8.1- Transport Systems In Multicellular Animals Flashcards
What is the need for specialised transport systems in multicellular animals?
- High metabolic demands- diffusion over the long distances is not enough to meet the demands.
- SA:V ratio- gets smaller as organisms get bigger. Diffusion distances increase, amount of SA available reduced.
- Transporting molecules:
- hormones created in one place but needed in another.
- waste products of metabolism from cells to excretory organs.
- digested food from organ to every cell for use in respiration.
What is an open circulatory system?
- a circulatory system with a heart but few vessels to contain the transport medium.
- haemolymph is pumped straight from the heart through short vessels into the haemocoel of the animal.
- found mainly in invertebrate animals. (Insects)
- when heart relaxes, haemolymph is sucked back in via pores called ostia.
What is the haemocoel?
The large open body cavity of the animal.
- in the haemocoel the transport medium is under low pressure.
- comes into direct contact with the tissues and cells. This is where exchange (not gas) between the transport medium and the cells happens.
- in this cavity, haemolymph directly bathes organs and tissues, allowing diffusion.
- haemolymph moves around haemocoel due to movement of organism.
What is haemolymph?
Insect blood.
- doesn’t carry oxygen or carbon dioxide.
- transports food and nitrogenous waste products and the cells involved in defence against disease.
- it circulates but steep diffusion distances for effective diffusion cannot be maintained.
- the amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demands.
What is a closed circulatory system?
The blood is enclosed in blood vessels and doesn’t not come directly into contact with the body cells.
- the heart pumps blood around the body under pressure and quickly and the blood returns directly to the heart.
- substances enter and leave the blood by diffusion through walls of blood vessels.
- amount of blood flow adjusted by widening/narrowing blood vessels.
- most contain a blood pigment that carries respiratory gases.
Where are closed circulatory systems found?
All vertebrate groups, including mammals.
- squid, earthworms, starfish
What is a single closed circulatory system?
Blood travels only once through the heart for each complete circulation of the body.
- blood passes through two sets of capillaries before returning to heart:
1. Exchanges oxygen and carbon dioxide.
2. Substances exchanged between blood and cells.
As a result of passing through 2 narrow vessels, blood pressure in system drops so blood returns slowly = limits efficiency so activity of animal is low.
Where can a single circulatory system be found?
In fish, however they are an exception to the fact of low activity due to the slow return of blood to the heart.
- they have an efficient single circulatory system so can be very active. Mainly due to countercurrent system allowing max uptake of oxygen from water.
- their body weight supported by water so don’t need to control body temp.
- this reduces metabolic demands and combined with effective gaseous exchange, allows activeness even with single closed circulatory system.
What is a double closed circulatory system?
Blood travels through heart twice for each circuit of the body:
1. Pulmonary circulation- Blood pumped from heart to lungs to pick up O and drop off CO2. Returns to heart.
2. Systemic circulation- blood flows through hear and is pumped out all around body before returning again.
Each circuit only passes through one capillary network so high pressure and fast blood flow can be maintained. (Most efficient transport system)
Where are double closed circulatory systems found?
In active land animals that maintain their own body temp.
Most mammals and birds.
