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