HS-LS1-5

Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

HS-LS1-6

Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules. 

HS-LS1-7

Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed resulting in a net transfer of energy.

HS-LS2-5

Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.

HS-PS1-5

Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

HS-PS1-6

Refine the design of a chemical system by specifying a change in conditions that would produce increased amounts of products at equilibrium.

HS-LS4-4

Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Lessons

Projects

Experiments

Lesson Summary: Introduction to the basic requirements for life, photosynthesis, and respiration.

Time Estimates: 30 minutes.  

Learning Outcomes: 

1. I can distinguish between the two most common trophic strategies.
2. I can justify if an organism is living based on the characteristics of life.
3. I can describe how carbon recycles through an ecosystem.
4. I can describe the structure and function of mitochondria.
5. I can model the structure and function of a chloroplast.
6. I can compare and contrast mitochondria and chloroplasts organelles work within a cell to maintain homeostasis.

Classroom Prep: None

Guiding Questions

1. What characterizes a living organism, and what does life need to survive?
2. What is the structure and function of mitochondria?
3. What is the structure and function of chloroplasts?
4. What are the ingredients and byproducts of both photosynthesis and cellular respiration?
5. How do photosynthesis and cellular respiration influence one another?
6. What role does carbon play in the biological processes of life?

Key Terms: trophic strategy, autotrophy, heterotrophy, cellular respiration, mitochondria, ATP, chloroplast, homeostasis, proton, ion

Time

Activities:

Learner outcomes:

“I can...”

Let me prove it! Respond to the questions in this column

5 mins

Read the paragraph below describing the difference between autotrophy and heterotrophy.

Distinguish between the two most common trophic strategies.

Is a Venus Flytrap an autotroph or a heterotroph? Can it be both? Why or why not?

Life needs, in the most general sense, a source of energy and a source of carbon. How a specific organism gets these supplies determines its trophic strategy. The two most common trophic strategies are autotrophy and heterotrophy. Autotrophic organisms create their energy from inorganic starting sources, like the sun or energetic molecules. Organisms that photosynthesize are autotrophs. Heterotrophs derive their energy from either autotrophs or other heterotrophs, as they cannot create their  energy from inorganic starting sources. A cow or a lion are examples of heterotrophs.

5-7 mins

Read the paragraph below describing the essential characteristics of life.

Justify if an organism is living based on the characteristics of life.

Defend or refute the statement “fire is a living thing,” using what you have learned about life requirements.

Respiration/Metabolism: Respiration is the release of energy from energetic substances in all living cells. Living things break down food within their cells to release energy for carrying out the following processes.

Movement: All living things move. It is obvious that a leopard moves, but what about the tree in which a leopard sits? Plants move as well, though it may be too slow to see with the naked eye. Single-celled plant-like organisms, which we will discuss here, can also move through with cellular machines that propel them through the water or across surfaces.  

Excretion: All living things excrete. As a result of the many chemical reactions occurring in cells, they have to get rid of waste products, which might poison the cells. Excretion is removing toxic materials, the waste products of metabolism, and substances in excess from an organism’s body.

Growth: Growth is seen in all living things. It involves using energy to produce new cells. The permanent increase in cell number and size is called growth. Growth is observed in both multicellular and unicellular organisms.

Reproduction:  All living organisms can produce offspring, either asexually or sexually.

Sensation: All living things can sense and respond to stimuli around them, such as light, temperature, water, gravity, and chemicals.

5-7 mins

Read the paragraph below describing the form of a mitochondrion and its function: respiration.

Watch this video on Mitochondria:

How Mitochondria Produce Energy

Describe the structure and function of mitochondria.

What is the energy source for respiration? How do the mitochondria use this energy?

An organelle is a membrane-bound compartment within a eukaryotic cell that performs a specialized task. Examples include the ribosomes and endoplasmic reticulum, which perform protein synthesis by reading DNA and translating base pairs into amino acids.

