A flea is a tiny wingless insect with a flat body designed to easily navigate through
animal hair. Fleas tend to live on furred mammals and have mouth parts designed
to suck blood from these mammals. The animals which carry the flea derive no
known benefits from the flea. Which of the following best describes the interactions
between fleas and mammals?
A Parasitism, because the flea is benefitting and the mammal is harmed.
B. Predation, because the flea obtains its energy from the mammal's blood.
Predation, because the flea may transmit diseases to the mammal.
D. Parasitism, because the flea is benefitting and the mammal is not harmed.

A. Parasitism, because the flee is benefitting and the mammal is harmed.

Explanation:

Parasitism is when one organism which is a parasite lives on another which is the host, and gaining benefits from it and at the same time maiming havoc to it. Parasitism is common among living organisms. Animals are most times the host to a range of parasitic organisms which include viruses, bacteria, fungi,protozoa, also flea, tick, mites etc.

Parasites like fleas, tick and leeches live on the body surface of their host, which is make them ectoparasites while those that live inside their hosts are endoparasites.

A is the answer. The flea is benefitted by the dog´s blood but the dog is harmed.

the right is separation by density .

take the blood which is a good example of a heterogeneous mixture.

blood is a vital liquid in our body, which transports oxygen from the air to our lungs so we can breathe. it is also used to eject wastes, such as carbon dioxide, to bring cells and molecules of the immune system to the tissues, and to spread hormones throughout the body. it corresponds to plasma, red blood cells, white blood cells, platelets and hemoglobins combined.

in medical tests centrifugal force is used to separate the different components of the blood.

in general, the centrifugation will allow to separate and analyze the different components of the blood, to know if the rate of white blood cells in the blood of a patient, for example, is normal, and therefore to know if his system immune is integrity.

under the action of centrifugal force, the solid components in the blood are drawn to the bottom of the tube in which the blood is contained. the centrifugal force then acts as an accelerated settling. it separates plasma from red blood cells and white blood cells.