revision powerpoint b2 topic 2

Misconception: We need oxygen to breathe

NO!

We breathe to get oxygen into our bodies. This travels in the blood to all cells to be used for aerobic respiration.

• ALL: Recall the equation for respiration and explain what respiration is and where it occurs. (Grade C)• MOST: Discuss how the circulatory system facilitates respiration, including how glucose and oxygen get to cells and

the removal of carbon dioxide. (Grade B)• SOME: As above, but also examining the idea of diffusion concentration gradients (Grade A – A*)

Aerobic Respiration – what is it and where does it occur?

All organisms are made of cells.Cells need energy to function. Aerobic respiration is an enzyme catalysed (speeds up the rate of the reaction) chemical reaction that occurs in all cells.

Aerobic respiration is the chemical reaction that releases energy from glucose molecules when it reacts with oxygen. The glucose is like the cells “fuel”.



What type of cells need lots of energy?

Muscle cells when exercising – they contract to cause movement. This requires energy.

Growing and dividing cells – for the building of new cell materials.



JOURNEY OF

OXYGEN• ALL: Recall the equation for respiration and explain what respiration is and where it occurs. (Grade C)• MOST: Discuss how the circulatory system facilitates respiration, including how glucose and oxygen get to cells and


Journey of oxygen from air to cell



Gas exchange takes place in the alveoli–oxygen is transferred into the blood and carbon dioxide moves out of the blood.

Each alveolus has a thin wall so that gas exchange between

Gas exchange

the lungs and the blood can take place quickly.



What happens in the alveoli?



The heart pumps the oxygenated blood round the body to all cells.

The blood carries oxygen and dissolved food to all the body’s cells so that respiration can take place.

Blood



The cells then use the oxygen

They combine the oxygen with glucose to make



JOURNEY OF

GLUCOSE• ALL: Recall the equation for respiration and explain what respiration is and where it occurs. (Grade C)• MOST: Discuss how the circulatory system facilitates respiration, including how glucose and oxygen get to cells and


Journey of glucose from bread to cell



The blood carries oxygen and dissolved food to all the body’s cells so that respiration can take place.

Blood





C6H12O6 + 6O2 6CO2 + 6H2O (+ energy).

Aerobic respiration equation



Movement of substances. Oxygen and glucose move from the blood in capillaries into cells by diffusion.Diffusion is the random movement and spreading of particles.

The particles diffuse down a concentration gradient. Basically, particles move from an area where they are in a high concentration to an area where they are in a low concentration.

Explain in as much detail as you can what is happening in the pictures.

Think about:What the arrows represent.Where the substances have come from and where they are going to. Where there is a high concentration of each substance and where there is a low concentration. Which way will the substances move.

For higher levels you must talk about concentration gradients.



An alveolus





This is the process of gas exchange.

Thinking about what you know – why do breathing and heart rates increase when

we exercise? Discuss your explanation with your group and then finish this sentence with your explanations.

When we exercise our breathing rate increases because …When we exercise our heart rate increases because…



Explain why your heart rate and breathing rate increase during exercise. `




we exercise? When we exercise our breathing rate increases because … exercise requires energy which comes from respiration. Respiration requires oxygen which we get from breathing so our breathing rate increases to get more oxygen into the blood that can be delivered to respiring muscle cells.




we exercise? When we exercise our heart rate increases because… the blood contains glucose, and red blood cells which carry the oxygen needed for respiration in the muscle cells. This means the substances get to respiring cells quicker so the respiration rate can increase.As more oxygen is coming into the alveoli and diffusing into the blood – the increase in heart rate also means oxygen is taken away from the alveoli quicker – so maintaining a concentration gradient. Both actions also help to remove CO2 quicker. • ALL: Recall the equation for respiration and explain what respiration is and where it occurs. (Grade C)• MOST: Discuss how the circulatory system facilitates respiration, including how glucose and oxygen get to cells and


Key points

• All living organisms use respiration to release the energy from glucose.

In aerobic respiration oxygen reacts with the glucose in side cells to release the energy from glucose.

Carbon dioxide and water are produced as waste products. It can be modelled using the word equation:

oxygen + glucose → carbon dioxide + water

and energy is released.



