13447489
Descripción
Fichas por Amy Warrell, actualizado hace más de 1 año
|
Creado por Amy Warrell
hace alrededor de 6 años
|
|
| Pregunta | Respuesta |
| What is tissue fluid? | Environment surrounding cells of all multicellular organisms |
| Why is diffusion alone often not sufficient for organisms to survive? | Most cells too far from exchange surface |
| What transport system do larger organisms need and what does this maintain? | Mass transport system maintains a diffusion gradient |
| Higher metabolic rate = _____ exchange needed | More |
| Materials that need to be exchanged | Respiratory gases (O2, CO2) Nutrients (glucose, amino acids etc) Excretory products (urea, CO2) Heat |
| Two ways in which exchange occurs (excluding exchange of heat) | Passively - diffusion, osmosis Actively - active transport |
| As organisms become larger, volume increases at a ______ rate than surface area | Faster |
| Features developed by organisms for effective exchange | Flattened shape - no cell ever far from surface Specialised exchange surfaces with large areas to increase SA:volume |
| 5 features of specialised exchange surfaces | 1. Large SA relative to volume of organism 2. Very thin - short diffusion pathway 3. Selectively permeable 4. Movement of environmental medium to maintain gradient 5.Transport system for movement of internal medium to maintain gradient |
| Why are specialised exchange surfaces often located inside an organism? | They are easily damaged and dehydrated |
| When an exchange surface is located inside an organism, what must there be a means of? | Moving external medium over the surface (e.g. breathing to ventilate lungs in mammals) |
| SA:volume = ______ ÷ ______ | Surface area ÷ volume |
| Single-celled organisms have a ______ SA:volume | Large |
| How does gas exchange happen in single-celled organisms? | O2 absorbed by diffusion across body surface (cell surface membrane); CO2 from respiration diffuses out [cell wall does not affect this] |
| What is the tracheae in insects? | Internal network of tubes supported by strengthening rings to prevent collapsing. Divided into smaller dead-ended tubes - tracheoles - which extent throughout all body tissues |
| 3 ways in which respiratory gases move in and out of the tracheal system in insects | 1. Along a diffusion gradient 2. Mass transport 3. Ends of tracheoles filled with water |
| How do respiratory gases move in and out of the tracheal system along a diffusion gradient? | Respiring cells use up O2 so concentration of O2 at ends of tracheoles falls, creating diffusion gradient which causes gaseous O2 to diffuse from atmosphere into cells. CO2 is removed via a concentration gradient in the opposite direction. |
| Diffusion in air is ______ than in water | Faster |
| How do respiratory gases move in and out of the tracheal system by mass transport? | Contraction of muscles squeezes trachea, forcing large amounts of air in and out |
| How do respiratory gases move in and out of the tracheal system due to the ends of the tracheoles being filled with water? | In periods of major activity, muscle cells carry out anaerobic respiration - produces lactate which is soluble so lowers water potential of cells. Water moves into cells via osmosis which draws air further into tracheoles. Final diffusion pathway is in a gas |
| What can gas exchange due to ends of tracheoles being filled with water lead to? | More water evaporation |
| How do gases enter and leave the tracheae? | Spiracles |
| What are spiracles? | Tiny pores on body surface which may be open and closed by a valve |
| Why are the spiracles mostly kept closed? | To reduce water loss |
| Limitations of the tracheal system in insects | 1. Relies mostly on diffusion of gases which requires short diffusion pathway to be effective 2. Length of diffusion pathway limits size that insects can be |
| Fish are relatively ______ so have a ______ SA:volume | Large Small |
| Why is the body surface of a fish not adequate to supply or remove respiratory gases? | It has a waterproof and gas-tight outer covering |
| What specialised exchange surfaces have fish evolved? | Gills |
| Structure/features of the gills | - Located behind the head - Made up of stacked up gill filaments - Gill lamellae at right angles to filaments |
| What happens to water once taken in by the mouth of the fish? | Forced over gills and out through an opening on each side of the body |
| The flow of water over gill lamellae is in the ______ direction to the direction of blood flow | Opposite |
| What is the term describing the opposite directions of water and blood flows? | Countercurrent flow |
