The continents that are now separated by the Atlantic Ocean once formed a single landmass.
All of our current continents were once connected as one single landmass named Pangea. Pangea broke apart into different continents. Fossils found in Africa have been found in South America, and etc.
Explanation:
Immunity is the ability of an animal to resist infection.
There are two types of immunity in the body; INNATE OR INHERITED IMMUNITY AND ACQUIRED IMMUNITY. Inherited immunity it is the type of immunity that one is born with. It is passed from parent to offspring.
Acquired immunity is immunity to particular infections that is not inherited but has developed in the animal's life as it interacts with its environment. Acquired immunity can develop naturally in which case it is called NATURAL ACQUIRED IMMUNITY OR ARTIFICALLY.
ACTIVE IMMUNITY is the form of acquired immunity in which the body produces its OWN antibodies against infections. While PASSIVE IMMUNITY is the form of acquired immunity in which an individual is PROTECTED AGAINST INFECTION BY RECEIVING ANTIBODIES.
NATURAL ACQUIRED IMMUNITY
when attacked by the same pathogens again, they don't became seriously ill. this is because memory cells are able to recognise the antigens and stimulate the immune system to produce antibodies against the pathogens. This is known as NATURAL ACTIVE ACQUIRED IMMUNITY. It develops when one recovers from an infection.
During pregnancy, the mother passes antibodies across the placenta to the foetus. At birth the baby gets antibodies from the mother through breast milk. This is natural passive acquired immunity.
The process of having to apply a tourniquet in a person’s
leg due to injury and with continuous bleeding in order to stop it is called
hemostasis. This process, the hemostasis, is a process of having to stop the
flow of blood which is important in scenarios like this, in order for the
patient to prevent of having to lose more blood.
Striated muscles contain repeating sarcomeres of overlapping arrays of long, thin actin and thicker myosin filaments. Myosin filaments contains the myosin heads, which are enzymes that can bind to actin, split and make use of the energy from ATP. When muscle contraction starts, myosin heads bind to actin, change their configuration on actin, liberating the products of ATP hydrolysis and causing slide of the actin and myosin filaments. The action of the proteins troponin and tropomyosin on the actin filaments regulates vertebrae striated muscle contraction. The release of calcium ions from the sarcoplasmic reticulum is triggered by the nervous stimulation which causes depolarization of muscle membrane. Calcium ions bind to troponin and thus cause or allow the tropomyosin strands on the actin filament to move so that the part of the actin surface where myosin heads need to bind is uncovered. Contraction then occurs and only stops when the sarcoplasmic reticulum pumps calcium out of the muscle interior.
So basically, what triggers the uncovering of the myosin binding site on actin is the calcium ions binding to troponin and changing configuration.
