Microscopy Notes

Today we learnt about microscopes.

Parts of a microscope:
Arm: Supports the body tube and is the part that you can grasp to carry the microscope. Pick up your microscope by its arm, keeping it upright, and supporting it underneath with your free hand. Set it gently on your lab desk.
Base: Gives the microscope a firm, steady support.
Ocular lens (Eye piece): Magnifies ten times (l0x). This lens is often unattached, and thus it may fall out unless the microscope is kept upright.
Objective Lens: Magnifies the object by the factor marked on the particular lens. Low power (l0x) gives the smallest image, high power gives a large image (40x), and oil immersion gives the largest image (l00x). Sometimes a very low power scan objective (4x) replaces the oil immersion lens. *Objective lenses are always used in order: low, high, oil immersion.
Nosepiece: The revolving part to which objectives are attached. It must be firmly clicked into position when the objective is changed. Rough treatment can cause it to snap off.
Body tube: Joins the nosepiece to the ocular lens.
Stage: Supports the slide that is held onto it by stage clip, and has a hole so that light can shine up through the specimen. Always centre the specimen over this hole.
Coarse adjustment: Moves the body tube or stage up and down, depending on the design of the microscope, to approximately the right position so that the specimen is in focus. This knob is used only with the low power.
Fine adjustment: Moves the body tube (or stage) up and down to precisely the right position so that the specimen is perfectly in focus. Use it to achieve fine focus with the low power objective and for all focusing with the high power and oil immersion objectives.
Light source: Usually a small electric light beneath the stage that is controlled by a push-button light switch. Sometimes a mirror is used to reflect light from another source into the microscope.
Iris diaphragm: Regulates how much light goes through the specimen. It is controlled by a lever that is moved back and forth.
Condenser: A lens located above the diaphragm which concentrates the light before it passes through the specimen. Its position is controlled by a knob on microscopes in which it is adjustable
Letter 'e' magnified:

 

http://www.fossweb.com/delegate/ssi-foss-ucm/Contribution%20Folders/FOSS/multimedia_ms_1E/DiversityofLife/media/microscope.htm

http://www.udel.edu/biology/ketcham/microscope/scope.html

Is It Alive Practical Part 2

(continued from Is It Alive Practical Part 1)

PART 2

Criteria of living things tested: Requires water & nutrition (food)

Procedure:

• Label each separate sector of the petri dish A, B, C, D and E.
• Fold the facial cotton and line each sector with cotton.
• Pour the content of each tube in the respective sector that you have labeled. (You may need to rinse off all the substance with another 3ml of water.)
• Add more water to make sure that the cotton is thoroughly wet.
• Tape the sides of the petri dish and bring back to your class to continue with the observations.
• Write your observation every day for the next 3 days using the same table format.

Table 3

Substance	Changes Observed			Inference/ Evidence of Life
	After 10 min	After 24h	After 36h
A	Looks wet (from water)	Unchanged.	Unchanged.	Unaffected by water --> not alive
B	Has mixed with the water to form sludge. Bad odour.	Unchanged. Many small droplets found above it.	More condensation found above it.	Many small droplets + water vapour --> signs of respiration. --> alive
C	Grew larger. Appears to have absorbed water.	Grew larger.	Unchanged.	Can grow. But may just be absorbent. --> alive?

Information gathered from groupmates:

D: Grew green shoots and leaves.
E: Unchanged.
EXTRA: When E was soaked in a saline solution for 48h, it hatched into sea monkeys!

Reflection 2: What is Life?

Here are my reflections about "What is Life?" after the "Is it Alive?" experiment and reading 3 articles on What is Life.

What are some of the definitions of life used by scientists?
Trifonov said that life is self-reproduction with variables.
In his paper one of the possibilities he put forth to combine all the key terms he found was: Life is metabolizing material informational system with ability of self-reproduction with changes (evolution), which requires energy and suitable environment.
Koonin suggested that life requires replications with an error rate below the sustainability threshold.
Foong May Yeong suggested that life is an entity or property that is amenable to (natural) selection without a purpose (direction).
Some definitions by various scientists studied by Radu Popa include life is something capable of metabolism, and life has the capacity to evolve.

Why do multiple definitions of life exist?
Different scientists express the definition of life in different ways, and each definition is partially correct or has a point. It is very difficult to come up with a universally accepted definition of life, because life comes in various forms and people have different perspectives on this issue.

How difficult is it, in your opinion, to define life? What makes it so difficult?
I think it is extremely difficult to define life. As I said earlier, people have different definitions of life so it is difficult to come up with a universally accepted definition of life. In addition, there is always the possibility that somewhere in our universe, not on Earth, there are life forms that do not fit our typical descriptions of life. Therefore we will never really know if our definitions of life fit all life forms or not.

How were “living things” defined for you in Primary 3? What is good about that definition? Is it inadequate in any way? How so?

In Primary 3, "living things" were defined as things that needed air, water and food to survive. This definition is simple and easy to remember, and it is also true and relevant enough for Primary 3s. However, it is inadequate in the sense that it has exceptions and may be ambiguous. For example, the term "air" actually refers to oxygen. Furthermore not all creatures require oxygen to respire, for example yeast which uses anaerobic respiration.

 

What is your definition of life now?

After reading the articles, my definition of life is: Life is an entity that can evolve and reproduce, and requires energy to survive. (It may also require certain things to fuel the life processes that allow it to produce energy, like water).

