Practise IB ESS SL 2.1.11 by identifying density-dependent factors and tracing negative feedback that returns host, parasite and animal populations towards equilibrium.
A new parasite is introduced into an ecosystem and manages to infect a host species. Outline how the host and parasite species may reach an equilibrium over time.
The parasite species may grow slowly to begin with because there are only a few of them to reproduce;
b. They will then grow at an increasing/exponential rate as the numbers reproducing increase;
c. Eventually they may begin to cause a fall in the number of hosts;
d. This will cause a subsequent decline in the number of parasite species;
e. This in turn will allow the host species to recover;
f. This reciprocal/cyclical fluctuation may continue indefinitely;
g. Achieving a negative feedback mechanism/dynamic equilibrium;
h. hosts that are best able to tolerate the parasite are the most likely to survive/reproduce/increase in numbers;
i. parasites that kill their hosts often struggle to reproduce as efficiently, so the milder versions might be more likely to survive/reproduce/increase in numbers;
j. -which in means over time parasites are less deadly and hosts are less affected;