APES Video Notes 3.2 - K-selected & r-selected species

Scientific concepts / nature phenomena presented

r-selected vs. K-selected reproductive strategies

K-selected species (“quality over quantity”)

• Typically larger and longer-lived
• Few offspring at a time with high parental investment (e.g., food, warmth, defense)
• Slower time to sexual maturity and multiple reproductive events over the lifespan
• Lower biotic potential → slower population growth
• More vulnerable after disturbances because populations recover slowly

r-selected species (“quantity approach”)

• Typically smaller and shorter-lived
• Many offspring at once
• Little to no parental care
• Fast time to sexual maturity and often reproduce once
• High biotic potential (maximum reproduction rate) → rapid population growth
• Often more likely to become invasive due to fast reproduction and rapid population establishment

Biotic potential

• Defined as the maximum reproduction rate of a population
• Higher in r-selected than in K-selected species

Spectrum rather than binary categories

• Not all organisms fit perfectly into K or r categories
• Many species fall in between (intermediate strategies)

Invasiveness and ecological disturbance

K-selected disadvantages

• Slow reproduction/recovery after disturbances (e.g., forest fires, disease, environmental change)
• “Double whammy” effect: young are vulnerable and parental care matters, so loss of a parent often means loss of offspring
• Vulnerable to competitive exclusion by fast-reproducing invasive species
• Lower adaptability due to:
  • Longer generation times
  • Smaller population sizes
  • Less genetic diversity

r-selected advantages

• Rapid repopulation after disturbance
• Faster establishment and potential to outcompete K-selected species
• Greater ability to persist and expand in new environments

Examples mentioned

• K-selected examples: elephants
• r-selected examples:
  • Spiders (hundreds of offspring)
  • Oysters (contrasted as little/no parental care)
• Intermediate examples (spectrum):
  • Chimps and an unspecified “Haley” (likely a transcription error), presented as highly K-selected
  • Hare: mother hare provides care; ~10–12 offspring at a time
  • Frog: produces many offspring with some parental care (e.g., poison dart frog carrying tadpoles on her back)

Data analysis / relationship in an ecosystem

• A table/analysis about population density relationships between zebra mussels and unionid mussels in the Hudson River

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Methodology / approach outlined

• Teaching objectives and skills practiced:
  • Concept explanation: identify a trait of an r-selected species that increases its likelihood of becoming a successful invasive species
  • Data analysis: describe the relationship between zebra mussel and unionid mussel population densities in the Hudson River

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Researchers or sources featured

• No specific scientific researchers, papers, or institutions were named.
• The only named person is the video host: Mr. Speeds.