The mitochondrion is an organelle whose function is to perform cellular respiration. When an organism intakes food, it requires a mechanism to break that food down into individual components, then built into useful molecules and create energy. The mitochondria perform this task in all eukaryotic cells, breaking down glucose and using the energy within those broken bonds to make ATP.

The mitochondrial function stages are complex and are broadly classified into three categories: core glycolysis, the Krebs cycle, and the electron transport chain. Each of these steps requires energy input, but the reactions are such that the output energy is more than the input because of energy stored in glucose's chemical bonds. These reactions end at the electron transport chain, which brings reaction energy (in the form of electrons) down in a stepwise manner, pushing hydrogen ions through the membrane at each step. Those hydrogen ions flow back through the membrane using an enzyme named ATP synthase that creates stored energy in the form of ATP.

Mitochondria create products at each step, which are molecules no longer useful once stripped of their chemical bond energy. Essential products are carbon dioxide (CO2) and water, but other products are made and excreted or used in reactions elsewhere in the cell. In a heterotrophic cell, the mitochondria receive energy from food, i.e., grass from a cow. But some organisms are autotrophic and cannot “eat” their energy. Where do the autotrophs get the starting molecules to perform cellular respiration?

5-7 mins

Read the paragraph below describing the form of a chloroplast and its function: photosynthesis.

Watch this video:

Travel Deep Inside a Leaf - Annotated Version | California Academy of Sciences

Model the structure and function of a chloroplast.

Draw a model showing the path carbon dioxide takes throughout photosynthesis. Include the enzymes and any other molecules involved in the process.

Eukaryotic photosynthetic autotrophs must use the chloroplast, a specialized organelle, to create energy from light. Eukaryotes also use chloroplasts; however photosynthetic prokaryotes must use other methods, as we will explore later.

The chloroplast is a complementary organelle to the mitochondria in autotroph. It receives the water and carbon dioxide by-products of respiration and uses them to convert light energy into stored chemical energy. It does this first in the light reactions, which uses the energy from light to break apart water and transport its electrons through an electron transport chain similar to that of the mitochondria. The proton gradient created from the light reaction turns ATP synthase to make ATP and creates other energetic molecules. The light reactions then provide that energy to the dark reactions or Calvin cycle, which capture CO2 gas using an enzyme called RuBisCO and build the structures of glucose and other carbohydrates off of that skeleton. In this method, cells can store more energy than ATP, and provide fuel for respiration.  

3-5 min

Read the paragraph below describing how respiration and photosynthesis balance each other.

Compare and contrast how mitochondria and chloroplasts organelles work together to maintain homeostasis.

After watching the videos, create a Venn diagram below comparing and contrasting the form and function of mitochondria and chloroplasts.

As mentioned above, photosynthesis and respiration complement one another by providing each with their required molecules. The carbon dioxide created in mitochondrial respiration can be fixed and used during photosynthesis, and the ATP created by photosynthesis is used to break apart glucose during respiration. This reaction’s products mentioned above can be used in other physiological processes not involving energy creation, such as maintaining the proper intracellular concentration of certain salts and water. These processes allow the cell to balance these reactions and maintain homeostasis or a proper physiological balance.

Lesson Summary: This lesson is a general introduction to microalgae. Microalgae is our model organism in all the experiments we conduct throughout this module; algae will be introduced in this lesson. More on model organisms in Lesson #3.

Time Estimate:  30 minutes.  

Learning Outcomes: 

1. I can compare terrestrial and aquatic photoautotrophs morphology and life history.
2. I can differentiate macroalgae from microalgae based on morphological characteristics.
3. I can describe and classify examples of prokaryotic and eukaryotic microalgal life.  
4. I can analyze the evolutionary need to develop a method for forming membrane-based concentration gradients.
5. I can identify various forms of algal life in non-aquatic environments.
6. I can create a methodology for a lab scenario.

