Chapter 7. Chapter 7: Population Ecology

What are the reproductive strategies of r and K-adapted species...?

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?

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
UNkoR/99cts+yyaoDZiZVqjf/cx5jkRGOfZ3n1BKQEQvMS8xCEWOKdqbUW4562RdFI72UjBWjKrz2iW/X5tJcGphs6YEvCxAZJqp/Svr7gpUrRfoFFGFIg== Species that have a high biotic potential and that share other characteristics such as short life span, early maturity, and high fecundity.
axaUKwJ8OvgQwZOhCwX7upkzxYInd5BMybaQEoDUaLK691wKD2hQOehaicheTJQ5n9VE2gTmjfozU1whFLEhFSFaxFyBCg39JoPmKULIZ1dhRUzv4ZtIzQ== How quickly a population can potentially increase, reflecting the biology of the species (life span, fecundity, maturity rate, etc.).
1S2pV1XliER/gMx9l0r0f1vuvE20qAWZp1+3p5S8T0deSy3pb8kl8AfACn3CPLgd7DiVq7pHLuqz1WLp7TuSWu3Xsv190yWfH+1CNDqcbwT3Jxs0PcpDWw== 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

Question 7.1

K0HZGcLGAnzH2IUjibwjiFdO7cl/vVSETF+pISuQpi2UTWZMZ50J91mopqOdqneUU9bwfQIYgoiTAvKpiHxh39vuICc3QmZN3YbV4X+xOpTbhwA1otHAzmH9RijsuiK+efsj9TlBNgthEN2wSulem2FwpcE+XZpYDuZxF4X+NHbi2KoNeDIYteZAGMZWgYFQ/B0DxJS37dQ=
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Question 7.2

JMta7FSk2cYg8ZqOcdIKyoR5eR+7rA7nGb0zRQYlNXzW2RDhukXp95gYyOZg6nLRikgTt/5gqSPW8Q/q8sfz2nV7ZY3hXJyUPnB+dxKpHQOJwMTIoDfpCsG5ZT40ejNazUFmeMclVvk/w37xzRqRSjkthvNAoeaFnC35pGincze3ONXKGrjHgZfxLDAyL/RZqPCuQHeE5I6ERq4iuSPfiOWa5/xBr/LaXhjXK10g/zj9dBt5pEPJj0VnqqcP6sbZ5RCDdYHHPXO3aLcUnFT0LzwNxaNO+JIWWA5ih1ZH0XsPaG2u8o30l1FcLk5u788xBGLnbat3t7dSHR04RfYjSMQXzKwXekX0nC57NsEOXCtYlAN4GkKKj2P7jhyGJi1LV5KHb4BmhC32kTKUr+02HEcGftWr4kI9pxaiM1T2X+pc74RkjqYkEodAxrrXSqyF
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Question 7.3

YzalvTsxFjwJ17LYuBSbvHoMAjh78hbkgTpiETeb607/A5PBq2TzwDAFE+bmpBcJylFJq3H5QNgx5kthdiIeT+CuzXHQGEWTIgqN9RMem2/sITIM75BtRRS2/GIxFaSEhawFJAuZ4S9y4ndQ4+Gc17OIKdDUlDBy/10OZTL5BR//WM8jcy/gMbMoqt3C/NH2MJ+3I0R6uqo3UtGR+Ykbm5UmpLJe7JMHEFvuat3dc8dGP0W8jbK42K+zTowC9EPTxfiiJgRYmeQD0/t0+zRiC/K3SarT+7Sp
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Question 7.4

zTFICd45egXdA52GILXElmJ2xHdRe+7/hBg3s6daJwNwwwIm+53s6RdcZ21Q7DW7LQIcaakIE5C9ENW2792rOq/gmPoIcljJc6C+QOMsPA3GCgDmY3iQYUgY/zA2nGBv9JpW+qytSLmUQoMwVaqXVCeNZoLZCVFmwf0OmVL2KTtjSaE7kWYVp/MSxp8nv/DeWyYPP+ZjrbRxbRtA/SxoIh7mk5/kDU9HxmNUbEl4TcenCt94mQQ6E+si6JuVwnGcOS64Yh4yCYt6fbeFtql1jlA6Tmzyy8IDma0moCWSV8Qnxx5fsM/kM7ECV4KXaoPMVChm1w==
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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

Question 7.5

Are humans r- or K-selected? 6Bwvr9f59IohfVKeCYz1VIUTh2ijhwTdHyw1p3+MA1v1OMJoihzJwJH3Z2PdPQJo

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Question 7.6

Thought Questions: Many species do not fit neatly into the r- and K-selected categories. For each organism below, give at least one reason that it could be considered an r-selected species and at least one reason that it could be considered a K-selected species.

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A) Oak trees: r-characteristics include having many, small offspring with low parental care. K-characteristics include having a long life span, slow growth, longer time to maturity, and low adaptation to unstable environments.

B) Sea turtles: r-characteristics include many small offspring with little parental care that are often prey. K-characteristics include long life span, slow body growth, older age at reproduction, and many reproductive events.