transport systems in animals Flashcards
what does transport mean
the movement of substances such as oxygen, nutrients, hormones, waste and heat around the body
what is a single circulatory system
one in which the blood flows through the heart once for each circuit of the body
what is a double circulatory system
one in which the blood flows through the heart twice for each circuit of the body
what do all living cells need
a supply of oxygen and nutrients to grow and survive. they also need to remove waste products so these do not build up and get toxic
why don’t very small animals need a separate transport system
all their cells are surrounded by or close to the environment they live in so diffusion is sufficient for their needs
why would diffusion be slow to meet the requirements for larger animals
larger complex animals with lots of cells have a larger diffusion distance.
why are specialised transport systems needed
- as multicellular organisms get bigger, the surface area to volume ratio gets smaller. they have a bigger diffusion distance and small surface area available to absorb or remove substances
- hormones or enzymes may be made in one place but needed in another
- food will be digested in one place but needs to be transported to every cell
- multicellular organims have high metabolic rates so need lots of oxygen and water and produce lots of waste products - diffusion alone is not enough
- waste products of metabolism need to be removed from the cells and transported to excretory organs
what are the features of a good transport system
- a liquid transport medium or fluid to carry nutrients, oxygen and wastes around the body (blood)
- vessels that carry the transport medium
- pumping mechanism that creates pressure that will push the fluid around the body (heart)
- exchange surfaces that enable substances to enter the blood and leave it again where they are needed (capillaries)
- two circuits, one to pick up the oxygen and another to deliver it to the tissues
what is a mass transport medium
when susbtances are transported in a mass of fluid with a mechanism for moving the fluid around the body
what are the two types of circulatory system
open and closed circulatory systems
what is an open circulatory system
they contain few vessels to contain the transport medium. the transport medium is pumped straight from the heart into the body cavity of the animal.
what is the open body cavity called in an open circulatory system
haemocoel
how is the transport medium carried in the haemocoel
the transport medium is under low pressure and comes in direct contact with the tissues and the cells. the transport medium returns to the heart through an open ended vessel
where is an open circulatory system found
in invertebrates (insects and molluscs)
what is insect blood called
haemolymph
what does haemolymph not have
oxygen and carbon dioxide
what does haemolymph transport
waste products and cells involved in defence against disease
where is the heart located in an insect for e.g (OCS)
heart extends along the length of the thorax and abdomen of the insect
what is the problem with haemolymph
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 heart do in OCS
pumps haemolymph that moves arond the haemocoel due to the movement of the organism
what does the haemolymph do in OCS
directly bathes organs and tissues enabling diffusion
what is ostia
pores.
when the heart relaxes the haemolymph blood is sucked in via these pores
what is a closed circulatory system
blood is enclosed in blood vessels at all times and doesnt come into contact with the cells of the body
how does the heart pump blood in a CCS
heart pumps blood around the body under pressure and relatively quickly and the blood directly returns to the heart.
blood is pumped through a series of progressively smaller vessels and the blood returns to the heart via a series of progressively larger vessels
how do substances enter and leave the blood in CCS
substances enter and leave the blood by diffusion through the walls of the blood vessels
how can the amount of blood flowing to a particular tissue be adjusted in CCS
by widening or narrowing blood vessels
what do most closed circulatory systems have
a blood pigment that carries the respiratory gases
where are closed circulatory located
in vertebrates and invertebrates
where do substances diffuse in and out of the blood
in the capillaries
what is a single closed circulatory system
blood flows through the heart and is pumped out to travel all around the body before returning to the heart
how many times does the blood travel through the heart in a single closed circulatory system
only once for each complete circulation of the body
how many sets of capillaries does the blood pass in a SCCS
two set
1) exchange of oxygen and carbon dioxide
2) substances exchange between the blood and the cells
why does the blood return to the heart quite slowly in a single closed circulatory system
as a result of passing through two sets of narrow vessels, the blood pressure considerably drops so blood returns to the heart quite slowly.
what does the slow return of blood to the heart mean
the efficiency of exchange is limited and therefore animals with a single closed circulatory systems have low activity levels
give an example of an animal with a SCCS
fish
describe the path of blood in a fish
heart –> gills –> body –> heart
why are fish an exception
unlike other animals with a SCCS they have an efficient SCCS making them very active. their countercurrent exchange system in their gills allows them to take a lot of oxygen from the water
where does the blood become oxygenated in a fish
gill capillaries
where does the blood become deoxygenated in a fish
body capillaries
why can fish be active with their single closed circulatory system
- they have an efficient gaseous exchange system
- their body weight is supported by the water in which they live.
- they don’t maintain their own body temperature which greatly reduces their metabolic demands on their body
what type of closed circulatory system do mammals and birds have and why
double closed circulatory system. they are very active as they maintain their own body temperature
which is more efficient for transporting substances around the body
double closed circulatory system
how many circulations does a double closed circulatory system include
two
what is the pulmonary circulation
consists of all the vessels involved in transporting blood between the heart and the lungs.
how does blood travel in the pulmonary circulation
blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide and then returns to the heart
what does the systematic circulation consist of
consists of the vessels involved in transporting blood between the heart and the body excluding the lungs
how does blood travel in the systematic circulation
blood flows through the heart and is pumped out to travel all around the body before returning to the heart again
describe the path of blood in a double closed circulatory system
heart –> body –> heart –> lungs —-> heart
how many times does the blood travel for each circuit of the body in a DCCS
twice
how many capillary networks does each circuit pass through in a DCCS
each circuit (to the lungs and the body) only passes through one capillary network
what does the single capillary network in a DCCS do
maintains a relatively high pressure and fast flow of blood
how many chambers does the heart have
four
how many times does blood pass the four chambered heart
twice
where does the blood become oxygenated in a mammal
lung capillaries
where does the blood become deoxygenated in a mammal
body capillaries
what are the advantages of a single circulation
- does not require complex organs
- less complex
what are the disadvantages of a single circulation
- low blood pressure
- slow movement of blood
- activity level of the animal tends to be low
what are the advantages of a double circulation
- the heart can pump blood further around the body
- high pressure
- fast flow of blood
what are the disadvantages of a double circulation
- higher pressure may damage heart valves that maintain the flow of the blood in the right direction
