BY2 Adaptations for Gaseous Exchange

What is gas exchange?

The process by which oxygen reaches cells and carbon dioxide is removed from them

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What four things must an efficient gas exchange surface be/have?

1 - Large surface area 2 - thin 3 - permeable 4 - moist

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*9 Name three factors that affect the rate of diffusion of substances into cells.

- Surface area - Thickness of membrane - Permeability - Concentration gradient - Temperature

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Name an advantage of the flatworms shape.

Increases the surface area to volume ratio

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What is ventilation?

A mechanism to move the respiratory medium whether it be air or water over the respiratory surface

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*10 Why do large multicellular animals require specialized exchange sufaces?

With increase in size there is a higher metabolic rate and a greater requirement for oxygen for respiration. There is also a smaller surface area to volume ratio so oxygen needs to diffuse over a greater distance.

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*11 Name three different animal exchange surfaces.

- Gills - Lungs - Tracheae

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Why do aquattic organisms have problems with gas exhange?

- Water contains far less oxygen than air - Water is more dense than air

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What are the two main groupings of fish?

- Cartilaginous fish - Bony fish

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Desribe the gill of cartilaginous fish e.g. sharks

Just behind the head there are gill clefts which open at gill slits.

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Do cartilaginous fish have parallel flow or counter current flow?

Parrallel flow

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Describe the ventillation mechanism in cartilaginous fish

Water is taken into the mouth and is forced through the gill slits when the floor of the mouth is raised.

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Describe the gill of a bony fish

The gills are covered with a flap called the opercullum. There are four pairs of gills in the pharynx, each gill is supported by a gill arch with many pairs of gill filaments covered in gill lamella and gill plates

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*12 Name three structural features of fish gills which make them efficient gaseous exchange organs.

- Large surface area - Thin - Permeable - Good blood supply

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Name three things that gills provide

- A specialized rather than using the whole body surface - A large surface area which is extended by the gill filaments - An extensive network of blood capillaries to allow efficient diffusion

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Name the steps of ventilation

- Mouth opens - Operculum closes - Floor of buccal cavity is lowered - The volume increases - The pressure decreases and the water flows in

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Why is counter current flow more efficient than parallel flow

As the concentration gradient is maintained over the whole length of the gill fillament/plate/lamella

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How much of the oxygen is removed from water in counter current flow in fish?

80%

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*13 How does counter current flow improve the efficiency of oxygen uptake?

Maintains a concentration gradient over the whole length of the gill filament. Also, exchange occurs over a longer period.

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What is the transition of an aquatic organism to terrestrial organism called for example tadpoles to frogs?

Metamorphosis

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How do amphibians respire?

Larvae respire via gills. Inactive adults use moist skin as it is a sufficient method however when active for example during mating season they use simple lungs

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Give three examples of amphibians.

Newt, frog, toad

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Name three examples of reptiles

Crocodiles, lizards, snakes

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How do reptiles move?

They move on all four limbs without the trunk of there body touching the floor

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How do reptiles respire?

Through complex internal lungs with a large surface area

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Name one feature in a birds gaseous exchange that is more efficient than other vertebrates.

The ventilation mechanism

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Describe the respiratory system within a bird

There are many air sacs which increase efficiency, ventillation of the lungs is brought about by the movement of ribs, during flight the flight muscles are used to ventilate the lungs

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Why is the diffusion pathway short is insects?

As all respiring cells are nor far away from tracheoles

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Describe the gaseous exchange system in insects?

Gas exchange occurs though paired holes called spiracles that run the length of the body, spircles lead to a system of chitin lined air tubes called tracheae which then lead to smalled tubes called tracheoles taking oxygen to respiring cells.

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Name another feature of the spiracles in insects other than gaseous exchnage?

Open and close like valves allowing ventilation, particularly in periods of activity such as flight

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*14 How do insects prevent excessive water loss from their tracheal system?

By having valves that can close spiracles when the insect is inactive

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*15 Suggest why the tracheal system limits the size of insects.

