I think it may be conservation.
Circulatory system.....circulates blood (a vital delivery system of oxygen) throughout the whole body when tissues need it the most and with a constant supply.
Answer:
The suprachiasmatic nuclei enable the nervous system to respond to daily light/dark alterations through their stimulation of melatonin.
Explanation:
Melatonin is a hormone produced naturally by the body. Its function is to regulate the body's circadian cycle. This hormone is stimulated and begins to act by changing between a light environment and a dark environment. This stimulation interacts with the suprachiasmatic nuclei making the nervous system understand this change and luminosity of the environment and respond to the action of melatonin.
Answer:
Mutation, Gene flow/Migration/Immigration of gene and Recombination
Explanation:
For any species there are majorly three sources of genetic variations –
a) Mutation – This leads to change in the genetic code with in the DNA of an organism. Sometimes mutation does not produce any effect on the organism. Mutation can produce both positive and negative impact. Its effect is observed in long run as its rate is slow.
b) Recombination – When an organism undergoes sex, his/her genes recombine with the genes of mating partner. The rate of recombination is faster than the rate of mutation
c) Gene flow /Migration/Immigration of gene – In this gene travel from one set of population to the other. The frequency of gene in the mixed population lies between the original population gene frequency and the migrated or donor population gene frequency
Do you have any choice answers? As far as I know, the organisms that appeared first was micro-organisms. Hope this helps.
