Sensory Ecology Flashcards
What is sensory ecology?
The study of how organisms acquire and respond to information
What two types of questions does sensory ecology deal with?
Mechanistic questions
Functional questions
What are the 8 sensory systems?
Vision Olfaction Audition Taste Mechanoreception Thermoreception Magnetoreception Electroreception
Why is it bluer the deeper into the ocean you go?
Red and green wavelengths are absorbed more and UV light is scattered more
What is the average depth of the ocean? After what depth is there no light from sunlight?
4000 metres
After 1000 metres
What is the primary sense for the majority of animals?
Sight
What is the issue with artificial light?
It is a global anthropogenic pollutant and a major threat to the natural world
What does anthropogenic mean?
Originating in human activity
What is light?
An electromagnetic wave, but in sight only the electric field is important, not the magnetic part
What is the equation for wavelength?
Wavelength = speed / frequency
What are the properties of speed, frequency and wavelength to remember?
Speed - always constant in a vacuum
Frequency - always constant and tells us about energy
Wavelength - colour
What wavelengths are what colour?
<400mn - ultraviolet 400-500nm - blue 500-600nm - green 600-700nm - red >700nm - near infrared
What is the structure of the eyes of the Robber fly and what genus is it in?
Genus Holocephala
Eyes highly sensitive with high acuity - they capture prey with a constant bearing angle strategy
What type of eye do most animals have?
Compound eyes
What type of eye do many vertebrates have?
Camera eye
How is an image formed in the human eye?
The focusing is done by the cornea and lens together. An image is formed on the retina at the back of the eye
Why is vision blurry in water?
Water has a lower refractive power so there is a smaller difference in refractive power between the cornea and the water. Images focused far behind the retina
What two types of photoreceptor cell do vertebrates possess?
Rods and cones
What do cones provide to vision?
Colour sensitivity
What are the three types of cones?
Short wavelength - blue sensitive
Mid wavelength - green sensitive
Long wavelength - red sensitive
What animals have four types of cones and what are they known as? What is the extra cone type?
Many fish and birds, they are known as tetrachromats
The extra cone is ultraviolet sensitive
How does light stimulate rods and cones?
Light moves through the eye, through the cell bodies rods and cones to the visual pigments at the more distant end of the rods and cones.
What eyes does a nautilus have?
Pin hole camera eyes - they possess adjustable pupil that dilates or constricts in response to sudden changes in light intensity. Gives them relatively high resolution considering they have no lens, although the image will always be quite dark as there is only a limited area for light to enter the eye
What feature do deep-sea sharks possess and what is its benefit?
They have a reflecting mirror called a tapetum st the back of their eye. The mirror is made from
How many types of invertebrate eye are there? How many of those are compound eyes?
10
8 are compound eyes
What are superposition eyes?
An invertebrate eye which forms a single erect image
Light from different angles goes to different photoreceptors
What are apposition eyes?
Eyes that form multiple inverted images
All light from one facet goes to the same photoreceptor cells
Of the 10 types of invertebrate eyes, how many of what eye type are there?
3x superposition (compound) 5x apposition (compound) 1x mirror 1x simple (camera type)
What type of eye does a fiddler crab have?
Apposition compound eye
Which eyes are more sensitive, apposition or superposition?
Superposition
What organisms have simple eyes?
Box jellyfish larva Polychaete larval ocellus Flatworm Inverse cup eye of planarian flatworm Lens eye of juvenile box jellyfish
How do pigments provide colour to organisms?
We see the colour of the reflected light. Pigment colour looks very different to organisms who have ultraviolet sensitivity - gives different areas different brightness
What do bifocal eyes allow?
Image separation
What is the difference between constructive and destructive waves?
Two constructive waves together intensity the colour, whereas two destructive waves together removes colour
How is structural colour produced?
Constructive interference creates the iridescent and metallic looking colours we see in beetles, fish and butterflies. The periodicity of the structure has to be about the same as the wavelength of light
What is periodicity?
The quality or character of being periodic; the tendency to recur at intervals
Example of structural colour - morpho butterflies (genus)
Nano-structured materials create multiple reflections that interfere with each other constructively. Morpho butterflies have scales with ‘christmas tree’ structures which cause structural interference and colouration. Adding water to a scale fills the air gaps and changes the refractive indices, therefore changing the colour
What percentage of the world population lives under light-polluted skies?
80% worldwide
99% in US and Europe
What is the angle of polarisation?
The mean angle at which electric fields of multiple waves oscillate
What is the degree of polarisation?
Describes how close the angles of the waves are to each other. If the degree of polarisation is 1, then all the electric fields are oscillating in the same direction
Measure of how much of light present is polarised
How do animals use the polarisation of light?
As a source of visual information
How do insects use celestial polarisation?
They use it for navigation - the angle of polarisation is always at 90 degrees to the direction of the sun
How does light pollution affect skylight polarisation?
It can mask polarisation, which can affect organisms which rely on skylight polarisation for navigation
What temperature do hyper-thermophiles live in?
80-110 degrees Celsius
Mainly bacteria and Archaea
What are Archaea?
Single-celled microorganisms with no nucleus or other membrane bound organelles which use sulphur instead of oxygen as an electron acceptor during cellular respiration
They are prokaryotes, and are of interest in industries for catalysis reactions and heat tolerant enzymes
Features of thermophilic bacteria
Similar use of sulphur in poor oxygen environments to archaea
High levels of saturation in lipids helps keep the membranes stable
What is the earlier evidence of life and what type of organism was it thought to be
Stromatolites - fossilised layers of thermophilic bacteria
What are ‘black smokers’?
