So that the next generation could inherit the previous adaptations and instinct and be similar to the parents. if that didn't happen, a cat might give birth to a giraffe
Answer
Applying Wein's displacement

1) for sun T = 5800 K


2) for tungsten T = 2500 K


3) for heated metal T = 1500 K


4) for human skin T = 305 K


5) for cryogenically cooled metal T = 60 K


range of different spectrum
UV ----0.01-0.4
visible----0.4-0.7
infrared------0.7-100
for sun T = 5800
λ 0.01 0.4 0.7 100
λT 58 2320 4060 5.8 x 10⁵
F 0 0.125 0.491 1
fractions
for UV = 0.125
for visible = 0.441-0.125 = 0.366
for infrared = 1 -0.491 = 0.509
The potential energy decreases while the kinetic energy increases.