Lecture 7 Flashcards
What are the 5 things to think about when adapting to life in the water?
Density, viscosity, oxygen content, heat capacity & conductivity and electrical conductivity
What are the pros of water in regards to density?
It supports an animal’s body, therefore, no need for weight-bearing skeleton & enables organisms to grow larger than terrestrial forms
What are the problems associated with viscosity?
It’s 18x denser than air so organisms must generate thrust to overcome drag
What part of a water organism’s body generates thrust?
The distal or tail end of the animal
What are the two types of drag?
Viscous and inertial drag
What is viscous drag?
Friction of water on the body
What is inertial drag?
Pressure differences through water displacement
Explain some components within viscous drag?
Affected by body surface and shape and it’s fairly constant across swimming speeds
How can viscous drag be reduced?
Smooth scales and mucous
What kind of body has a high viscous drag?
A thin body with a high surface area for muscles. Eels
Describe intertial drag
Affected by body shape, increases with speed and a thick body displaces a lot of water and results in high inertial drag
What is the common shape amongst sea animals to help cope with the different kinds of drag and increase the effectiveness of travel?
A torpedo/fusiform like shape with width/length ratios around 0.25
What also effects thrust?
The shape of the tail. A high aspect (width/length) ratio gives higher thrust relative to drag
Explain the availability of O2
O2 availability is low therefore demands efficient extraction from the water. This is why tidal ventilation is hard, hence one way flow of water over gills
Explain how water travels over the gills of fish
Buccal pumping sends the water over the gills and secondary lamellae
What is the countercurrent exchange system?
The blood flow travels opposite to the water flow to prevent exchanges from reaching an equilibrium and maximizing exchange of gases
What does the blood flow through?
The secondary lamellae
How do fish adjust buoyancy in the water? How does this work?
They use their impermeable swim bladder. They hold air within the swim bladder.
Where is the swim bladder located?
Between the peritoneal cavity and the vertebral column and occupies 5% volume in marine and 7% in fresh water teleosts
Is buoyancy depth dependent true or false?
True
How does a fish control their buoynacy if they want to move down in the water?
A fixed volume of air within the swim bladder will become compressed as pressure increases
How does a fush control their buoyancy if they want to ascend?
They must release gas. Some do this through a pneumatic duct to the stomach
What kind of fish have this pneumatic duct to control buoyancy?
Physostomous fish
Explain the actions of a goldfish controlling its buoyancy
They gulp it down and burp it up
What are physoclistous fish and how do they control their buoyancy?
They’re closed-bladder fish who’ve lost the pneumatic duct connection and regulate gas by secreting it from the blood
What is the rete mirabile?
It is a gas gland that has capillaries and a counter-current exchange system
Name some other things that the rete mirabile does
Releases lactic acid and acidifies blood
What does the acidification of blood do in physoclistous?
Causes haemoglobin to release oxygen
Explain how the rete mirabile function?
Oxygen accumulates until its rpesure exceeds that of the swim bladder. It then diffuses into the gas bladder and increases its volume.
How does a physoclistous release gas from the rete mirabile?
It releases a muscular valve (ovale) so oxygen can diffuse into the blood
How do sharks control buoyancy?
They have an oily liver
What are bottom dwelling sharks?
Negatively buoyant and have fewer and smaller oil vacuoles
What do fish (like deep sea fish) that make long vertical movements tend to rely on?
They tend to rely on more lipids than gas for buoyancy
Water conducts heat faster and is a more stable thermal environment than air, true or false?
True
Light is scattered and visibility isn’t as strong in water so what do organisms tend to use to compensate for this?
Mechanical and electrical sensitivity
Name some of the mechanical senses organisms use
Internal ear, gravity detectors and sound pressure wave detection
Explain the lateral line system
It is a line of dots on the lateral sides of an organism. It has clusters of neuromast organs dispersed over the head and body.
What are the two things that the neuromasts can lie in?
Tubular canals or epidermal depressions
What is a kinocilium?
Hair cells that are asymmetrically placed in a cluster of microvilli and is associated with two nerves
What does each nerve associated with the kinocilium do ?
One carries impulses from hairs with one orientation and the other from those reversed 180 degrees
Explain the cupula in association with detecting water flow
Pairs of hairs are within the cupula. When the hairs bend, either excites or inhibits nerve signals and signals the direction of water currents
How do electric eels generate an electrical current?
Electrocytes. Muscle cells that have lost the ability to contract but are specialised for generating an ion current flow
What are stenohaline fish?
Can only tolerate moderate changes in the salinity of water
What are euryhaline fish?
Can tolerate wide changes in the salinity of water and can often change between fresh and salt water
Explain the kidneys of a fish
Millions of tubular nephrons produce urea & remove excess water/salts/waste from blood. Blood filters through glomerulus to form ultrafiltrate