• Respiration takes place inside cells. Glucose and oxygen diffuse into the cell from surrounding blood capillaries and carbon dioxide diffuses from the respiring cells into the blood capillaries.

• Gas exchange in the lungs allows oxygen to diffuse into the capillaries from the air breathed in, and carbon dioxide to diffuse out of the capillaries into the air, which is breathed out.

• Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration.



Explain why this is an advantage?



A: Red blood cells carry oxygen. Oxygen is needed for respiration. Respiration is a chemical reaction that releases energy. The more oxygen there is supplied to a cell, the more energy it

can release using respiration.

Eero has more red blood cells than usual so more oxygen will reach his muscle tissue. The increased rate of respiration in his muscle cells allows them to contract faster without tiring, giving him an advantage over other athletes.



• Anaerobic respiration – occurs without enough oxygen

ALL: Compare anaerobic respiration to aerobic respiration and give the word equation for it. (Grade C)MOST: Calculate heart rate, stroke volume and cardiac output. Explain why anaerobic respiration occurs. (Grade B)SOME: Examine why heart rate and breathing rate remain high after exercise, and how lactic acid is broken down (Grade A)

A person doing intense exercise

Cramp after intense exercise

The equation for anaerobic respiration (respiration that occurs without oxygen).


A person doing intense exercise (during really intense exercise we cannot supply enough oxygen to muscles quickly enough, so anaerobic respiration occurs).

The equation for anaerobic respiration (glucose is broken down to release energy without oxygen).

Cramp after intense exercise – the lactic acid produced during anaerobic respiration can cause cramp.

Anaerobic means ‘without oxygen’So anaerobic respiration occurs without oxygen

Glucose is broken down (without oxygen) to form lactic acid (+ some energy)

Glucose Lactic acid (+ energy)


There are 2 main disadvantages to this:

1. Does not produce as much energy as aerobic respiration (as the glucose is only partly broken down, and some of the energy remains stored in the lactic acid)

2. When lactic acid builds up in the bloodstream it causes muscle cramp.


Aerobic respiration Anaerobic Respiration

Reactants are glucose and oxygen. Produces energy.Occurs all the time.Does not cause cramp.

Reactant is glucose.Occurs during intense exercise (burst activiites. Produces energy – but less than aerobic respiration.Lactic acid build up causes cramp.


Why is there not enough oxygen to meet the demand for “burst” activities.


Why is there not enough oxygen to meet the demand for these kinds of activities. (Explain why

anaerobic respiration occurs). Grade B Model Answer: Burst activities such as weightlifting, 100m race etc require a large amount of oxygen in a short space of time.

Intense exercise cannot supply oxygen to our muscles quickly enough. Cells start to break down glucose without oxygen and release energy. This is anaerobic respiration.

This doesn’t happen as much with things like jogging as there is enough oxygen to supply to the muscles.


Calculate heart rate, stroke volume and cardiac output. (Grade B)

Stroke volume = The volume of blood the heart can pump out with one beat

Cardiac output = The volume of blood the heart can pump out in one minute

Heart rate = number of heart beats per min(stroke volume and heart rate both increase with exercise – so therefore cardiac output also increases – this delivers more blood to respiring muscles faster).

Cardiac output = stroke volume x heart rate


• Cardiac output = stroke volume x heart rate

Calculate heart rate, stroke volume and cardiac output. (Grade B)


Beats per min

Stroke volume = The volume of blood the heart can pump out with one beatCardiac output = The volume of blood the heart can pump out in one minuteHeart rate = number of heart beats per min(stroke volume and heart rate both increase with exercise – so therefore cardiac output also increases – this delivers more blood to respiring muscles faster).

1. At rest, an athlete’s heart rate is 60 beats per minute, and stroke volume is 76 cm3. During exercise these increase to 160 beats per minute and 105 cm3. Calculate the increase in cardiac output.

A: At rest, output = 60 × 76 = 4560 cm3/min During exercise, output = 16 800 cm3/min Increase in output = 16 800 – 4560

= 12 240 cm3/min


2. An athlete has a heart rate of 83 beats per minute and a stroke volume of 52 cm3. What is her cardiac output? Show your working.

