Organisms exchange with the environment Flashcards
Describe the structure of
fish gills
-Gill filaments stacked on top of each other.
-Gill lamellae project at right angles to the gill filaments, this increases the surface area of the gills.
-The gill filaments and lamellae have a good blood
supply
Describe how a fish
exchanges gases
- Water is taken in through the mouth of the fish and
forced out over the gills. through an opening on the
side of the body.
-Gases are exchanged between the water and the blood vessels in the gills.
Explain the difference
between parallel flow and
counter-current flow
-parallel flow = blood and the water flow in the
same direction
-countercurrent flow= blood and the water flow in opposite directions.
Explain how
counter-current flow
increases the rate of gas
exchange
-Rate of gas exchange is increased because
counter-current flow maintains a diffusion gradient between the water and the blood over the whole
length of the gill.
Describe the relationship between the size of an organism or structure and its surface area to volume ratio
The larger an organism the smaller its surface area to volume ratio.
Describe how larger organisms increase their surface area to volume ratio
Larger organisms require specific exchange surfaces with large surface areas to obtain the substances they need.
Explain how surfaces are specially adapted to facilitate exchange
- large surface area relative to the volume of the organism to increase the rate of exchange
- thin so diffusion distance is short and materials can cross exchange surface rapidly
- selectively permeable to allow materials to cross
- movement of the environmental medium to maintain diffusion gradient
- transport system to ensure movement of internal medium to maintain diffusion gradient”
Describe the relationship between SA:vol and metabolic rate
Organisms with a high metabolic rate exchange more materials and therefore need a larger surface area to volume ratio
Describe how single celled organisms exchange gases
Single celled organisms are small and therefore have a large surface area to volume ration. This is sufficient to exchange the substances required
Describe how an insect exchanges gases
-Spiracles - pores on surface of insect leading to tracheae, can be opened and closed
-Tracheae - internal network of tubes supported by strengthened rings to prevent collapse.
-Tracheoles - smaller dead end tubes leading from tracheae. Extend through the body of the insect direct to respiring tissues providing a short diffusion pathway from air to cells.
Explain how insects exchange gases
- Diffusion gradient - respiration in cells uses oxygen, concentration falls in ends of tracheoles, produces a diffusion gradient causing oxygen to diffuse down from the atmosphere. The opposite applies to carbon dioxide
- Mass transport - contraction of muscles squeezes trachea and enables mass movement of air
- Water in tracheoles - intense activity causes muscle cells to respire anaerobically, producing soluble lactic acid which lowers water potential of muscle cells, water moves into cells from tracheoles by osmosis, lowering volume in tracheoles, drawing air further in and allowing it to diffuse in gas phase rather than liquid which is more rapid.”
Describe how plants exchange gases
-Gas exchange occurs by diffusion in the leaves of plants and volumes and types of gases depend on the balance between the rates of photosynthesis and respiration.
Explain the adaptations of leaves for efficient gas exchange
-Leaf is designed so that cells are close to external air and diffusion occurs in the gas phase.
-Stomata: found on the underside of the leaf and allow gases to enter. Many stomata so short diffusion pathway to cells
-Spongy mesophyll: has air spaces so large surface area compared with tissue volume, gases readily come into contact with cells, rapid diffusion
Explain how xerophytic plants balance the need to exchange gases with the need to conserve water
Plants have a large SA for photosynthesis.
To reduce water loss by evaporation:
- waterproof covering (waxy cuticle) on leaves
- Close stomata
- reduced SA:vol eg pine needles
The following adaptations trap air with high water potential to reduce water potential gradient
- rolled leaves
- hairy leaves
- stomata in pits”
Explain how terrestrial insects balance the need to exchange gases with the need to conserve water
Exchange surface has large surface area but the insect has:
- small SA:vol
- waterproof covering - chitin and a waterproof cuticle
- spiracles can be closed to reduce water loss
Describe the structure of the human gas exchange system
“Contained within the ribcage for protection and to allow ventilation to occur
Trachea - flexible airway from mouth to bronchi, has cartilage for support. Walls made of ciliated epithelium and goblet cells
Bronchi - two branches of trachea, similar structure to trachea
Bronchioles - branches from bronchi, muscular walls control air flow to alveoli
Alveoli - tiny air sacs at the end of bronchioles. made of epithelium with elastic fibres and collagen between alveoli”
Explain the functions of the human gas exchange system
To allow a large volume of oxygen and carbon dioxide to be exchanged between the blood and the environment. The gases are needed and produced by respiration
Describe the sequence of events that lead to inspiration and expiration
INSPIRATION
-External intercostal muscles contract - internal intercostal muscles relax
-Ribs pulled upwards and outwards
-Diaphragm contracts and flattens
EXPIRATION
-Internal intercostal muscles contract - external intercostal muscles relax
-Ribs move downwards and inwards
-Diaphragm relaxes and moves upwards
Explain how and why air is moved in the lungs during inspiration and expiration
INSPIRATION
-Volume of thorax increases
-Pressure in lungs decreases
-Atmospheric pressure greater than pulmonary pressure - air moves in to lungs
EXPIRATION
-Volume of thorax decreases
-Pressure in lungs increases
-Pulmonary pressure greater than atmospheric pressure - air moves out of lungs
Explain what is meant by pulmonary ventilation and how it is calculated
-Pulmonary ventilation rate is the total volume of air that is moved into the lungs during one minute.
Calculated by: tidal volume x breathing rate
Describe the features of the gas exchange surface in humans
Large surface area, thin, movement of internal and environmental medium to maintain diffusion gradient
Explain how the alveolar epithelium is adapted to maximise gas exchange
-Single layer of cells for short diffusion pathway
-Millions of alveoli allowing a very large surface area
-Good blood supply with many capillaries whose walls are one cell thick for a short diffusion pathway
Describe the purpose of digestion
To hydrolyse large molecules into small ones for absorption from the ileum into the blood
Describe structure and function of organs of the digestive system
-Salivary glands: near mouth. Pass amylase via a duct into the mouth
-Oesophagus: carries food from mouth to stomach
-Stomach: muscular sac, produces enzymes to digest protein, stores and digests food
-Pancreas: gland secreting pancreatic juice containing protease, amylase and lipase
-Ileum: long muscular tube, walls and glands secrete enzymes. villi and microvilli to increase surface area
-Large intestine: absorbs water
-Rectum: stores faeces and egests them via the anus
