OLT 2

h https://www.sohu.com/a/258846963_100262161

2. Nutrient and Gas Requirements

Inquiry question: What is the difference in nutrient and gas requirements between autotrophs and heterotrophs?

Students:

2.1 investigate the structure of autotrophs through the examination of a variety of materials, for example: (ACSBL035)

a) dissected plant materials (ACSBL032)

b) microscopic structures

c) using a range of imaging technologies to determine plant structure

2.2 investigate the function of structures in a plant, including but not limited to:

– tracing the development and movement of the products of photosynthesis (ACSBL059, ACSBL060)

2.3 investigate the gas exchange structures in animals and plants (ACSBL032, ACSBL056) through the collection of primary and secondary data and information, for example:

a) microscopic structures: alveoli in mammals and leaf structure in plants

b) macroscopic structures: respiratory systems in a range of animals

2.4 interpret a range of secondary-sourced information to evaluate processes, claims and conclusions that have led scientists to develop hypotheses, theories and models about the structure and function of plants, including but not limited to: (ACSBL034)

a) photosynthesis

b) transpiration-cohesion-tension theory

2.5 trace the digestion of foods in a mammalian digestive system, including:

a) physical digestion

b) chemical digestion

c) absorption of nutrients, minerals and water

d) elimination of solid waste

2.6 compare the nutrient and gas requirements of autotrophs and heterotrophs

Make sure you are familiar with respiration and photosynthesis from previous work, especially the summary equations.

There is quite a bit of overlap of the syllabus statements for IQ2 and IQ3, so consider the overview:

Plants have different types of tissues with different functions. Some are for growth (meristem in the roots and shoots), some support (sclerenchyma in the stem), some for accessing raw material gases and releasing waste product gas (stomates), some for producing nutrients (mesophyll), transporting water from the roots to the other parts of the plant, especially the leaves for photosynthesis (xylem), some for distributing nutrients formed in photosynthesis to the other parts of the plant (phloem).
Photosynthesis is the process by which most autotrophs generate their own nutrient requirements.
Plants require carbon dioxide for photosynthesis (producing oxygen) and this occurs in the presence of sunlight. Plants require oxygen for cellular metabolism in mitochondria, and this occurs all the time.
We will return to both transport and gas exchange in IQ3.

View videos:

OLT #5 https://www.youtube.com/watch?v=haaajLdFCzw&list=PLeFSFSJ9WqSASZJCSnyez8vWD5jMDu0FR&index=5 [9.55 mins]
OLT #6 https://www.youtube.com/watch?v=2FrqghztIAo&list=PLeFSFSJ9WqSASZJCSnyez8vWD5jMDu0FR&index=6 [15.58 mins]

2.1 investigate the structure of autotrophs through the examination of a variety of materials, for example:

a) dissected plant materials using a range of imaging technologies to determine plant structure (ACSBL032)

Practical 2.2a.1 Investigation of Cells

Inspect prepared slides under microscope
Make wet mounts and inspect under microscope

View videos:

Making cross-sections by hand (stems) https://www.youtube.com/watch?v=YU0DYrU_0FM [4.45 mins]
Making cross-sections by hand https://www.youtube.com/watch?v=GlCOQijkIKc [3.25 mins]
Cheek cell practical https://www.youtube.com/watch?v=GXqrpb91JPg [6.01 mins]

05_b_making_wet_mounts_21.ppt

View video:

OLT #7 https://www.youtube.com/watch?v=6uo8cNLlr-w&list=PLeFSFSJ9WqSASZJCSnyez8vWD5jMDu0FR&index=7 [11.30 mins]

2.1 investigate the structure of autotrophs through the examination of a variety of materials, for example:

b) microscopic structures, using a range of imaging technologies to determine plant structure

Transverse sections of leaf

Photomicrographs (stained)

1. https://slideplayer.com/slide/7960437/25/images/21/Cross+section+of+a+dicot+leaf.jpg 2. https://sites.google.com/a/otsegoknights.org/biology/_/rsrc/1476664855889/home/5-cell-energy/lesson-5-2/dicot-leaf-cross-section_268171.jpg

