How dose ecosystem behave as a system

Which of the following statements is true? 1. the mantle of the earth is made of solid nickel and iron. 2. the crust of the earth is made of solid nickel and iron. 3. the inner core is made of solid nickel and iron.

Many people try to eliminate fat from their diets. which is one reason it is necessary for humans to eat fat? a. eating fat is the fastest way to get energy. b. fat eliminates triglycerides from the body. c. saturated fats clear out the blood vessels. d. fat nerves transmit signals. , this is for apex in summer school.

Most animal cells membranes have proteins that pump ions out of the cell and potassium ions into the cell