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Organisms and Populations — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYOrganisms and Populations5 Marks
Question

i. Which of the above represents the increase or decrease of population?
ii. If N is the population density at time $t$, then what would be its density at time $(t+1)$ ? Give the formula.
iii. In a barn there were $30$ rats. $5$ more rats enter the barn and $6$ out of the total rats were eaten by the cats. If $8$ rats were born during the time period under consideration and $7$ rats left the barn, find out the resultant population at time $(t+1)$.
iv. If a new habitat is just being colonized, out of the four factors affecting the population growth, which factor contributes the most?
✓

Answer

  1. a and d represents increase of population and b and c represent decrease of population.
  2. $N_t+1 = N_t + [(B + I) - (D + E)]$
  3. Here, $N_t = 30;$
$I = 5; E = 7;$
$D = 6;$
$B = 8$
Putting the value in $Nt + 1$
$= N_t + [(B + I) - (D + E)] N_t + 1$
$= 30 + [(8 + 5) - (6 + 7)]$
$= 30 + [13 - 13]$
$= 30 + 0$
$= 30$ rats.
  1. Immigration contributes the most.

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