Transport In Animals

Question 1

Explain how spiracles in insects support gas exchange

Answer 1

Insects are covered with a protective exoskeleton made up of the the polysaccharide chitin. Gases such as oxygen and carbon dioxide cannot easily pass through theexoskleton . As a result there are small openings on the surface of the exoskeleton called spiracles which allow gas exchange

Question 2

Explain how the tracheae in insects support gas exchange

Answer 2

Spiracles lead into a network of tubes called tracheae which are relatively wide with a diameter of 1mm. The trachea extends down and along the insects body - short diffusion pathway

The walls of the tracheae are reinforced by spirals of chitin which prevents the tracheae from collapsing - constant flow of gas / volume maintained.

Question 3

Explain how Tracheoles in insects support gas exchange

Answer 3

Tracheoles extend from the tracheae which are very fine tubes. They have a diameter of 1micrometre of less - short diffusion pathway

Each tracheole is a single cell that has extended to form a hollow tube into the insects cells - close proximity to cells.

The narrow diameter and close proximity of Tracheoles to cells result in a short diffusion distances for gases moving between the cells and Tracheoles. This allows oxygen to diffuse from the air into the Tracheoles to cells for aerobic respiration and CO2 is diffused out.

The huge number of Tracheoles provide a very large surface area for gas exchange. This allows insects to maintain a very rapid rate of aerobic respiration (during flight)

Question 4

Explain how tracheal fluid in insects support gas exchange

Answer 4

The end of Tracheoles contain a tracheal fluid. During intense activity cells around Tracheoles undergo anaerobic respiration. This produces lactic acid which lowers the water potential of cells. The water moves into the cell which reduces the volume of targetable fluid, drawing air down into the Tracheoles. (More tracheole surface for gas exchange)

Question 5

Explain the passive process of gas exchange in insects

Answer 5

Gas exchange is a passive process- oxygen diffuses down into the concentration gradient from the high concentration in the external air into the Tracheoles where the concentration Is lower.

Carbon dioxide diffuse down the concentration gradient from the relatively high concentration in the Tracheoles out to the external air

Question 6

Explain how the size of insects support gas exchange

Answer 6

The small size of insects reduce the distance required for diffusion to take place

Question 7

What problems do insects face in their gas exchange system and how is this prevented.

Answer 7

Walls of Tracheoles are moist and the ends of Tracheoles contain tracheae fluid. This means water vapor can diffuse out of an insect via the spiracles. However, each spiracle is surrounded by a muscular sphincter which closes the spiracle and reduces water loss.

Question 8

Describe how some insects have evolved to increase the rate of gas exchange

Answer 8

Insects have three main body segments:

Some insects con contract muscles to change the volume of the thorax and abdomen which causes pressure changes in the Tracheae and Tracheoles pushing air in and out.

This bulk movement of air is called mass transport.

In some sections, the tracheae contain an expanded section called an air sac. The change in the volume of the thorax and abdomen can squeeze the air sacs causing air to move into the Tracheoles

Insects also use the air sacs when spiracles have been closed for water conservation

Question 9

What are bony fish

Answer 9

bony fish are a large group of fish, which have evolved a skeleton made of bone.

Question 10

What are example of bony fish

Answer 10

Tuna, cod,trout, salmon

Question 11

Why do bony fish face significant problems during gas exchange

Answer 11

Bony fish are large and active organisms with a very high oxygen requirement

The large size of fish result in a very low surface area to volume ratio

Scaly surface of bony fish don’t allow gases to pass through

Question 12

Why have bony fish evolved to have a Specialised gas exchange system

Answer 12

The concentration of oxygen in water is much lower than in air thus bony fish evolved to have a Specialised gas exchange system. This is done to extract the maximum amount of oxygen from water

Question 13

Explain how the operculum of bony fish support gas exchange

Answer 13

A flap of tissue slightly behind the head on either side of the fish is called an operculum. Behind that is the operculum cavity which contain gills.

Question 14

Explain how gas exchange works within bony fish

Answer 14

Oxygen-rich water enters the fish through the mouth. The water passes over the gills where it diffuses from the water into the blood and carbon dioxide diffuses from the blood into the water. Finally, the water passes out through the operculum opening

Question 15

Explain the structure of gills and gill filaments

Answer 15

Gills consist of several bony gills arches. Extending from each gil arch are a large number of Gil filaments.

