When wild plant and animal populations are logged, fished, or hunted, only the oldest or largest individuals tend to be taken. Many of the commercially important species are long lived and are slow to begin reproducing. If harvesting is not regulated carefully and exploitation is intense, what impact does harvesting have on a population's age structure? How might harvesting affect the population's life table and growth rate?

Verified step by step guidance

1. Identify the impact on age structure: When only the oldest or largest individuals are harvested, the age structure of the population shifts towards younger individuals. This reduces the proportion of mature, reproducing individuals in the population.
2. Understand changes in the life table: The life table, which summarizes the survival and reproductive rates of individuals at each age, will show higher mortality rates for older age classes due to harvesting. This can lead to fewer individuals reaching reproductive age, altering the overall fecundity (birth rates) of the population.
3. Analyze the effect on population growth rate: With fewer mature individuals to reproduce, the growth rate of the population may decline. This is because the growth rate is dependent on birth rates minus death rates, and with harvesting, the death rate of reproductively mature individuals increases.
4. Consider genetic implications: Selective harvesting of the largest or oldest can also lead to a genetic shift in the population. Traits that might have contributed to longevity or size might become less common, potentially affecting the health and viability of future generations.
5. Evaluate the need for regulation: To prevent negative impacts such as population decline or genetic shifts, it is crucial to implement and enforce sustainable harvesting practices. Regulations might include limits on the size or age of individuals that can be harvested, or setting quotas on the number of individuals that can be taken from a population.

Key Concepts

Population Age Structure

Population age structure refers to the distribution of individuals of different ages within a population. It is crucial for understanding reproductive potential and survival rates, as different age groups contribute differently to population dynamics. In the context of harvesting, targeting older individuals can skew this structure, leading to a decline in younger, reproductive individuals and potentially reducing the population's ability to sustain itself.

Life Table

A life table is a demographic tool that summarizes the survival and reproduction rates of individuals at various ages within a population. It provides insights into the life expectancy and reproductive output of different age classes. Harvesting practices that disproportionately remove older individuals can alter the life table, leading to decreased overall survival rates and potentially affecting future population growth.

Population Growth Rate

Population growth rate is the rate at which the number of individuals in a population increases or decreases over time, influenced by birth rates, death rates, immigration, and emigration. Intense harvesting can reduce the growth rate by removing key reproductive individuals and disrupting age structure, ultimately leading to population decline. Understanding this concept is essential for managing sustainable harvesting practices.