Molecular recognition in adaptive immunity is based on a large array of receptors, each of which identifies a characteristic present exclusively on a specific portion of a specific molecule in a specific pathogen. As a result, adaptive immunity recognizes and responds with amazing specificity.

The adaptive immune response, also known as the acquired immune response, develops more slowly after the innate immune response. This immune response is increased by prior exposure to the invading pathogen, as indicated by the terms adaptive and acquired.

Adaptive reactions include the production of proteins that inactivate a bacterial toxin and the targeted kilowatt-hour.

• The term hemocytes refers to the major immune cells of insects are called hemocytes.

The attached image shows Phagocytosis, for which this diagram depicts events in the ingestion and destruction of pathogens by a typical phagocytic cell.

One kind of hemocyte generates a defensive chemical that aids in the entrapment of big pathogens such as Plasmodium, the single-celled mosquito parasite that causes malaria in humans. Many additional hemocytes produce antimicrobial peptides that circulate throughout the insect's body and inactivate or kill fungus and bacteria by disrupting their plasma membranes.

Insects' innate immune responses are tailored to certain disease groups. When a fungus infects an insect, recognition proteins attach to fungal cell wall components, activating a transmembrane receptor called Toll.

Toll then stimulates the synthesis and release of antimicrobial peptides that particularly kill flies.

Physical and chemical barriers, as well as cell-based defenses, mediate innate immunity in both invertebrates and vertebrates. Recognition proteins specific for wide groups of pathogens are required for the activation of innate immune responses.

Most mollusks and arthropods have an open circulatory system in which the hemolymph bathes organs directly.

Vertebrates have a closed circulatory system, which means that blood flows through a network of pumps and arteries.

Blood, blood arteries, and a two- to four-chambered heart comprise vertebrates' closed circulatory system. Blood pumped by the ventricle of the heart travels to the arteries and then to the capillaries, which are sites of chemical interaction between blood and interstitial fluid.

Veins transport blood from the capillaries to the atrium, which then transports it to the ventricle. The circulation of fish, rays, and sharks is facilitated by a single pump. Two pumps are coupled in a single heart in air-breathing vertebrates.

Circulatory systems connect exchange surfaces to cells all over the body. A gastrovascular cavity promotes exchange between the environment and cells that may be accessed via diffusion in animals with basic body designs.

Because diffusion over large distances is sluggish, most sophisticated creatures have a circulatory system, the number, and separation of which reflect adaptations to varied habitats and metabolic demands. The lymphatic system, which also protects against infection, removes fluid from capillaries and returns it to the blood.

In animals, double circulation is driven by coordinated cycles of cardiac contraction.

The right ventricle is responsible for pumping blood to the lungs, where it loads O2 and unloads CO2. The left atrium receives oxygen-rich blood from the lungs, which is then pushed to the bodily tissues via the left ventricle. The right atrium is where blood returns to the heart.

The cardiac cycle, which is the full sequence of the heart's pumping and filling, consists of a time of contraction, known as systole, and a period of relaxation, known as diastole. The pulse (the number of times the heart beats per minute) and cardiac output (the volume of blood pumped by each ventricle per minute) can be used to measure heart function.

The heartbeat is initiated by impulses from the right atrium's sinoatrial (SA) node (pacemaker). They cause atrial contraction, which is subsequently delayed at the atrioventricular (AV) node before being carried through the bundle branches and Purkinje fibers, causing ventricular contraction.

The neurological system, hormones, and body temperature all have an impact on the pacemaker.

Whole blood is made up of cells and cell fragments (platelets) floating in plasma, a liquid matrix. Plasma proteins have an effect on blood pH, osmotic pressure, and viscosity, as well as lipid transport, immunity (antibodies), and blood coagulation (fibrinogen). Red blood cells, also known as erythrocytes, carry oxygen.

White blood cells, or leukocytes, are made up of five different kinds that fight bacteria and foreign substances in the blood.

Platelets play a role in blood clotting by initiating a chain reaction that transforms plasma fibrinogen into fibrin.

A multitude of illnesses impedes the circulatory system's function. An abnormal type of hemoglobin affects erythrocyte structure and function in sickle cell disease.

A gas undergoes net diffusion from where its partial pressure is greater to where it is lower at all gas exchange locations. Because air has a greater O2 concentration, lower density, and lower viscosity than water, it is more favorable to gas exchange.

The form and arrangement of respiratory surfaces are different amongst animals. Gills are body surface out folding that are specialized for gas exchange in water. Ventilation and countercurrent exchange between blood and water improves the efficiency of gas exchange in some gills, notably those of fish. Insects use a tracheal system, which is a branching network of tubes that transports O2 directly to cells.

Breathing mechanics differ greatly amongst animals.

Positive pressure breathing, which drives air down the trachea, is used by amphibians to ventilate their lungs. Birds utilize a system of air sacs as bellows to maintain air moving through their lungs in just one direction, preventing incoming and outgoing air from mingling. Negative pressure breathing, which draws air into the lungs as the rib muscles and diaphragm flex, is used by mammals to ventilate their lungs. Incoming and exiting air mix, reducing ventilation efficiency.

Pigments that bind and transport gases are examples of gas exchange adaptations.

Gradients in partial pressure in the lungs encourage net diffusion of O2 into the blood and CO2 out of the circulation. In the remainder of the body, the situation is the inverse. Respiratory pigments like hemocyanin and hemoglobin bind O2, boosting the quantity of O2 carried by the circulatory system significantly.

Some animals have evolved characteristics that allow them to meet extreme O2 needs. Deep-diving animals accumulate O2 in their blood and other tissues and gradually deplete it.