Materials Needed:  None

Guiding questions: 

1. What other organisms use photoautotrophy besides terrestrial plants?
2. How can microalgae be distinguished from macroalgae?
3. How diverse are microalgae?
4. How have prokaryotic microalgae evolved to photosynthesize in the absence of a chloroplast?
5. Which methods can be used to observe microalgae?

Key Terms: algae, macroalgae, microalgae, polyphyletic, cyanobacteria, photopigment, flagella, extremophiles, epifluorescence microscopy, flow cell/flow cytometry, concentration gradient

Time

Activities:

Learner outcomes:

“I can...”

Let me prove it! Respond to the questions in this column

5-10min

Read the below paragraph describing the different environment inhabited by algae, and view this slide presentation:

Compare terrestrial and aquatic photoautotrophs morphology and life history.

Can you think of any photoautotrophs that appear to be terrestrial (in structure and function) but spend their lives at least partially submerged? Hint: they are common in Florida and serve as nurseries for sharks, alligators, and many fish!

Photoautotrophy by plants and trees are the foundation of the terrestrial food web, with all higher trophic-level consumers relying on photosynthesis to capture energy otherwise unavailable to them. If that is true, it stands to reason that marine and freshwater ecosystems must also have a base of photoautotrophs providing energy to the rest of the environment.

Compared to land-based plants living in the air, photoautotrophs in liquid environments must undergo significant morphological and physiological changes to adapt. While terrestrial plants may be the most accessible photoautotrophy examples, they only produce around 50% of the oxygen that humans and all other organisms breathe. The additional 50% is made in the world’s oceans and lakes by a diverse group of algae organisms! Algae carry out photosynthesis without the assistance of a root system, leaves, or other rigid structures possessed by plants.

1-2 min

Read the below paragraph distinguishing macroalgae from microalgae.

Differentiate macroalgae from microalgae based on morphological characteristics.

Name three general distinctions between microalgae and macroalgae?

Research the following organisms and classify them as either macroalgae or microalgae:
Giant Kelp, Sargassum seagrass, Chlorella vulgaris, Bubble algae, Arthrospira.

“Algae” is a very general term covering both prokaryotic and eukaryotic life, so we divide it into two different categories: macroalgae and microalgae. Macroalgae are large and multicellular, containing groups like kelp, seaweeds, and seagrasses. Microalgae, which we will focus on in these lessons, are often unicellular or colonial organisms that contain all necessary photosynthetic and respiratory machinery within a single cell.

3-4 min

Read the below paragraph briefly describing microalgal diversity
Watch this video:

Algae Corner: What are Algae?

Describe and classify examples of prokaryotic and eukaryotic microalgal life.

What are cyanobacteria? How have they adapted to photosynthesize with their specific cellular machinery? Why is this adaptation necessary?

Break “polyphyletic” into its component words, and then explain what the whole word means using the sum of its parts.

Classify each of the following as either prokaryotic or eukaryotic microalgae: Synechococcus, Arthrospira, Gymnodinium, Teleaulax amphioxeia, Prorocentrum.

Microalgae are incredibly diverse and polyphyletic or contained in multiple branches in the tree of life. Cyanobacteria, or blue-green algae, are prokaryotes named for the color given to them by the photopigment chlorophyll a. Eukaryotic microalgae groups are commonly referred to as their photopigment color (red algae, green algae, brown algae, etc.) or other morphological characteristics they possess, like the cellular flagella that enable them to move throughout their liquid environment.

5-7 min

Read the below paragraph describing how prokaryotes have adapted to the photosynthetic requirement for a membrane.

Analyze the evolutionary need to develop a method for forming membrane-based concentration gradients.

Explain in your own words the problem faced by prokaryotic photoautotrophs in regards to concentration gradients, and how they have adapted.

All microalgae must have a membrane to embed the photosynthetic machinery that allows for creating a proton (H+) concentration gradient. This membrane is integral to photosynthesis’s light reactions because the ATP synthase must pass H+ ions along the concentration gradient.  Eukaryotic microalgae form chloroplasts as terrestrial plants do, with stacked discs called grana connected by a thylakoid.

