B2.2 - The Challenge Of Size Flashcards
The larger the organism or structure, is the surface area to volume ratio higher or lower?
Lower
The amount of oxygen required for respiration is determined by the amount of ….
Living cells in the organism
What is the formula for Fick’s Law (the rate of diffusion)?
Surface area x difference in concentration
______________________________________________
Length of diffusion path (membrane thickness)
How do alveoli contribute to more effective gas exchange in human lungs?
Significantly increases the surface area to volume ratio, allowing more effective gas exchange between blood capillaries.
What is the site for nutrient absorption?
The small intestine
What are villi?
Simple folds on the walls of the small intestine, which increase surface area.
Microvilli further increase this surface area
Why are transport systems needed in multicellular organisms?
Multicellular organisms have a small surface area to volume ratio. They need transport systems to be able to get all of the substances that cells need to the correct place.
Why is it that as organisms get larger they need more complex transport structures?
They are larger, so they need to be able to get nutrients and oxygen/carbon dioxide across a larger space.
What are the three parts of the circulatory system?
Heart
Blood vessels
Blood
What are the two types of blood?
Oxygenated, high in 02
Deoxygenated, high in CO2
Why can’t the two blood types mix?
The circulatory system is in two parts
This is called a double circulatory system
Which side of the heart transports deoxygenated blood?
Right side
Which side of the heart transports oxygenated blood?
Left
What is the function of the arteries?
Transports oxygenated blood at high pressure away from the heart
How do arteries adapt to their function?
The small size of the lumen means the blood will be under high pressure
The elastic fibres allow the artery to stretch under pressure
The thick muscles contract to push the blood along
What is the function of the veins?
Transports deoxygenated blood at low pressure back into the heart from the body
How do veins adapt to their function?
The large size of the lumen means that the blood will be under low pressure
What is the function of the valves?
To stop blood from going in the wrong direction
What is the function of the capillaries?
The link between arterioles and venules (smaller branches of the arteries and veins)
Essential for the exchange of materials between blood and body cells - can only occur through them
How are capillaries adapted to their function?
They have thin walls so oxygen, nutrients and waste can pass in and out of them
Arteries or veins?
Carries blood away from the heart
Arteries
Arteries or veins?
Returns blood to the heart
Veins
Arteries or veins?
Thicker walls
Arteries
Arteries or veins?
Wider lumen
Veins
Arteries or veins?
High pressure
Arteries
Arteries or veins?
Lower pressure
Veins
Arteries or veins?
Valves
Veins
Arteries or veins?
Blood is oxygenated and bright red
Arteries
Arteries or veins?
Contains less O2 and deoxygenated
Veins
What is the definition of myogenic?
Contracts without nerve stimulation
What is unique about the heart compared to other muscles?
Made of cardiac muscle found nowhere else in the body
Never tires
Many heart cells contract to form a …
Heart beat
How many chambers are in the heart (and name)?
4
Left/right atrium
Left/right ventricle
What are the top 2 chambers of the heart called?
Left/right atrium
What are the bottom 2 chambers of the heart called?
Left/right ventricle
What is blood flow through the chambers controlled by?
One-directional valves
How do valves prevent backflow?
Blood naturally pushes against the valve, but it remains firmly shut
Why does the left ventricle need a thicker wall?
It has to pump blood all over the body, so it needs to generate a stronger “squeeze” on the blood
What are the two transport systems in the plant?
Xylem
Phloem
What is the function of the xylem tissue?
Transports water and mineral ions from the roots up to the stem, leaves and flowers
How do the roots take in water?
Osmosis
How do the roots take in mineral ions?
Active transport
What is the function of the phloem tissue?
Transports dissolved sugars produced during photosynthesis from the leaves to all other areas of the plant.
What is translocation?
The movement of dissolved sugars in the plant
Where are sugars taken to during translocation?
Meristems to take make new plant cells
Storage tissues in the roots, providing an energy store
What is a vascular bundle?
The structure formed by the phloem and xylem tissues
What are the two functions of the vascular bundle?
Transport of nutrients
Provides support for the plant
What are the key differences between the xylem and phloem?
Phloem has 2-way flow
Xylem has 1 way flow
Xylem transports water and mineral ions
Phloem transports dissolved sugars
No end walls between xylem cells
Sieve plates (cell walls with small holes) between phloem cells
Phloem goes from leaves to rest of plant
Xylem goes from roots to rest of plant
Xylem walls made of lignified dead cells
Phloem walls made of living phloem cells
What is transpiration?
The loss of water from the leaves of the plant
What is the transpiration stream?
The constant flow of water from the roots, through the xylem and out of the leaves
How do roots adapt for osmosis?
Root hairs increase surface area for osmosis
How does water enter the xylem?
Water diffuses from the soil into the root hairs.
Travels from cell to cell until it reaches the centre of the root and inside the xylem
How is water lost from the leaves?
The guard cells open and close the stomata.
Water then evaporates from the cells in the leaf and water vapour diffuses out of the leaf
What are the four factors affecting transpiration?
Temperature
Light intensity
Air movement/wind
Humidity
What is the formula for rate of transpiration?
Rate of movement = distance
__________
Diameter
How does water get up through trees?
The cohesion-tension theory states that water can move up against gravity because the molecules stick together
State and explain where you are most likely to find most stomata in a leaf?
You are most likely to find stomata on the bottom of the leaf, as it prevents the leaf from drying up too quickly
What is the role of guard cells in the opening and closing of the stomata?
They surround each stoma and help regulate the rate of transportation by opening and closing the stomata
The main trigger to opening and closing the stomata is light
What are the factors affecting transpiration?
Light intensity
Temperature
Air movement
Humidity
How does light intensity affect transpiration?
Provides more heat energy for the plant, increasing the rate at which the water evaporates
How does temperature affect transpiration?
Provides more heat energy for the plant, increasing the rate at which the water evaporates
How does air movement affect transpiration?
Increased air movement moves water vapour away from the plant, which keeps the water potential outside of the plant low.
This keeps a higher concentration gradient, so the rate of osmosis will be higher.
How does humidity affect transpiration?
The more humid it is, the lower the rate of transpiration, because there will be a higher water potential outside of the plant.