What Is Life? Characteristics of Living Things

Characteristics of living things:
1. Responds to stimuli
2. Requires nutrition*

*Nutrition: 4 stages:
Feeding (putting food in mouth)
Digestion - Physical (chewing/mastication), Chemical (enzymes)
                 - Purpose: To break food into simple, diffusible forms
Absorption (absorbing these simple, diffusible forms)
Assimilation (making use of these simple, diffusible forms)
--> There are 3 forms of carbohydrates:
Monosaccharides (e.g. glucose, basic forms which our bodies can absorb)
Disaccharides
Polysaccharides (e.g.cellulose, glycogen (a storage form of carbohydrates), starch (storage in plants only)

3. Requires oxygen - so that they can respire**
(exception: anaerobic life forms!)

**Respiration: 2 types:
Aerobic
- Process: glucose + oxygen --> respiration--> energy + water + carbon dioxide
Anaerobic (in the absence)
- Process: glucose --> respiration --> energy + alcohol + carbon dioxide
(the above process is alcoholic fermentation in plants - replace glucose with grapes for wine and wheat for beer)
- Creatures that use this form of respiration: yeast, microscopic lifeforms in deep sea vents, volcanos
- We use anaerobic respiration with aerobic respiration when running
(the process for this is the same except alcohol is replaced with lactic acid. This is stored in our muscles and causes muscle cramps when its maximum level is reached. It makes you gasp for oxygen to break down the lactic acid)

4. Requires water
5. Grows
6. Dies eventually - life cycle
7. Produces waste

Is It Alive Practical Part 1

For this experiment, we were given 5 substances (A, B, C, D, E) and were supposed to determine if they were living things.

PART 1A

Criteria of living things tested: Requires water & nutrition (food)

Procedure:

• Label the tube A, B, C, D and E.

• Pour substance A in tube A and repeat for all the substances.

• Add 3ml of water to each of the tube. Mix well.

• Start your stop watch.

• Observe. Write your observations in the journal. Use the suggested table format (Table 1) provided below.

• After 10mins, record the observation again.

 

Table 1

Substance	Evidence of Life (Inference)	Observations		Is it Alive? Yes/No
		0 minutes	10 minutes
A	None	Not moving, floating,  water slightly murky. Odourless. Brownish-yellowish colour	Unchanged	No
B	Bubbles appeared- respiration	Milky, creamy white, sticky, smells bad.	Slightly mushy and bubbles appeared at the bottom, liquid level rose	Yes
C	They grew and took in water	Clear transparent spheres	They expanded, water level decreased till none left	Yes
D	None	Odourless, most sink to the bottom, some float. Colours range from red to deep purple	Same	No
E	Took in water	Brown in colour, Floating to the top. Feels grainy	Water level decreased	Yes

PART 1B

Procedure: Repeat earlier steps with glucose instead of water.

Table 2

Substance	Evidence of Life (Inference)	Changes Observed after 10 minutes
A	Not alive	Unchanged
B	Bubbles appeared - respiration - alive	Sticky, mushy, many bubbles found at the top
C	Grew - alive	Stuck together, grew larger and rougher
D	Not alive	Liquid murkier
E	Not alive	Floated to the surface

(done 5/7/13)

Criteria for Living Things

What is Life?
Group discussion on the defining criteria of living things

S/N	Criteria (for a living thing)	How Would You Test this Criteria	Challenges
1	Requires Oxygen	Place it in a controlled environment. Wait. Measure the composition of the air (less oxygen, more carbon dioxide/water vapour)	It could chemically react with components in the air, not due to respiration.
2	Responds to Stimuli	Introduce changes in its environment (light/dark, temperature changes, sound, other organisms)	Its response may be unnoticeable. It may not respond to such changes in environment.
3	Requires Nutrition	Observe it in its natural environment. See if it consumes food/water.	It may not need much nutrition at the time or all the time. It may not consume food but instead produce energy (plants).
4	Has Cells	Use a microscope to test if it has cells.	It might be a single-celled organism.

Reflection 1: Remarkable Female Scientists

Choose a scientist that you admire and research more on her. Research on her work (discipline), training, special interests and skills and her legacy. What are some of her works that impact our daily lives? How can I relate to her contribution in their field of expertise? What traits (habits of mind) do they have that make them remarkable?

The scientist I have chosen to write about is Sylvia Earle. She is an American oceanographer, aquanaut, author and lecturer. Her research concerns marine ecosystems with special reference to exploration, conservation, and the development and use of new technologies in the deep sea. She has led more than 50 expeditions worldwide involving more than 6000 hours underwater. She was the captain of the first all-female team to live underwater and set a record for solo diving in 1000 meter depth.

Her dedicated advocacy for the world's oceans has certainly contributed to the conservation of marine environments. She has inspired many people, including me, to do what we can to protect the environment. Her exploration of the deep sea has contributed significantly to what we know about the marine ecosystem.

I think Sylvia Earle was extraordinarily perserverant and determined. She spent such a long time exploring the deep sea and also advocating for the conservation of the world's oceans, for example by presenting speeches and lecturing. When I listened to her TED Prize talk, I was inspired by her wonder and amazement by the glory of the oceans and her urgency to awaken us from our ignorance about the role the oceans play in our lives and the importance of maintaining their health. She made me think about what the world would be like without the oceans and the horrifying effects of global warming.

People ask: Why should I care about the ocean? Because the ocean is the cornerstone of earth's life support system, it shapes climate and weather. It holds most of life on earth. 97% of earth's water is there. It's the blue heart of the planet — we should take care of our heart. It's what makes life possible for us. We still have a really good chance to make things better than they are. They won't get better unless we take the action and inspire others to do the same thing. No one is without power. Everybody has the capacity to do something.

---Sylvia Earle