Crossing over occurs at the four-strand stage when two homologous chromosomes, each consisting of a pair of sister chromatids, are paired. Each crossover involves just two of the four strands and generates two recombinant strands.
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Answer:
1) Skull and Vertebral column
2) Meninges
3) Cerebrospinal fluid.
Explanation:
Central Nervous system:
CNS is the abbreviation of Central Nervous system. CNS controls the whole body functions so it is the most important component of the body. CNS consist of two parts 1) Brain and 2) Spinal cord
Both of these organs are very important and hence need to be protected. Nature provided these organs with certain protective mechanisms these includes
1) Skull and Vertebral column:
Skull is present around brain and vertebral column is present around spinal cord. These structure provides mechanical support to soft parts of CNS.
2) Meninges:
These are the membranes that provide antiseptic environment to the brain and hence protect it from microbes and other harmful substances.
3) Cerebrospinal fluid:
This fluid is present inside meninges which nourishes the brain and protect it from mechanical stresses.
Id say it would be 59 milliseconds
Answer : B is the heaviest puppy amongst all.
Explanation : There are three comparisons shown in the figure, out of which B is assumed to be heaviest amongst all on the basis of following assumptions.
When weighing A and C puppy, A was found to have lighter weight than C. So, in this case C is the heavier puppy.
In second case, when C and D are weighed, both are found to be equal in weight.
Then last comparison was with B and D puppies where, D was observed to be of light weight and B proved to be the heaviest.
Therefore, the conclusion is that B is the heaviest puppy in comparison with rest others.
