Exchange

Question 1

heat can take place in two ways

Answer 1

• passively by diffusion and osmosis

- actively by active transport

Question 2

Behavioural and physiological adaptions to aid exchange

Answer 2

• Animals with a high surface area: volume ratio tend to lose more water as it evaporates from their surface
• To support their metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods such as seeds and nuts
• Smaller mammals may have thick layers of fur or hibernate when the weather gets really cold
• Larger organisms living in hot regions such as elephants and hippos find it hard to keep cool as their heat loss is relatively slow.

Question 3

An organism’s surface area to volume ratio affects how quickly substances are exchanges

Answer 3

• Smaller organisms have a higher surface area to volume ratio than larger organisms
  Calculating volume of cylinder: pie x pie radius x height

Question 4

Body shape

Answer 4

Any animal with a compact shape have a small surface area relative to their volume this reduces heat loss from their surface. Whereas animals with a less compact shape have a larger surface area relative to their volume, this increases heat loss from their surface.

Question 5

Exchange organs

Answer 5

• Single-celled organisms: in single celled organisms, substances can diffuse directly into the cell across the cell-surface membrane
• In Multi-cellular organisms, diffusion across the outer membrane is too slow because
• Some cells are deep within the body - long diffusion distance
• Larger animals have a low surface area to volume ratio which means its difficult to exchange enough substances to supply a large volume of animal

Question 6

Mass transport

Answer 6

• MASS TRANSPORT: efficient system to carry substances to and from individual cells
• Mass transport (circulatory system) which uses blood to carry glucose and oxygen around the body. It also carries hormones, antibodies and co2
• Mass transport in plants involve the transport of water and solutes in the xylem and phloem

Question 7

Heat exchange

Answer 7

Body size: the rate of heat loss from an organism depends of its surface area. If an organism has a large volume it has a small surface area. – this makes it harder to lose heat from its body whereas if an organism has a small volume it has a large surface area which means its easier for heat to be lost and in order to generate enough hear they have a high metabolic rate

Question 8

Gas exchange surfaces

Answer 8

• Gas exchange occurs over a gas exchange surface
• Organisms need oxygen and carbon dioxide to diffuse across gas exchange surfaces as quickly as possible
  Most gas exchange surfaces have two things in common that increase the rate of diffusion:
• They have a large surface area
• They’re thin – this provides a short diffusion pathway

Question 9

Gas exchange in single-celled organisms

Answer 9

• Single-celled organisms absorb and release gases by diffusion through the cell surface membranes.
• They have relatively large surface area, a thin surface and a short diffusion pathway so there’s no need for a specialised gas exchange system.

Question 10

Gas exchange in fish

Answer 10

GAS EXCHANGE IN FISH
- There’s a lower concentration of oxygen in water than in air so fish have special adaptations to get enough oxygen. Fish have gas exchange surface which is the gills
Structure of the gills:
Water that contains oxygen enters the fish through its mouth and passes out through the gills. Each gill is made of lots of thin plates called gill filaments. Gill filaments give a large surface area for exchange of gases and this increases the rate of diffusion. Gill filaments are covered in lamellae which increase the surface area even more. Lamellae have lots of blood capillaries and a thin surface later of cells to speed up diffusion between water and blood

Question 11

Countercurrent exchange principle

Answer 11

Blood and water that flow over the gill lamellae:
- Blood that is already well loaded with oxygen meets water which has it’s maximum concentration of oxygen from the water. Therefore diffusion of oxygen from the water to the blood takes place
- Blood with little oxygen in it meets water which has had most of oxygen removed. Diffusion of oxygen from the water to blood takes place
> diffusion gradient for oxygen uptake is maintained across the entire gill lamellae. 80% of the oxygen available in the water is absorbed into the blood. if it was flowing the same way, only 50% of the available oxygen would be absorbed by blood

Question 12

Gas exchange in insects

Answer 12

• Insects have tracheae and they’re supported by strengthened rings to prevent them from collapsing. The tracheae divide into smaller dead-end tubes called tracheoles. The tracheoles extend throughout body cells

Question 13

Spiracles

Answer 13

Gases enter and leave tracheae through tiny pores called spiracles on the body surface. When the spiracles are open, water evaporate from the insect

• most of the time insects keep their spiracles closed to prevent this water loss
• spiracles open to allow gas exchange

Question 14

Respiratory gases move in and out of the tracheal system in 3 ways:

Answer 14

• Along a diffusion gradient: Oxygen is used up and its concentration towards the ends of the tracheoles . This creates a diffusion gradient that causes gaseous oxygen to diffuse from the atmosphere along the tracheae and tracheoles
• Mass transport: The contraction of muscles in the insects can squeeze the trachea enabling mass movements of air in and out
• This further speeds up the exchange of respiratory gases
• The ends of the tracheoles are filled with water: When the insect is less active the ends of the tracheoles contain fluid. It is where the fluid and gas meet (= the fluid/gas interface), that exchange of gases occurs (oxygen is taken up, carbon dioxide is given off).

