Name: Avril, Emily
Date: 29.06.12
Title: Is it Alive?
Aim: To find out whether substances A-E are alive or not

Magnifying Tool

Magnification range

Hand lens  2x (big lens)4-10x (small lens)
Stereoscopefor viewing three-dimensional, opaque objects, such as flowers, insects, mineral specimens, fossils or coins.  20-50x
Light/Compound microscope

  1. for viewing small cells, or thin sections of organs or tissues placed on a glass mounting slide (2D)
  2. The specimens must be thin enough that light can pass through them from below
 40x-1000x

Physical Appearances of substance A, B, C, D and E

Attributes of a sample

  • Size (use common substances as analogies)
  • Shape
  • Colour
  • Texture
  • Smell
Substance Smell Appearance
A Mouldy, damp irregularly-shaped
granular
brown
particles of various sizes, as fine as sand
B Mouldy, damp and warm like pet food/bread Tiny particles
smooth
rod-shaped, more uniformly shaped
muddy-white
C Odourless Regularly shaped
Spherical
Transparent
smooth particles
D Odourless Brown/Black
irregularly-shaped, mostly spherical
smooth particles
E Earthy Tiny
Brown/white
Smooth
spherical particles

Three different types of liquids – water, glucose and salt water are also provided to test the reactions of the substances to these liquids.

Why were these liquids chosen?

  • Water – It is a basic necessity for most kinds of life on Earth. So if a substance is alive, it is likely to react to water.
  • Salt water – some kinds of life may react to salt water but not fresh water, such as marine organisms. It is chosen for the same reason as water.
  • Glucose –Most kinds of life need to respire, a chemical process encompassing food (i.e. glucose) being converted to energy, water and carbon dioxide. So if the substances were alive, they would be likely to react to it and produce CO2 bubbles.

Table 1: Observation of substances A, B, C, D and E in water

Substance
Physical appearance Changes observed after 10min

Inference/ Evidence of life

A  Irregular brown particles at the bottom of the test tube, the water is cloudy. Some particles have dissolved.  No change observed in the particles.
B Sediment at the bottom of test tube, water is cloudy. Some particles have dissolved.  Water is very cloudy and there is a thick substance at the bottom of test tube Formed new substance.
C Particles have expanded and look bumpy. They rest at bottom of test tube  Particles have expanded even more and look coarse. The water level has dropped and some particles are now above the water level C has absorbed water and expanded.
D  Some particles have turned red, tiny white particles at bottom of test tube 2 particles which have turned red are floating. Most particles have turned red. D turned red.
E Many particles are floating at top of water, some are suspended while the rest are at bottom of test tube.  Some particles that were once floating have now sunk to the bottom of test tube. No change observed in the particles.

Table 2: Observation of substance A, B, C, D and E inglucose

Substance Changes observed after 10 mins Inference/Evidence of life
A All particles are resting at bottom of test tube. Water is slightly cloudy.
B Bubbles formed. B has respired
C Slightly enlarged
D Some particles turned red
E Most particles are floating at the surface with some sediment at the bottom

 

 

 

 

 

 

 

 

 

Table 3: Observation of substance A, D and E on wet cotton wool

Substance

Changes observed

Inference/

Evidence of life

After 10 min

After 24h

After 36h

A

 The particles’ colour have changed from muddy brown to a darker muddy brown. Some particles appear slightly translucent.  No changes to particles.  No changes to particles.  –

D

 No changes to particles.  Some particles have split open and germinated. White shoots are growing both upwards and downwards from them. Some shoots have penetrated the cotton wool.  The shoots growing upwards have grown oval green leaves at their tips. D has germinated and is growing. D is alive.

E

 Some particles have turned white.  No changes to particles  No changes to particles  –


(Clockwise from top left) Substances A, D, E after 30hrs


Part 4: All 5 substances were soaked in salt water for 24hrs.

Observations:

  • Substance E: started to move by itself. When viewed under stereoscope, it appeared as tadpole-like organisms swimming by beating “gills” along their sides.

CONCLUSION

Substance

Is it Alive?

Evidence for living or nonliving

Yes

No

A

  √  It did not show any characteristics of life.

B

 √ It respired when it came into contact with glucose.

C

 √ It did not show any characteristics of life.

D

 √ It germinated and grew into seedlings when placed on wet cotton wool for 24 hours.

E

 √ It started to move on its own and respond to stimuli after being soaked in salt water for 24 hours.

Possible identities of substances

A – Sand

B – Yeast

C – Water babies

D – Seeds (from Brassica family)

Another strange member of the Brassica family! Taken from Reader’s Digest August 2012 edition.

E – “Artemia” aka brine shrimp

  • Anthropod
  • part of a genus of aquatic crustaceans known as brine shrimp
  • A prehistoric creature, existed since the Triassic
  • Found in inland saltwater lakes, can live in waters of up to 250% salinity
  • Produces dormant eggs (cysts) which are hatched when needed as food for fish or for testing the toxicity of chemicals
  • also sold as “Sea-Monkeys”

Investigation 1 – Is it alive?

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