But wait, everything we know about prokaryotic life so far says that they lack membrane-bound organelles! Cyanobacteria and other prokaryotic microalgae have managed to get around this by forming free thylakoid membranes through mechanisms that are not yet well defined by current research. These membranes are not encased within a chloroplast or stacked into grana, as thylakoids are within a chloroplast. In this way, prokaryotes have adapted to create concentration gradients in the service of photosynthesis.

2-3 min

Read the below paragraph describing the diversity of microalgal habitats.

Identify various forms of algal life in non-aquatic environments.

Research and report in 1-2 sentences an example of each of the following:

Thermophiles, barophiles, cryophiles, and acidophiles.

The experiments conducted in this kit use aquatic and marine strains, but microalgae are in all environments! Algae are plentiful in terrestrial soils and often assist in the growth of plants and trees. They are also in sea and glacial ice, where the action of water freezing captures the cells within the ice crystals to photosynthesize there. Certain types of algae can also promote the formation of a cloud condensation nucleus and live in the atmosphere as an aerosol!

Algae have also adapted to live in extremely adverse environments. These organisms are broadly called extremophiles, and can live in extremely high-temperatures (thermophiles), extremely low temperatures (cryophiles), high pressures (barophiles), and very high acidities / low pH (acidophiles). Cyanobacteria were first discovered living at the edge of high-temperature hot spring pools and geysers, which shows just how common and prevalent microalgae can be in extreme environments!

5-7 min

Read the paragraphs below describing the methods used to observe algae.

Create a methodology for a lab scenario.

If you had a solution of two algae species, one blue-green cyanobacterium, and one eukaryotic red alga, you wanted to count the cells under a microscope. These two species have the same spherical morphology. How would you differentiate between the two species using the methods learned above?

Macroalgae can be observed and studied without the assistance of a microscope, due to their multicellular nature. Microalgae, on the other hand, are often microscopic, and as such, require more specialized observation methods.

Light microscopes are the most commonly used method to observe individual microalgal cells. If we want to discriminate between different species, we can also shine laser light at specific wavelengths to highlight different photopigments within the cells! This method is known as epifluorescence microscopy and leads to beautiful and informative images (as shown).  We can also run aquatic algae through a flow cell machine to concentrate the microalgae into a stream of water one cell wide. We can then take a picture with a microscope of each cell as it flows through, or we shine laser light onto it to observe fluorescence. This method is known as flow cytometry.

Lesson Summary: This lesson is a significant turning point for the module’s flow, encouraging the students to think critically about the information they’ve learned so far. This lesson is intended to get the students to start thinking about experimental design that they will work more closely with later in the module.

Time Estimates:  25 minutes.  

Learning Outcomes: 

1. I can explain the importance of and discern the criteria for a model organism in science.
2. I can differentiate between and give examples of qualitative and quantitative observations.
3. I can observe algae beads as a model organism and predict how they are used in scientific discovery.

Materials Needed:  None

Guiding Questions

1. What is a model organism?
2. What are the two kinds of observations that a scientist can make?
3. Give examples of both kinds of observations
4. After observing the algae beads, describe them in comparison to other model organisms, what might be some advantages and disadvantages of using them in an experiment?

Key Terms: Observation, qualitative, quantitative, model, algae beads

Time

Activities:

Learner outcomes:

“I can...”

Let me prove it! Respond to the questions in this column

4-5 min

Read the paragraph below describing the necessity and characteristics of model organisms.

Watch these video-1:

MODEL ORGANISMS

 video-2:

Why do scientists use model organisms?

Explain the importance of and discern the criteria for a model organism in science.

How does a scientific model help scientists?

Would humans make a good model organism? Why or why not?

Often we cannot directly measure the subject of our interest to the level of detail needed for scientific determination. Perhaps we wish to theorize on yet-to-be-discovered organisms, like astrobiologists searching for analogs to Martian life in Earth’s soil. To study things like this, we can either create a model ourselves using technology or observe similar systems or organisms to reasonably conclude from.