Diagrammatic representation

3. https://lh3.googleusercontent.com/proxy/h7y--_Ilt8fh2Ctn3CUNGUVcjrONMLtG5OwGYiT2vlGaSG-WHyDlW6Sj24jcmTpEtQ30BcyFKkoWjJanOIrtN5dStxYt1eN89U0eA6YzJJzRUK6aZnbtNpAsYCmwFHySYtcIjw

Electron micrograph (stained) tomato leaf stomate

4. https://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Tomato_leaf_stomate_1-color.jpg/750px-Tomato_leaf_stomate_1-color.jpg

View video:

OLT #8 https://www.youtube.com/watch?v=AGwpAVYXJzE&list=PLeFSFSJ9WqSASZJCSnyez8vWD5jMDu0FR&index=8 [9.08 mins]

Transverse section of stem

Photomicrographs (stained)

1. https://www.flickr.com/photos/146824358@N03/35471582446 2. https://commons.wikimedia.org/wiki/File:Figure_30_01_02f.jpg

Transverse section of a root

Diagram representation

1. https://upload.wikimedia.org/wikipedia/commons/e/e3/Root%28cross_section%29.jpg

Photomicrograph (stained)

2. https://live.staticflickr.com/4300/36045154705_5918185b7c_b.jpg

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2.2 investigate the function of structures in a plant, including but not limited to tracing the development and movement of the products of photosynthesis (ACSBL059, ACSBL060)

View video:

OLT #9 https://www.youtube.com/watch?v=N-Bz2t4B7jw&list=PLeFSFSJ9WqSASZJCSnyez8vWD5jMDu0FR&index=10 [12.22 mins]

REVIEW

View videos:

Vascular plants in evolution: for interest

Crash Course: Winning= Vascular Plants https://www.youtube.com/watch?v=h9oDTMXM7M8 [11.53]

Structure of Plants

M2L3-1 Autotrophs - Macroscopic Structures https://www.youtube.com/watch?v=0I1E12LO4tc [6.13 mins]
Plant Structure: to 10.50 for overview of structure of plant only, don't worry about the detail https://www.youtube.com/watch?v=zHp_voyo7MY [13.36 mins]

Photosynthesis

Amazing Process of Photosynthesis https://www.youtube.com/watch?v=pFaBpVoQD4E [4.53 mins]
Photosynthesis and Transportation in Plants https://www.youtube.com/watch?v=cMte2VCtZ-I [7.12]

Nutrition and Transport

M2L3-2 Autotrophs - Transport Systems https://www.youtube.com/watch?v=NZ4lOnoOtLc [5.19 mins]
Plant nutrition and transport https://www.youtube.com/watch?v=bsY8j8f54I0 [14.20 mins]

2.3 investigate the gas exchange structures in animals and plants through the collection of primary and secondary data and information, for example:

a) microscopic structures: alveoli in mammals and leaf structure in plants

i) The leaf

The structure of the leaf is adapted for gas exchange. The cells in the spongy mesophyll (lower layer) are loosely packed, and covered by a thin film of water. There are tiny pores, called stomata (or stomates) in the surface of the leaf. Most of these are in the lower epidermis, away from the brightest sunlight.

The stomata control gas exchange in the leaf. Each stoma can be open or closed, depending on how turgid (tight) its guard cells are.

In the light, the guard cells absorb water by osmosis, become turgid and the stoma opens.

In the dark, the guard cells lose water, become flaccid (loose) and the stoma closes.

Diffusion of carbon dioxide, oxygen and water vapour into (or out of) the leaf is greatest when the stomata are open.

Images below and text (adapted) from https://www.bbc.co.uk/bitesize/guides/zxtcwmn/revision/2

View video:

M2L4P1 Gas Exchange https://www.youtube.com/watch?v=n5lfX9tXXAQ&t=28s [9.22 mins]

View video:

What are stomata? https://www.youtube.com/watch?v=UqPn7elPhys&list=PLuvczWTLJXAu_Co-DRNi5uBQUCtCdXVsm&index=32 [3.47 mins]

TASK 2.3a.1

Complete a table or Venn diagram to compare (similarities) and contrast (differences) gas exchange structures processes in animal lungs (alveoli) and plant leaves (stomates)

Some resources as starting points:

TASK 2.3a.2

Adapted from https://www.bbc.co.uk/bitesize/guides/zxtcwmn/revision/3

Consider the following information about an experiment and answer the questions.

