The controlled experiments are performed by the scientists, when they want to study the changes in the sample on changing a single variable. So, the correct answer is option (b).
In case, all variables are kept same, no changes would be observed in the experiment sample. A controlled experiment can be performed on living thing as well as non living. But, controlled experiment cannot be performed on the things which are influenced by a lot of variables, as they cannot create realistic results. So, the option (a), (c), and (d) are incorrect.
Answer: gas in the air, pollution
Explanation:
In order to produce an effective immune response within the body, the person must be injected with a dosage of a virus or bacteria, and for it to be allowed to grow in the person, which replicates just enough to stimulate a response from the immune system.
Answer:
In in vitro plant tissue culture, indolbutyric acid and other auxins are used to initiate root formation in a procedure called micropropagation. The micropropagation of plants is an asexual propagation or propagation technique that is based on the organogenetic potential of plant cells, which consists of cultivating in vitro on appropriate substrates, isolated cells, portions of yolk meristems, vegetative apices at the beginning of their development or microstaquillas. Small samples of plants used are called explants. Auxins such as indolbutyric acid can be used to cause mass formation of undifferentiated cells called corns. Callus formation is often used as a first step in the micropropagation process since, by exposure to certain auxin hormones, callus cells can be induced to form other tissues such as roots.
Indolbutyric acid is often used to promote the rooting of stakes. In a study in Camellia sinensis, the effect of three different auxins, indolbutyric acid, indolacetic acid and 1-naphthalenacetic acid on root formation was measured. According to the authors, indolbutyric acid produced a higher root yield compared to other auxins.9 This effect of indolbutyric acid is consistent with that found in other studies; This hormone is considered the most commonly used auxin for root formation, 10 because it is much more potent than indolacetic acid and other synthetic auxins.7
Jatropha curcas is a species in which there is an improvement in the quality of the rooting of the stakes with the addition of indolbutyric acid in the middle (longer root length, number of roots, percentage of rooted stakes, and dry root weight) , 11 although not always the effect on rooting is statistically significant.