83 x 52 = 4,316 cm3 / min


2. 0.07dm3 x1000 = 70 cm3 x150 beats per min

10,500 cm3 / min

Or

0.07 dm3 x 150 = 10.5 dm3 / min


Definition of EPOC


After you have finished exercising, you carry on the fast and heavy breathing for a short while.

After exercise, the fast / heavy breathing continues as the extra oxygen is needed to break down the lactic acid and also to release energy for other cell processes (egcell repair).

Lactic acid is broken down (using oxygen) into carbon dioxide and water.This need for extra oxygen after exercise used to be called “oxygen debt” but is now

termed “excess post‐exercise oxygen consumption” or EPOC.This is why breathing and heart rate remain high after exercise.The time taken for your pulse rate and breathing rate to return to normal is the

recovery time.


Key points

© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not copyright free. This

document may have been altered from the i i l

• During exercise the muscle cells need to produce lots of energy from respiration. The heart rate and breathing rate both increase to carry more oxygen and glucose to the respiring cells.

• The volume of blood circulated in a given time (cardiac output) depends on the heart rate and the stroke volume (volume of blood pumped out on each beat). This can be modelled by the word equation:

cardiac output = stroke volume × heart rate


© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not copyright free. This document may have

• During intense exercise the muscle cells cannot get enough oxygen to increase the rate of aerobic respiration even more, and so they start to respire anaerobically as well. Glucose is broken down without oxygen to release energy. Lactic acid is produced as a waste product:

glucose → lactic acid and energy is released.



• Anaerobic respiration releases less energy than aerobic respiration. The lactic acid that can cause cramp in muscles if it builds up is taken to, and broken down in the liver, using oxygen, into carbon dioxide and water. This is why breathing and heart rate remain high for a short time after exercise.

• The amount of extra oxygen needed to break down the lactic acid after exercise is called excess post-exercise oxygen consumption (EPOC) – formerly called ‘oxygen debt’.


Pub Quiz1. What is the equation for anaerobic respiration?2. Give 2 differences between anaerobic and aerobic respiration. 3. Explain why the breathing rate goes up during exercise.4. What is stroke volume?5. How can you calculate stroke volume?6. Explain why heart rate goes up during exercise? 7. Why does anaerobic respiration occur in people who do intense

exercise but not steady exercise?8. How is lactic acid broken down? 9. What does EPOC stand for?10. What is EPOC required for?


Answers1. What is the equation for anaerobic respiration?Glucose Lactic acid (+ energy).2. Give 2 differences between anaerobic and aerobic respiration. Anaerobic respiration produces less energy. Anaerobic respiration occurs without oxygen.3. Explain why the breathing rate goes up during exercise.Breathing rate increases to get more oxygen into the blood, that’s is taken to muscle cells for respiration to make more energy. 4. What is stroke volume? The volume of blood the heart can pump out with one beat.5. How can you calculate stroke volume? Cardiac output divided by heart rate.


Answers6. Explain why heart rate goes up during exercise? Enables the extra oxygen to get to the muscle cells quicker and CO2 be removed. 7. Why does anaerobic respiration occur in people who do intense

exercise but not steady exercise? During intense exercise the oxygen is not supplied to muscles quick enough as it is for steady exercise.

8. How is lactic acid broken down? By oxygen into carbon dioxide and water.

9. What does EPOC stand for? Excess post‐exercise oxygen consumption. 10. What is EPOC required for? The lactic acid produced during

anaerobic respiration requires extra oxygen to break it down; also, increased oxygen is required to release energy for other processes in cells after exercise. e.g. cell repair.


Respiration Quick RevisionAerobic respiration:

Glucose + oxygen water + carbon dioxide (+ energy)

Anaerobic respiration: Occurs without enough oxygen reaching muscle cells. Produces lactic acid build up which causes cramp.

Glucose Lactic acid (+ energy)

Eating carbohydrates provides a source of glucose for respiration (to provide more energy) as carbohydrates broken down into glucose by enzymes.

Respiration Quick RevisionBreathing rate increases to inhale more oxygen into the body. More CO2 is exhaled also.

Heart rate increases to pump blood faster to muscles. The blood carries the oxygen and glucose to muscle cells for respiration.

This releases energy for muscle contraction. Faster blood means CO2 is removed quicker also.

Respiration Quick revision

When oxygen is breathed in it goes to the alveoli in the lungs.

