What feature of gas exchange surfaces shortens the distance gases must diffuse between organisms and their environment?
Thin diffusion surface
Efficient gas exchange surfaces minimise the path length for diffusion.
What process allows oxygen to enter and carbon dioxide to leave a single-celled organism across its surface membrane?
Diffusion
Movement occurs down a concentration gradient without energy input.
In insects, what small external openings allow gases to enter the tracheal system?
Spiracles
Spiracles can open or close to regulate gas exchange and limit water loss.
What are the larger air tubes in insects that carry air from spiracles into the body?
Tracheae
These tubes are strengthened by chitin to prevent collapse.
What very fine tubes in insects deliver oxygen directly to respiring tissues?
Tracheoles
Tracheoles provide a large surface area for gas exchange with cells.
In fish gills, what thin plates contain capillaries and provide a large surface for gas exchange?
Gill lamellae
These structures maximise surface area and minimise diffusion distance.
What larger structures in fish gills support rows of lamellae?
Gill filaments
Water flows over filaments while blood flows through lamellae.
What principle describes water flowing over fish gills in the opposite direction to blood flow?
Counter-current principle
Maintains a diffusion gradient along the entire length of the lamellae.
True or False:
In the counter-current principle, blood and water flow in the same direction across the gill surface.
False
Opposite flow maintains a steep diffusion gradient for oxygen uptake.
What tiny adjustable pores in dicot leaves allow gases to enter and leave the leaf?
Stomata
Guard cells control the opening and closing of stomata.
What internal leaf tissue contains large air spaces that facilitate gas diffusion?
Mesophyll
The spongy mesophyll provides a large internal surface area.
What compromise must terrestrial insects balance when regulating spiracle opening?
Gas exchange and water loss
Opening spiracles allows oxygen entry but increases evaporation.
What type of plant shows adaptations to reduce water loss in dry environments?
Xerophytic plants
Examples include cacti and marram grass with specialised leaf structures.
What small air sacs in the lungs provide the main surface for gas exchange?
Alveoli
Humans have millions of alveoli creating a very large surface area.
What small airways branch from bronchi and lead to alveoli?
Bronchioles
They regulate airflow within the lungs.
What two tubes carry air from the trachea into each lung?
Bronchi
Each bronchus branches repeatedly to form bronchioles.
What structure connects the bronchi to the throat and is supported by rings of cartilage?
Trachea
The cartilage prevents the airway from collapsing during breathing.
What muscular sheet separates the thoracic cavity from the abdominal cavity and plays a key role in breathing?
Diaphragm
Contraction flattens the diaphragm and increases thoracic volume.
During inhalation, what happens to the diaphragm?
Contracts and flattens
This increases thoracic volume and lowers pressure in the lungs.
True or False:
External intercostal muscles contract during inhalation to raise the rib cage.
True
This increases thoracic volume and helps draw air into the lungs.
What equation is used to calculate pulmonary ventilation rate from breathing measurements?
PVR = tidal volume × breathing rate
Fill in the blank:
Pulmonary ventilation rate equals tidal volume multiplied by ______.
Breathing rate
Expressed as PVR = tidal volume × breathing rate.
What feature of the alveolar epithelium allows rapid gas diffusion between air and blood?
Single cell thick
The epithelium and capillary walls form a very thin diffusion barrier.
True or False:
Smoking and air pollution can increase the incidence of lung disease by damaging gas exchange surfaces.
True
Damage can reduce efficiency of ventilation and gas exchange.
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3.1.1 Monomers & Polymers9
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3.1.2 Carbohydrates22
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3.1.3 Lipids17
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3.1.4 Proteins39
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3.1.5 Nucleic Acids32
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3.1.6 ATP11
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3.1.7 Water11
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3.1.8 Inorganic ions8
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3.2.1 Cell structure52
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3.2.2 Cell division20
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3.2.3 Transport across cell membranes20
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3.2.4 Cell recognition & the immune system36
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3.3.1 Surface area to volume ratio13
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3.3.2 Gas exchange24
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3.3.3 Digestion & absorption16
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3.3.4 Mass transport39
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3.4.1 DNA, genes & chromosomes13
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3.4.2 DNA & protein synthesis14
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3.4.3 Genetic diversity & meiosis14
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3.4.4 Genetic diversity & adaptation20
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3.4.5 Species & taxonomy20
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3.4.6 Biodiversity within a community12
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3.4.7 Investigating diversity12
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3.5.1 Photosynthesis23
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3.5.2 Respiration17
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3.5.3 Energy & ecosystems20
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3.5.4 Nutrient cycles15
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3.6.1 Stimuli & Response62
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3.6.2 Nervous coordination53
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3.6.3 Skeletal muscles14
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3.6.4 Homeostasis57
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3.7.1 Inheritance12
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3.7.2 Populations15
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3.7.3 Evolution may lead to speciation22
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3.7.4 Populations in ecosystems24
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3.8.1 Gene Mutations and Protein Structure14
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3.8.2 Control of Gene Expression44
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3.8.3 Applications of Genome Projects10
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3.8.4 Gene Technologies and Their Applications46
