B3 Organisms Flashcards
What are the properties of gas-exchange surfaces?
Thin, permeable to gases, large surface area to volume ratio (SA:V), moist
How does diffusion happen?
Diffusion happens through concentration gradients
The higher the gradient, the faster the diffusion
e.g. oxygen is consumed during cell respiration, meaning the concentration of oxygen within a cell is always low
How do different organisms respire?
Complex organisms have ventilation systems
What is ventilation?
Moving air into and out of the lungs
Fish move fresh water through gills
How do mammals do gas exchange?
Air goes from mouth/nose to trachea
Trachea splits into two bronchi (bronchus)
Bronchus goes into lung, where it splits into several bronchioles
Bronchioles end in sack-like structures (alveoli)
How do lungs work?
Lungs are driven by muscular movement as they are not muscle tissue
Instead, lungs rely on muscles surrounding to draw air in and out
Diaphragm is the muscle group
How do alveoli work?
An alveolus is made of type 1 pneumocytes (thin cells for diffusion)
Inside alveolus are type 2 pneumocytes (produce a substance called surfactant, which reduces surface tension and produces moisture)
Alveoli are surrounded by capillaries
What do capillaries do?
Capillary walls are made up of thin, single cells to allow easy diffusion
Red blood cells travel through capillaries, and as they pass alveoli they pick up oxygen
How do lungs inhale?
During inhalation:
- diaphragm and external intercostal muscles contract
- abdominal and interior intercostal muscles relax
- volume of the chest cavity increases
- pressure decreases
- air is pulled into lungs
How do lungs exhale?
During exhalation:
* abdominal and interior intercostal muscles contract
* diaphragm and external intercostal muscles relax
* volume of the chest cavity decreases
* pressure increases
* air is forced out of the lungs
What is ventilation rate?
The number of inhalations/exhalations per minute
What is tidal volume?
The volume of air inhaled/exhaled in each breath
What is vital capacity?
The maximum amount of air the lungs can hold
What is inspiratory reserve volume?
The amount of air a person can inhale after a normal breath
What is expiratory reserve volume?
The amount of air a person can exhale after a normal breath
How are plants adapted for gas exchange?
Upper epidermis
Palisade mesophyll
Xylem
Phloem
Spongy mesophyll
Lower epidermis
Stomata (stoma) are found on the undersides of leaves
What are stomata?
Openings for gas exchange and water loss
What are the epidermis?
Upper and lower epidermis, layer to protect the leaf
What are the cuticles?
Waxy layers to prevent water loss
What is the palisade mesophyll?
Are in leaf where lots of photosynthesis occurs
What is the xylem?
What is the phloem?
What is the spongy mesophyll?
Highly adapted for gas exchange
Spongy because of holes
