A biologist collects plant samples from 5 different ecosystems, finding 32, 28, 36, 30, and 34 unique species respectively. She also identifies 12 species common across all ecosystems. What is the total number of distinct plant species recorded across all sites, assuming only the common species are shared? - Coaching Toolbox

Understanding the Context

Exploring Biodiversity Across Five Unique Ecosystems

In a groundbreaking field study, a dedicated biologist has cataloged plant diversity across five distinct ecosystems, uncovering a rich tapestry of life that highlights both regional uniqueness and remarkable commonality in nature. The scientists collected samples from each site and identified between 30 and 36 unique plant species, with exact counts of 32, 28, 36, 30, and 34 species respectively.

To understand the full scope of biodiversity, researchers focused on species that appeared across all five environments. Through careful analysis, it was determined that 12 species are shared consistently throughout all five ecosystems—species commonly distributed despite differing environmental conditions.

Calculating Total Distinct Plant Species

Key Insights

Understanding the total number of distinct species requires distinguishing between unique and shared species:

• The highest single ecosystem sample recorded 36 unique species.
  
• The smallest recorded 28, but all samples contained a core set of 12 species common to every site.

Assuming no other overlap beyond these 12 species (which aligns with the minimum shared baseline), the total number of distinct plant species observed can be calculated as follows:

Let’s denote:

• Total unique samples across ecosystems: the sum across all sites minus redundant counts of shared species.

Since the 12 species are universally shared, they should only be counted once, even though they appear in each site’s tally. The remaining species in each ecosystem’s total are unique to that site:

Final Thoughts

• Ecosystem 1: 32 total – 12 shared = 20 unique
  
• Ecosystem 2: 28 total – 12 shared = 16 unique
  
• Ecosystem 3: 36 total – 12 shared = 24 unique
  
• Ecosystem 4: 30 total – 12 shared = 18 unique
  
• Ecosystem 5: 34 total – 12 shared = 22 unique

Now summing unique species from each site:
20 + 16 + 24 + 18 + 22 = 100 unique plant species

Adding the 12 shared species that appear everywhere ensures every recorded species is valid and properly included across the full ecosystem survey.

Final Calculation:

Total distinct plant species = 100 unique + 12 shared species = 112 distinct species

This comprehensive study underscores the importance of multi-site ecological sampling. Even with considerable variation in species count per ecosystem, the presence of shared species like the 12 widespread ones reveals interconnected ecological networks. The biologist’s work not only documents biodiversity but also provides a foundation for conservation planning across diverse habitats.