A bottleneck in genetics is an event that kills off or isolates a large portion of the population.
Explanation:
The more individuals in a population, the greater the genetic diversity. A genetic bottleneck happens when the number of individuals in a population gets greatly reduced. This happens as a result of random chance. For example, a storm might come through and knock down a bunch of trees. Birds that live in the trees may get harmed and those that survive now have to find a new home, so they migrate to other areas leaving behind a small population. This is important because the fewer individuals there are, the less genetic diversity and therefore, the less ability of the population to adapt. If you have lots of different genes available and a new disease arises in the population, it's more likely that some individuals will survive. If you only have a few genes available, it is less likely any individuals will survive. This can lead to really quick adaptation and evolution of a species.
They have to have a higher density than water to have the ability to stay on the sea floor. Otherwise they would just float to the surface of the water