Oxygen diffuses from a high concentration in the alveoli to a low concentration in the blood capillary.

Respiration quick revisionCardiac output – blood pumped in 1 min

Stroke Volume – blood pumped in 1 sec

Heart rate – Number of beats per minute.

Cardiac output = stroke volume X heart rate

A reduced cardiac output / stroke volume / heart rate means less blood pumped around the body in one minute. How would this affect respiration in muscle cells?

Plants and photosynthesis

Photosynthesis Equation

SunlightWater + Carbon Dioxide ‐‐‐‐‐‐‐‐‐‐ Glucose + Oxygen

Chlorophyll

Symbol equation? Can you balance it?What are the energy transfers?

Respiration Equation

Glucose + Oxygen ‐‐‐‐‐‐‐‐‐‐Water +Carbon (+ Energy)Dioxide

Symbol equation? Can you balance it?What are the energy transfers?

What is this picture showing? Think back –can you remember the test for starch?

Boil a leaf and soak in ethanol to remove the chlorophyll.

Add iodine to the leaf, if starch is present iodine will go from orange to blue / black.

These are both plant cells – which is from a leaf and which is from a root? How do you know? How is the one

that is from the leaf adapted for its job.Cell 1 is from a root. It does not contain chloroplasts as roots are in the dark.

Cell 2 is from a leaf and contains many chloroplasts which contain chlorophyll which absorbs light energy for photosynthesis.

Try to label the cross section of the leaf

Cross section of a leaf

Match the adaptation to the function to establish how the leaf is adapted for

photosynthesis. Use the cards to help you work out how the structure of the leaf is adapted for photosynthesis.

Write an extended piece of writing establishing the adaptations of a leaf and how they help it to photosynthesise efficiently.

6 marker

How is a leaf adapted to its function?

Model AnswerA: Many chloroplasts in leaf cells contain chlorophyll, which absorbs light energy for photosynthesis. Leaves are broad and flat, which provides a large surface area so as much light can be absorbed as possible. Guard cells that open the stomata in daylight to allow CO2 to diffuse in.

• The lower surface of the leaf has tiny holes (stomata) that allow gases to enter and leave the leaf by diffusion.

• Air spaces inside the leaf gives the surrounding cells a large surface area to volume ratio for efficient gas exchange.

• Leaves have a network of veins, which deliver water needed for photosynthesis (as well as glucose needed for respiration) and take away the glucose produced in photosynthesis.

Match up the adaptation to how it helps the plant photosynthesise.

Broad and flatCells with many chloroplastsAir spacesGuard cellsStomataNetwork of veins

contain chlorophyll, which absorbs light energy for photosynthesis. open the stomata in daylight to allow CO2 to diffuse in.

a large surface area to volume ratio for efficient gas exchange. allow gases to enter and leave the leaf by diffusion.

provides a large surface area so as much light can be absorbed as possible. which deliver water needed for photosynthesis (as well as glucose needed for respiration) and take away the glucose produced in photosynthesis.

Limiting Factors

• Eg if there is lots of carbon dioxide, water and a nice warm temperature then photosynthesis will happen, but there is dim light so photosynthesis happens slowly – light is limited and so is the limiting factor.

• To make photosynthesis happen faster, you have to increase light intensity.

Water transport

• Osmosis and active transport

What do these structures do?How are they adapted to their

function?

• Label your root hair cell diagram and explain how it is adapted to its function.

Roots and Root hair cells• Roots anchor a plant to the ground• They take in water and mineral salts• Root surfaces are covered in thousands of tiny root hair cells.

• Root hair cells have long extensions. These increase surface area for water and mineral salts (nutrients) to be absorbed.

• Root hair cells have thin cell walls for quick and easy absorption.

ALL: Explain the adaptation of roots for taking up water and minerals. (Grade C)MOST: Define osmosis and consider the differences and similarites between osmosis and diffusion. (Grade

B)SOME: Discuss the movement of molecules by active transport (Grade A)

Diffusion

The movement of molecules from a high concentration to a low concentration.



Osmosis is the diffusion of water molecules only from a region of high concentration of water molecules to an area of lower concentration of water concentration, through a partially permeable membrane (a membrane that allows small molecules to fit through but not large ones).Water from the soil enters root hair cells by osmosis.



