The skin is an example of a non-specific defense.
For example, bacteria or diseases have trouble entering a healthy person's skin because it is formed by closely packed cells with multiple layers and a substance called keratin that protects is.
On the other hand, the immune system is a specific defense mechanism.
When bacteria is able to enter the body in cases of fever for example, the immune system is activate and sends out protector cells such as the white blood cells to combat infection.
As you move down a group, atomic radius increases
C. The nuclear envelope contains the nucleus and forms a barrier between it and the cytoplasm
Answer:
6400 years
Explanation:
Given that;
N/No =(1/2)^t/t1/2
No = amount of radioactive material originally present
N = amount of radioactive material present at time t
t= time taken for N amount of radioactive material to remain
t1/2 = have life of the radioactive material
2.5/40 = (1/2)^t/1600
1/16 = (1/2)^t/1600
(1/2)^4 = (1/2)^t/1600
4 = t/1600
t = 4 * 1600
t = 6400 years
