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Organisms Exchange Substances With Their Enviroment, Chemical Digestion,…
- Organisms Exchange Substances With Their Enviroment
Exchange
Plants (Leaf)
6.4
Stomata
- Minute pores
- On the leavesStoma surrounded by guard cells
- Guard cells open and close the stomatal pores
- In this way controlling rate of gaseous exchange
Limiting Water Loss
- Waterproof waxy cuticle
- Thick cuticle - less water can escape
- Stoma pits or grooves - traps still moist air to reduce water potential
Fish
6.3
The Gills Multiple Gill lamellae are at a right angle to Gill FilamentsCountercurrent Exchange Principle
Water flows through gill lamellae in the opposite direction to the flow of blood Arrangement means =
- Blood already loaded with oxygen meets water with a max concentration of oxygen = diffusion
- Blood with little oxygen meets water with some oxygen removed = diffusion
Advantage
- Oxygen intake is maintained across entire gill lamellae
Insects
6.2
Tracheal System
Pathway = Spiracles - Tracheae - Tracheoles - Fluid-filled ends
Strengths:
Keeping spiracles closed prevents water loss
Weaknesses:
Relies on diffusion - for this diffusion pathway must be small - as a result, limits the size insects can attain
Limiting Water Loss
•Small surface area to volume ratio - minimises area that water is lost
•Waterproof coverings - rigid outer layer of chitin covered in waterproof cuticle.
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Enzymes and Digestion
6.9
Digestive System
Rectum
- stores faeces then removed though anus (egestion)
Pancreas
- large gland, below stomach, secrets pancreatic juice containing:
- proteases to hydrolyse proteins
- lipase to hydrolyse lipids
- amylase to hydrolyse starch
Stomach
- muscular sac, enzyme-producing inner layer (proteins), store and digest food
Salivary Glands
- secrete amylase into the mouth to hydrolyse starch into maltose
Oesophagus
- carries food from mouth to stomach
Ileum
- (small intestine)
- long muscular tube
- have villi and then microvilli on the epithelial cell of each villus
- give them a large surface area
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Chemical Digestion
- Hydrolyses large molecules into smaller ones.
- Hydrolysis - splitting a molecule by adding water to the chemical bonds that hold them together
Enzymes:
Carbohydrases - carbohydrates ~ monosaccharides
Lipases - lipids ~ fatty acids
Proteases - proteins ~ amino acids
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