Answers to exploration questions: genetic and ecosystem biodiversity

If you are wondering where the suggested answers came from, you can review the videos and article in this tutorial.

1.     In a few sentences, explain why inbreeding can be a threat to the survival of a species.

Answer: A complete explanation would mention that inbreeding often occurs when the population size of a species is small and the only available mates include close relatives. The more closely related two individuals are, the more similar their genetic make up is likely to be. So close relatives, like siblings or cousins, have genetic information more similar to each other than to non-relatives. This means that if one is carrying an allele with harmful information, the relative is more likely to be carrying it also. When close relatives mate, their genetic similarities increase the chances of harmful genetic combinations appearing in the offspring. These harmful genetic combinations lower the probability that the offspring will survive and reproduce successfully, thus threatening the survival of the already small population. This phenomenon is called inbreeding depression. For more information about inbreeding depression, you can check out this website: http://evolution.berkeley.edu/evolibrary/article/conservation_03

2.    After watching the videos in this tutorial, your friend asks you to describe a scenario that might lead to a genetic bottleneck for a species. Be sure to include a specific example of a known bottleneck that has occurred in nature.

Answer: A complete explanation would mention that when the population size of a species had been greatly reduced in the past and the species almost went extinct, the species is said to have gone through a "genetic bottleneck". With the population size being very small, there is usually a lot of inbreeding and the genetic variation is low. Any event – natural or caused by humans – that drastically reduces the number of individuals and therefor the genetic variation in a population or species can cause a bottleneck. Examples of such events include the spread of an infectious, deadly disease; a significant change in the environment; excessive hunting by humans).

A known example of a genetic bottleneck is that of the American bison (Bison bison), also called the American buffalo. If you do a little research online or in the library, you will learn that bison once roamed North America in massive herds with an estimated total population of 30 to 60 million individuals. But as American settlers moved westward, bison were hunted so relentlessly that the species was near extinction in the late 1890s, with only 750 individuals estimated to remain. This severe reduction in the population meant that much of the bison’s genetic diversity was lost.