Features of Specialised Exchange ?
Large SA;Vol ratio → increases diffusion rate
Thin walls → shortens diffusion pathway
Extensive blood supply → maintains concentration gradient
Selectively Permeable → controls what is exchanged
How does gas exchange occur in insects
Air enters the tracheal system through open spiracles.
Air moves into tracheae and diffuses into tracheoles.
Oxygen dissolves in water in tracheal fluid and diffuses from tracheoles into body cells.
Carbon dioxide diffuses out of body cells into the tracheoles.
Air is then carried back to the spiracles via the tracheae and released from the body.
Components of digestion
Salivary Glands → Contain amylase → (Starch to maltose)
Oesophagus
Stomach → digests foods (esp proteins), produces acid to destroy pathogens & has muscular walls
Liver → produces bile salts → help digest lipids
Pancreas → contains enzymes
Small Intestine (ileum) → folded walls into villi increase SA & thin to shorten diffusion pathway
Large Intestine → absorbs water
Rectum & Anus → Store and release faeces
Describe Inhalation
External intercostal muscles contract and ribcage is pulled up and out
Diaphragm contracts and flattens
Thorax volume increases and pressure decreases so air is drawn in down pressure gradient
Describe Exhalation
External intercostal muscles relax and ribcage moves down and out
Diaphragm relaxes and becomes dome shaped
Thorax volume decreases and pressure increases so air is forced out by elastic recoil in lungs
How do insects limit gas exchange ?
Exoskeleton is covered in waxy cuticle
Spiracles can close
What are the adaptations for gills?
Lamellae increase surface area
Lamellae are thin → decrease diffusion pathway
Gills have good blood supply → maintains conc. gradient
Describe counter-current flow system
Blood and oxygen flow in opposite directions
So concentration gradient is maintained across whole length of lamellae
As there is always more oxygen in water than in blood
How can plants limit water loss ?
guard cells that open and close stomata
waxy cuticle
How do xerophytes limit water loss ?
thick waxy cuticle → reduces water loss
rolled leaves → maintain humid air around stomata so shallower concentration gradient
hairy leaves → maintain humid air around stomata so shallower concentration gradient
stomata in sunken pits → maintain humid air around stomata so shallower concentration gradient
small leaf SA:Vol → reduces SA for evaporation
State the adaptations of the human gas exchange system
Trachea → rings of cartilage to prevent collapsing, muscle can contract to control airflow & elastic fibres so can stretch out and spring back
Bronchi → produces mucus to trap dirt and cilia move dirty mucus to throat
Bronchioles → elastic fibres so can stretch out and spring back
Describe the role of micelles in the absorption of fats into the cells lining the ileum
Micelles include bile salts and fatty acids
They make the fatty acids more soluble
They carry fatty acids to epithelial cell lining
They maintain higher concentration of fatty acids