8) Explain the causes of an evolutionary arms race between consumers and the spe

Question

8) Explain the causes of an evolutionary arms race between consumers and the species that consume. (Ch. 14) 9) If one species provides a habitat as part of a mutualistic relationship, what is the probable effect on the abundance and distribution of the other species? (Ch. 17) 10) Explain how ants and acacia trees fulfill the definition of a mutualistic relationship. (Ch. 17) 11) If cleaner fish consume both parasites and scales from larger fish, what would determine whether the interaction is best categorized as mutualism or parasitism? (Ch. 17) 12) What might prevent a species in a mutualism from reaping the benefits from a partner without providing a benefit in return? (Ch. 17)

Explanation / Answer

8) The causes of an evolutionary arms race between consumers and species are;

i. Battles for survival

ii. Development of defense systems over other species

iii. Brood parasitism

iv. Fastest running to kill the prey

v. Chemical mimicry

vi. Predator and prey evolve side by side but only one of the two species that helps to drive adaptation

vii. Predator induced macroevolution

viii. Distaste of toxins

ix. Altruistic suicide

x. Built up resistance

Predator/prey coevolution can lead to an evolutionary arms race. For example, many molluscs, such as Murex snails, have evolved thick shells and spines to avoid being eaten by animals such as crabs and fish. These predators have, in turn, evolved powerful claws and jaws that compensate for the snails' thick shells and spines.

9) If species X provides a habitat to species Y as part of a mutualistic relationship, then the probable effect on the abundance and distribution of species Y is, Species Y will not be able to survive outside the range of the species X.

Ex: Ants and Acacia trees

10) Several species of Acacia like Acacia cornigera, Acacia collinsii, and Acacia drepanolobium have a mutualistic relationship with the ants (like Pseudomyrmex ferruginea).

i. The presence of mutualistic ants greatly reduces bacterial abundance on surfaces of acacia leaves thereby keeping the plant healthy.

ii. In return ants get food (from Beltian bodies at leaf tips rich in nutrients help for their nourishment) and shelter (tree's swollen thorns called 'domatia' act as dwelling areas for ants) from the trees.

iii. Ants protect Acacia from animal attacks like elephant where the ants swarm the trunk of the elephant and bit when attempted to consume the tree's leaves. They also provide defense against many herbivores and harmful insects.

11) The cleaner fish consuming both parasites and scales of larger fish is often categorized into Mutualism. It is also termed as 'Cleaning symbiosis'. The Cleaner fish are highly specialized fish that pick parasites off the skin of other fish. It provides a valuable service to the other fish by picking off and cleaning its customers of parasites and dead tissue. Often, parasites are simply small crustaceans that live between the scales of fish and feed on its tissue. The cleaner fish presents itself infront of larger fishes by some peculiar body movements. Similarly, when a fish wants its suface to be cleaned, it sends its signals to the cleaner fish, by keeping its body stationary, spreading its fins and gills. As soon as the cleaner receives the signal from larger fish, it starts its duty. In this way, the cleaner fish is getting its food and larger fish getting its surface cleaned.

Ex: Cleaner Wrasse

12) Sometimes, organisms receive a benefit at the cost of other organisms. This cheating is common in many mutualistic relationships. This is commonly believed to destroy a mutualistic interaction. If cheaters gain an advantage over more beneficial partners, the mutualism could break down. Cheating in mutualism is where it is more for one of the species to have an increase in its fitness while reducing the fitness of the other since it is not able to receive the same benefits as the cheating organism. Being specialized to their partner can prevent mutualists from becoming cheaters.

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