A leaf was placed in a stoppered boiling tube containing some hydrogen carbonate indicator solution to investigate the effect of light intensity on gas exchange due to photosynthesis.

Hydrogencarbonate indicator is used to show carbon dioxide concentration in solution. The table shows the colour that the indicator turns at different levels of carbon dioxide concentration.

The table below shows the colour that the indicator turns at different levels of carbon dioxide concentration. The levels of CO2 will be low when photosynthesis is occurring and removing it.

Indicator Table

CO2 level Indicator turns

Highest Yellow

Higher Orange

Atmospheric level Red

Low Magenta

Lowest Purple

The table below shows the results.

Results Table

Tube 1 Tube 2 Tube 3 Tube 4

Light turned on ✓ ✓ ✓ ✓

Paper on tube Black Tissue None None

Leaf Living Living Living Dead (boiled)

Colour at end Yellow Magenta Purple Red

CO2 level

Photosynthesis

Use the indicator chart at the top to select the words for the appropriate levels and add them to the results table above.
In which tubes did photosynthesis take place?

Place ticks and crosses. Use a triple/double/single tick or cross to indicate amount.
Explain your decisions.

2. What does a comparison of the results in tubes 3 and 4 show?

3. What does a comparison of Tube 1 with Tubes 2 and 3 show?

Task 2.3a.3 Simulation - Effect of CO2 concentration on rate of photosynthesis

Visit: https://iwant2study.org/lookangejss/biology/ejss_model_photosynthesis/photosynthesis_Simulation.xhtml NOTE: Requires Java.

Click on the image to reach the active simulation screen.
Click on bar top left and select Activity 2 CO2 (it will be set to default Activity 1 Light). Note the CO2 concentration is 0.05%.
Click start. Wait 60 seconds for the bubble cout to finish. Record value in a table.
Move the slider (click on the box in the middle of the double arrow and slide the arrow system up) to 0.10%. Repeat Step 2.
Continue for 0.15, 0.20, 0.25, 0.30.
Graph your results.

Discuss:

Describe the graph between 0% and 0.15% of carbon dioxide.
What does the graph between 0% and 0.15% of carbon dioxide tell about the relationship between carbon dioxide concentration and rate of photosynthesis?
Describe what happens to the graph after 0.15% carbon dioxide.
What does this tell about the relationship between the carbon dioxide concentration and rate of photosynthesis when carbon dioxide concentration exceeds 0.15%?

Practical 2.3a.1 Viewing Stomates

View videos:

Making a stomata slide https://www.youtube.com/watch?v=jjinctgL8_Y&list=PLuvczWTLJXAu_Co-DRNi5uBQUCtCdXVsm&index=33 [2.49 mins]

Practical 2.3a.2 Respiration in Plants

https://www.rookieparenting.com/do-plants-breathe-science-experiment/

Materials

water
plant (e.g. a flower or a leaf. Pick it from a living plant, not one that has fallen onto the ground)
sunlight

Equipment

shallow bowl

Instructions

Submerge the plant into a bowl of water. The flower or leaf may float to the top, but try to make at least part of the plant stay underwater.
Put the bowl under sunlight.
After an hour, look for air bubbles in different parts of the plant.

Repeat

Do air bubbles form if you leave the plant in the dark?

Practical 2.3a.3 Plant Respiration

https://aspb.org/wp-content/uploads/2016/05/5_PLANTS-RESPIRE-TOO-Respiration-and-energy.pdf

Materials/group:

10 or 25 mL graduated cylinder
Test tube rack
6 test tubes with stoppers (3 are for student-designed experiments)
100 mL of water at pH 7
Dropper bottle of phenol red pH indicator (0.04% aqueous solution)
pH paper strips
5-6 small beakers
Metric ruler
Germinating seeds of various types (radish, peas, corn, etc)
Germinating seeds that have been boiled for 10 minutes (or microwaved for several minutes in water)
Marking pens
Colored pencils
Paper towels

Procedure:

1. Obtain 100 mL of water. Test the pH (using pH paper test strips) of this solution. Record.

2. Place 3 test tubes in a test tube rack and label each with the date, plant material, and your name. Add 10 mL of water to each of the 3 test tubes. Then add 3 drops of phenol red pH indicator into each test tube and record the color.