A good model organism is easy to maintain and manipulate, accessible, cheap, and constant enough to draw statistically significant conclusions from your experimentation.

Examples of models or model organisms employed in science include:

1. Multivariate climate models are used to simulate heat flux between the atmosphere, earth, and oceans.
2. Blackhole gravitational mathematics algorithms are used to process and render the first-ever image of such a celestial body.
3. C. elegans roundworms are used as model organisms in evolutionary, developmental, or molecular biology.
4. Mice and primates are used as test subjects in biomedical and vaccine research.

2-5 min

Read the points below summarizing the different observations scientists can make, as well as the two most common forms of experimentation.

Watch this video:

Flubber - Creation Scene

Differentiate between and give examples of qualitative and quantitative observations.

Based on the video what observations does Professor Brainard make about Flubber? Are these QUANTITATIVE or QUALITATIVE observations? Defend your position. What other types of observations could he have made about his creation?

What kind of data can scientific study generate?

Qualitative: describing the quality of something using non numerical, subjective terminology

1. Long
2. Heavy
3. Happier

Quantitative: describing something using measurable metrics

4. Length in centimeters
5. Mass in grams
6. Concentration of cortical serotonin in picograms/cm3

Which one is better? Both are important, and often when exploring a new topic qualitative observations spark curiosity and quantitative observations prove the hypothesis.

How can scientists study?

7. Experimental studies: These are the stereotypical scientific studies, with manipulation of an independent variable and hypothesis forming about a dependent variable's response. .
8. Observational studies: These studies are more akin to surveys of an entire environment, where the scientist's efforts are focused on data collection without manipulation of variables.

1-2 min

Read the below paragraph describing our test bed for this module: algae beads

Watch this video:  Algae Beads Introduction- Algae Research Supply

Observe algae beads as a model organism and predict how they are used in scientific discovery.

After learning about algae beads, what do you think would make them a good model system? List three reasons for or against.

How can algae beads be used to model photosynthesis and respiration?

Because algae can occasionally be apathetic to teaching schedules and refuse to grow or grow to insufficient density, sodium alginate beads can provide a compact and easy-to-use alternative for classroom experimentation. Algae are grown in liquid cultures, suspended in an alginate solution, then dropped into a chemical that hardens the droplets. Each drop forms an algal bead. All of the nutrients required for algal growth are retained within the bead, and the size of the gel matrix comprising the bead allows for passive diffusion of certain small molecules like ions. These provisions allow for the creation of a discrete unit of experimentation that is easy to replicate.

Lesson Summary:  This lesson is designed to give students a better understanding of what light is and how photosynthetic organisms catch and process the light. This information is important to understand prior to experimenting with light-intensity or light-color.  

Time Estimates:  30 minutes.  

Learning Outcomes: 

1. I can explain where PAR fits into the EM spectrum, and how wavelength affects photon energy.
2. I can relate the inverse square rule to algal growth.
3. I can predict the performance of hypothetical organisms based on the relationship of  primary and accessory photopigments working together in photosystems.
4. I can justify how and why phytoplankton possess different photopigments.

Classroom Prep:  None

Guiding Questions

1. What is light?
2. How does light intensity decrease with distance?
3. How do plants capture light?
4. Why are plants green?
5. What are the outputs of photosynthesis?

Key Terms: electromagnetic (EM) radiation, photosynthetically active radiation, wavelength, frequency, photon

Time

Activities

Learner outcomes

I can…

Let me prove it. (write responses)

5  mins

Read the paragraph below describing Electromagnetic Radiation and Photosynthetically Active Radiation.

Watch the video: Photosynthesis: Crash Course Biology #8

Minutes 2 to 8 in the video  above are a great explanation of the light dependent reactions in photosynthesis.

Explain where PAR fits into the EM spectrum, and how wavelength affects photon energy.

