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Adaptations for gas exchange (2.2) - Coggle Diagram
Adaptations for gas exchange (2.2)
Specialised exchange surfaces
Surface area to vol. ratio
In single celled organisms - short diffusion pathway
In multicellular organisms - larger distance as s.a to vol. ratio is higher, so a specialised exchange surface is needed
Features
Large s.a
Root hair cells
Thin (Short diffusion pathway / distance)
Good blood supply (Maintain gradient)
Moist - Dissolve gases
Mammalian gaseous exchange system
Lungs (Organ system)
Large surface area
Surrounded by a ribcage
External + Internal intercostal muscles
Can contract to raise + lower the ribcage
Diaphragm - separates the lungs from the abdomen
Gas exchange occurs at the alveoli - tiny sacs filled with air
Air enters through the nose, trachea, bronchi and bronchioles
Airways are held open with rings of cartilage
Rings are incomplete as the oesophagus is located behind the trachea where food is brought down
Bronchi + Trachea have a similar structure
Bronchi - Narrower + composed of several layers making a thick wall, the wall is cartilage
Cartilage (inside / loose tissue) - a layer of glandular and connective tissue, elastic fibres, smooth muscle and blood vessels.
Cartilage (inner) - epithelial layers of ciliated epithelium and goblet cells
Structures + Functions
Cartilage - Supports the trachea + bronchi, prevents lungs from collapsing during a pressure drop in exhalation
Ciliated epithelium - Present in bronchi, bronchioles + trachea, moves mucus towards throat preventing lung infection
Goblet cells - Involved in mucus secretion, found in (Same as ciliated epithelium), Mucus traps bacteria + dust to reduce risk of infection, with the help of lysozomes
Elastic fibres - Stretches when we exhale + recoils when we inhale, controls flow of air
Smooth muscle - Ability to contract, controls the flow of air to + from alveoli by constricting the airway
Inspiration
Intercostal muscles contract, Raising ribcage + pleural membrane
Difference between the pressure of the lungs and atmosphere causes air to enter the lungs
Diaphragm contracts and moves down (Flattens)
Volume in the thorax increases, meanwhile the pressure decreases
Practical
Spirometer
Used to measure lung vol.
Vaseline
Freshly cut branch
Definition
Vital capacity - maximum vol. of air that can be inhaled / exhaled in a single breath (Varies on gender, age, size...)
Tidal vol. - Vol. of air we breath in + out at each breath at rest
Can be exceeded, during exercise, where inspiratory reserve is reached in an attempt to amount of of air breathed in.
Breathing rate - Num. of breaths per minute, calculated from the spirometer by counting the number of peaks per minute
Residual volume - Vol. of air that is always present in the lungs
Bony fish
Has a small s.a to vol. ratio
Has no permeable membrane
Four pairs of gills
All supported by a gill arch
With multiple lamellae on each of them participating in gaseous exchange
Blood + water flow in opposite directions - COUNTER CURRENT FLOW
The lamellae is held apart by water flow, out of water they stick together (Decreasing s.a)
Ventilation
Mouth opens
Operculum closes
Floor of buccal cavity is lowered
Allows water to flow in
External pressure > Mouth pressure
The opposite occurs for forcing water out + through the gills
Cartilaginous fish
Gill Pouches - The 5 gills located on either side
Open to the outside by gill slits
Parallel flow - Less efficient than bony fish
Only works where conc. are equal - blood's O2 conc. is limited to 50% of its possible max value
No specialised ventilation mechanism - Must keep swimming for ventilation
Insects
Oxygen is transported directly to tissues undergoing respiration
Spiracles (located on thorax + abdomen)
Trachea + Tracheoles
At rest ends of tracheoles contain a large vol. of watery fluid
Respiration occurs at a slower rate in water than air, so during high activity fluid is decreased / withdrawn
Leaves
Malate theory
Chloroplasts in the guard cells make ATP
ATP is used to actively transport K+ into guard cells
Starch is converted into Malate ions
The malate ions and K+ ions decrease the water potential
Water moves in by osmosis and change in water potential
Stomata pore opens
This is for daytime
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Guard cells become turgid as a result of the water flowing in
Structure
Cuticle + Upper epidermis - A waxy, waterproof layer preventing excessive evaporation of water, with no chloroplasts allowing light to pass through the outer layer easily
Palisade mesophyll - Main site of photosynthesis, palisade cells contain a large number of chloroplasts for photosynthesis
Spongy mesophyll - Has air spaces which are connected to out atmosphere through stomata + facilitates gas exchange between mesophyll and atmosphere, also site of photosynthesis
Lower epidermis - Contains Guard cells, which control the opening + closing of the stomata
Guard cells open when turgid, and close when flaccid
Special gas exchange
Amoeba
Unicellular Protoctist
Simple diffusion
Features
Large s.a to vol. ratio
Thin cell membrane - fast diffusion
Unicellular - Short diffusion distance
Flatworm
Cutaneous Respiration, Skin breathing / diffusion
Cutaneous - Skin
No respiratory + circulatory system
Oxygen diffuses into skin
Shape of organism - Large s.a to vol. ratio, cells are closer to surface
Short diffusion distance
Extremely low metabolic rate + very slow movement
It is flat - meaning a large s.a to vol. ratio
Earthworm
Cylindrical - s.a to vol. ratio is lower than flat form
Moist skin - Mucus secretion for simple diffusion
Low need for oxygen - low metabolic rate + slow movement
Circulatory system - capillaries pass close to skin, gases can be transported to surface
Haemoglobin present in blood
Carbon dioxide carried in blood + diffuses out of skin