B2.2- The Challenges Of Size Flashcards
What is a surface area to volume ratio?
The surface area of an object is the total number of all the exterior areas of the object.
E.g. dice
Area of one face x six faces
Volume = length x width x depth
= surface area : volume
Why is surface area to volume ratio important?
The larger the organism , the lower the surface area : volume ratio.
Multicellular organisms cannot use simple diffusion to survive, as diffusion over the greater distance cannot occur fast enough.
How have multicellular organisms adapted?
Multicellular organisms have developed different adaptations to increase the surface area : volume ratio at exchange surfaces.
E.g. to maximise the rate of diffusion of oxygen into the bloodstream, lungs contain many alveoli , increasing the surface area of lungs.
To maximise the diffusion rate, the walls of the small intestine contain fingerlike villi , increasing the area of the intestine wall .
Why are transports needed?
Once a required substance has diffused into the body, it must be transported to where it is needed.
In animals, the circulatory system is the main transport system. The blood carries materials to where they are required.
Plants also have a transport system- xylem tubes carry water and mineral ions around a plant and phloem tubes transport sugars and amino acids.
What is the circulatory system?
Your circulatory system is made out of your heart and your blood vessels.
Blood transports substances around your body to the cells that need them, it also carries away waste products.
What is a double circulatory system?
Blood flows through the heart twice during each circuit of the body.
The blood that is coloured red is oxygenated blood = high level of oxygen .
The blood that is coloured blue is deoxygenated this means it has low levels of oxygen.
How does the double circulatory system work?
Your heart pumps blood to your body organs and tissues. Here oxygen and glucose diffuses out of the blood into the cells.carbon dioxide diffuses out of the cells into the blood. the blood then travels back to the heart which then pumps it to the lungs. in the lungs carbon dioxide diffuses out of the blood to be removed from the body and oxygen diffuses in. The blood returns to the heart and the cycle starts again
What are the four main blood vessels?
Pulmonary Vein
Aorta
Vena Cava
Pulmonary artery
What are blood vessels?
There are three main types of blood vessels
Arteries
Veins
Capillaries
They are all tubelike substances that transport blood around the body. The hollow cavity in the centre is called the lumen.
What is the structure of an artery?
Thick outer wall
Thick layer of muscle and elastic fibres
Small lumen
Smooth lining
What is the structure of a vein?
Fairly thin outer wall
Thin-layer of muscle and elastic fibres
Large lumen
Smooth lining
What is the structure of a capillary?
Very small lumen
Wall made of a single layer of cells
What do arteries do?
Arteries Carry blood away from the heart under high-pressure.
What do veins do?
Veins return blood to the heart. They have valves to stop blood flowing the wrong way.
What do capillaries do?
Capillaries link arteries and veins in tissues and organs.
The semipermeable walls are only one cell thick, so substances can easily move through them.
What is the pulse rate?
When your heart beats, blood is forced into arteries from the ventricles. This makes the artery expand, and then spring back (recoil) when the blood passes. You can feel this as your pulse.
What is inside your heart?
Your heart is made of cardiac muscle, only found in the heart.
Cardiac muscle cells are unusual.
The contract without receiving a nerve impulse from your brain.
Many heart muscle cells contract together to produce a heartbeat (70 bpm).
Heart diagram description
heart contains four chambers.
two smaller chambers at the top called atria (atrium)
The two larger chambers at the bottom of the ventricles.
Valve separate the chambers.
What does the aorta do?
Carries oxygenated blood around the body.
What is in blood?
You have 5 L of blood in your body. Blood is made up of: Red blood cells White blood cells Plasma Platelets
What do red blood cells do?
Small biconcave cells that have no nucleus and contain haemoglobin.
They carry oxygen.
They fit through the lumen of the capillary one cell at a time.
What is white blood cells?
Large cells that contain a nucleus.
They fight disease by making antibodies.
What is a plasma?
Straw coloured liquid that blood cells float in.
90% of plasma is water.
Many materials are transported (digested food, waste, hormones, antibodies)
What is platelets?
Tiny structures that help the blood to clot
How does a plant transport materials?
A plant has two transport systems.
One of them is xylem tissues
The second one is phloem tissues.
What does xylem tissue do?
Xylem tissue transports water and mineral ions from the roots to the stems, leaves and flowers.
Water diffuses into the root by osmosis.
Mineral ions are taken in by active transport.
What do phloem tissues do?
Transports dissolved sugars produced during photosynthesis from the leaves to all other areas of the plant. This is translocation.
Sugars are taken to meristems where they are needed for making new plant cells. This provides an energy store.
What is the structure of the xylem?
The xylem vessels are made from dead xylem cells.
There are no cell walls at the end of the cells.
The rest of the xylem cellular cell wall is thickened. This helps to provide support.
One way only
What is the structure of the phloem?
Phloem vessels are made of living cells.
The cell walls of the cells do not completely break down.
Instead sieve plates are formed.
The connection of phloem cells effectively forms a tube which allows dissolved sugars to be transported.
It is a two way flow
How do vascular bundles provide support?
In the leaf they form a network that supports the softer leaf tissue
In the stem they are located around the outer edge, providing the stand with strength to resist bending in the breeze.
In the root they are found in the centre enabling the route to act as an anchor – the root can vent as the plant moves in the wind.
What factors affect the rate of transpiration?
Light intensity
Temperature
Air movement
Humidity
How to measure the rate of transpiration?
Rate of movement = distance (mm) / time (s)
What is transpiration?
Transpiration is the loss of water from a plant leaves. The water loss must be replaced by uptake through the roots.
What is the transpiration stream?
The constant flow of water from the roots, through the xylem and out of the leaves
How does water enter the xylem?
Water diffuses from the soil into the root hairs by osmosis
How is water lost from leaves?
Stomata on the surface of leaves allow carbon dioxide to diffuse in for photosynthesis.
Guard cells allow the stomata to open and close.
While the stomata are open, water evaporates from cells inside the leaf creating concentration gradient between the air inside the leaf and the surrounding air.
Water vapour then diffuses out of the leaf into the air.
Why do plants wilt?
If a plant loses water faster than it takes in, it may wilt. The leaves collapse and droop.
The stomata close, stopping photosynthesis and prevents further water loss.
Plant will remain wilted and will eventually die if it does not receive water.
What does a potometer do?
It measures how quickly a plant shoot takes up and loses water.
What is the features of alveoli
- large surface area
- thin membrane
- good blood supply
- ventilated
