Exchanges of substances

Insect tracheal system components

tracheae: network of large tubes extending throughout the insects body

tracheoles: smaller highly branched tubes, providing a larger surface area for diffusion

spiracles: small openings on the exoskeleton that regulate gas exchange and are designed to reduce water loss

insect gas exchange system adaptations

-large surface area→ many, highly branched tracheoles

-short diffusion distance→ walls of tracheoles are only 1 cell thick

-spiracles→ controls water loss, when open, oxygen can diffuse in, when closed, water loss is reduced, hairs on the outside reduce water loss

-steep diffusion gradient→ oxygen constantly used up in respiration, so more oxygen can rapidly diffuse in through the tracheoles

-ventilation by body movement→ large insects use rhythmic body movements to actively ventilate their tracheal system

fish adaptations

-gill arches covered in gill filaments, covered in gill lamellae, increased surface area, as well as the highly folded structure

-short diffusion pathway- gill lamellae are 1 cell thick

-counter current system- blood flows in the opposite direction to water flow, to create a diffusion gradient

-many capillaries in the gill lamellae, short diffusion pathway

leaf adaptations

-large surface area- more stomata

-thin structure- short diffusion distance

-stomata

-guard cells- control opening and closing of stomata

-air spaces- diffusion pathway through the leaf

why don’t leaves have a specialised transport system for gases?

no cells are far enough from the external air

plants have a low metabolic rate, so less need for gaseous exchange

xerophytes

plants adapted to live in dry conditions

xerophytes adaptations

-sunken stomata- to trap moisture

-hairs-trap moisture

-small needle like leaves -reduces surface area for water loss

-rolled leaves- stomata in the middle for protection against wind

-reduced stomata- less places for water to escape

-thick waxy cuticle- stops water loss by evaporation

-deep root systems- reaches deep underground water sources

trachea

tube that carries air from the mouth or nose to the lungs, consists of c ring shaped cartilage so it doesn’t collapse

bronchi

two branches from the trachea leading to each lung

bronchioles

smaller branches of the bronchi, leading to the alveoli

alveoli

tiny air sacs where gas exchange occurs

alveolar epithelium

oxygen diffuses over this and the capillary endothelium into the blood by simple diffusion

carbon dioxide diffuse over this and the capillary endothelium out of the blood by simple diffusion

adaptations of the alveoli

-many so large surface area

-wall is 1 cell thick so short diffusion distance

-rich blood supply so steep concentration gradient, blood carries oxygenated blood away

-ventilation so oxygen is always moving into the lungs, maintaining the diffusion gradient

-elastic fibres allowing the walls to stretch for maintaining airflow

is inhalation active or passive?

active

inhalation

-ribs move up and out → external intercoastal muscles contract

-diaphragm contracts and flattens

-thoracic volume increases, pressure decreases

-air moves into the lungs against the concentration gradient, requires energy (active)

expiration

-external intercoastal muscles relax, ribs move in and down

-diaphragm relaxes and returns to dome shape

-thoracic volume decreases, pressure increases

-air is forced out of the lungs

tidal volume

volume of air inhaled or exhaled in a normal breath

breathing rate

number of breaths taken per minute

ventilation rate

total volume of air moved in and out per minute

breathing rate

number of breaths/ time in seconds x60

calculating tidal volume

measure the height of one normal breath cycle

calculating ventilation rate

tidal volume x breathing rate

lung disease could cause

-reduced surface area- slower flow of oxygen into blood

-increased diffusion distance

-reduced ventilation- narrow airways

-loss of elasticity

risk factors leading to lung disease

-damages lung tissue

-smoking can lead to mucus build up