NEET Test 54

A black body is a body that has high absorptivity and high emissivity. So if any radiation falls on it, it can absorb at all and also able to emit all the radiation.
 Note: There is no perfect black body in the universe.
 

• A black hole does not emit anything other than Hawking radiation so it can't be.

• Red roses do not absorb red color.

• green leaves do not absorb green color.

• A Blackboard can absorb all radiation.

To find the empirical formula first Get the mass of each element by assuming a certain overall mass for the sample (100 g is a good mass to assume when working with percentages). Here the mass will be same as the percentages in 100g. Now, Convert the mass of each element to moles and then find the ratio of moles of each element. 

For Carbon = 1.256/1.256 moles 

For Hydrogen = 6.289/1.256 = 5 

For Oxygen = 4.39/1.256 = 3.50 

Hence the empirical formula is C₁₀H₇O₂

• Any organisms or plants who can not regulate their internal environment and their body temperature changes with ambient temperature are known as conformers.
• E.g., the osmotic concentration of body fluids in aquatic animals, changes with that of ambient water osmotic concentration, therefore they act as conformers.
• Conformers had not evolved to become regulators because-

(a) Thermoregulation and osmoregulation mechanisms are energetically expensive for many organisms particularly for small animals like shrews and humming birds.
(b) Small animals relative to their volume have large surface area due to which they lose body heat very fast when it is cold outside. Therefore, they have to spend much energy to generate body heat through metabolism.

(a) Natality is the number of births during a given period of time in the population that are added to the initial density. 
(b) Mortality is the number of deaths in the population during a given period. 
(c) Immigration is the number of individuals of the same species that from somewhere came into the habitat during the time-period under consideration. 
(d) Emigration is the number of individuals of the population who had left the habitat and gone elsewhere during the time-period under consideration. 

• Population size will increase; if number of (B + I) > Number of (D + E)
• Where, B = number of births (Natality), I = number of immigrants, D = number of deaths (Mortality), E = number of Emigrants.

• Relative density of a species is the ratio of total number of individuals of species per total number of individuals of all species multiply by 100.
• In certain cases, there is no need to know absolute population densities in such cases relative densities serve the purpose equally well.
• E.g., relative density is used for measuring out the total density of fishes in a lake by counting the number of fishes caught per trap.
• Relative density can be calculated by following formula-

Relative density of a species= Total number of individuals of species / total number of individuals of all species* 100.

• Biomass is the mass of living biological organisms in each area or ecosystem at a given time.
• Indirect count- Population size measurement can also be carried out indirectly without counting or seeing the organisms.
• Total number- Counting all the individual of space.