89.Which statement is correct for r-selected species?
(1) Large number of progeny with large size
(2) Small number of progeny with large size
(3) Large number of progeny with small size
(4) Small number of progeny with large size

Introduction

In ecology, r-selected species are known for their rapid reproductive strategies, allowing them to thrive in unpredictable and changing environments. The core of r-selection is producing many offspring with minimal investment in each, a tactic that increases the odds that some will survive despite high mortality risks. But what exactly is the hallmark feature of r-selected species? Let’s explore the correct answer and why it matters.

The r-Selection Strategy

r-Selected species are adapted to environments where resources can be abundant but unpredictable, and where population densities fluctuate widely. Their evolutionary strategy is to maximize reproductive output, focusing on quantity over quality.

Key Traits of r-Selected Species

• Early sexual maturity: Individuals reproduce at a young age.

• Short life span: Life cycles are rapid, allowing for multiple generations in a short period.

• Minimal parental care: Offspring are usually left to fend for themselves.

• Small body size: Both adults and offspring tend to be small.

• High fecundity: Many offspring are produced in each reproductive event.

Evaluating the Options

Let’s consider the provided choices:

1. Large number of progeny with large size

   • Not typical. Large offspring require more resources per individual, which is not the r-selected way.

2. Small number of progeny with large size

   • This describes K-selected species, which invest heavily in each offspring.

3. Large number of progeny with small size

   • Correct!

   • This is the classic r-selected strategy: produce many small offspring, each with a low probability of survival, but with the hope that at least some will make it to adulthood.

4. Small number of progeny with large size

   • Again, this is a K-selected trait.

Why Produce Many Small Offspring?

• Survival in Unpredictable Environments:
  By producing many small offspring, r-selected species ensure that at least some will survive sudden changes, predation, or resource shortages.

• Rapid Colonization:
  High offspring numbers allow these species to quickly colonize new or disturbed habitats.

• Minimal Investment per Offspring:
  Less energy is spent on each individual, allowing parents to maximize the number of progeny.

Examples of r-Selected Species

• Insects: Houseflies, mosquitoes, and aphids lay hundreds of eggs, most of which do not survive.

• Annual plants: Weeds and grasses produce abundant seeds, many of which never germinate.

• Small fish and amphibians: Many lay thousands of eggs with little or no parental care.

r-Selected vs. K-Selected Species: A Quick Comparison

Conclusion

The correct statement for r-selected species is:
They produce a large number of progeny with small size.

This strategy is highly effective in unpredictable environments, ensuring population persistence through sheer numbers rather than high investment in individual survival.

Correct answer:
(3) Large number of progeny with small size