Pheromones - SAQ

Question 1

Pheromones

Answer 1

A chemical messenger that is sent from one animal which has an effect on a different animal

Question 2

How do pheromones resemble to hormones?

Answer 2

Chemical messengers

Secreted by glands

Question 3

How are pheromones different to hormones?

Answer 3

They are not released into the bloodstream, but are secreted to act outside the body

A communication between individuals of the same species

Question 4

Examples of animals using pheromones

Answer 4

Butterflies, prawns and mammals such as mice and monkeys

Question 5

Why are we not sure whether humans have pheromones?

Answer 5

The detection of pheromones in mammals usually relies on the vomeronasal sensory organ (VNO)

This is a collection of neurons deep in the nose that transmits signals via the accessory olfactory bulb to the hypothalamus in the brain.

So far, neither the VNO or the accessory olfactory bulb has been shown to exist in humans, though both exist in the foetus up to about 18 weeks.

Question 6

Why did Wedekind study MHC?

Answer 6

As there is a possibility that it is linked to smell and therefore a pheromone

Question 7

What does MHC stand for?

Answer 7

Major Histocompatibility Complex

Question 8

What is MHC?

Answer 8

A group of genes that play an important role in the immune system

Every individual has quite a unique MHC footprint

MHC genes make molecules that enable the immune system to recognise pathogens

The more diverse the MHC genes of the parents the stronger the immune system of the offspring

Question 9

Why might MHC be advantageous to have pheromones?

Answer 9

MHC genes are expressed co-dominantly – that is, that we inherit the MHC alleles from both of our parents and they are expressed equally.

It would be beneficial, therefore, to have evolved systems of recognizing individuals with different MHC genes and preferentially selecting them to breed with to maximize immune responses.

Question 10

What study is used for pheromones?

Answer 10

Wedekind

Question 11

When was Wedekind study?

Answer 11

1995

Question 12

Aim of Wedekind (1995)

Answer 12

To determine whether one’s MHC would affect mate choice.

Question 13

Sample of Wedekind (1995)

Answer 13

49 female and 44 male students from the University of Bern, Switzerland

Question 14

What information was taken from the participants?

Answer 14

Each participant was “typed” for their MHC, and a wide variance of MHC was included in the sample.

It was noted if the women were taking oral contraceptives.

The students probably did not know each other as they were from different courses

Question 15

What were the men asked to do?

Answer 15

The men were asked to wear a T-shirt for two nights and to keep the T-shirt in an open plastic bag during the day.

They were given perfume-free detergent to wash clothes and bedclothes and perfume-free soap for showering.

They were asked not to use any deodorants or perfumes, to refrain from smoking tobacco or drinking alcohol, to avoid all spicy foods and to not engage in any sexual activity.

Question 16

What were the women asked to do?

Answer 16

Two days later, the women were asked to rank the smell of 7 t-shirts, each in a cardboard box with a “smelling hole.”

The women were tested whenever possible in the second week after the beginning of menstruation, as women appear to be most odour-sensitive at this time.

The women were also asked to prepare themselves for the experiment by using a nose spray for the 14 days before the experiment to support regeneration of the nasal mucous membrane if necessary – as well as a preventive measure against colds or flu.

Each woman was also given a copy of Süskind’s novel Perfume to sensitive their smell perception.

Question 17

Results of Wedekind (1995)

Answer 17

Women scored male body odours as more pleasant when they differed from their own MHC than when they were more similar.

This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives.

This suggests that the MHC may influence human mate choice.

Question 18

What are signalling pheromones?

Answer 18

Produce rapid behavioural effects in animals - specifically, they lead to mating behaviour.

Question 19

What to discuss on pheromones?

Answer 19

Pheromones
Pheromones vs hormones
Examples of animals using pheromones 
Why we're not sure about 
MHC - what is it - why it might be a pheromone
Wedekind (1995)