What is Photosynthetically Active Radiation? Where does it fall on the electromagnetic spectrum?

Fill in the following sentence:

If all photosynthetic organisms require electromagnetic (EM) radiation in the solar spectrum of visible light, then the light available falls between wavelengths of ______ and ______.  This is called PAR, or ________________________________________.

Based on what you have learned about the electromagnetic spectrum and photon energy, why might photosynthetic organisms use the visible light spectrum instead of a gamma ray or infrared light.

All photosynthetic organisms require electromagnetic (EM) radiation, which is the visible light received from the sun. The light that organisms use in a given environment is known as Photosynthetically Active Radiation (PAR), which falls between wavelengths of 400-700nm. This energy is “quantized” into packets called photons. Photons can be described by their wavelength in nanometers (nm) or frequency in units called μmol photons (). In most cases, both units are used, i.e., 20 umol photons () of 640nm wavelength light, because photons exhibit both wave and particle-like qualities.

Shown here is a visual of the electromagnetic spectrum.

On the left side of our solar spectrum are the short wavelength, high energy photons. The solar spectrum includes ultraviolet or UV light, which humans apply sunblock to use as protection. On the right side of the solar spectrum are the longer wavelength photons. This includes the blackbody radiation that we perceive as heat or the waves used to communicate using radios or cell phones. In the middle of the two are photons of PAR, which we perceive as light and photoautotrophs capture to begin photosynthesis.

6 mins

Read the below paragraph describing the inverse square law.

Relate the inverse square rule to algal growth.

What is the Inverse Square Rule?  How does this relate to the growth of algae?

From a source of light, there is a finite amount of photons. Light spreads out from the source once emitted, which means that the farther travel from the source, the fewer photons you receive. It follows the inverse square rule, which states that a light source's observed intensity is inversely proportional to the square of the distance from source to observation.

5 - 7 mins

Read the paragraph below describing accessory and primary photopigments.  

Watch this time lapse video:

Youtube: Chromatography Time Lapse - Photosynthetic Pigments in Spinach

Predict the performance of hypothetical organisms based on the relationship of  primary and accessory photopigments working together in photosystems.

Would a photosystem lacking accessory photopigments still perform photosynthesis? Why or why not?

Why are different species of algae composed of different photopigments? How does this adaptation help them compete?

Chloroplasts have enzymes named photosystems (PSI and PSII) that contain molecules known as photopigments. These chemicals capture light as it passes by and funnels it into the reaction center of the photosystem. As light hits the molecule, its chemical structure undergoes a conformational change called isomerization. Changing the photopigment structure allows energy that used to be stored in chemical bonds to continue its path down the electron transport chain in the process of ATP synthesis.

Around the reaction, center are accessory photopigments that assist with funneling the light into the primary photopigment. Accessory photopigments help catch light that would otherwise not be captured by the primary photopigment, thus increasing photosynthetic efficiency.

5 mins

Read the paragraph below describing photopigment diversity.

Justify how and why phytoplankton possess different photopigments.

Are the accessory photopigments or primary photopigments most often modified by algae?

Why do microalgae modify their photopigment composition? Give two reasons

How might a photosystem be different in an algal bloom found on the surface of alade from an algae found at the bottom of a lake?

The photopigment in the primary reaction center is chlorophyll a. This is mostly constant across all species of microalgae; however the accessory photopigments can vary wildly. Molecules like phycobiliproteins, carotenoids, and rhodopsins can all be present in the accessory areas. Microalgae change which pigments are used to take advantage of the wavelengths of light they are experiencing, also known as spectral tuning.

The variable composition of photopigments in microalgal species gives different cell colors, and different optimal environments to photosynthesize. Spectral tuning gives algae the ability to, for example, live at deeper depths in the ocean where the red light is less intense than the surface. Algae can adapt their photopigments to react better to blue light, which reaches lower depths than red light and thus avoid competition for nutrients and light at the surface.