate from each other and the two newly synthesised DNA strands will come together to form a DNA molecule.
Here the cells were first grown in heavy 15N medium so all the DNA molecules had 15N and thus were heavy. Then the cells were transferred to 14N medium where only lighter 14N were available for replication process.
In first generation, 14N DNA molecules were synthesised from 15N DNA molecules so 1/2 DNA molecules were 15N and other half were 14N. In the second generation, 14N molecules will give rise to new 14N molecules and 15N molecules will also give rise to 14N molecules hence 1/4 molecules will be 15N (heavy) and 3/4 will be 14N (light).
