Biology Chapter 6 Flashcards
For efficient gas exchange, should surface area be comparatively small or large compared to its volume?
Large
Small organisms generally have relatively ____ surfaces compared with their volumes
Large
Large organisms have relatively ____ surfaces compared with their volumes
Smaller
Why is diffusion alone insufficient for the needs of many organisms?
Oxygen would take too long to diffuse through the organism
what are 2 ways organisms have overcome slow diffusion?
- Flattened, no cell far away from the surface
2. Specialised gas exchange organs
5 features of adapted exchange surfaces:
- Large surface area to volume ratio
- Very thin
- Partially permeable
- Movement of environmental medium
- Movement of internal medium
Why are specialised exchange surfaces located on the inside of the body?
They are thin and can be easily damaged
Gas exchange in single-celled organisms occurs by:
Diffusion
2 ways in which insects can reduce water loss:
- Waterproof covering
2. Small surface area to volume ratio
What are tracheoles:
Small branches of the trachea
What increases ventilation in insects?
Muscle movements
What are spiracles?
Tiny pores on the surface of the body
Describe 2 ways in which gases can move in and out of the tracheal system:
- Along a diffusion gradient, as oxygen is used up in respiration and carbon dioxide is produced. Therefore, oxygen moves in and carbon dioxide moves out
- Ventilation, aided by the movement of insect’s muscles
Why must insects be small in order for this system of gas exchange to function properly?
Short diffusion pathway
What is the name of the specialised gas exchange system in fish?
The gills
Where are the gills located?
Behind the head
What is the function of the gill lamellae?
To increase the gill surface area
What is the countercurrent flow?
Water if forced over the gill lamellae in the opposite direction to the way the blood flows through the lamellae
Why is the countercurrent flow important?
To ensure maximum possible gas exchange
Gas exchange in plants is similar to:
insects
2 features of the plant gas exchange system:
- All cells close to external air
2. More rapid diffusion in the gas phase
Adaptations for rapid diffusion in plants:
- Flat, thin shape
- Stomata
- Air space network in the mesophyll
What are stomata?
Tiny pores, mainly distributed on the underside of the leaves
What is the function of the guard cells?
To open and close the stomata
Why is closing stomata important?
To prevent them from loosing too much water
Suggest how the air spaces aid photosynthesis
Having spaces allows the carbon dioxide that enters through the stomata on the underside of the leaf to reach the palisade cell which are located nearest the sunlight. This allows an adequate supply of carbon dioxide for photosynthesis
What are xerophytes?
Plants living in dry conditions that have developed adaptations to limit water loss
Give 5 adaptations of xerophytes to reduce water loss
- Thick, waxy cuticle to form a waterproof barrier
- Rolling of leaves to reduce water potential gradient, so reduced evaporation and so transpiration
- Hairy leaves to reduce water potential gradient, so reduce evaporation and so transpiration
- Stomata in pits or grooves, so reduced evaporation and so transpiration
- Reduced surface area to volume ratio, so reduced evaporation that can tale place from the leaf, so reduces transpiration
What is the structure of the trachea?
Flexible tube supported by cartilage. Walls are made of muscle, and epithelium is ciliated with goblet cells that provide mucus
What is the function of trachea?
Provides a non-collapsible airway. Mucus traps dirt and microorganisms and is delivered to the throat
What is the structure of the bronchi?
Two divisions of trachea. Similar in structure to trachea, supported by cartilage which reduces as the bronchi decrease in size
What is the structure of the bronchioles?
Made of smooth muscle lined with epithelial cells - can constrict
What is the function of bronchioles?
Control the air flow into and out of the alveoli
What is the structure of the alveoli?
Stretchy air sacs of collagen and elastic fibres
What is the function of the alveoli?
Main gas exchange surface
An asthma attack involves constructing of the air passages. Which of the parts above would you expect to constrict the most and why?
Bronchioles, as they are made of muscle with little cartilage to support them
What occurs when air pressure in the lungs is greater than air pressure outside?
Expiration
Which 2 sets of muscles are involved in the mechanism of breathing?
- Diaphragm muscles
2. Intercostal muscles
Relaxation of the internal intercostal muscles leads to:
Expiration
Contraction of the external intercostal muscles leads to:
Inspiration
Is inspiration active or passive?
Active
What happens to the internal intercostal muscles while the external ones are contracting?
They relax
Which 2 events increase the volume in the lungs?
- ribs move upwards and outwards
2. Diaphragm flattens
How does increased lung volume affect pressure?
Decreases it
Is expiration active or passive?
Largely passive
What is the resting position of the diaphragm?
Dome-shaped
What is the main cause of expiration during normal quiet breathing?
The elastic recoil from the tissue of the lungs
which 2 factors can we measure to calculate pulmonary ventilation?
- Tidal volume
2. Ventilation rate
How does oxygen move through the gas exchange system?
Trachea to the bronchi to the bronchioles to the alveoli down the pressure gradient to the alveolar epithelium to the capillary endothelium to the blood down the diffusion gradient
