Transport systems in multicellular animals 8.1 Flashcards
What is the need for specialised transport systems in animals
-The metabolic demands of the most multicellular animals are high (they need lots of oxygen and food, they produce lots of waste products) so diffusion over the long distance is not enough to supply the quantities needed
-The surface area to volume (SA:V) ratio gets smaller as multicellular organisms get bigger so not only do the diffusion distances get bigger but the amount of surface area available to absorb or remove substance becomes relatively smaller
-Molecules such as hormones or enzymes may be made none place but needed in another
-Food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism
-Waste products of metabolism need to be removed from the cells and transported to excretory organs
what is the function of circulatory systems
- carries substances (O2, CO2, nutrients, waste, hormones) around an organism
what features do most circulatory systems have in come
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 meant by mass transport system
When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
Large multicellular animals usually have either an open or closed circulatory system
Describe the structure of an open circulatory system
In an open circulatory system there are very few vessels to contain the transport medium. It is pumped straight from the heart into the body cavity of the animal (haemocoel).
In the haemocoel the transport medium is under low pressure. It comes into direct contact with the tissues and the cells. There is where exchange takes place between the transport medium and the cells. The transport medium returns to the heart through an open-ended vessel.
In what animals are open-circulatory systems found
open-ended circulatory systems are found mainly in invertebrate animals, including most insects (gas exchange takes place in the tracheal system) and some molluscs.
What is insect blood called and what does it transport
what are some drawbacks of it
Insect blood is called haemolymph. it doesn’t carry oxygen or carbon dioxide. It transport food and nitrogenous waste products and the cells involved in defence against disease
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 is in the structure of the body cavity in an insect
The body cavity is split by a membrane and the heart extends along the length of the thorax and the abdomen of the insect.
Describe the structure of a closed circulatory system
In a closed circulatory system, the blood is enclosed in blood vessels and does not come directly into contact with the cells of the body. The heart pumps the blood around the body under pressure and relatively quickly, and the blood returns directly to the heart. Substances leave and enter the blood by diffusion through the walls of the blood vessels.
What can the transport medium in a closed circulatory system do that the transport medium in an open closed circulatory system
The amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels.
(Most closed circulatory systems contain a blood pigment that carries the respiratory system, unlike insect blood which is in a open circulatory system)
what animals are closed circulatory systems found in
Closed circulatory systems are found in many different animal phyla, including echinoderms (animals such as sea urchins and starfish), cephalopod molluscs including the octopods and squid, annelid worms including common earth worms, and all of the vertebrate groups, including the mammals
What are the different types of closed circulatory system
Single closed circulatory system
Double closed circulatory system
What defines a single closed circulatory system
The blood passes through 2 sets of capillaries before it returns to the heart.
what occurs when the blood in a single closed circulatory system passes through the 2 sets of capillaries
In the first, it exchanges oxygen and carbon dioxide. In the second set of capillaries, in the different organ systems, substances are exchanged between the blood and the cells. As a result of passing through these 2 sets of very narrow vessels, the blood pressure drops considerable so the blood returns to the heart quite slowly.
What are the drawbacks of a single closed circulatory system
- blood returns to heart slowly due to low blood pressure
^means organisms with this cannot be very active
what do the 2 main circulations of the double closed circulatory system involve
-Blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide, and then returns to the heart.
-Blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
