n the search to discover the agents that cause mad cow disease, scrapie in sheep, and CJD and kuru in humans, diseased brain tis
sues were passed through a fine filter to remove bacteria. The filtrate was still infectious, indicating that something smaller than bacteria, either viruses or organic molecules, must be the causative agent. If a virus was responsible for these brain diseases, then the infectious agent would contain either RNA or DNA. Other possibilities were that the agent was a carbohydrate, fat, or protein. Tissue filtrates were treated with agents that destroyed just one of these chemicals and then injected into a healthy animal, with the results as follows. What is the infectious agent? •Amylase digests carbohydrates; tissue filtrate still infects healthy test animal. •Lipase digests fats; tissue filtrate still infects healthy test animal. •Formaldehyde and/or heat denatures DNA and RNA; tissue filtrate still infects healthy test animal. •Trypsin digests protein; tissue filtrate does not infect healthy test animal.
Pathogens may be defined as the disease causing organism and capable of inducing immune response in the organisms. The organisms that can acts as pathogen are virus, bacteria and nematodes.
Different experiments have been performed to find the infectious agent. The digestion of trypsin protect the animals from the disease. This means the infectious agent must be protein as the protein digestion disrupts the pathogenicity of the organism.
A predator can be defined as an organism that makes the other organisms die to obtain them as food. Prey is the living being which is typically inferior and killed by the predator. Adaptation is a change in the physiology, morphology and genetic makeup of the organism which makes it suitable for survival in an unfavorable environment. Natural selection is the differential survival and reproduction of the organisms which exhibit better traits over the others
The population of the mottled fish is likely to increase due to natural selection. As the mottled fish color pattern match with that of the mottled background of the bottom of the lake. This will help the mottled fishes to camouflage the predator wading birds. These mottled fishes will remain undetected from the predator wading birds. The trait of the mottled pattern will be adapted by the light sandy brown fishes and the trait will be passed on the next generation as well. Hence, the proposition of the mottled fish will increase
Hence, the right answer is "the proportion of mottled fish will increase over time"
Frogs have smooth or slimy skin that is moist, whereas toads have thicker, bumpy skin that is usually dry. All toads are poisonous, while frogs are not.
