Gas Exchange Topic 3 Flashcards
How does a mousse have a larger surface area to volume ratio that a hippo?
The mouse is smaller in volume so relative to its own volume it has a large surface area. A hippo has a larger volume so relative to its own volume it has a smaller surface area
How do single called organisms exchange substances with their environment
By simple diffusion due to a short diffusion pathway
Why is diffusion across the outer membrane too slow for multicellular organisms
There is a long diffusion pathway to supply enough substances for a small sa;v ration
Describe and explain the structure of gills of a fish
Each gill is made of thin plates which give a large surface area for exchange of gases which increases the rate of diffusion
Lamellae further increase the SA and they have a wide network of capillaries and a thin layer for a short diffusion pathway
Explain the counter current system
Blood and water flow in opposite directions which creates a concentration gradient across the whole length of the gill since water with a relatively high oxygen concentration always flows next to the blood with a low oxygen concentration
Explain gas exchange in dicotyledonous plants
Mesophyll cells are the main gas exchange surface in the leaf
They have a large surface area
Gases move in and out through stomata in the epidermis, they are controlled by guard cells so that the stomata can open and close to control water loss
How is gas exchanged in insects
Air moves in through spiracles and into the trachea
The trachea branch into smaller tracheoles which have thin permeable walls which go to individual cells so oxygen diffuses directly into respiring cells.
Co2 from the cells move down its own concentration gradient towards spiracles to be released into the atmosphere
How is water loss controlled in insects
Muscles can close the spiracles
They have a waterproof, waxy cuticle and tiny hairs around the spiracles to reduce evaporation
How is water loss controlled in plants
Stomata are open in the day for gas exchange so the water enters the guard cells to make them turgid to keep stomata open
Give examples of xerophtic adaptions
Stomata is sunken in pits to trap water vapour - this reduces the water potential gradient between the leaf and the air which reduces the amount of evaporation
Layers of hair on the epidermis to trap water vapour around the stomata
Curled leaves protects the leaf from the wind to reduce evaporation
What happens during inspiration
External Intercostal muscles and diaphragm muscles contact which causes the ribcage to move upwards and outwards.
This increases the volume of thoracic activity so the lung pressure decreases which causes air to flow down the pressure gradient into the lungs
What happens during expiration
The internal intercostal muscles contract and the diaphragm relaxes which causes the ribcage to move downwards and inwards
The volume of thoracic activity decreases and the pressure in the lungs increases which forces air out of the lungs down the concentration gradient
Tidal volume
Volume of air in each breath
Ventilation rate
Number of breaths per minute
Forced expiratory volume
Maximum volume of air that can be breathed out in one second
