 Third, consider the upper half of  Figure 5  and regions 6 and 7. There are correspondingly two different types of living agents that are not Darwinian individuals: some parts of organisms such as hearts (region 6) and (again, perhaps more controversially), groups of organisms such as coral reefs (region 7). As physiological individuals, hearts are alive but they do not reproduce or relate to reproducers in the manner that Darwinian individuals do. As suggested at the end of  section 6.1,  a coral reef may also be an example of this kind of biological individual at the group level. Coral reefs don’t feature the type of reproduction-involving life cycles characteristic of organisms, and some of the same facts about reproduction likely disqualify them from being Darwinian individuals. Yet perhaps the reefs (in addition to their constituent individuals) have a better chance than eusocial insect colonies of counting as living agents.