The fertility rate is much higher in africa done in the united states describe the difference between these two regions that causes the difference in fertility rates

Due to the differences in education, medical services and ideology of reproduction

Explanation:

The difference between the fertility rate is majorly due to the distinction is social practices such as

a)US literacy rate is high and hence they are more aware towards having safe sex and that too at a specific age. While in Africa majority of people are illiterate and get involve into sexual activity without any knowledge irrespective of their time

b)People in US prefer to have sex with protection and hence they do not reproduce every time they have sex while in African countries sex is performed without protection and hence there are high chances of reproducing.  

c)In US people give birth to child when they are capable enough to support his/her need and demand, while in African countries people prefer to have children as a mode of support in their old age.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]