Many pairs of Gil filaments extend from each gill arch. Gil filaments are covered with numerous gill lamellae which are also sometimes called gill plates

Question 16

How does the gill lamellae exchange gas

Answer 16

Water flows between the gill lamellae. Oxygen diffuses from the water into the bloodstream and carbon dioxide diffuses from the blood stream into the water

Question 17

How is lamellae adapted for efficient diffusion of gases

Answer 17

Gill lamellae have a massive surface area for gases to diffuse over.

There is a very short diffusion distance through the walls of the lamellae into the blood stream

Gill lamellae have any extensive network of blood capillaries

A Steep concentration gradient of oxygen is maintained as once oxygen is diffused into the bloodstream its carried away.

The counter-current exchange system: Blood with a low concentration of oxygen passes into the capillaries of the gill lamellae. As it passes through the gill lamellae, oxygen diffuses from the water into the blood. Oxygen- rich blood now passes out the gill lamellae and leave the gills ( the flow of blood is opposite to water flow). A steep concentration gradient for oxygen is maintained

Question 18

Explain parallel flow

Answer 18

Initially, the water will have a much greater oxygen concentration than blood -high rate of diffusion of oxygen from the water into the bloodstream.

However, after a short distance the concentration of oxygen, is the same in both the blood and water. (Equilibrium takes place and diffusion stops_)

No more than 50% of the available oxygen in the water can diffuse into the blood

Question 19

Why is a counter-current system good for gas exchange

Answer 19

There will always be a concentration gradient for oxygen.

This means that equilibrium is never reached.

Diffusion of oxygen takes place right across the length of the lamellae. 80% of oxygen in the water diffuses into the bloodstream

Question 20

How do bony fish maintain constant water flow through the gas exchange system

Answer 20

Non-bony fish (sharks), the flow of water though the mouth and over the gills is caused by the fish swimming forward. However, bony fish allows water flow to occur even when the fish is not swimming.

When a bony fish opens its mouth, water flows into the mouth space (buccal cavity). The floor of the buccal cavity drops down increasing the volume available for water.

The fish shuts the operculum and increase the volume of the opercular cavity, which contains the gills.

Due to the increased volume, the pressure in the opercular cavity falls. At the same time, the floor of the buccal cavity lifts upwards

This increases the pressure of the water causing the water to flow over the gills in the opercular cavity

Now the fish closes its mouth and opens its operculum. At the same time, the sides of the opercular cavity squeeze inward on the water. This increases the pressure of the water, forcing it out of the operculum.

Question 21

Why do mammals require a high oxygen demand

Answer 21

Low surface area to volume ratio

They are very active animals

They maintain their body temperature thus the require an increased rate of aerobic respiration

Question 22

Explain the process of inhalation

Answer 22

The diaphragm contracts,flattening, and lowering. At the same time, the external intercostal muscles contract, moving the ribs upwards and outwards.
​
The volume of the thorax increases so the pressure in the thorax is reduced.
​
The thorax has a lower pressure than the atmospheric air, so air is drawn through the nasal passages, trachea, bronchi, and bronchioles into the lungs.

The air pressure in the lungs is now less than atmospheric pressure air is drawn into the lungs
​
Air is drawn into the alveoli and the elastic fibres between the alveoli stretch

Inhalation is an active process as it requires muscle contraction

Question 23

Explain the process of exhalation

Answer 23

The muscles of the diaphragm relax so it moves up into its resting domed shape. The external intercostal muscles relax so the ribs move down and inwards under gravity. The elastic fibres in the alveoli of the lungs return to their normal length

The effect of all these changes is to decrease the volume of the thorax.

The pressure inside the thorax is greater than the pressure of the atmospheric air.

The elastic fibers between the alveoli also recoil, helping to push air out

The air moves out of the lungs until the pressure inside and out is equal again.