In the diagram above, water will move by diffusion from solution B (where there is a high conc of water molecules) to a lower concentration of water molecules in sol A. Water moves down the concentration gradient.

The sucrose (sugar) molecules do not move as they are too big.



Sol B

Sol A

Look at this animal cell.

A solution is where a solute (sugar or salt) is dissolved in a solvent (usually water).

Where is the dilute solution? (Dilute = high percentage of water, low percentage of solute).

Where is the concentrated solution? (Concentrated = low percentage of water and high percentage of solute).

Which way would the water move? What effect would this have on the cell?

Sugar / saltWater molecule

ALL: Explain the adaptation of roots for taking up water and minerals. (Grade C)

MOST: Define osmosis and consider the differences and similarites between osmosis and diffusion. (Grade B)

SOME: Discuss the movement of molecules by active transport (Grade A)

Look at this animal cell.

Where is the dilute solution? (Dilute = high percentage of water, low percentage of solute).

Where is the concentrated solution? (Concentrated = low percentage of water and high percentage of solute).

Which way would the water move? What effect would this have on the cell?

Sugar / saltWater molecule

ALL: Explain the adaptation of roots for taking up water and minerals. (Grade C)

MOST: Define osmosis and consider the differences and similarites between osmosis and diffusion. (Grade B)

SOME: Discuss the movement of molecules by active transport (Grade A)

Osmosis and plant cellsWater moves into root cells by osmosis from an area where they are in a high concentration (in soil) to an area of low concentration (in roots) through a partially permeable membrane. The water is then taken up the plant in xylem vessels to all parts of the plant. This makes the plant cells turgid or stiff so that they are able to hold the plant upright.

If plant cells lose water they become flaccid and eventually the cell membrane shrinks away from the cell wall. The cell is plasmolysed. (Pics next)

ALL: Explain the adaptation of roots for taking up water and minerals. (Grade C)MOST: Define osmosis and consider the differences and similarites between osmosis

and diffusion. (Grade B)SOME: Discuss the movement of molecules by active transport (Grade A)

What would happen to red blood cells if they were:

a) Placed in pure water? b) Placed in a concentrated sugar solution?

Explain your answers.

ALL: Explain the adaptation of roots for taking up water and minerals. (Grade C)MOST: Define osmosis and consider the differences and similarites between osmosis

and diffusion. (Grade B)SOME: Discuss the movement of molecules by active transport (Grade A)

Osmosis and red blood cells• If a red blood cell is placed in pure water then the concentration of water molecules is higher outside the cell than inside, so water enters the cell by osmosis. As the membrane is weak the cell will burst.

• Red blood cells shrink when placed in concentrated solutions of sugar as water moves out of them by osmosis, because the concentration of water molecules is higher inside the cell than outside. This makes the cell shrivel up.



Grade C: Explain the adaptation of roots for taking up water and minerals

• Roots anchor a plant to the ground and take in water and mineral salts

• Root surfaces are covered in thousands of tiny root hair cells.

• Root hair cells have long thin extensions that can reach into surrounding soil for water.

• The long extensions increase surface area for water and mineral salts to be absorbed.

• Root hair cells have thin cell walls for quick and easy absorption of water / mineral salts.



Grade B: Define osmosis and consider the differences and similarites between osmosis and diffusion.

• Osmosis is the movement of watermolecules from a high water concentration to a low water concentration through a partially permeable membrane.

• Similarities: Neither osmosis or diffusion require energy (passive transport). Both are movement of substances from a high to a low concentration.

• Differences: Osmosis is the movement of water molecules only. Osmosis is the movement through a partially permeable membrane. Diffusion can happen wihout a membrane – egair freshener diffusing through the air.



Active Transport• The red circles represent

mineral salts. • Mineral salts are taken into

the root hair cell by active transport.

• How do you think active transport differs to the movement of water (osmosis)?



Grade A: Discuss the movement of molecules by active transport

• Active transport is the movement of molecules across a cell membrane against its concentration gradient (from low to high concentration). In root hair cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as nitrates or other mineral salts.

• This process uses energy from respiration.