| What happens in countercurrent flow? | - Blood already well loaded with O2 meets water with its maximum concentration of O2; diffusion takes place - Blood with little O2 meets water that has had most but not all O2 removed; diffusion takes place - Water always has more O2 than blood |
| How does countercurrent flow allow for efficient gas exchange in fish? | Diffusion gradient is maintained across the entire width of the gill lamellae (80% of available O2 is absorbed into the blood) so O2 diffuses into blood for whole width |
| What would happen if the flow of water and blood was parallel in the gills? | Diffusion gradient would only be maintained across part of the gill (only 50% of available O2 absorbed); concentrations of O2 would reach equilibrium |
| What gases are exchanged during photosynthesis? | CO2 taken in O2 produced |
| What can reduce gas exchange with the external air? | Using gas produced in one process in another |
| Name 6 parts that could be labelled on a diagram of the structure of a leaf | Waxy cuticle Upper epidermis Palisade mesophyll Spongey mesophyll Lower epidermis Guard cells/stomata |
| 3 adaptations of a leaf for rapid diffusion of gases | 1. Many stomata so no cell is far from a stoma - short diffusion pathway 2. Multiple interconnecting air spaces - gases can come directly into contact with mesophyll cells 3. Large SA of mesophyll cells |
| What are stomata? | Minute pores occurring mainly on leaves |
| Where on a leaf are stomata primarily found and why? | Underside/lower epidermis To reduce water loss |
| What is the role of guard cells? | To open/close the stomatal pores by becoming turgid/flaccid; this controls the rate of gaseous exchange |
| What is another term for the stomatal pore? | Stomatal aperture |
| Guard cells have a ______ outer wall and a ______ inner wall | Thin outer wall Thick inner wall |
| What do plants do to balance the conflicting needs of gas exchange and controlling water loss? | Stomata are closed at times when water loss would be excessive |
| For exchange surfaces inside organisms, how saturated with water vapour is the air around them? | 100% = less water loss |
| What specifically in insects conflicts with water conservation? | Thin and permeable surfaces with large SA - insects can easily dehydrate |
| What adaptations do insects have to reduce water loss? | - Small SA to volume ration to minimise the area over which water can be lost - Waterproof coverings on body surfaces; rigid exoskeletons of chitin covered with a waterproof cuticle - Spiracles which can be closed (largely when insect is at rest) |
| What issue does the waterproof covering of insects pose and how is this overcome? | Cannot use body surfaces to diffuse respiratory gases Internal network of tracheae instead |
| Why can't plants have a small SA:volume ratio? | Have to photosynthesise which requires large surfaces for capture of light, and gas exchange |
| What is the term for plants that survive in very dry conditions? | Xerophytes - adapted to limit water loss through transpiration and evaporation |
| What are some of the adaptations of plants to reduce water loss? | - Thick cuticles; up to 10% of water loss can occur through the waxy cuticle even though it is a waterproof barrier; the thicker the cuticle the less water lost. - Rolling up of leaves: protects lower epidermis and traps a region of still air which becomes saturated with water vapour; reduces water potential gradient between leaf and outside. - Hair on leaves: thick layer, especially on lower epidermis, again traps still, moist air next to the leaf surface. - Stomata in pits or grooves: traps still, moist air next to leaf. - Reduced SA:volume ration of leaves: better to be circular in cross-section rather than broad and flat. |
| Give an example of a plant with a thick cuticle | Holly |
| Give an example of a plant that makes use of rolling up leaves | Marram grass |
| Give an example of a plant with hair on its leaves | One type of heather Lambs ears |
| Give an example of a plant with stomata in pits/grooves | Pine trees |
| Why do mammals need to exchange large quantities of O2/CO2? | Relatively large organisms so have to support a large volume of living cells. They maintain a high body temp which is related to them having high metabolic and respiratory rates. |
| Why are the lungs located inside the body? | - Air is not dense enough to support and protect such delicate structures - The body as a whole would otherwise lose lots of water and dry out |
| What are the lungs supported and protected by? | Ribcage |
