BI0004 - Lecture 12 - Signalling 1
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What are 'External' signals?
Receiving and responding between animals
Signalling between plants and animals
What are signals between cells?
- Nerve impulses
- Sensory reception
- Plants / Animals
What types of signals are there?
What part of the electromagnetic spectrum do humans see?
Humans see in the visible spectrum and only directly perceive a tiny fraction of the world
Which animals see in the infra red range?
Just two animals known to see in the infrared range:
1. Pit vipers and boas use infrared to detect warm-blooded prey at night.
2. Some beetles e.g. species of Buprestidae, whose larvae infest trees recently killed by fire, uses infrared to locate smoldering tree trunks.
Vipers and boas do not use their eyes to detect heat released by their warm-blooded prey – they use pit organs
How do insects see?
They can see in the ultraviolet part of the spectrum too
How can cats and dogs see?
Cats and dogs can see the colour blue, but are insensitive to red, yellow, and green.
Rely more on contrast and movement.
What types of colour vision are there?
- Monochromatic vision – no pigments
- Pinnipeds (e.g. seals)
- Cetaceans (e.g. whales)
- Dichromatic vision – 2 pigments
- Many insects,
- Most mammals, including dogs
- Trichromatic vision – 3 pigments
- Primates (humans), bees and some other insects
- Tetrachromatic vision – 4 pigments
- Some butterflies
What are visual signals used for?
Attracting a mate
Displaying dominance or submission
Indicating food sources
How do honeybees communicate?
Honeybee dance language
Workers surround a returning forager bee
A round dance shows food is close by
- Distance is relayed by duration of each waggle and number of waggles per dance
- Direction is indicated by the angle of the dance relative to the vertical i.e. in relation to the sun
What is bioluminescence?
Animals producing light as a visual signal
Not worms but beetles.
The light-producing organs of the female glow-worm are contained in the last three abdominal segments
Light is produced by enzymatic reaction between the substance luciferin and oxygen.
The light emitted is pale green and can be switched on and off
The light attracts the male glow-worm, who quickly fly towards the light
What is aposematic colouration?
- Warning colouration
- i.e. advertisement- Honest signal
There are many ‘poison dart’ frog species in S. America. They have extremely toxic skin secretions and highly distinctive colour patterns.
Handle with care!!!!!!!
What is batensian mimicry?
Batesian mimicry occurs when a harmless species mimics a harmful one.
Mimicry can involve behaviour, but also shape and colour pattern
Hawkmoth larva puffs up its head to mimic the head of a snake
What is deceptive coloration?
Deceptive coloration: moth with "eyeballs“
Shock and awe tactics to repel potential predators
What are pheromones?
- Small molecules released into external environment
- Volatile or water-soluble
- Functions include:
- Marking trails
- Leading to food
- Defining territories
- Warning of predators
- Attracting mates
What is bombykol?
The pheromone bombykol is released by the female silkworm moth to attract a mate
Bombykol is detected by special chemical receptors on the antennae of the male
The antennae of the silkworm moth Bombyx mori are covered in hairs (lower panel), which contain some of the most sensitive chemoreceptors known and detect female sex pheromones
What complex pheromonal communication system do honey bees have?
Honey bees have 15 glands that produce different pheromones
A range of pheromones are secreted by the queen, drone and worker bee
- Alarm pheromones i.e. released when the bee stings another animal and promotes defensive behaviour
- Foot print pheromones i.e. left where bees walk and helps search for food
Nasonov pheromones which orient forager bees back to the colony
How do minnows use chemical communication?
Injured minnows produce an alarm pheromone that induces a fright response in other fish
Artificial introduction of the alarm pheromone promotes the fright response
What do territorial mammals do?
Territorial mammals mark territories by olfactory signals
Provides information on:
Transmits information about the sender e.g. female ready for mating
Avoids dangerous encounters between animals
What do bird sounds do? (Auditory communication)
Indicate territory and attracts a mate
- Divided up into songs and calls:
- Songs:- long and complex , heard mainly in breeding season
- Calls:- short, produced all year and signals flight or danger
Each species has own song repertoire
Repertoire varies with each bird
: auditory communication is particularly important in woodlands where visual cues are difficult to see due to the tree canopy
Woodland birds are not very colourful
Rely on song/calls for communication
How can auditory communication be crucial in social groups?
Example: Alarm calls in vervet monkeys
Produce a complex set of alarm calls
- Call varies with predator:
- Barking sound – leopard
- Short double cough – eagle
- Chutter - snake
Young vervets learn the calls by re-enforcement by the adult
What are infrasound and ultrasound?
Humans are deaf to ultra and infrasound, but other animals to use it to communicate.
When elephants trumpet, they also produce infrasound reaching other elephants as far as 10 kilometres away
Mammals such as dolphins and whales communicate with utrasound ‘clicks’
What is tactile communication?
Touch e.g. grooming, stroking, beak tapping is an important form of communication:
Strengthens bonds between group or mating pairs
What does drosophila courtship involve?
Drosophila courtship involves visual, chemical, tactile and auditory communication:
Male visually recognises female and female produces pheromones
Male taps female’s abdomen with his foreleg
Male vibrates wing to produce a courtship song
What is the benefits of signalling between plants and animals?
Plants need pollination by animals to reproduce
Animals get food reward
What is pollination?
Pollination: The transfer of pollen from the male anther to the female stigma
What is the function of a flower?
Function of a flower:
To attract pollinators with colourful petals, scent, nectar and pollen
Colour is an advertisement in many plants (and animals!)
Many flowering plants rely on animals for cross-pollination:
In pollination, what is the benefit for the pollinators?
Plants advertise their pollen and nectar rewards with:
- - Bees see blue, yellow, UV
- - Birds see red
- - Bats don’t see well, so flowers are white.
- Nectar or honey guides:
- - a visual guide for pollinator to locate the reward (e.g. pansy flower)
- - For insects: nectar, carrion or dung smell
What benefit do insects have when finding nectar?
Insects see UV and can detect the nectar guides provided by the plant which are not visible to the human eye
NB. Some nectar guides are visible e.g. Dalmatian toadflax (right) has yellow flowers with orange nectar guides
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