organisms exchnaging substances with the environment

What does the amount of oxygen need depend on?

• amount of living cells

• Rate need to respire

The requirement of oxygen is related to volume of an organism and the rate depends on surface area

What type of surface area do small organisms have

• high surface area to volume ratio

• Get all oxygen they need by diffusion through their body surface as its a semi permeable membrane

What’s the insects gaseous exchange systems

• insects have microscopic air filled pipes called tracheae → used for gas exchange

• Air moves into tracheae through pores on a surface called spiracles

• Oxygen travels down concentration gradients towards insect cells

• Tracheae branches into smaller tracheoles which have thin permeable walls → means oxygen can directly diffuse into cells

• Carbon dioxide from cells move down the concentration gradient towards spiracles into atmosphere

• Rhythmical abdominal movements move air in and out the spiracles. This reduces pressure for oxygen to go into tracheae

What’s tracheae

Microspic air filled pipes that are used for gas exchange in insects

Respiratory system in insects

• evolved mechanisms to conserve water

• Have tiny pores on their exoskeleton called spiracles that open and close

• These lead to an internal network of tubes called the tracheae. Their shape is maintained by reinforcing rings that spiral through the walls of the tracheae

Tracheal system in insects → mass transportation

• respiratory gases move in and put of tracheal system by: - mass transport. - diffusion down the concentration gradient

• Insects use rhythmic abdominal movements that change the volume of the bodies and flush air from one end of the body to the other. This is called mass transport

Tracheal system in insects → diffusion

• cellular respiration reduces concentration of oxygen and increases concentration of carbon dioxide at the end of tracheols

→ this creates a concentration gradient so oxygen diffuses from the atmosphere towards cells and carbon dioxide does the opposite

How do insects adapt to increased activity

• When most active their muscles produce lactate

• Lactate lowers the water potential of muscles in a cell, so water moves from tracheoles to muscle cell via osmosis

• This decreases the volume of fluid in tracheoles and draws air further into them. This increases diffusion, allowing rapid intake of oxygen

• When insects fly the lactate fills up ion tracheoles and osmosis removes them. Insects lose water and don’t have a continuous supply so causes them to dehydrate → to prevent this insects close spiracles

How do insects conserve water lose

• valve allows spiracles to open and close. Usually closed to limit water evaporation

• During periods of high activity, spiracles are opened to increase air flow in tracheoles. This leads to greater water loss

• Terrestrial insects → gas exchange is a compromise between obtaining enough oxygen and minimising water loss through spiracles

How does gas exchange happen in fish

• evolved gills as an internal gas exchange surface

• During ventilation, fish open and close their mouth to chnage pressure of the buccaneers cavity which is space in the mounts. This sucks water into the cavity and forces it across the gills

• Gills composed of gill filaments which are stacked together

• Gills have many protrusions at right angles called gill lamellae → used to increase surface area

• When water is taken in it flows through mouth and exits either side of the body

• Flow of water over gill lamellae and the flow of blood within them are in opposite directions. This is called a countercurrent flow. → maintains the concentration gradient across lamellae

What’s a countercurrent flow

• when the flow of water over the gills Gills composed lamellae and the flow of blood within them are in opposite directions

• process:

  • blood with a low saturation of oxygen first meets water that is fully saturated with oxygen. This means oxygen can diffuse from water to blood

  • As the water flows alongside the blood, the oxygen of the saturation of the water decreases and the oxygen saturation increases

  • The concentration gradient is decreasing but oxygen continues to diffuse from the water to the blood

  • Because blood and water are flowing in oppose directions, the amount

What’s a concurrent (parallel) flow

When the water over the gill lamellae and the blood within them flow the same direction

What are gills supported by

The gill bar/ arch

• made of borne or cartilage

What’s the space between the gill bars called

A gill slit

• each gill has two rows of filaments and these are covered with folds

Diffusion in fish gills

• as water passes through the gills, the gas exchange occurs in lamellae

• This means there’s a short diffusion pathway

• Gills provide large surface area

• Gills have an extensive network of blood capillaries to maintain the diffusion. Haemoglobin is used to carry oxygen

Ventilation in fish gills

• can ventilate passively or actively

  • passively → fish swim forward with mouth open, - fish point mouth upstream

  • Actively(bony fish) → more efficient

    1. Mouth opens and operculum closes

    2. Buccal floor lowers so buccal cavity volume increases . As the volume increases the pressure decreases and the water flows in

    3. Mouth closes

    4. Buccal floor raises so pressure increases

    5. Operculum opens so water is pushed out through the gills

What is inhalation

• intercostal muscle pulls up

• Diaphragm moves up

• Increases volume so pressure decreases to allow air to rush in

What’s exhalation

• intercostal muscles relax

• Diaphragm relaxes

• Volume decreases so pressure increases allowing air to rush out

What are the two mechanisms of breathing

• inspiration (active)

• Expiration (passive)

What’s inspiration (active)

1. Muscles contract

   • External intercostal muscles contract, lifting ribcage

   • Diaphragm muscles contract, pulling it downwards

2. Volume of lungs increase

3. Pressure inside lungs decrease

4. Air rushes into lungs from trachea to attain a pressure equilibrium

What is expiration

1. Muscles relax

   • external intercostal muscles relax, rob cage falls

   • Diaphragm muscles relax and it moves upwards

2. Volume of lungs decrease

3. Pressure induce lungs increase

4. Air rushes out of lungs to attain pressure equilibrium

What’s a spirometer

• a device that measures volume of air passing through it during breathing.

