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4.5.1Genetics, Variation and Interdependence

Courtship — AQA A Level Biology 7402 Revision Notes & Topical Questions

5 min read 9 parts Lesson 28 of 46 1 quiz

📚 AQA A Level Biology 7402 Hub / Topical Revision
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Lesson summary

4.5.1 Courtship — AQA A Level Biology 7402 notes: Explain why courtship behaviour is needed before mating and how it helps to identify members of the same species.Courtship is a sequence of behaviours performed by one or both partners before mating.

  • reproductive behaviour
  • interbreed to produce fertile offspring
  • Species recognition
  • Sex recognition
  • Fertility and readiness
  • Synchronisation

Section 1 of 9What is courtship?

Courtship is a sequence of behaviours performed by one or both partners before mating. It is a form of reproductive behaviour and it takes place in many animals, from insects to birds and mammals. In AQA terms, courtship is a necessary precursor to successful mating: without it, fertilisation is unlikely to happen, or the offspring will be wasted effort.

A species is a group of organisms with similar morphological, physiological, biochemical and behavioural features, which can interbreed to produce fertile offspring. Courtship is one of the behavioural features that holds a species together.

Section 2 of 9Why courtship matters

Mating with the wrong partner wastes gametes, energy and time. Courtship therefore carries out several jobs:

Species recognition
Species recognition it makes sure that a mate belongs to the same species, so that mating produces fertile offspring and does not produce infertile hybrids (for example a mule from a horse and a donkey).
Sex recognition
Sex recognition it identifies a partner of the opposite sex, which matters in species where males and females look alike.
Fertility and readiness
Fertility and readiness it signals that the partner is sexually mature, healthy and receptive. In many females, ovulation is triggered or timed by courtship.
Synchronisation
Synchronisation it brings both partners into breeding condition at the same time so that gametes are released or mated together.
Pair formation
Pair formation in species that rear young together, it forms a pair bond and reduces aggression between partners.
Mate choice
Mate choice a vigorous display shows good health and good genes, so the choosing partner selects a high quality mate. This is a form of sexual selection.

Section 3 of 9Courtship is species specific

The more complicated and specific a courtship display is, the less likely it is that two species will be confused.

Courtship is species specific
Courtship patterns are controlled by genes and are inherited, so closely related species that share a habitat often show different displays.
Examples include the different calls of male frogs, the flashing patterns of fireflies (each species flashes with its own timing), the dances of sticklebacks and the songs of birds.

A display usually works as a chain: each signal given by one partner is the stimulus for the response of the other.

Courtship is species specific
If any step is missed or wrong, the sequence stops and mating does not occur.
Pre-zygotic isolating mechanism
A mismatch at any step is a barrier to breeding with another species, so courtship acts as a pre-zygotic isolating mechanism.
Over many generations, such isolation between populations can lead to the formation of new species (speciation).

Section 4 of 9Courtship and classification

Because courtship is a behavioural feature that reflects genetic differences, it helps taxonomists to decide whether two populations are really separate species.

Courtship and classification
Where two populations look nearly identical but will not respond to each other's courtship, they are likely to be different species.
In theory, the biological species idea works well; in practice it fails for organisms that reproduce asexually, for fossils and for species that cannot be observed breeding, so courtship is one source of evidence among several (such as anatomy and DNA).

Courtship behaviours are also used in captive breeding programmes. If a rare species does not display properly in a zoo, mating may fail even when both animals are healthy, so keepers have to recreate the correct conditions.

Section 5 of 9Link to other topics

Courtship links to natural selection (4.4): displays that attract mates increase reproductive success, so the alleles for them become more frequent. It links to speciation, to taxonomy (the next lessons in this topic) and to conservation, where successful breeding of endangered animals depends on understanding their behaviour.

Section 6 of 9Courtship in named examples

Examples show how varied courtship can be.

Three-spined stickleback
In the three-spined stickleback, the male develops a red belly and performs a zigzag dance; the female responds by swimming towards him with a swollen belly, which stimulates him to lead her to the nest.
Each step is the trigger for the next.
In many birds, males perform songs and display flights, and in some species the female selects the male with the most elaborate plumage or the best song, which may signal good health.
Pheromones
In insects, chemical signals (pheromones) attract mates over long distances and are also species specific.

Data questions often present a table of responses of females to males of different species. Look for the cases where the response is strong only to the female's own species. This shows that the signal is species specific and that courtship leads to reproductive isolation.

Section 7 of 9Exam-style questions

  1. Courtship behaviour in animals is a necessary precursor to successful mating. Explain why. [3]3 marks

  2. Two species of firefly live in the same wood. Males of species A produce one flash every 2 seconds; males of species B produce three quick flashes. Females reply only to the pattern of their own species. Explain how this helps to keep the two species separate. [3]3 marks

  3. Suggest why a courtship display is usually made up of a series of steps rather than a single signal. [2]2 marks

Section 8 of 9Key terms

TermMeaning
CourtshipBehaviour before mating that allows recognition of a suitable mate and prepares both partners for fertilisation.
SpeciesA group of similar organisms able to interbreed to produce fertile offspring.
Species recognitionIdentifying a potential mate as belonging to the same species.
Pre-zygotic isolating mechanismA barrier, such as different courtship, that stops fertilisation between species.
Sexual selectionSelection by mate choice or competition for mates, favouring traits that increase mating success.
SynchronisationBringing the breeding condition of both partners into the same time.
HybridOffspring of two different species, often infertile.

Section 9 of 9Exam technique

1
Saying courtship is only about attracting a mate. It also identifies the species, the sex and the readiness of the partner, and it reduces wasted mating.
2
Saying that animals which cannot interbreed to give fertile offspring must look different. Different species may look almost the same; behaviour such as courtship may be the main difference.
3
Confusing courtship with mating or with sexual selection in general. Courtship is the behaviour before mating; sexual selection is the resulting selection pressure.
4
Writing that courtship behaviour is learned in all species. In many animals it is largely innate and inherited, which is why it is species specific.

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