exchange - 3a Flashcards
What is the cohesion- tension theory?
This is the theory that water is drawn from the soil because the water molecules are cohesive (stick together) so when it is pulled up the leaf other water molecules will follow.
The tension is created from water moving up the plant against the force of gravity from roots to leaves
Describe what happens to make the volume of thorax increase during inspiration
The external intercostal muscles and diaphagm contract
The rib moves inwards and upwards so the diaphragm then flattens
The volume therefore increases as the lungs can expand as pressure decreases
What is tidal volume?
The volume of air in each breath
Describe how oxygen gets from lungs into blood
It passes through the alveolar epithelium and then through capillary endothelium into the haemoglobin in blood
Why does fibrosis scar tissue cause a reduced tidal volume?
The scar tissue is less elastic and is thicker than normal lung tissue, so they cannot expand as much which means they cannot hold as much air
How does the counter current system in fish aid gas exchange?
The water and blood flow in opposite directions which creates a steep concentration gradient along the entire length of a gill
Blood flows through lamallae in one direction and water over lamallae in another
Water with high 02 conc flows into blood with lower 02 conc
Oxygen will diffuse into blood from water down the gradient
What is the phloem tissue?
This transports organic substances like sugars up and down the plant
What is the xylem tissue?
The xylem tissue transports water and mineral ions in a solution from roots to leaves
Gill structure
- The gill is made up of gill filaments
- They are covered in tiny structures called lamallae
- Lamallae have a thin surface area and good blood supply
What is transpiration ?
The evaporation of water from a plants surface
- water evaporates through the moist cell wall and accumulates in the air spaces in the leaf
- water will move out through the stomata down the water potential gradient into the air (lower potential of water)
What is the ventilation rate?
The number of breaths per minute
Describe the features of alveoli and affect on diffusion
moist - helps gases pass membrane
one cell thick - short diffusion pathway
capillary network - good blood supply
collection - high surface area
steep concentration gradient between oxygen and carbon dioxide between alveoli and capillaries (maintained by blood flow and ventilation)
Structure of xylem
long, tube like
- formed from dead cells joined end to end
- no end walls so water can pass uninterrupted
factors affecting transpiration?
- light intensity
- wind levels
- humidity
- temperature
Give two adaptations a large animal might have to survive in a hot environment
- large ears to increase surface area
- spend time in water
What is the structure of the phloem?
- Tubes
- Made of sieve cell tube element ( living cells that form the tube for transporting solutes)
- Made of a companion cell for each sieve tube ( they carry out living functions for sieve cells eg -> providing the energy for transport of solutes)
Where do gases move in and out of leaves
Through the stomata in the epidermis
Give two reasons why diffusion is too slow in multicellular organisms for them to absorb and excrete substances this way?
1) They have a higher surface area : volume ratio so slower diffusion as less area is exposed to the environment
2) Some cells are deep within the body so the distance between them and the outside environment is too great for diffusion to take place
Give adaptations that a xerophyte has in order to reduce water loss?
- waxy cuticle
- stomata sunk in pits
- curled leaves with stomata inside
- hairs on epidermis
- reduced number of stomata
What is a xerophyte?
A xerophyte is a plant that has adaptations in order to survive dry, windy and warm conditions where water loss is the main issue.
What is translocation ?
movement of solutes to where they are needed in a plant
Explain how an animals shape can help to control its temperature
- If they have a COMPACT shape they have a lower sa:v so LESS HEAT LOSS
- If they have a LOOSER shape they have a higher sa:v so MORE HEAT LOSS
Do large animals have a higher or lower SA:V ratio than small animals
Lower surface area:volume ratio
Give two things that all gas exchange surfaces have in common
- thin
- large surface area
- steep concentration gradient maintained
Name 2 substances an animal needs to release into the surroundings
Carbon dioxide / urea
Describe the structure of fish gills
- The gill is made up of gill filaments
- They are covered in tiny structures called lamallae
- Lamallae have a thin surface area and good blood supply
What is forced vital capacity?
This is the maximum volume of air that is possible to breath forcefully out of the lungs after a really deep breathe in.
What is the main gas exchange surface for a dicotyledonous plant?
The surface of mesophyll leaves
Give two adaptations a small animal may have to survive a cold environment
- Size
- Shape
- Fur
- Hibernation
- High metabolic rate
What is the difference between source and sink?
The source is where solutes are produced ( high conc)
The sink is where solutes are used up (low conc)
What is a MASS TRANSPORT system?
A mass transport system is one in multicellular organisms that allow them to exchange substances between their cells and the environment
What is forced expiratory volume (FEV1)
The maximum volume of air that can be breathed out in one second
What happens to fev1 (forced expiratory volume) during an asthma attack?
There would be less air breathed out in one second as the airways have become inflamed and irritated by a large amount of mucus being produced which causes a restriction
why do single celled organisms not need a gas exchange system
They have a thin diffusion pathway through their cell surface membrane which creates a high surface area to exchange gases
Name two substances an animal needs to take in from its environment
oxygen / nutrients / water
Why is the rate of gas exchange in someone with fibrosis slower than in a healthy person?
Thicker tissue so slower rate of diffusion
How does air get into an insect tracheae?
Through the spiracles on surface of body
Will the rate of heat loss at a given temperature be greater for an animal with a high or low surface area : volume ratio?
HIgh surface area : volume ratio as the animal is at a smaller size
What happens to make air leave the lungs during forced expiration
The external intercostal muslces relax and the internal intercostal muscles contract
The rib moves downwards and inwards
