transport systems in animals Flashcards
(59 cards)
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
