Unit 2 (2.2) Flashcards
Adaptations for gas exchange
How does an organisms size relate to it’s surface area?
The larger the organism, the lower surface area to volume ratio
How does surface area to volume ratio affect transport of molecules?
The lower the sa/v ratio the further the the distance the molecules must travel to reach all parts of the organism. Diffusion alone is not always sufficient in organisms with small sa/v ratios
Why do larger organisms require mass transport and specialised gas exchanged surfaces?
Small sa/v ratio
Diffusion insufficient to provide all cells with the required oxygen and to remove all carbon dioxide
Large organisms more active than smaller organisms
Four features of efficient gas gas exchange surface
Large SA
Short diffusion distance
Steep diffusion gradient
Ventilation mechanism
Gas exchange mechanism in earthworms
cylindrical, multicellular organisms with relatively small SA/V ratio (compared to flatworm)
Slow moving and low metabolic rate, therefore require little oxygen
Rely on external surface for gas exchange
Gas exchange in the amoeba
Unicellular organism with large SA/V ratio
Thin cell membrane provides short diffusion distance
Simple diffusion across the cell surface membrane is sufficient to meet demands of respiratory process.
What do large active animals with high metabolic rates need
To have ventilating mechanisms to maintain gradients across respiratory surfaces
Gas exchange mechanism in flatworms
Multicellular organisms with a relatively small SA/V ratio (compared to amoeba)
However, flat structure provides large surface area and reduces the diffusion distance
Simple diffusion is sufficient to meet demands of respiratory process.
Ventilation process in bony fish
Buccal cavity volume increases and pressure decreases to enable water to flow in
Contraction of the buccal cavity forces water across the gills
Pressure in the gill cavity rises, opening the operculum. Water leaves
Organ of gaseous exchange in fish
Gills
Common features of the specialised respiratory surfaces of larger animals, and the adaptation of respiratory surfaces to environmental conditions
Fish have gills for aquatic environments and mammals have lungs for terrestrial environments
How is a steep diffusion gradient maintained across the entire gas exchange in bony fish
Due to counter current flow
Define counter current flow
Blood and water flow in opposite directions across the gill plate.
What flow is exhibited in cartilaginous fish?
Parallel flow
Define parallel flow
Water and blood flow in the same direction across the gill plate.
Features of counter current flow
Bony Fish
Steep diffusion gradient maintained, allowing rate of oxygen across the the whole gill plate.
High rate of diffusion
More efficient- more oxygen absorbed by the blood
Featured of parallel flow
Cartilaginous fish (eg. Sharks)
Diffusion gradient not maintained
Lower rate of diffusion
Less efficient- less oxygen absorbed into blood.
Humans adaptation for gas exchange
Alveoli providing a large SA, and thin diffusion pathway, maximising the volume of oxygen absorbed from one breath. They have a plentiful supply of deoxygenated blood, maintaining a steep concentration gradient.
Adaptations of the insect tracheal system to life in a terrestrial
environment
Spiracles can be opened or closed to regulate diffusion
Bodily contractions speed up the movement of air through the spiracles
Highly branched tracheoles provide larger surface area
Impermeable cuticle reduces water loss by evaporation
Components of human respiratory system
Trachea
Pleural membrane
Bronchus
Lung
Rib
Diaphragm
Alveoli
Intercostal muscle
Bronchioles
Pleural membrane
Thin, moist layers of tissue surrounding the pleural cavity that reduce friction between the lungs and inner chest wall.
Lung
Exchanging oxygen and carbon dioxide through the process of inhalation and exhalation
Trachea function
Primary airway, carries air from nasal cavity
lined by ciliated epithelial cells which move mucus
Bronchus
Narrower than the trachea, divisions of the trachea that leads into lungs
Rib
Ribs protect internal organs
Diaphragm
The diaphragm is a dome-shaped, flat sheet of muscle under the lungs. It contracts and relaxes with the intercostal muscles during breathing.
Alveoli
The alveoli are sacs that fill with air when you breathe in. Oxygen in the alveoli diffuses into the bloodstream and carbon dioxide in the bloodstream diffuses into the alveoli, large surface area for gas exchange
Intercostal muscles
A set of muscles found between the ribs on the inside that are involved in forced exhalation.
Bronchioles
Many small divisions of the bronchi that allow the passage of air into the alveoli. Contain smooth muscle to restrict airflow to the lungs but do not have cartilage.
Mesophyll cells
These are cells within the mesophyll tissue, located between the upper and lower epidermis.
Upper epidermis with waxy cuticle
This reduces water loss from the leaf surface.
Air spaces
These are interconnecting spaces that run throughout the mesophyll layer.
structure of angiosperm leaf
Upper epidermis with waxy cuticle
Air spaces
Mesophyll cells
Stomata
Lower epidermis
Vascular tissue (xylem and phloem)
Stomata
These are small pores surrounded by guard cells on the underside of leaves that can open and close.
Lower epidermis
This is the bottom layer of cells in a leaf that contains the stomata and guard cells.
Stomata adaptation for gas exchange
It contains many stomata which enable the evaporation of water and inward diffusion of carbon dioxide.
Vascular tissue
(xylem and phloem)
This transports water and nutrients.
Palisade mesophyll layer for photosynthesis
It receives most light so contains the greatest concentration of chloroplasts
Spongy mesophyll layer adapted for photosynthesis
Contains air spaces that reduce the diffusion distance for carbon dioxide to reach the chloroplast in the palisade layer
Contains some chloroplasts