Because it relies on diffusion to bring oxygen to the respiring tissues. If insects were larger it would take too long for oxygen to reach the tissues

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*16 State two advantages of using tracheal system for gas exchange.

- Rapid - No respiratory pigment required - Reduced water loss - Oxygen supplied directly to tissues - No transport system required

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Describe the position of the lungs

Enclosed within an airtight compartment called the thorax, at the bottom of which is a sheet of muscle called the diaphragm

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What gives the lungs a large surface area?

The alveoli

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Why is the diffusion pathway short in the human respiratory system?

The alveoli have only a single layer of epithelial cells and the blood capillaries also have only a single layer of cells

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What do mammals use to ventilate there lungs?

The negative pressure breathing forcing air into the lungs, in order for this to happen the pressure in the lungs must be lower than atmospheric pressure

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Describe the stages of inspiration in the ventilation of the lungs

External intercostal muscle Contracts - Ribs Up and Out - Diaphragm Contracts and flattens - volume of thorax Increase - pressure in thorax Decreases - atmospheric pressure Greater so air flows in

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Describe the stages of expiration in the ventilation of the lungs

External intercostal muscles Relaxes - Ribs Down and in - Diaphragm Relaxes - volume of thorax Decreases - pressure in thorax - Increases atmospheric pressure Less so air moves out

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*17 List in the correct order the structures that air passes through from the gas exchange surface to atmosphere.

- Alveoli - Bronchioles - Bronchus - Trachea

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*18 What is the function of cartilage in the trachea?

Preventing trachea collapsing during inspiration

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List the main factors which make the leaf an efficient gas exchange surface.

- Lead blade thin and large SA - Spongy mesophyll allows circulation of gases - Plant tissues permeated by air spaces - Stomatal pores allow gas exchange

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How does gas exchange occur through the stomata?

Along a concentration gradient

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What factors effect the direction of diffusion when gases are inside the leaf?

- Environmental factors - The needs of the plant

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*19 State the functions of the palisade and spongy mesophyll layers.

Paliside mesophyll; is the sight of photosynthesis Spongy mesophyll; exchange of gases from atmosphere to chloroplasts of paliside mesophyll.

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*20 State two differences between gas exchange in a plant and gas exchange in a terrestrial insect.

- Insects may create mass flow and plants do not - Insects have smaller SA:V ration than plants - Insects have tracheae along which gases can diffuse and plants do not - Insects do not interchange gases wheres plants do

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What are the main gases released from a plant at night?

Carbon dioxide as respiration occurs

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An adaptation for photosynthesis is the leaf having a large surface area, why is this?

To capture as much sunlight as possible

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Name the adaptations of a leaf to be good at photosynthesis, apart from large surface area

- Can orientate themselves to get maximum exposure to the sun - Thin to allow light to penetrate lower layers - Cuticle and epidermis allowing light to penetrate mesophyll - Palisade are elongated and dense

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Part two of name adaptations

- Palisade contain cholorophyll - Chloroplasts can rotate to allow maximum absorption - Inter cellular air spaces in the spongy mesophyll low gases to diffuse

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*21 State the two distinguishing features of a guard cell

Chloroplasts and uneven thickening of inner and outer walls

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Why do the cells that cause opening and closing of the stomata change shape?

Changes in turgor

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Is in the inner or the outer wall of guard cells thicker?

Inner wall

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What does the closing of the stomata do?

Reduces water loss

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What is transpiration?

The evaporation of water from a plant through the stomata

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Describe the mechanism of the stomatal opening during the day

- Chloroplasts in the guard cells photosynthesis producing ATP - Using ATP K+ ions pump into the cell membranes of the epidermal cells whcih actively transports K+ into guard cells - Stored starch is converted to malate

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Continued

- Water potential in guard cells is lowered causing water to enter by osmosis - Guard cells become turgid and curve apart because of there thick inner walls and so the pore widens.

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BY2 Adaptations for Gaseous Exchange

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