Fig. 1 shows a field biologist measuring the forearms of bats caught briefly beside a newly cleared woodland corridor. Before trees were removed, most bats ...
Question 1 Report
Fig. 1 shows a field biologist measuring the forearms of bats caught briefly beside a newly cleared woodland corridor. Before trees were removed, most bats travelled through a sheltered route between two caves. The open corridor is now windy and contains fewer insects. Within this bat species, forearm length varies. Bats with longer forearms may fly more efficiently across the exposed space, so they may obtain more food and produce more offspring. The biologist released every animal after recording its measurements.
In the first year, the mean forearm length was 41 mm. After 12 years, the mean was 46 mm.
(a) Identify the type of variation shown by forearm length in these animals. [1]
(b) Calculate the change in mean forearm length over the 12 years. [1]
(c) Explain why the proportion of bats with alleles for longer forearms could increase in this population. [4]
(d) Suggest two pieces of evidence, other than forearm measurements, that would strengthen the biologist's conclusion that natural selection has occurred. [2]
(e) Give two reasons why the biologist should return each bat to the same area after measurement. [2]
Answer Details
(a) Continuous variation. [1]
(b) 46 - 41 = 5 mm. [1]
(c) There is inherited genetic variation in forearm length. [1] Longer-forearmed bats are more likely to cross the open corridor/find enough insects and survive. [1] They reproduce more successfully. [1] They pass alleles for longer forearms to more offspring, increasing the allele frequency over generations. [1]
(d) Any two from: evidence that longer-forearmed bats have higher survival rates; evidence that they produce more offspring; DNA evidence showing increased frequency of relevant alleles; insect counts showing less food in the open corridor; records showing the environmental change remained present. [2]
(e) Any two from: reduces harm/stress to the animals; maintains the local population; allows animals to continue breeding; avoids moving a species into an unsuitable habitat or spreading disease. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