Palisade cell

Phloem Cell

Xylem Cell

Stomata

ALL: Label a diagram of phloem and xylem and outline what their functions are. (Grade C)MOST: Establish how a potometer works and use it to explain what we mean by a transpiration stream.

(Grade B) SOME: Predict how changes in environmental conditions around the plant effect water movement.

(Grade A)

What are xylem and phloem?

What do they do?



(Grade A)

Xylem and phloem• Plants have transport systems (a bit like arteries and veins for animals) to move food, water and minerals around. These systems use continuous tubes called xylem and phloem.

Xylem – transports water and dissolved mineral salts. The inside of the cells are hollow. Xylem vessels are dead cells.

Phloem – glucose is converted to sucrose and transported in phloem tubes. Phloem have sieve tubes and is living tissue.



(Grade A)

Which cells transport nutrients?Plants contain two types of cell adapted for transportation.

Phloem cells transport sugars produced in the leaves up and down the stem.

Xylem cells transport water and minerals up the stem from the roots to the shoots and leaves. This transport occurs in one direction only.



(Grade A)

Water evaporates through the stomata

Water enters the plant via the roots by osmosis

Xylem cells carry water up the stem of the plant

through theXylem tubes

Water vapour moves away

from the leaf by diffusion .

Minerals are taken in via

active transportALL: Label a diagram of phloem and xylem and outline what their functions are. (Grade C)MOST: Establish how a potometer works and use it to explain what we mean by a transpiration stream.


(Grade A)

How does water get transported from the roots to the leaves against gravity?

As water is moving into roots by osmosis, water is evaporating from the stoma of leaves. This is called transpiration. This loss of water from the leaves pulls water (containing dissolved minerals) up through the xylem vessels from the roots by capillary action.

The more water is lost through transpiration, the more water will move into the roots by osmosis (if water is available). This is good as it will enable a plant to recover quickly if too much water is lost through transpiration.

Plants use capillary action to bring water up from the to the rest of the plant. The water molecules are attracted to the molecules of the inside of the stem. This attraction forces the water up.

What is transpiration?

Although it may seem bad for plants, transpiration actually moves water from the roots to the top of the plant, without using energy.

Water always moves from an area of high concentration to an area of low concentration. This movement of water is a type of diffusion called osmosis.

Transpiration is the loss of water by evaporation from plants.

Plants lose water when they open the stomata in the leaves to let in carbon dioxide.

Air around the plant usually contains less water than the cells of the plant, so water evaporates into the air.

What is a potometer? Apparatus used to measure the rate of water loss from a plant (transpiration).

How to prepare a potometer• Cut a leafy shoot and put end into

water so it doesn’t taking up any air. • Put the whole of the potometer into

water. Move until all air bubbles come out.

• Put the end of the stem into the bung; grease with Vaseline and then put the bung into the potometer. (Prevents evaporation of the water to the air).

• Ensure tap is closed, then lift the potometer out of the water.

• Leave the end of the capillary tube out of the water until an air bubble forms then put the end into a beaker of water.

Which order? Cut a leafy shoot and put end into water so it doesn’t taking up any air.

Ensure tap is closed, then lift the potometer out of the water.

Put the whole of the potometer into water. Move until all air bubbles come out.

Leave the end of the capillary tube out of the water until an air bubble forms then put the end into a beaker of water.

Put the end of the stem into the bung; grease with Vaseline and then put the bung into the potometer. (Prevents evaporation of the water to the air).

Factors that affect transpirationFactor Effect Why?

Brighter Light Transpiration increases The stomata (openings in the leaf) open wider to allow more carbon dioxide into the leaf for photosynthesis

HigherTemperature

Transpirationincreases

Evaporation and diffusion are faster at higher temperatures

Windy Transpiration increasesWater vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf

High Humidity Transpiration is slower(decreases)

Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air



(Grade A)

Comparing transpiration in different plants.

Some plants may have greater leaf surface area (bigger leaves) and so will lose water by transpiration faster.

Some plants may have more / bigger stomata and so will lose water faster.

Movement of water

Once the water has got into the roots, it needs to transported upwards to the leaves.



(Grade A)

Guttation

• Guttation is the loss of water from the edges of leaves caused when water is pushed up from the roots. This occurs at night when stomata are closed.



