Module 3 Exchange and transport 7. Exchange surfaces 7.4 Ventilation and gas exchange in insects

Learning Objectives Success Criteria Demonstrate knowledge, understanding and application of the mechanisms of ventilation and gas exchange in insects Identify the insect tracheal system as the site of gaseous exchange (Grade E - D) Understand the mechanisms of ventilation and adaptations of gas exchange in insects (Grade C –B) Apply understanding to the examination and drawing of a insect trachea (Grade B – A) FISH DISSECTION?

Starter What challenges do insects face living on the land? What adaptations do they have to ensure their survival?

Insects are adapted to conserve water Small Surface area :Volume ratio to minimise water loss from the body surface Waterproof coverings e.g. In insects the exoskeleton is covered with a waterproof cuticle (impossible for gases to diffuse) Insects have developed a breathing system of tubes that carry oxygen directly to the tissues/organs of body Spiracles that open and close by sphincters

Insects are adapted for gas exchange Insect Tracheal System Tracheal tubes run from the body surface into the tissues Transport gases directly between the external environment and the body cells

Anatomy of insect gas exchange system The thorax and abdomen) have a pair of lip-like openings called spiracles Tracheal tubes connected to each spiracle branch into a series of tracheoles Tracheoles repeatedly divide until their numerous microscopic ends penetrate into individual body cells Towards the end of the tracheoles there is tracheal fluid which limits the penetration of air for diffusion

Adaptations of insects for gas exchange Oxygen demand increases = spiracles open Trachea lined with chitin (impermeable to gases) = keeps them open even when bent Tracheoles = permeable to gases , = very small size, so can spread between cells = large surface area = moisture on walls so oxygen diffuses to cells When oxygen demands are high, lactic acid builds up in tissues, so water moves out of tracheoles by osmosis, exposing more SA for gas exchange Complete worksheet gas exchange

Insects with high energy demands For example larger beetles, locusts and grass hoppers Collapsible enlarged trachea or air sacs Act as air reservoirs used to increase the amount of air moved through the gas exchange system by ventilating movements of the thorax and abdomen Ventilation by rhythmic abdominal movements Further speeds up the exchange of respiratory gases by generating mass movements of air in and out of the tracheal tubes by the changing pressure in the trachea and tracheoles by the movement of muscles

Histology of exchange surfaces http://www.histologyguide.org/Slide_Box/01_Introduction.html Look at slides of exchange surfaces for Alveoli Gills Trachea in insects Make a labelled diagram using skills previously learned

Homework Complete exam questions

Plenary Compile a table to compare the gas exchange systems of a human, an insects and a bony fish What structures of the gas exchange systems allow the features below? human fish insect Large surface area Short diffusion path Steep concentration gradient