Question 15

How are gas exchange in plants similar to insects

Answer 15

• no living cell is far from external air and therefore a source of oxygen and carbon dioxide
• Diffusion takes place in the air which makes it more rapid than if it was in water

Question 16

adaptations of leas for rapid diffusion:

Answer 16

• short fast diffusion pathway
• air spaces have a large surface area
• no cell is far from a stomata meaning the diffusion pathway is short
• air spaces occur through out the mesophyll so that gases can readily come in contact with mesophyll cells
• large surface area of mesopyll for rapid diffusion

Question 17

Stomata

Answer 17

• each stomata is surrounded by a pair of guard cells
• guard cells can open and close the stomatal pore so they control the rate of gaseous exchange
• terrestial organisms lose water by evaporation
• closing the stomata when water loss would be excessive

Question 18

limiting water loss in insects

Answer 18

• small surface are to volume ratio to minimise the area over which water is lost
• waterproofing over their body and is covered with waterproof cuticle
• spiracles: openings of the tracheae at the body surface and can be closed to reduce water loss

Question 19

limiting water loss in plants

Answer 19

• terrestrial plants have a waterproof covering over pats of the leaves and the ability to close stomata
• xerophytes limit water loss through transpiration
• xerophytes are adapted to living in an area with no water

Question 20

Human gas exchange: structure and functions

Answer 20

• lungs: lobed structures made up of bronchioles which end in alveloi
• Trachea: flexible away supported with rings of cartilage which prevent the trachea from collapsing. Tracheal walls are made up of muscle lined with epithelium and goblet cells
• Bronchi: divsions of trachea each leading into one lung, they produce mucus to trap dirt particles
• Bronchioles: series of branching subdivisions of bronchi. Walls are made up of muscle lined with epithelial cells. the muscle allows them to contract so they can control the air in and out of alveloi
• Alveoli: alveoli are air sacs, between the alveoli there are some collagen and elastic fibres and the elastics allow the alveloli to stretch so they can fill up with air when breathing in

Question 21

two sets of intercostal muscles:

Answer 21

• internal intercoastal muscles: whose contraction leads to expiration
• external intercoastal muscles: whose contraction leads to inspiration

Question 22

Inspiration

Answer 22

• its an active process because it uses energy:
• external intercoastal muscles contract increasing the volume of the thorax
• diaphragm muscles contract causing it to flatten, increasing the volume of the thorax
• ribs are pulled upwards and outwards causing the volume of the thorax to increase
• increased volume of thorax result s in reduction of pressure in the lungs
• atmospheric is now greater than pulmonary pressure and so air is forced into the lungs

Question 23

Expiration:

Answer 23

its a passive process so it doesn’t require much energy:

- the internal intercoastal

Question 24

Expiration:

Answer 24

its a passive process so it doesn’t require much energy:

• the internal intercoastal muscles contract, while the external intercoastal muscles relax
• the ribs move downwards and inwards, decreasing the volume of the thorax
• the diaphragm muscles relax and is pushed up again by the contents of the abdomen that were compressed during inspiration so the volume of the thorax is therefore further decreased
• decreased volume of the thorax increases the pressure in the lungs
• the pulmonary pressure is now greater than that of the atmosphere and so air is forced out of the lungs

Question 25

What’s the site of gas exchange in mammals:

Answer 25

the alveoli, which has a thin, partially permeable exchange surfaces and have a large surface
- has to be an internal medium and environment medium to maintain a diffusion gradient

Question 26

Role of alveoli in gas exchange

Answer 26

• each alveolus is lined with epithelial cells
• alveolus is a network of pulmonary capillaries
  Diffusion of gases between the alveoli and the blood will be rapid because:
  They have a very thin lining to allow oxygen to diffuse into the blood easily. Surrounded by a network of blood capillaries to pick up and transport oxygen. There is an exchange of gases between the air sacs and their surrounding capillary blood vessels. … Carbon dioxide diffuses from the blood into the air sac

Question 27

major parts of the digestive system

Answer 27

• Oeseophagus: carries food from mouth into stomach
• Stomach: muscular sac with an inner layer that produces enzymes, stomach’s job is to store and digest food especially protein, it has special glands that produce enzymes which digest protein`
• ileum: long muscular tube where food is further digested in the ileum by enzymes produced by it wall and glands, the ileum are folded into villi which increase surface area and is then further increased by millions of tiny projections called microvilli this adapts to its purpose of absorbin the products of digestion into blood
• Large intestine: absorbs water and most of the water is absorbed from the secretions of digestive glands
• Rectum: final section of the intestines, the faeces are stored here before being removed via anus (process called egestion)