4- gas exchange

Question 1

gas exchange in insects- structure

Answer 1

• spiracles: external openings that act as entry and exit points for gases
• trachea and tracheoles: spiracles lead to larger tubes called tracheae, which further divide into minute tubes, the tracheoles, reaching individual cells
• air sacs: air sacs act as air reservoirs or bellows. they increase the volume of air moved through the respiratory system. they have flexible walls so that changes in pressure caused by ventilating movements of the abdomen inflate and deflate them

Question 2

gas exchange in insects- adaptation

Answer 2

• direct delivery: the tracheal system enables direct oxygen delivery to tissues, bypassing the need for a circulatory system for oxygen transport
• passive diffusion: gas exchange happens by passive diffusion, requiring no energy
• spiracle regulation: insects can control the opening and closing of spiracles to reduce water loss

Question 3

gas exchange in insects- process

Answer 3

• entry of air: air enters the body through spiracles
• oxygen transportation: oxygen travels down the tracheae and tracheoles
• diffusion: oxygen diffuses directly into the body cells and carbon dioxide diffuses out

Question 4

gas exchange in fish- structure

Answer 4

• gills: fish have gills, located on either side of the fish’s pharynx
• gill filaments: each gill has many long, thin gill filaments that increase the surface area
• gill lamellae: each gill filament is covered with thousands of tiny lamellae, which further increase the surface area for gas exchange

Question 5

gas exchange in fish- adaptation

Answer 5

• large surface area: the vast surface area provided by the gill filaments and lamellae facilitates efficient gas exchange
• thin walls: gills possess thin walls, enabling quick and effective diffusion of gases
• counter- current flow: fish utilise a counter-current flow system where the blood in the gill capillaries flows in the opposite direction to the water passing over the gills, maintaining a constant concentration gradient for maximum oxygen uptake

Question 6

gas exchange in fish- process

Answer 6

• water intake: fish intake water containing dissolved oxygen through their mouths
• passage over gills: this water then passes over the gills
• diffusion: oxygen diffuses from the water into the fish’s bloodstream, while carbon dioxide produced by the fish’s metabolic activities diffuses out into the water

Question 7

gas exchange in mammals- structure

Answer 7

• lungs: mammals have a pair of lungs, each divided into lobes
• bronchi and bronchioles: air enters the lungs through the trachea, which divides into two bronchi, each leading to a lung. bronchi further divide into smaller bronchioles
• alveoli: bronchioles end in tiny air sacs known as alveoli, where gas exchange occurs

Question 8

gas exchange in mammals- adaptation

Answer 8

• large surface area: the alveoli provide a vast surface area for gas exchange
• thin walls: alveoli have extremely thin walls, allowing for efficient gas exchange
• rich blood supply: a dense network of capillaries surrounds each alveolus, promoting faster gas exchange
• moist lining: the moist lining of the alveoli helps in dissolution and diffusion of gases

Question 9

gas exchange in mammals- inhalation process

Answer 9

• intercoastal muscles contract -> ribs move up and out
• diaphragm contracts -> moves downwards
• thorax expands -> pressure decreases -> air moves into lungs
• oxygen rich air is inhaled into the lungs, travelling down the trachea, bronchi and bronchioles to reach the alveoli

Question 10

gas exchange in mammals- diffusion in alveoli

Answer 10

• oxygen diffuses across the walls of the alveoli and capillaries into the blood
• simultaneously, carbon dioxide diffuses from the blood into the alveoli

Question 11

gas exchange in mammals- exhalation

Answer 11

carbon dioxide- rich air is exhaled, completing the gas exchange process

Question 12

waxy cuticle in leaf

Answer 12

prevents water loss

Question 13

upper epidermis in leaf

Answer 13

transparent layer allowing maximum light penetration

Question 14

palisade mesophyll layer in leaf

Answer 14

vertically stacked cells with high chloroplast count

Question 15

spongy mesophyll layer in leaf

Answer 15

contains air spaces for increased surface area, for gas exchange

Question 16

lower epidermis, guard cells and stomata in leaf

Answer 16

guard cells regulate the stomata’s opening and closing to prevent excessive water loss

Question 17

photosynthesis and respiration in plants

Answer 17

• during daytime, stomata open when conditions favour photosynthesis
• opening of the stomata allows carbon dioxide in and oxygen out

Question 18

stomata opening mechanism

Answer 18

K+ ions move into the guard cells via active transport, causing water to follow by osmosis due to decreased water potential. this makes guard cells turgid, leading to the stomata opening

Question 19

lenticels in woody plants

Answer 19

area of loosely arranged cells acting as pores in lignified (woody) plants

Question 20

lenticels function

Answer 20

enable gas exchange in woody plants

Question 21

label

Answer 21

Question 22

structure of the heart- chambers

Answer 22

four chambers- two upper atria, two lower ventricles

Question 23

structure of heart- valve system

Answer 23

• regulates blood flow and prevents back flow of blood
• atrioventricular valves: tricuspid (right) bicuspid/mitral (left), tendinous chords prevent atrioventricular valves from turning inside out due to the pressure when the heart contracts
• semilunar valves- pulmonary (right), aortic (left)

Question 24

structure of heart- septum

Answer 24

• composed of muscle and connective tissue
• prevents oxygenated and deoxygenated blood from mixing

Question 25

structure of heart- myocardium

Answer 25

- cardiac muscle - the muscular wall of the heart - thicker in the left as a higher pressure is needed to pump blood around the body