Chimneys formed from deposits of iron sulphide, which is black
What is a hydrothermal vent?
A fissure in the planet’s surface from which geothermal heated water issues
What are ‘white smokers’?
Chimneys formed from deposits of barium, calcium and silicon, which are white
What can come bacteria oxidise?
Hydrogen sulphide
What animals make up hydrothermal vent communities?
Crustaceans and worms
What happens to vent crabs as they grow?
They lose the optics (focusing abilities) of their eyes as they grow, using only a flat retina
What can the temperatures in hydrothermal vents reach?
300-400 degrees Celsius
What is an example of a species with extreme drought tolerance?
Selaginella lepidophylla (desert plant)
What do Antarctic fishes possess that lower the freezing point of most of their body fluids below the freezing point of seawater?
Biological antifreezes
What is the freezing point of seawater?
-1.9 degrees Celsius
What must the antifreezes not do to the fish?
They must not substantially increase their osmotic pressure
Does antifreeze appear in Northern hemisphere fishes?
Yes, but only seasonally
What is the difference in volume of the hydrosphere compared to the terrestrial biosphere?
It is 10x higher
What are the uses of bioluminescence?
Predators use it for lure
Prey use it as an anti-predator defence
At what depth have snailfish been found?
7700m
How do deep sea eyes have greater sensitivity?
They are tubular eyes so have large lenses with a large collecting power
What adaptation does a spookfish have?
It has 4 eyes - 2 normally facing upwards and 2 downwards. The secondary eyes can act as a curved ‘rear view’ mirror and reflect light onto an accessory retina, producing an image. The mirror structure is a layer of crystals which are arranged optimally to shine light onto the secondary retina
How does the angler fish attract prey?
Using lures
Most deep sea fish have visual pigments sensitive to what wavelengths?
460-490 nm
How do dragon fish search for prey?
They use photophores under their eyes to produce a ‘search light’ for prey
Which species emits red-red light, which is invisible to other deep-sea animals? How is it able to see this red light?
Malacosteus niger
It enhances its long-wavelength sensitivity using a derivative of chlorophyll as a red light photosensitiser for the visual pigment
What are a common forms of camouflage in the deep sea?
Transparency
Pigmentation
Where are the majority of transparent species found?
In the pelagic region of the open ocean
What are examples of some transparent animals?
Medusae (polyp) Ctenophore (comb jellies) Polychaetes (annelids) Gastropods (snails/slugs) Fish
How does pigmentation work as camouflage?
Animals living at greater depths use red or black pigments for camouflage as red sensitivity is minimal in the deep sea
Where does transparency work best?
Where there is light - the upper mesopelagic zone as they can hide under diffuse downwelling illumination but not direct illumination
Why doesnt transparency work under direct illumination?
Reflections will give the animal away
What depth is the mesopelagic zone?
200-1000m
Why is there a shift to red and black pigmentation at deeper depths?
Silhouettes under downwelling light is not a problem as it is too dark, and blue bioluminescence must be absorbed to avoid detection
What is the depth of the the Bathypelagic zone?
1000-4000 metres
What can squid do to remain camouflaged?
They can alternate between transparent and producing a red pigment, depending on whether they are illuminated with blue light or not
What is a swim bladder?
Controls buoyancy - some deep sea fish have lost their swim bladder, whilst others can pressurise it to very high levels so it doesn’t implode
Up to what pressure can animals store pure oxygen in their swim bladder?
200 atmospheres - 2000m deep
What is the result of increasing the pressure on cell membranes?
Decreased fluidity - membranes turn gel-like
What are 5 lipids that deep sea animals have in their cell membranes?
Fatty acids Glycerolipids Glycerophospholipids Sterol lipids Sphingolipids
What type of fatty acids allows the membrane to remain fluid at high pressures or low temperatures?
Unsaturated fatty acids - increasing the level of unsaturation stops the membranes phase separating and some components going into a gel phase at high pressures
What is the name of the adaptation that allows cell membranes to maintain a functional state at temperatures or pressures that are too high or low and may cause the membrane to transition to a non-functional state?
Homeoviscous adaptation
What do different amino acid properties affect?
Compressibility - a shift in the amino acid sequence of the visual pigment changes the compressibility of the protein
What type of formula relates the compressibility of a protein with its amino acid sequence?
Empirical formulas - they can be used to determine if the compressibility of visual pigments of fish a cephalopods vary in animals that live deeper and at higher pressures
What is the correlation between depth and protein compressibility?
Protein compressibility negatively depends on depth - visual pigments in deeper-living animals are less compressible
What type of evolutionary mechanism has reduced the compressibility of visual pigments in many deep sea animals?
Convergent evolutionary mechanism
What is anthropocentric bias?
Humans think every living thing views the world in the same way that we do - humans are the centre of the universe
What are passive senses?
They collect information using available energy (e.g. sunlight, ambient sounds)
What are active senses?
They probe the environment with self-generated energy and analyse how the environment modified the outgoing energy
What do our senses perceive from electromagnetic waves?
Vision
Thermoreception
What do our senses perceive from mechanical stimuli?
Hearing Touch Acceleration Balance Pressure and current Proprioception Thermoreception