| How does the ribcage move? | Intercostal muscles |
| What ventilates the lungs? | A tidal stream of air |
| What are the lungs? | A pair of lobed structures made up of a series of highly branched tubules which end in tiny air sacs |
| What structures does air move through in the lungs to get to the exchange surface? | Trachea Bronchi Bronchioles Alveoli |
| What is the trachea? | A flexible airway supported by rings of cartilage. Tracheal walls are made of muscle lined with ciliated epithelium and goblet cells. |
| Why is it important for cartilage to support the trachea? | To prevent it collapsing when air pressure falls when breathing in |
| What are the bronchi? | Two divisions of the trachea, each leading to one lung. They are similar in structure to the trachea and secrete mucus and have cilia to move mucus to throat. The larger the bronchus, the more cartilage. |
| What are the bronchioles? | Series of branching subdivisions of the bronchi. Walls are made of muscle lined with epithelium. Muscles allow them to control the flow of air in and out of the alveoli. |
| Why is it important for the bronchioles to control flow of air in the alveoli? | To prevent them bursting |
| What are the alveoli> | Minute air sacs at the end of the bronchioles. Collagen and elastic fibres are found between them - elastic fibres allow them to stretch as they fill with air and spring back in order to expel CO2. Lined with epithelium. |
| What is the gas exchange surface in the lungs called? | Alveolar membrane |
| What is breathing/ventilation? | Process of moving air in and out of the lungs in order to maintain a diffusion gradient of gases across the alveolar epithelium |
| What sets of muscles bring about pressure changes within the lungs? | Diaphragm - sheet of muscles separating thorax and abdomen Intercostal muscles - lie between the ribs (internal intercostal muscles and external intercostal muscles) |
| What is inspiration? | Where air pressure in atmosphere is greater then that inside lungs, air is forced into lungs |
| What kind of process is inspiration? | Active process |
| Describe the process of inspiration | - External IMs contract, internal IMs relax - Ribs pulled upwards and outwards (increases volume of thorax) - Diaphragm muscles contract so it flattens (more increase in volume) - Pressure in lungs thus decreases - Atmospheric pressure now greater than pulmonary pressure, so air is forced into the lungs |
| What is expiration? | Where air pressure in the lungs is greater than that in the atmosphere so air is forced out of the lungs |
| What kind of process is expiration? | Largely passive |
| Describe the process of expiration | - Internal IMs contract, external IMs relax - Ribs pulled downwards and inwards (decreases volume of thorax) - Diaphragm muscles relax so it is pushed up by abdominal contents that were previously compressed (more decrease) - Pressure in lungs is thus increased - Pulmonary pressure is now greater than atmospheric pressure, so air is forced out of lungs |
| What is pulmonary ventilation? | Total volume of air moved into the lungs in 1 minute |
| What is tidal volume? | Volume of air normally taken in per breath when the body is at rest |
| What is breathing rate? | Number of breaths taken in 1 minute |
| How would you calculate pulmonary ventilation rate? | |
| How big is the diameter of an alveolus? | 100-300μm |
| Why are the alveoli located inside an organism? | Very thin and delicate so need protection |
| How many alveoli are there in each human lung? | About 300 million (total SA = 70m2) |
| What are alveoli lined with? | Epithelial cells |
| How thick is the alveolar wall? | 1 cell thick |
| What are the alveoli surrounded by? | Network of pulmonary capillaries |
| Width of pulmonary capillaries | Very narrow - red blood cells are flattened against the capillary walls to fit |
| How thick is the capillary wall? | 1 endothelial cell thick |
| 5 reasons why diffusion of gases between the alveoli and the blood are very rapid | 1. Red blood cells are slowed as they pass through pulmonary capillaries - more time for diffusion 2. Distance between alveolar and red blood cells is reduced due to red blood cells being flattened against capillary walls 3. Very thin capillary and alveolar walls - short diffusion distance 4. Alveoli and pulmonary capillaries have large SA 5. Breathing movements constantly ventilate lungs and action of heart constantly circulates blood - ensures a steep diffusion gradient is maintained |
¿Quieres crear tus propias Fichas gratiscon GoConqr? Más información.