Shortcut Methods and Tricks:

1. Percentage calculation: To find the percentage of bones in the axial skeleton:

Percentage = (Number of axial skeleton bones / Total number of bones) × 100

Percentage = (80 / 206) × 100 ≈ 38.84%

2. Determining the number of sarcomeres: To calculate the number of sarcomeres in a myofibril:

Number of sarcomeres = Length of myofibril / Length of one sarcomere

Number of sarcomeres = (2.5 cm / 2 μm)

Since 1 cm = 10,000 μm, we can convert the myofibril length to micrometers:

Number of sarcomeres ≈ (2.5 cm × 10,000 μm / cm) / (2 μm) ≈ 12,500 sarcomeres

3. Calculating average heart rate: To find the average heart rate:

Average heart rate = (Upper limit + Lower limit) / 2

Average heart rate = (100 bpm + 60 bpm) / 2 = 80 bpm

4. Estimating total neurons in brain: To approximate the total number of neurons in the brain:

Total neurons ≈ Neurons in cerebral cortex + Neurons in rest of brain

Total neurons ≈ 86 billion + 14 billion ≈ 100 billion neurons

5. Estimating total cell membrane surface area: To estimate the total surface area of cell membranes:

Total surface area = Number of cells × Surface area per cell

Assuming a spherical shape for simplicity, the surface area per cell can be approximated using the formula for the surface area of a sphere:

Surface area per cell = 4πr2

where r is the radius of the cell. Let’s assume an average cell radius of 10 micrometers (μm).

Surface area per cell ≈ 4π(10 μm)2 ≈ 1257 μm2

Therefore, the total surface area of cell membranes:

Total surface area ≈ 1000 cells × 1257 μm2 ≈ 1,257,000 μm2