Animal Behaviour Questions and Answers

Answer: A

The migration is Anadromus (anadromous).

Anadromous fishes live and grow in the sea and move up rivers into fresh water to spawn. Salmon and the Indian hilsa are classic examples, with young fish returning to the sea to feed and grow.

Catadromous fishes do the reverse, living in fresh water and going to sea to breed, like freshwater eels that spawn in the Sargasso Sea. Oceanodromous fishes migrate only within the sea, such as tuna, and potamodromous fishes migrate only within fresh water. Both of these are forms of migration that never cross between the two.

Answer: D

The interaction is Altruism.

Altruistic behaviour benefits another individual at a cost to the actor's own survival or reproduction. Worker bees that never reproduce but rear their sisters, and ground squirrels that give alarm calls and draw predators to themselves, are the standard examples. Hamilton's kin selection explains it: the behaviour spreads when the benefit to relatives, weighted by relatedness, exceeds the cost.

In co-operation and mutualism both partners gain, so no one sacrifices reproductive success. In commensalism one partner gains and the other is unaffected, which again involves no sacrifice.

Answer: D

The claim that is not an advantage of schooling is Attainment of faster growth.

The recognised benefits of schooling are protection from predators (the confusion effect, many eyes watching, dilution of risk), better location of food (more individuals searching), hydrodynamic savings when swimming in formation, and easier access to mates at spawning time, which raises reproductive success.

Growth rate is not one of these benefits. If anything, competition for food within a school can slow the growth of some members. So avoiding predators, locating food and reproductive success are all advantages, and faster growth is the odd one out.

Answer: C

The menstrual cycle is an Infradian rhythm.

Biological rhythms are classified by period. Infradian rhythms have a period longer than a day; the human menstrual cycle, about 28 days, is the standard example, along with seasonal breeding and hibernation.

Circadian rhythms have a period of about 24 hours, such as the sleep-wake cycle and the daily cortisol peak. Ultradian rhythms are shorter than a day, such as the 90-minute cycle of sleep stages or pulsatile hormone release. Tidal rhythms, of about 12.4 hours, are found in coastal animals that follow the tides.

Answer: C

Inclusive fitness is an individual's reproductive success together with its relatives' reproductive success.

W.D. Hamilton showed that a gene can spread not only through an individual's own offspring but also by helping relatives, who share copies of the same gene. Inclusive fitness adds this indirect component, weighted by relatedness, to direct fitness; Hamilton's rule, \(rB \gt C\), follows from it and explains kin-directed altruism.

An individual's own reproductive success alone is direct (classical) fitness. Neighbours and partners are not counted unless related, since only shared genes matter.