Question 26

structure of the heart- pericardium

Answer 26

- the protective outer layer

Question 27

structure of the heart- coronary arteries and veins

Answer 27

- wrapped around the heart - supply the heart muscle with blood

Question 28

structure of the heart- arteries

Answer 28

- thick muscular walls: adapted to withstand high blood pressure - small lumen: helps maintain the high pressure - elastic fibres: allow the arteries to stretch and recoil with every heartbeat, smoothing out the pressure surges caused by the hearts contractions

Question 29

structure of the heart- veins

Answer 29

- thinner, less muscular walls: adapted for a lower pressure environment - larger lumen: facilitates the flow of blood despite the low pressure - presence of valves: prevent back flow of blood, ensuring unidirectional flow towards the heart - veins located between muscles: muscle contractions help squeeze the veins, pushing the blood along

Question 30

structure of heart- capillaries

Answer 30

- single cell thick wall: allows quick and efficient exchange of gases, nutrients and waste - small diameter- ensures that cells are never far from a capillary, allowing rapid diffusion - large surface area: facilitates the exchange of materials - slow blood flow: allows more time for exchange of materials

Question 31

double circulatory system

Answer 31

- high pressure blood pump: facilitates the pumping of blood to the body at a higher pressure, thereby ensuring efficient delivery of nutrients and oxygen to all body cells - seperation of blood types: separates oxygenated and deoxygenated blood, preventing the mixing of oxygen rich and oxygen poor blood, for more efficient oxygen delivery to tissues

Question 32

advantages of double circulatory system

Answer 32

- blood pressure to the body tissues is higher - blood pressure to the lungs is lower which avoids damaging the capillaries in the lungs and increases time for gas exchange - concentration gradient is maintained, as oxygenated and deoxygenated blood don’t mix - organisms can develop larger bodies

Question 33

single circulatory system in bony fish

Answer 33

- lower blood pressure: in a single circulatory system, the blood is pumped at a lower pressure, which may result in less efficient nutrient and oxygen delivery - blood mixing: in a single circulatory system, oxygenated and deoxygenated blood can mix, which decreases the overall efficiency of oxygen delivery to the body’s tissues

Question 34

order of cardiac cycle

Answer 34

atrial systole -> ventricular systole -> diastole

Question 35

atrial systole

Answer 35

- the stage where the atria contact, pushing blood into the ventricles

Question 36

ventricular systole

Answer 36

- the stage where the ventricles contact, pushing blood out of the heart and into the arteries - isovolumetric contraction: early phase where pressure builds with all valves closed - ejection phase: high pressure opens semilunar valves, blood is ejected to the aorta and pulmonary artery

Question 37

diastole

Answer 37

the period of relaxation where the heart fills with blood

Question 38

label

Answer 38

Question 39

myogenic stimulation of the heart

Answer 39

- the hearts ability to contract is myogenic, meaning it does not need external signals - sinoatrial node (SAN): initiates the electrical signal causing heart contraction - atrioventricular node (AVN): receives the signal from the SAN and after a short delay to allow the atria to contact, sends it in to the ventricles - bundle of his: carries the electrical signal down the AVN down the inter-ventricular septum. it then branches into the left and right bundle branches, which lead to the Purkinje fibres, triggering ventricular contraction

Question 41

sequence of the heartbeat

Answer 41

- initiation: the SAN sends an electrical signal that spreads across the atria causing them to contract (atrial systole) - delay at AVN: the signal reaches the AVN where it is delayed, allowing the atria to finish contracting and ventricles to fill with blood - conduction to ventricles: the signal is transmitted down the Bundle of His, through the bundle branches, and into Purkinje fibres, causing ventricles to contract (ventricular systole) - relaxation: once the signal has passed, the heart muscles relaxes (diastole) before the next cycle begins

Question 42

importance of myogenic stimulation

Answer 42

- autonomy: the heart can regulate its own rhythm, independant any of the nervous system - consistency: provides a steady and consistent heartbeat, for effective blood circulation - adaptability: while myogenic, the heart rate can still be adjusted in response to the body’s needs, via the autonomic nervous system

Question 43

label

Answer 43

Question 44

what is an ECG

Answer 44

an electrocardiogram is a graphical representation of the electrical activity of the heart

Question 45

P wave of ECG

Answer 45

- atrial depolarisation (contraction) by a wave of depolarisation from the SAN - start of atrial systole

Question 46

QRS complex of ECG

Answer 46

- ventricular depolarisation (contraction) - atrial repolarisation (relaxation) - Q = bundle of His/ Purkinje fibres excitation - R = start of ventricular systole - S = ventricles fully contracted

Question 47

T wave in ECG

Answer 47

- ventricular repolarisation (relaxation) - diastole

Question 48

pressure changes during the cardiac cycle

Answer 48

- atrial systole: a small increase in pressure as the atria contract and push blood into the ventricles - ventricular systole: a significant increase in pressure as the ventricles contract, pushing blood into the pulmonary artery and aorta - diastole: decrease in pressure as the heart relaxes and refills with blood. the pressure in the ventricles is lower than in the atria, which allows them to fill with blood

Question 49

interpreting data from ECG and pressure charts

Answer 49

- correlation of ECG and pressure changes: the peaks in an ECG (P wave, QRS complex, T wave) should correspond with changes in pressure within the heart - heart rate calculation: the distance between consecutive QRS complexes in an ECG can be used to calculate the heart rate - diagnosing heart conditions: abnormalities in the ECG trace or pressure changes can indicate heart conditions, such as arrhythmia, heart block or myocardial infarction

Question 50

importance of ECG and pressure data

Answer 50

- disease detection: can help identify and diagnose heart diseases and conditions - monitoring heart health: provides valuable information about the hearts electrical activity and blood pressure, essential indicators of heart heath - guide treatment: can inform treatment decisions and monitor the effectiveness of interventions