3. Test tube 1 will be your control. Do not place any plant material in this tube. Place this test tube in a beaker or container to hold the test tube upright. Place a stopper in the tube.

4. Pat dry the germinating seeds that have NOT been boiled. In test tube 2, add enough germinating pea seeds to fill one half of the tube, making sure the seeds are in the liquid. Place this test tube in a beaker or container to hold the test tube upright. Place a stopper in the tube.

5. Pat dry germinating seeds that have been boiled. In test tube 3, add enough BOILED germinating pea seeds to fill one half of the tube, making sure the seeds are in the liquid. Place this test tube in a beaker or container to hold the test tube upright. Place a stopper in the tube.

6. Let these tubes sit undisturbed for 30 minutes. Observe and record the color of the liquid in the tubes. Pour a small amount of the liquid from each tube into small clear containers and place a piece of pH test strip in each solution. Leave for 2 minutes, and then record the pH of each solution.

7. Pour the liquids back into the correct test tubes and put stoppers back into the tubes. Let these test tubes sit overnight.

8. Pour some of the liquid from each test tube into smaller clear containers. Note any color changes in the liquids. Check and record the pH of the liquids by placing pH paper strips in each and leaving for several minutes.

Observations:

- - Are the colors of the liquids different after 24 hours? How so?
  - If the colors are different, what might have caused the change?
  - Are the temperatures different after 24 hours? How so? If so, what might have caused the temperature change?

Practical 2.3a.4 Student-Designed Experiments:

Using the methods you learned in the activity above and the scaffold velow, design and carry out your own inquiry. Question topics you might consider include the differences between various plant parts, the differences between plant species, the conditions in which respiration takes place, etc.

ii) Alveoli

Alveoli are small sacs found in the lungs in mammal and reptile bodies.

They are the sites of gas exchange, input of oxygen to the blood from the lungs, output of carbon dioxide waste from the blood to the lungs .

https://upload.wikimedia.org/wikipedia/commons/thumb/c/c4/Gas_exchange_in_the_aveolus_simple_%28en%29.svg/2000px-Gas_exchange_in_the_aveolus_simple_%28en%29.svg.png

https://www.footprints-science.co.uk/?fbclid=IwAR3hbWF9YGjWOyQOhtPGXVlJQ7OC0vKr6N_bXcQQZu4f82VSXKbGdqAK_6U

Task 2.3a.4

Visit https://study.com/academy/lesson/alveoli-function-definition-sacs.html

View video
Make summary notes

Visit https://socratic.org/questions/what-are-structure-and-function-of-alveoli

Add to your summary notes

2.3 investigate the gas exchange structures in animals and plants through the collection of primary and secondary data and information, for example:

b) macroscopic structures: respiratory systems in a range of animals

TASK 2.3b.1

Group task: In your group, carry out a quick research of the respiratory systems in a given animal and report back to class.

spider
sponge
fish
caterpillar
humans ( we will consider this in detail in IQ3)

Top of Page

2. 4 interpret a range of secondary-sourced information to evaluate processes, claims and conclusions that have led scientists to develop hypotheses, theories and models about the structure and function of plants, including but not limited to:

a) photosynthesis

a) Photosynthesis

Read the following extract from THE THEORIES OF PHOTOSYNTHESIS IN THE LIGHT OF SOME NEW FACTS* H. A. SPOEHR published in 1916.

