Name: ________________________________
Date:___________________
Class: _____________
Global Context: Orientation in time and space
Key Concept: Systems
Natural selection – Formative Criteria A (1)
Stimulus
We conducted field surveys on an oceanic island with black, yellow and intermediate-coloured E. p. simodae snails. We captured and marked ~1800 individual snails and monitored their survival over 18 months. We quantified shell colours against images and examined the frequency distribution of shell colour variation. The variation exhibited a bimodal distribution with a far lower frequency of intermediate-coloured snails than of black or yellow snails. The population sizes of the three snail groups fluctuated synchronously with the changing seasons. Bayesian estimates showed lower survival rates for juvenile intermediate-coloured snails than for juvenile black and yellow snails, implying there was disruptive selection associated with shell colour.
Adapted from ( (Shun Ito, February 2020)
Questions
Section A: S Criterion A Strand i
These questions are about the interaction and relationships between organisms.
Define natural Selection. (level 1-2)
Compare and contrast the different types of natural selection with each other. (level 3-4)
Use the information provided in the stimulus to help answer question 3 to 4.
Discuss how the theory of Natural selection applies to the experiment mentioned in the stimulus. (level 5-6)
Explain how different sources of genetic variation contribute to the total diversity of individuals in a population. (level 7-8)
Bibliography
Shun Ito, J. K., February 2020. Disruptive selection of shell colour in land snails: a mark–recapture study of Euhadra peliomphala simodae. Biological Journal of the Linnean Society, Volume 129(Issue 2), p. Pages 323–333.
Criteria A
Achievement level
Level descriptor
Task specific
0
The student does not reach a standard identified by any of the descriptors below.
You did not reach a standard described by any of the descriptors below.
1 – 2
The student should be able to:
State scientific knowledge.
The student should be able to:
State definitions for the term:
Natural selection
3 – 4
The student should be able to:
Outline scientific knowledge
The student should be able to:
Outline scientific knowledge by outlining the difference and similarities between directional, stabilizing and disruptive selection.
5 – 6
The student should be able to:
Describe scientific knowledge
The student should be able to:
Describe scientific knowledge by discussing how the theory of natural selection can apply to the case study in the stimulus. Students have to refer to the different variations, and how some variations are favored above others based on environmental factors.
7 – 8
The student should be able to:
Explain scientific knowledge.
The student should be able to:
Explain how different sources of genetic variation contribute to the total diversity of individuals in a population.