Exhalation is a passive process as muscle relax and don’t require energy

Question 24

What is the function of the nasal cavity in humans

Answer 24

When humans breathe through their nose, air passes through the nasal cavity.Hairs in the nasal cavity trap dust particles and warm adn moistens the air before it enters the lung

Question 25

Explain the structure of the trachea

Answer 25

The walls of the wide tube contain rings of cartilage, which is a firm and flexible material. This prevents the walls of the cartilage from collapsing when we inhale

The trachea is very close to the oesophagus. The cartilage in the trachea form a c-shape rather than complete rings. This allows food to pass down the oesophagus easily

The walls are lined with ciliated epithelia and goblet cells. Goblet cells secrete mucus which traps dust particles and pathogens.

The ciliated epithelial cells have cilia extending from the cell membrane.

Question 26

Explain the function of the trachea

Answer 26

The ciliated epithelial cells have cilia extending from the cell membrane. The beating of the cilia moves the mucus up where it is then swallowed and the dust and pathogens are digested by the stomach enzymes

-walls of trachea contain smooth muscle which contract and constrict the trachea. When the muscles relax, the trachea dilate. This changes the amount of air recahing the lungs

Question 27

Explain the structure of the bronchus

Answer 27

-Similar structure to the trachea, with the same supporting rings of cartilage. However,smaller and the rings of cartilage are less abundant.

-walls of bronchus contain smooth muscle which contract and constrict the bronchus . When the muscles relax, the bronchus dilate. This changes the amount of air recahing the lungs

Question 28

Explain the function of the bronchus

Answer 28

-walls of bronchus contain smooth muscle which contract and constrict the bronchus . When the muscles relax, the bronchus dilate. This changes the amount of air reaching the lungs

Question 29

Explain the structure of bronchioles

Answer 29

• small bronchioles have no cartilage rings.
  ​
  -walls of bronchioles contain smooth muscle which contract and constrict the bronchioles. When the muscles relax, the bronchioles dilate. This changes the amount of air recahing the lungs
  ​
  -bronchioles are lined with a thin layer of flattened epithelium, making some gasesous exchange possible

bronchioles are much less smaller in size and have less cartilage. They lead into air sacs called alveoli

Question 30

Explain the structure of alveoli

Answer 30

-Each alveolus has a diameter of around 200-300 micrometre

Each alveolus consists of a layer of thin, flattened epithelial cell, along with some collagen and elastic fibres
​
The elastic tissue of the alveolus stretch and return to their resting size. To draw air in and out (elastic recoil)
​
Inner surface of alveoli is covered in a thin layer of solution of water, salts and lung surfactant
​
The Alveolar wall is one cell thick and flattened (squamous) {short diffusion pathway }
​
Moist thin lining (Oxygen can dissolve into solution)

Question 31

What is the function of the alveoli

Answer 31

Gases diffuse in and out of the blood.

Oxygen in the air is dissolved by the moisture inside the alveolar wall. The oxygen then diffuses into the red blood cells where it combines with haemoglobin. Carbon dioxide diffuses from the blood in the alveoli air space.

Question 32

How are alveoli adapted for the diffusion of gases

Answer 32

-millions of alveoli with a large surface area of each alveolus
​
-Thin layers (single epithelial cell thick) short diffusion pathway between the air in the alveolus and blood in capillaries
​
-Good blood supply supplies constant flow of blood (brings carbon dioxide and carries of oxygen- steep concentration gradient)
​
-Good ventilation breathing helps maintain the steep diffusion gradient for oxgen and carbon dixoide between the blood and air in the lungs (steep concentration gradient of oxygen and carbon dioxide)
​
The surfactant makes it possible for the alveoli to remain inflated. Through reducing surface tension at the air-water interface of the alveoli
​
The function of elastic fibres is to stetch (prevent bursting) and recoil back into its original position.This helps exhalation.

Question 33

Explain the structure of the nasal cavity

Answer 33

• large surface area with good blood supply, warm air to body temp
  ​
  -hairy lining, which secretes mucus to trap dust/ bacetria. This protects the lung tissue from irritation/infection
  ​
  Moist surfaces, which increases the humidity of incoming air, this reduces evaporation from exchange surfaces

Question 34

Explain the pleural membrane

Answer 34

A membrane which surrounds the lungs, between these membranes are pleural fluid which acts as a lubricant as the lung volume changes.