"It is now more than 135 years since the fundamental principles of the cosmical function of green plants was clearly recognised by Ingen-Houz, Priestley and Sénébier. The classical researches of de Saussure on the gaseous exchange of plants, which appeared shortly thereafter, still stand as the most thorough and masterly which have appeared in the history of the subject. Although the number of investigators who have worked on the problem of photosynthesis since the time of de Saussure runs into the hundreds, and our knowledge of the chemistry of the substances involved in the process has been greatly extended, it cannot be claimed that we have as yet taken any decided step toward an understanding of the chemistry of the process based upon observation or rigid experiment. However, the work of Sachs in the sixties, on the function of the chloroplasts, and the formation of starch therein, was the key to the chemical aspect of the problem, and served as a great stimulus to its further study. These researches established a direct relation between the carbon dioxide absorbed by the leaf and the starch formed therein. In fact, Sachs proved starch to be the first "distinctly recognisable" product in the process of photosynthesis. What then, is the course and sequence of chemical changes in the reduction of the simple compounds, carbon dioxide and water, to the highly complex starch?"

and

"The endosymbiotic theory suggests that photosynthetic bacteria were acquired (by endocytosis) by early eukaryotic cells to form the first plant cells. Therefore, chloroplasts may be photosynthetic bacteria that adapted to life inside plant cells."

From https://www.jstor.org/stable/pdf/43477478.pdf

TASK 2.4A.1

Research and enter into Google Tour, table or timeline form the names, working dates and contributions to our understanding around the process of photosynthesis of the following scientists:

Jan Baptista van Helmont
Joseph Priestley
Jan Ingenhousz
Jean Senebier
Julius Robert Mayer
Julius Sachs
Cornelis Van Niel

2. 4 interpret a range of secondary-sourced information to evaluate processes, claims and conclusions that have led scientists to develop hypotheses, theories and models about the structure and function of plants, including but not limited to:

b) transpiration-cohesion-tension theory

b) Transpiration Cohesion-Tension Theory

The function of xylem and phloem in transport is mainly to carry materials for photosynthesis to the photosynthetic cells and move the products away from those cells to other parts of the plant. In small plants this may be achieved through diffusion and active transport, however in larger plants specialised vascular (xylem and phloem) tissue has developed to serve this function.

The vascular system consists of xylem and phloem and the movement of materials from one part of the plant to another is known as translocation.

The transpiration stream in xylem occurs due to physical forces that result in water and ions being moved by passive transport. A column of water is drawn up by the stem, by the evaporation pull of transpiration – this is known as the transpiration stream. Once water has been absorbed into the roots (osmosis) along with mineral ions (diffusion and active transport), these substances move into the xylem. A small amount of root pressure results from the continual influx of ions and water – forcing the solution upwards, this is insufficient by itself. Most of the upward movement is a result of the transpiration stream – which is water is drawn up the xylem to replace water which is lost due to transpiration at the leaves.

Evidence for this theory

- Xylem are hollow and narrow – very little resistance to the flow of water

- The physical properties of water contribute to a continuous stream. Adhesive forces (between water and xylem walls) lead to capillarity (water rises up the narrow bore of the xylem) and cohesive forces (between water molecules) form a continuous stream

- A concentration gradient exists. The surface of the leaf has high osmosis pressure (low water concentration) due to transpiration. The centre of the leaf has a low osmosis pressure.

Explanation

Water loss at the surface of the leaf results in the osmotic movement of water across from adjacent internal cells into those that have just lost some water. This osmotic flow continues across the leaf – until it reaches the xylem tissue. When water molecules leave the xylem and move along the concentration gradient, this creates a tension in the column of water rising up the xylem. Due to the properties of adhesion and cohesion the water column does not break and so the entire water column is not pulled upwards. The combination of adhesive and cohesive forces, together with the pull of the transpiration – creates the transpiration stream. Mineral ions dissolved in the water are carried along by the transpiration stream and can move out by active transport – to reach the tissues where they are needed.

Or, in other words...

The Cohesion Tension theory of transpiration was proposed by botanist Henry Dixon in 1939.

