Snails + Water Weeds

Snails Ivory and blue mystery bulb snails

Apple Snails

Family Ampullariidae

Genus Pomacea

These Ampullariidae have both a gill and a lung

Snails use photosynthesis or

respiration?

Water Weeds - Wisteria

Hygrophila difformis

Aquarium plant Uses photosynthesis

Lab Setup

8 airtight containers 4 under a light 4 in the dark

Bottle # Contents

1, 5 Sprig of Hygrophila difformis

2, 6 Snail

3, 7 Sprig of Hygrophila difformis& Snail

4, 8 Nothing – Control

Water + Bromothymol Blue

WDYT?

What do you think?

What is going on in each container?

Why are we putting 4 containers in the dark and 4 in the light?

Why bromothymol blue? What does this do? Why should we have a control?

Initial Observation

What color is the water?

Will there be a change in what the liquid looks like after a couple of hours?

What gas exchange is occurring?

Get into your groups

Discuss your initial observations

Designate a speaker to talk about your group’s initial observations

Info that may change your mind…

Carbon dioxide dissolves in (and reacts with) water, forming carbonic acid, H2CO3

CO2(g) + H2O(l) ←→ H2CO3 ←→ H+(aq) + HCO3

–(aq)

The free hydrogen ions (H+) lower the pH of the solution, making it more acidic.

As CO2 dissolves in water, the pH of the solution will continue to decrease (becoming acidic). If CO2 is removed from the solution, the pH will increase (becoming more basic)

Bromothymol blue

A pH indicator such as BTB can therefore indicate the relative amount of CO2 dissolved in water based on the color of the solution.

Higher pH: Blue, basic

Lower pH: Yellow, acidic

Photosynthesis is Occurring

6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

Plant exposed to light Removes CO2 form the solution Raises the pH (more basic)

Cellular Respiration is Occurring

C6H12O6 + 6H2O + 6O2 → 6CO2 + 12H2O ⎯⎯⎯+ energy

Snail respires with or without light

Do plants have mitochondria? Can they respire? Look at Bottle 5.

Do plants have mitochondria? Can they respire? Look at Bottle 5.

Yellow Indicating acidic solution

CO2(g) + H2O(l) ←→ H2CO3 ←→ H+(aq) + HCO3

–(aq)

Where did the CO2 come from?

Where did the CO2 come from in Bottle 5?

The CO2 was produced as a result of cellular respiration by the plant.

Both cellular respiration and photosynthesis occur in green plants when light is available.

In Bottle 1, photosynthesis is the dominant process over respiration, resulting in a net decrease in CO2

HOWEVER, in the absence of light, the plant cannot photosynthesize; it can only respire

THEREFORE, there is a net increase in CO2 concentration and the pH drops as the CO2 dissolves, producing carbonic acid.

Bottle

Contents

P CR Bottle

Contents

P CR

1 Plant 5 Plant

2 P & S 6 P & S

3 Snail 7 Snail

4 Control

8 Control

Revised Observation

w/Light

Contents

BTB color

What happened?

w/o light

Contents

BTB color

What happened?

1 Plant 5 Plant

2 P & S 6 P & S

3 Snail 7 Snail

4 Control 8 Control

WDYT - now

Write a paragraph explaining what has occurred in the containers. Include information about the addition of

hydrogen ions or the removal of CO2

What is an ecosystem? What is sustainability