Answer:
The correct answer would be phenotypic variation.
Phenotype refers to observable traits or characteristics of an individual. For example, height, color, shape, et cetera.
Phenotypic variation refers to the sum total of variations in characteristics within populations of the same species.
In contrast, genotypic variation refers to the sum total of variations (such as allele frequency) present in the genome of populations of the same species.
Answer:
The photosynthetic rate refers to a determination of maximum rate at which leaves possess the tendency to fix carbon at the time of photosynthesis. The simple way by which the photosynthetic rate can be determined is by measuring the concentration of carbon dioxide produced.
It is known that the concentration of carbon dioxide, light intensity, and temperature are the three main elements, which affect photosynthesis. The enhanced concentration of carbon dioxide and higher light intensity results in higher photosynthetic rates.
In the given case where Elodea is used to study photosynthesis, it can be seen that at high light intensities, the concentration of bubbles increases as there is an elevation in the concentration of carbon dioxide.
The discovery of DNA, as well as understanding of its functioning and structure, may well be the most essential findings of the last century.
The impact of the discovery of DNA on medical and scientific advancement has been huge, whether it involves the manufacturing and creation of drugs to cure the deadly diseases or to identify the genes, which stimulate several of the diseases.
The understanding of DNA and its structural composition has led to the discovery of various technologies that helps in the fields like genetic testing, identifying viruses, crime investigation, production of genetically modified organisms, and various others.
DDT stands for dichloro-diphenyl-trichloroethane. The first kind of synthetic/artificial insecticides came into use in the 1940s. The earlier usage of DDT include: a) Killing of malarial vectors, b) Combatting Typhus and other insect borne human diseases, c) As a pest control in crops d) as a pest control in garden, live stock production and even at homes.
The negative impact of DDT could be felt for the first time when the pests that were earlier killed by use of DDT have now become pesticides resistant. In the 1950s in USA, the regulatory measures were adopted to reduce the usage of DDTs as its effects as a pesticides were no more long significant and also it was creating detrimental physical and psychological impacts on the human and environment.
It was in 1972 that the U.S. Environmental Protection Agency cancelled the order for banning the usage of DDT based on the adverse impact it produced on the environment, human and other life forms. Since then continuous studies are being conducted to analyse the impact of DDTs. In some later years it was established that DDT is the cause of producing tumors in liver.
Some of the common negative impacts produced by DDT as per the U.S. Department of Agriculture :
a) The non destructive nature – DDT can not be destroyed and thus it remains persistent in the atmosphere
b) It attacks the tissues of living organisms especially the animals and humans ( fatty tissue)
c) It can penetrate the atmosphere to deeper extent.
Now as per the current stuation, The use of DDT is controlled and other alternatives of pest control organisms is being deduced. As per the treaty of Stockholm Convention on POPs (Persistent organic pollutants) , usage of DDT for malarial control is justified but it puts a restrictive use of DDT as pesticides in other areas.
