Exchange (Chapter 6) Flashcards
Do smaller animals have a high surface area to volume ratio?
No they have a higher surface area to volume ratio
Do single celled organisms have mass transport systems and exchange organs?
NO- substances can diffuse directly into (and out of) the cell across the cell surface membrane. As diffusion rate is quick due to the small distance the substance has to travel.
Do multicellular animals have exchange organs and mass transport systems?
Yes
Why do multicellular organisms need exchange organs and mass transport systems?
Diffusion is slow because:
Some cells are deep in the body
Larger animals have a low surface area to volume ratio
How does body size affect heat exchange?
If an organism has a large volume its surface area is then relatively small. This makes it harder for it to lose heat from its body. And vice versa …
How does the shape of an animal affect heat exchange?
Animals with a compact shape have a small surface area relative to their volume- minimising heat loss from their surface. And vice versa
What depends on an animal being compact?
Temperature of its environment
List 4 other adaptations which aid exchange (that’s isn’t about body size/ shape)
- Small desert animals have kidney structure adaptations so that they produce less urine to compensate for their high SA:V which makes them loose water via evaporation
- To support high metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods eg. Seeds
- Smaller mammals may have thick layers of fur or hibernate when it gets cold
- Larger organisms living in hot regions- eg. Hippos, spend all day in water and elephants have large ears to increase surface area
What three adaptations do exchange surfaces usually have?
Large surface area : volume
Thin- providing a short diffusion pathway
Maintain a steep concentration gradient
Why can single celled organisms exchange gases across their body? (Via diffusion)
Relatively large surface area, a thin surface and a short diffusion pathway
So no need for a gas exchange system
What system do fish use for gas exchange?
Counter current system
Describe how fish use a counter-current system for gas exchange? (5)
- Water, containing oxygen, enters the fish through its mouth and passes out through the gills.
- Each gill is made of lots of thin plates called gill filaments, which give a large SA:VOL for exchange of gases.
- The gill filaments are covered in lots of tiny structures called lamella, which increase the surface area even more.
- The lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
- Blood flows through the lamellae in one direction and water flows over in the opposite direction. It maintains a large concentration gradient between water and the blood. Conc gradient of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.
What do insects use to exchange gases?
Tracheae
What are insect tracheae?
Microscopic air filled pipes
Explain insect gas exchange
Air moves into tracheae through pores on the surface called spiracles
Oxygen travels down the concentration gradient towards the cells
Tracheae branch off into tracheoles (which have thin permeable wall) and go to individual cells.
Carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into atmosphere
What do insects use to move air in and out of the spiracles?
Rhythmic abdominal movements
Describe the structure of a dicotyledonous plants leaf (top to bottom)
Waxy cuticle
Upper epidermis
Palisade mesophyll
Xylem and phloem (in vein)
Spongy mesophyll
Lower epidermis
Stomata and guard cells
Waxy cuticle
What gas do plants need for photosynthesis?
CO2
How are mesophyll cells adapted for gas exchange?
Large surface area
How do gases enter a leaf?
Through stomata
How are stomata controlled?
Guard cells can control wether stomata are open (for gas exchange) or closed (to stop water loss)
How do insects control water loss?
If they are loosing too much water, they close their spiracles using muscles. They also have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracles, which reduce evaporation.
How do plants reduce water loss?
Stomata open in day for gas exchange.
Water renters guard cell, making them turgid, which opens the stomata pore. If plant starts to get dehydrated, the guard cell will loose water and become flaccid, which closes the pore.
What are xerophytes?
They are plants adapted for life in warm, dry or windy habitats where water loss is a problem.