(Grade A)






(Grade A)

Water evaporates through the stomata

Water enters the plant via the roots by osmosis

Xylem cells carry water up the stem of the plant

through theXylem tubes

Water vapour moves away from the leaf by diffusion .

Minerals are taken in via

active transportALL: Label a diagram of phloem and xylem and outline what their functions are. (Grade C)MOST: Establish how a potometer works and use it to explain what we mean by a transpiration stream.


(Grade A)

Clip of transpiration

• http://techalive.mtu.edu/meec/module01/Transpiration.htm



(Grade A)

Transpiration

What is transpiration?

Although it may seem bad for plants, transpiration actually moves water from the roots to the top of the plant, without using energy.

Water always moves from an area of high concentration to an area of low concentration. This movement of water is a type of diffusion called osmosis.

Transpiration is the loss of water by evaporation from plants.

Plants lose water when they open the stomata in the leaves to let in carbon dioxide.

Air around the plant usually contains less water than the cells of the plant, so water evaporates into the air.

Movement of water up a stem



(Grade A)

Transpiration StreamIn plants, the transpiration stream is the uninterrupted stream of water and solutes which is taken up by the roots and transported via the xylem vessels to the leaves where it evaporates into the air.

The loss of water from the leaf pulls water and mineral salts up through the xylem from the roots.



(Grade A)

Predict how changes in environmental conditions around the plant effect water movement. Use group

discussion and mini whiteboard

Factors that increase evaporation of water from will also increase transpiration.

What factors do you think affect transpiration rate? How do you think each factor will affect transpiration rate (increase or decrease it)? Explain why this happens.

Factor Effect Why?

Factor Description Explanation

Light In bright light transpiration increases

The stomata (openings in the leaf) open wider to allow more carbon dioxide into the leaf for photosynthesis

Temperature Transpiration is faster in higher temperatures

Evaporation and diffusion are faster at higher temperatures

Wind Transpiration is faster in windy conditions

Water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf

Humidity Transpiration is slower in humid conditions

Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air

Factors that affect transpiration rate

The number of different species in an area ………

Where particular organisms are found…………..

The number of organisms of the same species.

An organisms surroundings, made up of factors such as air, water soil and other living organisms ………

A place an organism usually lives ...

An area in which all the living organisms and non‐living features form a stable relationship that needs no input from outside the area to remain stable.

Biodiversity

Distribution

Population

What are the posh science words for the definitions above?

Environment

Habitat

Ecosystem

Sampling• Ecologists study the biodiversity of life found in an ecosystem. They study the distribution and population of organisms.

• The data is then used to monitor changes in distribution of population.

• To do this ecologists use a range of different sampling techniques. It is not possible to look at the entire environment, so ecologists sample a section or small portion. Sampling several small sections is representative of the whole area.

• Random sampling means every point in a area has an equal chance of being selected.

Grade BcI can explain how scientists use various fieldwork techniques to collect data about samples and environmental conditions.

Grade BbI can justify the situations in which it would be suitable to use these particular methods.

Grade A/A*I can consider the controls I would use to collect valid data and or explain how I would reduce errors when using this technique.

There are different fieldwork techniques scientists use to collect organism data.

EquipmentQuadrat – thrown at random onto a field to count certain plants eg daisies. Pooter – Tube placed over small insect and other tube sucked. Insect issucked into the pot. Sweep Net – Swept through long grass as you walk to capture organisms living within the grass. Dipping Net – Used to capture organisms living in water. Pitfall Trap – Holes dug and pots placed in holes, then cover placed over it. Left overnight. Organisms captured counted next day. Data loggers – can digitally monitor changes in temperature, oxygen, CO2 and light levels.







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A B C D E F G H I J K L M N O

This is a daisy field. You can estimate the number of daisies on the field using quadrats.

It is 15 m wideAnd 16 mlength

You are going to place 12 quadrats randomly by choosing coodinates.

Every one write a coodinate in the back of your book.

Eg D, 10

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A B C D E F G H I J K L M N O

Imagine the survey was carried out in the quadrats and the following results were obtained.

Number daisies in each quadrat

QuadratCoodinates

1 2 3 4 5 6 7 8 9 10 11 12

Daisies




Place the quadrats on your field by drawing around the square – how would we deal with daisies half way in the quadrat and half out?

