Khoza M.M

Transport in Animals

Wyebank secondaryGrade 10

Life Sciences

Overview: Transport and Exchange

Every organism must exchange materials with its environment

Exchanges ultimately occur at the cellular levelIn unicellular organisms, these exchanges occur

directly with the environmentFor most cells making up multicellular organisms,

direct exchange with the environment is not possibleGills are an example of a specialized exchange

system in animalsInternal transport and gas exchange are functionally

related in most animals

Introduction • The cells of all organisms need energy for their

survival.• This energy comes from food which need to

undergo cellular respiration to release energy.• During cellular respiration CO2 also released and

O2 is required.• As a result of other metabolic activities cells give

off excretory wastes.

• Therefore, there must be a way for the cells organisms to receive food and get rid off CO2 and other excretory wastes.

• The very small organisms such as the unicellular Amoeba don’t need a transport system. Different substances diffuse in and out of their bodies across surface membranes.

• In larger organisms the process of diffusion will occur only up to a few cells into the body from the surface. Also with skin, fur and feathers acting as barriers the process is slowed.

• It is inefficient as necessary substances will not reach to cells in required time.

Simple organismsWhen your body is only 2-cell layers thick, you can get supplies in and waste out just through diffusion

• all cells within easy reach of fluid

HydraJellyfish

Why some animals do not need a transport system?

• The cells receive food directly from the water in which they live.

Example: In the phylum porifera (e.g sponges) and phylum cnidaria (e.g Jelly fish)

Fig. 42-2a

Circularcanal

Radial canalMouth

(a) The moon jelly Aurelia, a cnidarian

5 cm

• Also, oxygen enters the cells from the water, and carbon dioxide and other excretory wastes are shed into the water, by the process of diffusion.

• In slightly larger animals such as those belonging to the phylum platyhelminthes (e.g. Planaria), food reaches the cells by means of pouches in the gut.

• The cells of such animals which do not receive their food by diffusion from other cells.

• Their supply of oxygen and release of carbon dioxide and other excretory wastes, are by means of diffusion.

Examples are Porifera and Cnidarians

Why do animals need a Transport system?

• A transport system carries things to and from one place to the next.

• Diffusion will occur only up to a few cells into the body from the surface. Also with skin, fur and feathers acting as barriers the process is slowed.

• It is inefficient as necessary substances will not reach to cells in required time.

• In most other animals most of the cells are too far away from the cells that obtain food, or from those that are in direct contact with the environment.

• Examples are those that belongs to the phylum Annelida, Mollusca, Arthropoda and the vertebrates

• This means that diffusion is not good enough to transport digest food to all the cells;

• it is also inadequate to get rid of carbon dioxide and other excretory wastes from the cells.

• A special transport system is necessary to transport digested food, oxygen, carbon dioxide and other excretory wastes.

• The transport system of animal are each made up of blood tissue, blood vessels and a heart, making up a circulatory system.

• The pumping action of the heart puts the blood under pressure, forcing it through its blood vessels and then back again to the heart.

Open and Closed Circulatory Systems

• More complex animals have either open or closed circulatory systems

• Both systems have three basic components:• A circulatory fluid (blood tissue)• A set of tubes (blood vessels)• A muscular pump (the heart)

Open and closed blood systems

• In an open blood system, blood is pumped from the heart through blood vessels and reaches interconnected blood-filled spaces or sinuses called haemocoels.

• The organ lie within these haemocoels and receive their oxygen and food by diffusion from the blood which bathes (washes) them.

Open Circulatory System

• CO2 and other excretory wastes are also shed into the haemocoels by diffusion.

• This blood, laden with CO2 and other excretory wastes enters the heart, through small openings on it.

Haemocoel in which organs are present

• From the heart, the waste products are taken to excretory organs by blood.

• Most molluscs and arthropoda have an open blood system

Open Circulatory System• Open circulatory systems tend to be found in more

inactive animals.

• Most molluscs have an open system, but the highly active cephalopods (squid and octopus) have evolved a closed system.

• Insects have avoided limitation of their open system by their tracheal system for oxygen supply.

Open circulatory system

• Blood vessels lead into a cavity, which leads into a network of interior channels and spaces.

• Blood moves freely inside the body cavity in all directions.• Arthropods are a group of animals consisting mostly of insects that

have an open circulatory system.

Open Circulatory System

• Advantage - There is no diffusion barrier.

• Disadvantage - No mechanism for reducing flow to a specific part of an organ.

Feeding Energy Needs• Why do we need a circulatory

system?• supplies in

• fuel (sugars)• digestive system

• oxygen• respiratory system

• waste out• CO2

• respiratory system

• need to pick up & deliver the supplies & wastes around the body

• circulatory system

Closed blood system

• In a Closed blood system, the heart pumps blood into the large blood vessels.

• The smallest vessels which branch to form smaller and smaller vessels • The smallest vessels, called capillaries reach the organs.

• Here food and oxygen from the blood diffuses into the tissue fluid surrounding the cells of the organs .

• Also Carbon dioxide and other excretory wastes diffuses from the cells into the tissue fluid and then into the blood.

• The blood is then returned to the heart from where it is taken to the

Digestive system to pick up food. Lungs to pick up oxygen and

get rid of carbon dioxide and excretory organs to

get rid off excretory wastes

• Earthworms, larger molluscs i.e squids and octopuses and vertebrates have closed blood systems.

Closed Circulatory System• The blood is contained

within a completely closed system of vessels.

• Vessels form a closed loop, usually with some sort of pumping organ like a heart or contractile vessels.

• Vessels branch into smaller and smaller tubes that penetrate (enters) among the cells of tissues.

Closed Circulatory System

• Fine-scale control over the distribution of blood to different body regions is possible.

• Muscular walls of vessels can constrict and dilate (open) to vary the amount of flow through specific vessels.

• Blood pressures are fairly high and the circulation can be vigorous (forceful).

Advantages:

Closed circulatory system

• Blood vessels lead from one type of vessel to another, not into a body cavity (opening).

• Blood flows in one direction, continuously.

• Vertebrates have a closed circulatory system.

Worksheet 1

1. Fill in the missing words

1.1 During cellular respiration also Carbon dioxide released and Oxygen isrequired. 1.2 In some Animals Diffusion is not good enough to transport digest food to all the cells thus a special transport system is necessary to transport digest food , oxygen, carbon dioxide and other excretory wastes.

1.3 Carbon dioxide and other excretory wastes are also shed into the haemocoels diffusion.1.4 More complex animals have either open or closed circulatory systems but both systems have three basic components which are: 2.1 blood tissue; 2.2 blood vessels; 2.3 and a heart.

3. Give the correct biological term in the following statements

3.1 Here food and O2 from the blood diffuses into the tissue fluid surrounding the cells of the organs. Open circulatory system3.2 Blood vessels lead into a cavity, which leads into a network of interior channels and spaces. Closed circulatory system

Comparison of open and closed circulatory systems

  Open System Closed System

Organisms (/) Invertebrates Vertebrates

Location Of blood

Body fluid and blood freely fills the body cavity

Blood is contained in the arteries and veins

Efficiency of blood flow 

Slow and limited Fast and good

Examples of organisms 

Squid, octupus, gastropoda

Human being, cow,