Database Questions: Garter Snakes

DBQ Pg. 303-304

1.     (a) For each of the three populations calculate the percetages that were in the <5 and >5 groups. (3)

Lassen County Total = 567 + 114 = 681

Lassen County <5 % = (567 / 681) x 100 = 83.3%

Lassen County >5 % = (114 / 681) x 100 = 16.7%

Humboldt County Total = 149 + 314 = 463

Humboldt County <5 % = (149 / 463) x 100 = 32.2%

Humboldt County >5 % = (314 / 463) x 100 = 67.8%

Santa Cruz Total = 30 + 165 = 195

Santa Cruz <5% = (30 / 195) x 100 = 15.4%

Santa Cruz >5% = (165 / 195) x 100 = 84.6%

                 

(b)  Explain the differences in the behaviour of inland and coastal populations, in terms of natural selection. (4)

Coastal populations show a greater percentage of the population eating slugs more than five days while the inland population shows a greater number of the population eating slugs less than five days.

In coastal environments in California slugs are abundant so that coastal populations become more adapted to eating slugs through natural selection. Coastal snakes are adapted to eat slugs have an advantage and produce more healthy offspring. 


Slugs within inland areas are scarce so the inland populations of the garter snake are more adapted through natural selection to not eat slugs. Natural selection happens as inland snakes reliant on eating slugs struggle living within inland areas and their numbers begin to diminish, leaving the population of inland snakes not reliant on eating slugs to grow in the area. Inland snakes have a selection pressure to feed on other prey and these individuals are more successful. 

2.     Predict, with reasons, the result if garter snakes were moved from Lassen County to Santa Cruz. (3)

Garter snakes moved from Lassen County to Santa Cruz will face a greater abundance of slugs than they're used to. The Lassen County snakes will be less likely to survive in this new environment because they're more adapted to feed on other prey whereas in Santa Cruz there are more slugs. 

3.    Discuss the evidence from the bar charts for:

a.     The slug-eating response being inherited (2)

There’s a greater frequency of F1 hybrids accepted slugs during the first couple of days of the experiment. This is a similar characteristic of the Lassen County garter snakes that have the slug-eating response. The Lassen County and F1 hybrids have the same feeding pattern. 

b.     The alleles for slug eating being recessive (2)

In the F1 hybrid the behavioral pattern to not eat slugs seems to be prominent. This suggests that the gene to not eat slugs is dominant and the gene for eating slugs is recessive.

4. Suggest a type of receptor for the slug-eating snakes to detect slugs (1)

Chemoreceptors - they smell the slugs. They find the trail of the slug and follow it.