Ventilation & Gas Exchange In Fish, Insects & Plants

Reason fish need specialised gas exchange surface

Fish have small surface area to volume ratio and impermeable skin

Number of gills in bony fish

Four pairs

Function of gills

Gas exchange, oxygen diffuses into deoxygenated blood

Gill structure

Projections held apart by water to maintain surface area

Effect of absence of water

Gills stick together, fish cannot survive

Ventilation in fish

Maintains continuous unidirectional flow of water

First step of fish ventilation

Fish opens mouth and lowers floor of buccal cavity

Water movement across gills

Enters mouth, flows over gill filaments, exits operculum

Role of operculum

Acts as valve and pump, controlling water exit

Gas exchange in fish

Oxygen diffuses into blood, carbon dioxide diffuses out

Insects lack of circulatory transport

Oxygen delivered directly to tissues

Spiracles definition

Small openings in insects for gas entry and exit

Trachea definition

Large tubes in insect respiratory system

Tracheoles definition

Smaller tubes delivering oxygen to tissues

Gas movement in insects

Diffusion, mass transport via muscle contraction, volume changes

Leaf adaptations for gas exchange

Holes (stomata) for gas entry/exit

Function of stomata

Gases enter and leave leaves

Internal leaf adaptation

Air spaces increase surface area contact with mesophyll cells

Mesophyll cells function

Site of photosynthesis, require CO2 and O2