It states that water in xylem is pulled upward by air's drying power, which creates a continuous negative pressure called tension. The tension extends all the way from leaves to the roots that may be many metres below. Most of the water a plant takes up is lost by evaporation, typically from stomata on the plant's leaves in the process called transpiration. Transpiration's effect on water inside a plant is a bit like what happens when you suck a drink through a straw. Transpiration puts negative pressure (pulls) on the continuous columns of water that fill the narrow tubes of xylem. A column of water resists breaking into droplets as it moves through a narrow tube such as xylem tubes (water molecules are attracted to each other by strong physical attractive forces called hydrogen bonds; this sticking together is called cohesion). The negative pressure created by transpiration (tension) pulls on the entire column of water that fills the xylem tube.

Because of the water's cohesion, the tension extends from leaves that may be 30m in the air down through stems, into young roots where water is being absorbed from the soil.

1. https://biology4isc.weebly.com/a-plant-transport.html 2.https://commons.wikimedia.org/wiki/File:Transpiration_of_Water_in_Xylem.svg

View videos:

Background/Review: Transportation in plants https://www.youtube.com/watch?v=JFb-CWlz7kE [3.47]
L3P3 Transport Mechanisms https://www.youtube.com/watch?v=SyPiL27uAbY&t=427s [7.07 mins]
Transpiration cohesion-tension theory https://www.youtube.com/watch?v=ZJnAOYrwT4w [1.01 mins]

Practical 2.4b.1 Demonstration of Transpiration by Cobalt-Chloride Screen

http://www.biologydiscussion.com/experiments/top-13-experiments-on-transpiration-plants/56605

Materials:

Filter paper
cobalt-chloride solution
a potted plant
paper clips

Procedure:

Dip pieces of the filter paper in cobalt chloride solution (pink) and then dry off to a blue colour.
Press one on top surface and one on bottom using paper clips.
Leave overnight in a dry room.
Observe colour of the two pices of filter paper.

Explanation:

The dried blue coloured cobalt chloride paper turns red as it becomes moist. The stomata are confined mostly on the lower surface of the leaf, and therefore, the cobalt chloride paper of that surface becomes moist and turns red. The paper of the upper side of the leaf may also become pink to some extent, as few stomata are found on this side.

Practical 3.3b.2 Demonstration of Transpiration by Four-Leaf Experiment

http://www.biologydiscussion.com/experiments/top-13-experiments-on-transpiration-plants/56605

Materials:

4 large leaves
Vaseline
String
4 paper clips
2 retort stands

Procedure:

Take four large leaves.

Vaseline both the surfaces of the leaf B, lower surface only of leaf C, upper surface only of leaf D. Leaf A is the control.

Clip leaves separately to hang along a piece of string suspended between retort stands.

Observation and Explanation:

Take observations after a day or two. Typical observations are:

Leaf B, which is vaselined on its both the surfaces, looks fresh and green (no surface transpires).
Leaf C, vaselined on its lower surface (with stomata), and transpiration takes place only from the upper surface which is negligible, remains turgid and green like leaf B.
If few stomata are present on the upper surface of the leaf, then it shrivels to some extent. Leaf D is vaselined on its upper surface, which contains fewer or no stomata. Transpiration takes place from the lower stomatal surface, and the leaf shrivels to a large extent.
Leaf A is not vaselined and both the surfaces transpire freely releasing much water. The leaf wilts completely in this case.

This experiment shows that the rate of stomatal transpiration is higher than cuticular transpiration.

c) Phloem – pressure flow theory

Translocation in phloem tissue moves products of photosynthesis by active transport. The flow of materials in phloem is an active process that requires energy. The mechanism of flow is driven by an osmotic pressure gradient, generated by difference in sugar and water concentrations. It involves the active loading of sugar into the phloem at one end (source) and then the active unloading from the phloem into surrounding tissues at the other end (sink). The loading of sugar into the phloem attracts water to flow in (due to the differences in osmotic pressure). Materials flow to the sink. At the sink (roots or flowers) sugars and material are removed from the phloem by active transport. As sugars move out of the phloem, they draw water out with them (osmosis). This results in a lower osmotic pressure (due to the higher water concentration) in the phloem at the sink.

This difference in osmotic pressure between the source and the sink in the phloem drives the phloem sap to flow. The direction of the flow depends on where the sink areas are in relation to the source. Water can move into the phloem by osmosis at any point along the gradient. The flow is continuous as sucrose is continually added at one end and removed at the other.