Q51 - Contrasting Parasitic Strategies: Sam and Jack

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Sam is an imaginary single-celled organism. His body is covered with cilia which enable him to move. He has two nuclei: housekeeping genes are expressed in the macronucleus, while gene-expression tasks relevant to reproduction are undertaken by the micronucleus. Sam divides via a process called “schizogony”, whereby nuclei undergo multiple fission and then the cell itself divides. Sam can eat food particles and even bacteria through his mouth, a characteristic that helps him to live freely as a saprophyte. Sam has a monomorphic shape throughout its life cycle and experience enlargement and division, consecutively. Sam has decided to abandon his free-living lifestyle and transform into a merry parasite (with limited harm to the host). Jack is also a parasite and is more aggressive (damages its host) than Sam and his single-celled body is covered by an armour made out of protein. This protective layer is jagged and gives Jack a rugged look. Jack also has two nuclei. He has two flagella that allows him to move, attack, and penetrate. He is able to secrete enzymes that can degrade many animal tissues. immature individuals who belong to Jacks species lack traits mentioned above; they are small and proliferate rapidly. In addition, Immature individuals of Jack needs to find host to grow and cannot live independently. Indicate for each statement which strategy will be more suitable for Sam compared to Jack (statements A-E), and then, assuming Sam and Jack chose a common host, indicate which of the following statements are true or false (statements F-I).

Using the information and data, determine which of the statements are true or which are false.

A. Utilizing antigen shuffling, even though it is a costly trait.

B. Having a life cycle consisting of two hosts.

C. Choosing an r-selected host.

D. Secreting Samilosporin (an antibiotic which destroys many of bacterial species that are virulent for the host).

E. Transmitting to the next generation by infecting the gametes.

F. Sam will probably win the competition against Jack.

G. If a lethal bacterium spread through the population of the host, Sam's fitness will increase.

H. Sam's fitness is negatively correlated with Jack's abundance.

I. Sam's fitness is less affected by the life-history traits of the host than Jack's.

← Previous: Q50 Back to Theoretical 2 →

Question reproduced from IBO 2018, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)