The area is 15m X16 m = 240m2

If we place 12 quadrats it covers 5% of the field.

Count the daisies on your diagram and write your results in the table.




We can calculate the average number of daisies in each quadrat using:

total number of daisies ÷ number of quadrats

= ÷ 12 =

QuadratCoodinates

1 2 3 4 5 6 7 8 9 10 11 12

Daisies




There are 542daisies on the field.

How close was your estimate?

How could you improve the reliability of the data, and get a more accurate estimate?




Sources of error / validityPooter ‐ you have to see the organism to capture it – and get very close. Not all

organisms will be this easy to see / find / capture.

Sweep net – May need practice using the net. May depend on time of day that sampling takes place as to what is captured. Also, net tend to capture more organisms at the top of the grass and neglect organisms that dwell lower down

Pitfall trap – Some organisms may be trapped easier than others / if a predator and prey are caught there is nothing stopping the predator from eating the prey.

Quadrat – deciding whether an individual is within or outside the quadrat frame. Temptation to place the quadrat where you can see plenty of organisms leading to biased sampling.

Datalogger – Is the data logger accurate (has it been calibrated using known samples).




Each quadrat was 1 metre square.

So an average of ……. daisies per quadrat gives us an estimate of ………. daisies per square metre in this field.

If there are 240 metres2 in the field we do:

Average daisies per quadrat (m2) x 240m2 to get the estimate of daisies on the total field.

To get more reliable results – we could increase the number of quadrats used.




Organisms are rarely randomly distributed. They often occur in clumps.

This makes it difficult to estimate abundance with any accuracy.




Answer the questions in full sentences in your book

1. Name some factors that affect the size of a plant population.2. It is important that pitfall traps are not left unchecked for too long. Why do

you think this is?3. Population density is one way to record the abundance of an organism. What

do you need to know to calculate this value? 4. Light intensity and temperature change not only during the course of a day

but also from season to season. Describe how these factors change between winter and summer and suggest how this might affect the organisms that live in a woodland habitat.

5. EXTENDED WRITING TASK: Suggest why scientists spend time trying to find out which organisms are present in an area before a big building project goes ahead and explain how they get a good estimate of the numbers of each species present.



Grade A/A*I can consider the controls I would use to collect valid data and or explain how I would reduce errors when using this

h i


1 Name some factors that affect the size of a plant population.

A: Light, water, nutrients from the soil, space to grow, temperature, disease, grazing animals.


2 It is important that pitfall traps are not left unchecked for too long. Why do you think this is?

A: If a predatory animal falls into the pitfall trap it might eat some of the other animals caught in the trap!


3 Population density is one way to record the abundance of an organism. What do you need to know to calculate this value?

A: You need to know the actual area of the region under consideration (e.g. 500 m2) and the population size of the organism in the region (e.g. 1500 individuals). Then you can calculate the number of individuals per unit area (e.g. 1500/500 m2 = 3 individuals/m2).

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4. Light intensity and temperature change not only during the course of a day but also from season to season. Describe how these factors change between winter and summer and suggest how this might affect the organisms that live in a woodland habitat.


A: Some suggestions: light intensity increases in summer (and there is also more light due to increased day length), so plants can grow faster. Herbivores have more food so their populations increase, and therefore so do the populations of animals higher up the food chain. Temperature also increases in summer so plant growth will be faster (due to enzymes working faster). Mammals don’t need as much food to supply the energy needed to maintain their body temperature.


5. Suggest why scientists spend time trying to find out which organisms are present in an area before a big building project goes ahead and explain how they get a good estimate of the numbers of each species present.


A: To monitor whether change due to the site (such as increased noise; loss of habitat e.g. due to removal of large trees used for nesting and shelter; loss of food due to removal of plants; loss of water as a result of diverting a water supply) has an impact on species diversity and population sizes.


To find out if there are any rare species that need to be protected from the building works.

To monitor whether habitat creation or restoration measures (such as bat boxes, nest boxes or replanting) are working.

To get an accurate estimate of the numbers of each species present they would need to use sampling techniques to identify the species present in different habitats on the site.


Then they would need to scale up the population density estimates for their samples to a total population size estimate, using the total areas of each type of habitat.

Additional credit should be given for naming or describing an appropriate sampling method.

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