Gas exchange

Small organisms gas exchange

Simple diffusion is enough

Spiracles

Openings in the side of the body

Tracheae

Chitin lined tubes throughout the body of insnects for gas exchange

Tracheoles

Smallest tubes break off and contain fluid

Fluid in tracheoles

where gasses dissolve

sphincter

muscle that relaxes or tightens to open or close a passage in the body

why do spiracles close

reduce water loss

what is the point of air sacs

supply of air / oxygen

How are air sacs controlled

Contraction of thoracic and abdomen

Bony fish

Scales - no exchange through surface

Gill filaments

Large surface area

Rich blood supply

Short diffusion pathway

Gill arch

Bony structure for support

Gill rakers

Filter water + trap prey

Gill lamellae

Cover gill filaments

How many pairs of gills

4 pairs

Gill plates

Stacks of filaments

Operculum

Hard bony flap which covers the gills

How do fish take in water

Operculum opens

Floor of mouth cavity is lowered

Pressure difference causes water to flow in

Countercurrent flow

Steep concentration gradient maintained due to the flow of blood in the opposite direction to the water

Goblet cells

Secrete mucus - trap particles

Ciliated epithelium

Hair like structures waft mucus upwards

smooth muscle

adjust size of airways

Elastic fibres in lungs during ventilation

stretch during inhalation

recoil to force out more air during expiration

Cartilage in trachea

C-shape provide support - allows oesophagus ti expand

Inspiration

Intercostal muscles contract

Pleural membrane up + out

Diaphragm contracts to flatten

volume increased + pressure decreased

Exhalation - relaxed

Intercostal muscles relax - ribcage falls under gravity

diaphragm relaxes

Decreased volume + Increased pressure

expiration - forced

Internal intercostals contract - ribcage down + in

Abdominals contract pushing diaphragm upwards

Volume decreased + pressure increased

why are the cuticle and epidermis transparent

to allow light to mesophyll cells

What happens when a guard cell becomes turgid

Guard cell changes to open stomata

How does a guard cell become turgid

Water flows into guard cell via osmosis down a water potential gradient

Xerophytes

Plants adapted to survive in dry condition

Transpiration

Loss of water vapour from stomata / leaf surface