• Results can be displayed on a kymograph trace

What is total lung capacity

• The total volume of air the lungs can hold after a maximal inhalation.

• In an averaged size adult male (70kg) this is about 6 litres

What is tidal volume

• during relaxed breathing only a small part of the lungs total capacity is replaced with each breath

• Volume inhales and exhaled is known as tidal volume

• In averaged size male this is about 0.5 litres

What’s inspiratory capacity

• maximum possible volume inhaled after a relaxed exhalation is known as inspiratory capacity

• The accuracy of this requires the patient to breath out as much as possible

What’s expiratory capacity

• maximum possible volume exhaled after a relaxed inhalation is known as expiratory capacity

• Accuracy requires patient to breath out as much as possible

What’s vital capacity

• maximum volume of air that can exhaled after a maximal inhalation

• Useful when diagnosing respiratory problems

What’s residual volume

• amount of air left in the lungs free a maximal exhalation

• it’s the capacity of the airways and alveoli when deflated, and cannot be measured with a spirometer

What is the pulmonary ventilation rate

The rate that total volume of air is moved into lungs during one minute

What’s the equation fir pulmonary ventilation rate

Pulmonary ventilation rate (dm³ min^-1) = tidal volume (dm³) x breathing rate (min-1)

What’s the order of leaf structure

Top

1. Waxy cuticle

2. 2. Upper epidermis

3. Palisade mesophyll

4. Spongy mesophyll

5. Guard cells

6. Lower epidermis

Bottom

Whats the waxy cuticles function

Hydrophobic wax prevents water loss

What the upper and lower epidermis function

Maximises light getting into cells by being transparent. Means cells can photosynthesis and respire and create gas

Whats the palisade mesophyll function

• Contains most chloroplasts for greater rate of photosynthesis.

• thin so they can be stacked vertically better

Whats the spongy mesophyll function

• big spaces of air within leaf for circulation of oxygen, carbon dioxide and water vapour

Whats the guard cells function

• Controls water loss and the rate of gas exchange by opening and closing the stomata.

• Thicker walls

What’s the stomata’s function

Space that allows gas exchange

What mechanisms do plants use for gas exchange

• guard cells

  • when turgid (full of water) the stomata remains open, allowing air to enter leaf

  • When flassid (lacks water) the stomata closes, preventing water loss, CO2 or O2 from leaving

• Spongy mesophyll

  • air spaces allow CO2 to rapidly diffuse

How do stomata ope and close

• most stomata underneath leaf

  • 1 stomata is surrounded by 2 guard cells. Guard cells control the opening and closing of the cell. When turgid its swollen and stays open when it’s flaccid its collapsed so closes

• Potassium ions enter guard cells which decreases water potential and water enters by osmosis

• Potassium ions leave guard cells which increases water potential and water leaves by osmosis

How do plants control water loss

• plants lose water during gas exchange

• Plants use specialised pores in the epidermis, stomata, to minimise water lose

• Stomata open during day for gas exchange. Water enters guard cells making then turgid which causes stomata pores to open

• When plant begins to dehydrate, guard cells lose water and become flaccid so close the stomata pore, preventing water loss

What are xerophytic plants

Plants specially adapted to live in warm dry or windy habitats

• water loss is a problem so are adapted to live in these conditions

How are xerophytes adapted

1. Sunken stomata → sunken in pits to trap moist air reducing the concentration gradient of water between the leaf and the air

2. Hairs → on epidermis to trap moist air

3. Curled leaves (spikes) → have stomata in inside protecting them from wind which will also increase rate of diffusion and evaporation

4. Reduced number of stomata → prevents water loss

Waxy, waterproof cuticle → on leaves and stems to reduce evaporation

how are alveoli adapted for efficient gas exchange

• exists in groups at ends of alveoli ducts and create a large surface area which increases diffusion as more particles can diffuse acoss

• Covered in blood capillaries. The alveoli and capillary walls are made of flattened cells known as squamous epithelium, allowing efficient gas exchange as it creates a short diffusion pathway

  • Squamous epithelium consists of 1 layer of cells and capillaries are narrow so blood must squeeze through, which slows blood flow

• O2 diffuses into red blood calls and CO2 diffuses out the blood plasma. Some air replaced with each breath, maintaining the concentration gradient

• Contain white blood cells to keep mucus out