B2.1-3 Flashcards
What is the Surface area to volume ratio
It is the surface area per unit volume of an object
Why can a tapeworm rely on diffusion alone to get the substances it needs?
It has a large SA:VR so diffusion distances are small and nutrients can diffuse directly into the organism quickly enough to sustain life.
Why can’t multicellular organisms rely on simple diffusion to get the substances it needs?
Diffusion over a large distance cannot occur fast enough to meet the cells demands which is why they have developed different adaptations to increase the SA:VR at exchange surfaces.
What is the main transport system in animals
The circulatory system.
The blood takes the substances where they are required
What happens if a heart muscle becomes blocked with fat?
This could lead to a heart attack as no oxygen can reach the heart. This stops the heart from beating
What makes the circulatory system?
Heart and blood vessels
Why is the circulatory system a closed system?
Because blood remains within the heart and blood vessels
What is the double circulatory system
Blood flows through the heart twice during each circuit of the body
What is the function of the circulatory system?
The circulatory system is made up of blood vessels that carry blood away from and towards the heart
What are the main blood vessels
Arteries
Veins
Capillaries
What are the adaptations of the artery?
- Thich outer wall. This helps it withstand the high pressure waves that are created when the heart beats
The wall expands with each contraction then recoils to push the blood forward - thick layer of muscle and elastic fibres
- small lumen
-smooth lining
What are the adaptations of the vein?
- fairly thin outer wall. Thick vessel walls are not required as in the veins pressure is very low
- thin layer of muscle and elastic fibres
- large lumen
- smooth lining
- one way valves which keep the blood flowing back to the heart
What are the adaptations of the capillary
- very small lumen
- wall made of a single layer of cells
- their semi-permeable walls are one cell thick so substances can easily move through them
What does the heart do?
It delivers oxygen and nutrients to your cells and enables waste to be removed
What is the heart made of
Cardiac muscle
Why is cardiac muscle unusual?
They contract without receiving a nerve impulse
Describe how blood moves around the body
- Deoxygenated blood enters the right atrium
- It is pumped to the right ventricle where the heart beats.
- It is pumped to the lungs through the pulmonary artery to collect oxygen
- the blood returns to the heart through the pulmonary vein into the left atrium.
- it is them pumped to the left ventricle
- it is then carried around the body by the aorta
What is in blood?
Red blood cells
White blood cells
Plasma
Platelets
What do red blood cells do?
They contain haemoglobin which carry oxygen.
What do white blood cells do?
They fight disease by making antibodies or by changing shape to engulf micro-organisms
What does plasma do?
A liquid that red blood cells float in
Materials are transported by being dissolved in plasma
What do platelets do?
They help the blood to clot
