Nervous Response Earthworm

Donato. Esteban. Madriaga. Tolentino.

WHAT ARE EARTHWORMS?

Earthworms are segmented animals commonly found living in soil that is shaped like a tube (the gut) within a tube (the body). Its digestive system runs straight through its body and it conducts respiration through the cuticle covering of its skin. It has a simple, closed blood circulatory system.

The nervous system allows the body to respond to various changes in the environment.

Receptors are groups of specialized cells that can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. Receptors are often located in the sense organs.

An effector is any part of the body that produces the response.

Reflex actions are extra-rapid responses to stimuli. It also involves the nervous system, but bypasses the brain. When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response.

TAXIS VS. TROPISM

Tropism involves an organism (mainly plant) growing toward or away from a stimulus.

Taxis involves an organism (protist or animal) moving toward a stimulus.

MATERIALS:

Earthworms

MATERIALS:

Dissecting pan

MATERIALS:

Wet paper

MATERIALS:

Dissecting needle

MATERIALS:

A card with a 2 millimeter hole

MATERIALS:

Flashlight

MATERIALS:

Alcohol lamp (with matchsticks)

MATERIALS:

Glass rod

MATERIALS:

Xylol (Reagent)

Methodology

Wash the dissecting pan

Cover the pan with a sheet of

wet paper

Place an active live

earthworm

Methodology: Contact

Touch the earthworm’s

anterior part with the needle

Touch the earthworm’s

posterior part with the needle

Touch the earthworm’s

middle part with the needle

Methodology: Light

Use a flashlight to shine on the earthworm’s anterior part

Use a flashlight to shine on the earthworm’s posterior part

Use a flashlight to shine on theearthworm’s middle part

Methodology: Heat

Place the heated end of the rod on the earthworm’s

anterior part

Place the heated end of the rod on the earthworm’s

posterior part

Place the heated end of the rod on the

earthworm’s middle part

Methodology: Moisture

Line a clean and dry dissecting pan with a tissue paper

Dampen one half of the tissue and let the other half

stay dry

Place the worms at random locations.

Observe its location.

Methodology: Chemical

The tip of the glass rod (with xylol) was placed near the earthworm’s

anterior part

The tip of the glass rod (with xylol) was placed near the earthworm’s

posterior part

The tip of the glass rod (with xylol) was placed near the earthworm’s

middle part

Results: Contact

Results: Contact

Results: Contact

Results: Light

Results: Light

Results: Light

Results: Heat

Results: Heat

Results: Heat

Results: Moisture

DRY WET

Results: Moisture

DRY WET

Results: Chemical

Results: Chemical

Results: Chemical

Results

STIMULUS ANTERIOR REGION

MIDDLE PART

POSTERIOR REGION

CONTACT + - +LIGHT + - +HEAT + + +

MOISTURE + + +CHEMICAL + + +

DISCUSSION

References

Answers. Answers Corporation. Accessed on 27 July 2012 <http://wiki.answers.com/Q/What_is_the_difference_between_taxis_and_tropism>.

BBC. BBC Vision. Accessed on 27 July 2012 <http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/human/thenervoussystemrev1.shtml>.

Wikipedia. Wikimedia Foundation, Inc. Accessed on 27 July 2012 <http://en.wikipedia.org/wiki/Earthworm>.

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