Question

Imagine that you are constructing a life table like Table 53.1 for a different population of Belding’s ground squirrels. If 485 individuals are alive at the start of year 0–1 and 218 are still alive at the start of year 1–2, what is the proportion alive at the start of each of these years (see column 3 in Table 53.1)?

Short answer

The proportion of alive Belding’s ground squirrels at 0-1 year will be \(485 \div 485 = 1.0\), and in 1-2 years, it is \(218 \div 485 = 0.449\).

Step-by-step solution

Biotic and abiotic factors that affect population density

The reproductive success of any population depends on biotic factors and abiotic factors. Biotic factors include food, mates, competitors, predators, and diseases.

The abiotic factors include geographical area, temperature, climate, natural disaster, and availability of sunlight. The factors which decrease the population density are referred to as density-dependent limiting factors.

Life tables

Life tables are constructed to understand the survival and reproductive rates of the members of any population. The fate of the cohort, the members of a population from birth to death, is followed to formulate the life table.

The proportion of cohort in every age group is required to construct the life table. The tracking of produced individuals in each age group is also necessary.

Life table of Belding’s ground squirrels’ population

At the age of 0-1 year, 485 individuals are alive. At the beginning of the year, the proportion rate is calculated by dividing the number of populations by the alive number. That is,\(485 \div 485 = 1.0\). At the age of 1-2, only 218 individuals are alive. Therefore, the proportion of alive rate at 1-2 years would be \(218 \div 485 = 0.449\).

1.0 indicates that all 485 individuals are alive at the beginning, and at the age of 1-2, only 0.449 proportion of individuals are alive.