Chapter 7. Chapter 7: Population Ecology

Interactive Study Guide

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Guiding Question 7.3

What are the reproductive strategies of r- and K-adapted species, and how do these relate to population-growth patterns and potential?

Why You Should Care

Understanding how an organism divides up its resources between reproduction and maintaining itself helps scientists predict how a population of those organisms will grow, what role the organism likely plays in the ecosystem, and how likely populations of that organism are to crash in number. As an example, consider the classic pairing of a mouse and an elephant. Female elephants are pregnant for nearly two years before giving birth to (normally) one calf. They then care for that calf for 3 to 5 years before weaning and getting pregnant again. Elephant calves are born with few survival instincts and need to be taught by their mothers and relatives how to conduct themselves. Mice, on the other hand, take just 20 days to bear litters of around 10 pups, which are weaned and largely taking care of themselves in less than a month. Which species do you think is more likely to become threatened?

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term	Definition
	Species that have a high biotic potential and that share other characteristics such as short life span, early maturity, and high fecundity.
	How quickly a population can potentially increase, reflecting the biology of the species (life span, fecundity, maturity rate, etc.).
	Species that have a low biotic potential, share characteristics such as long life span, late maturity, and low fecundity, and that generally show logistic population growth.

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Infographic 7.5: Reproductive Strategies

Consider the table below when answering the questions that follow:

Features of typical r- and K-selected species	r-selected	K-selected
Life span	Short	Long
Body growth rate	Fast	Slow
Age at reproductive maturity	Early	Later
Number of offspring per reproduction event	Many	Few
Size of offspring relative to parent	Small	Large
Amount of parental care	Low–None	High
Adapted to unstable environments?	Yes	No
Often prey?	Yes	No
Niche specificity	No	Yes
Number of reproductive events in lifetime	One–Few	Few–Many

Table 7.1: Features of typical r- and K-selected species

5.

Are humans r- or K-selected?

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