Question

1. You have a lot of pet goldfish in a tank in your living room. You started your fish colony a couple of years ago from just 4 goldfish that were from the pet store (likely heavily inbred =very little genetic variation). One day you are cleaning the tank and notice a new juvenile fish with an unusual red spot on his tail. It is the only one in the population with this spot. What might be influencing this population? Why?

2. You are a chicken farmer in Hyattsville, MD and you have lots of chickens. Some lay brown eggs and some lay white eggs. By doing some quick counts over the past few weeks you see that your chickens lay about 80% white eggs and 20% brown eggs. A flash flood strikes your farm the next week. You save two of your 6 coops, the rest of the chickens are washed away. You move your remaining lucky chickens to higher ground, re-building the farm. Six months later, you re-do your egg count to find that your chickens are laying 60% brown eggs and 40% white eggs. What might be influencing this population? Why?

3. Bower birds are unique to Australia. These ground dwelling birds build elaborate grass nests and decorate them with brightly colored objects (often bits of trash and plastic) to attract a female. The birds use all sorts of colorful items and arrange their displays to try to be most appealing to the female (either using all one color of item or creating a rainbow jumble of plastic trash!) and arrange them artfully to attract females. The females choose their mates based on the brightness and elaborateness of the male’s nest displays. Why might these birds have evolved into such fantastic animal architects?

4. You decide to move to a remote island in Polynesia to conduct Anthropological ethnographic fieldwork. However, you refuse to leave your two Maine Coon cats behind, so you bring them with you to the island. The local stray cats on the island are all short haired, striped brown tabby cats. Your cats love to explore so you let them outside every night. A few years into your fieldwork you start to notice that the local island cats are looking different these days. You see many with bushy tails and some with long fur. What might be influencing this population? Why?

Answer 1

1. Inbreeding in the population for several generations will lead to recessive traits getting expressed due to homozygocity developing in the population. Some recessive traits are not expressed in a large population because of random mating and heterozygocity. But a small population where chances of homozygocity are more, new traits start getting expressed. That is why a new trait appeared in the population.

2. After the flash flood most of the chicken of white variety must have got killed and many brown chicken survived which is purely due to chance. Such a change in gene frequency due to chance alone is called genetic drift. Because of the genetic drift

allele frequency has changed and the population is considered to be evolving. Brown % increased from 20% to 60% and white decreased from 80% to 40%.

3. Here because the females are always choosing bright artistically displaying males for mating, evolution has resulted in bettering the trait. Selective breeding of the artistic males led to natural selection and evolution.

4. The Marine cats introduced in to the region led to new genes added to the original population. This is called gene flow. That led to new traits appearing in the population . This disturbs the frequency of other alleles.