3.2 Gas Exchange Flashcards
How do single celled organisms exchange with their environment?
Through their cell membrane
How does gas exchange take place in insects?
Insects have an internal network of tubes called tracheae which branch off into smaller tubes called tracheoles. Muscles can be contracted (abdominal pumping) in the insects which squeezes the tubes forcing air in and out of the spiracles. Also, oxygen moves into the tracheae by diffusion as it is used in respiration at the tissues at the end of the tracheoles and carbon dioxide leaves the tracheae by diffusion as it is being made at the end of tracheoles.
How does gas exchange take place in fish?
Fish use gills which are covered in lamellar to increase surface area. When water flows through the gills, oxygen in the water diffuses quickly into the bloodstream. Oxygen can diffuse from the water into the blood because of the counter-current system.
Explain how the counter-current system allows for efficient gas exchange in fish?
In the counter-current system, blood flows through the lamellae in the opposite direction of the flow of water through the gills. The counter-current system ensures there is always a steep concentration gradient between the water and the blood throughout the length of the gill.
How does gas exchange occur in plants?
Gas exchange happens in cells in the mesophyll layer. There are stomata mostly on the underside of the leaf (epidermis) that can open and close using guard cells to allow air to enter and leave the leaf. There are numerous interconnecting air spaces in the mesophyll layer which provide space for gas to come into contact with mesophyll cells.
How are insects adapted to control water loss?
- Spiracles which can be closed to prevent water loss
- Waxy cuticle which is waterproof
How are xerophytic plants adapted to control water loss?
- Fewer stomata - to avoid dehydration
- Sunken stomata - Traps moist air which decreases the water potential gradient between the inside and the outside of the leaves.
- Hairs covering the epidermis - Traps moist air and decreases water potential gradient between inside and outside of leaves.
- Curled leaves - shelters stomata from the wind
- Waxy cuticle on leaves and stems - waterproof
What is a xerophytic plant?
Plant adapted to dry conditions
Describe the pathway of gas exchange starting at the entrance
Trachea - Bronchi - Bronchioles - Alveoli
What three structures control ventilation in humans?
- Ribcage
- Intercostal muscles
- Diaphragm
How are alveoli adapted for efficient gas exchange?
- Many alveoli which are surrounded by many capillaries - provide large surface area
- Alveolar epithelium is made of a single layer of epithelial cells - short diffusion distance
- Quick transport of gases in blood stream - maintains concentration gradient
Describe the process of inspiration
- External intercostal muscles contract
- Diaphragm contracts and flattens
- Internal intercostal muscles relax
- Rib cage moves upwards and outwards
- Thoracic cavity increases in volume
- Pressure decreases in the lungs
- Pressure gradient is established
- Air flows into the lungs down the pressure gradient
Describe the process of expiration
- External intercostal muscles relax
- Diaphragm relaxes and moves upwards
- Internal intercostal muscles contract
- Ribcage moves downwards and inwards
- Thoracic cavity decreases in volume
- Pressure in lungs increases
- Pressure gradient is established
- Air is forced out of lungs down pressure gradient
What does a spirometer measure?
Volume of air expired and inspired
What is tidal volume?
Volume of air in a breath at rest
