3.1.2a/b Transport Systems in Animals Flashcards
What do transport systems do
Supply oxygen & nutrients to the sites where they are needed & remove waste products from the individual cells
5 points
Why do multicellular organisms need transport systems
- The metabolic demands of most multicellular animals are high (need lots of oxygen/food & produce lots of waste products), so diffusion over the long distances is not enough to supply the quantities needed
- The SA:V ratio gets smaller as multicellular organisms get bigger, so not only do diffusion distances get bigger, but the amount of SA available to absorb or remove substances becomes smaller
- Molecules sa hormones or enzymes may be made in one place but needed in another
- Very active so large no. of cells are all respiring very quickly, so they need constant/rapid supply of glucose & oxygen
- Waste products of metabolism need to be removed from the cells & transported to excretory organs
What is the purpose of specialised circulatory systems in multicellular animals
Multicellular animals have specialised circulatory systems (transport systems) which uses blood to carry
- glucose & oxygen around the body.
- It also carries nutrients, antibodies & hormones, & waste (like CO2)
Common features of most circulatory systems
- They have a liquid transport medium that circulates around the system (blood)
- They have vessels that carry the transport medium
- They have a pumping mechanism to move the fluid around the system
What is a mass transport system
When substances are transported in a mass of fluid w a mechanism for moving the fluid around the body, it is known as a mass transport system
2 types of circulatory systems
Large, multicellular animals usually have either an open circulatory system or a closed circulatory system
What is the haemocoel
Open body cavity of the animal
What is insect blood called
Haemolymph - it doesnt carry oxygen or CO2. It transports food & nitrogenous waste products & the cells involved in defence against disease
Issue with haemolymph in insects
- The body cavity is split by a membrane & the heart extends along the length of the thorax & the abdomen of the insect.
- The haemolymph circulates BUT steep diffusion gradients cannot be maintained for efficient diffusion. The amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demands
What does the open circulatory system of a locust do
Supplies the cells w food & removes the nitrogenous waste products
Where are open circulatory systems found
Mainly in invertebrate animals (eg. insects) - blood isn’t enclosed in blood vessels all the time. Instead, it flows freely through the body cavity
What is an open circulatory system
- In an open circulatory system, there are very few vessels to contain the transport medium. Blood is pumped straight from the heart into the body cavity (haemocoel) of the organism.
- In the haemocoel, the transport medium is under low pressure. It comes into direct contact with the tissues & cells. This is where exchange takes place between the transport medium & the cells. The transport medium returns to the heart through an open-ended vessel
OR
- The heart is segmented. It contracts in a wave, starting from the back, pumping the blood into a single main artery
- That artery opens up into the body cavity
- The blood flows around the insect’s organs, gradually making its way back into the heart segments through a series of valves
Where are closed circulatory systems found
All vertebrates (eg. fish & mammals) have closed circulatory systems - the blood is enclosed inside blood vessels
What is a closed circulatory system
- The heart pumps blood into arteries. These branch out into millions of capillaries
- Substances like oxygen & glucose diffuse from the blood in the capillaries into the body cells, but the blood stays inside the blood vessels as it circulates
- Veins take the blood back to the heart
How can the amount of blood flowing to a tissue by adjusted
By widening or narrowing blood vessels (in closed circulatory systems)
What do most closed circulatory systems contain
A blood pigment that carries the respiratory gases
What is a single circulatory system
- The blood flows through the heart & is pumped out to travel all around the body before returning to the heart.
- The blood travels only once through the heart for each complete circulation of the body
Where are single circulatory systems found
FISH
- In fish, the heart pumps blood to the gills, to pick up oxygen & then on through the rest of the body, to deliver the oxygen, in a single circuit
Where are double circulatory systems found
Birds & most mammals
- very active land animals that maintain their own body temp is made possible by their double closed circulatory system
What are double circulatory systems
involves 2 separate circulations:
- Blood is pumped from the heart to the lungs to pick up oxygen & unload CO2, & then returns to the heart (PULMONARY CIRCULATION)
- Blood flows through the heart & is pumped out to travel all around the body before returning to the heart again (SYSTEMIC CIRCULATION)
(see ss 14.01)
How many capillaries does blood pass through in single closed circulation
In a single closed circulation, blood passes through 2 sets of capillaries before it returns to heart
- In the 1st, it exchanges oxygen & CO2
- In the 2nd, in the diff organ systems, substances are exchanged between the blood & the cells
What is the effect of blood passing through 2 sets of capillaries in single closed circulation
- As a result of passing through 2 sets of very narrow vessels, the blood pressure in the system drops considerably so the blood returns to the heart quite slowly
- This limits the efficiency of the exchange processes so the activity levels of animals w single closed circulation tends to be relatively slow
What animal is an exception to the slow exchange in animals w single enclosed circulation
Fish - have countercurrent gases exchange mechanism in gills
Explain how fish can be so active with a single closed circulatory system
Their body weight is supported by the water & they do not maintain their own body temp. This greatly reduces the metabolic demands on their bodies & combined with their countercurrent exchange, explains how fish can be so active even w a single closed circulatory system
What is the effect of a double closed circulatory system
The blood travels twice through the heart for each circuit of the body. Each circuit - to the lungs & to the body - only passes through one capillary network, meaning a relatively high pressure & faster flow of blood can be maintained
How is oxygen supplied to an insect’s cells
The circulatory system supplies insect’s cells with nutrients, & transports things like hormones around the body.
HOWEVER, it doesnt supply oxygen - this is done by a system of tubes called the tracheal system
The 4 different types of circulatory systems
- Single
- Double
- Open
- Closed
What is an advantage of the mammalian double circulatory system
The heart can give the blood an extra push betwen the lungs & the rest of the body.
This makes the blood travel faster, so oxygen is delivered to the tissues more quickly
