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  • The earthworm’s body is well adapted1 for life in the soil. Click on the labels to see images and learn more.

    Click the green button to see what’s on the outside of an earthworm.

    Information on an earthworm's pharynx.Information on an earthworm's gizzard. Information on an earthworm's Information on an earthworm's aortic arches.Information on an earthworm's dorsal and ventral blood vessels.Information on an earthworm's cerebral ganglion. Information on an earthworm's circular muscles.Information on an earthworm's longitudinal musclesInformation on an earthworm's outside.

    Transcript

    Pharynx

    Earthworms push the pharynx out of their mouths to grasp hold of organic matter2. They pull the food back into their mouths and then wet it with saliva3.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Gizzard

    Earthworms do not have teeth, so they use the strong muscles of the gizzard (and grains of sand and soil) to grind up their food.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Intestine

    Once the food is ground up, it moves into the intestine where digestive4 fluids continue to break down the food so it can be absorbed.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Aortic arches

    Most earthworm species5 have five aortic arches or ‘hearts’ that move blood around the body. The number of aortic arches varies amongst species.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Dorsal and ventral blood vessels

    The dorsal blood vessel6 runs along the length of the upper side of the earthworm. It contracts and pumps blood to the aortic arches. The ventral7 blood vessel runs along the lower length of the earthworm.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Cerebral ganglion

    The earthworm’s ‘brain’. Earthworms have a simple nervous system. The cerebral ganglion is connected to a ventral nerve cord that runs the length of the body. Each segment is connected to this cord, allowing earthworms to move and respond to light, touch, chemicals8, vibrations and more.

    Acknowledgement: Sara L Roggemann, Three Flowers Photography

    Circular muscles

    Circular muscles surround each segment. When earthworms squeeze these muscles, they become long and thin. Circular muscles alternate with longitudinal muscles to help earthworms move.

    Longitudinal muscles

    Longitudinal muscles run the length of the earthworm. When these muscles contract, earthworms become short and fat. Longitudinal muscles alternate with circular muscles to help earthworms move.

    Rights: University of Waikato Published 12 June 2012, Updated 23 March 2017 Size: 350 KB Referencing Hub media
    1. adaptation: A change in the structure or function of something. In biology, a change in a species, as a result of natural selection. Individuals with a particular feature (adaptation) are more likely to survive and reproduce than individuals without this feature.
    2. organic matter: The decomposed remains of living organisms and their waste products.
    3. saliva: A watery fluid produced by the salivary glands in the mouth. It is made up of water, mucus, amylase, lipase and sodium bicarbonate.
    4. digestive system: The group of organs that are involved in the breakdown of food in the body, which includes the stomach and intestines.
    5. species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
    6. blood vessel: Any of the vessels, as arteries, veins, or capillaries, through which the blood circulates.
    7. ventral: The lower surface (the belly) of an animal.
    8. chemicals: Everything is made up of chemicals. All matter (anything made of atoms) can be called chemicals. They can be in any form – liquid, solid or gas. Chemicals can be a pure substance or a mixture.
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        adaptation

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      2. A change in the structure or function of something. In biology, a change in a species, as a result of natural selection. Individuals with a particular feature (adaptation) are more likely to survive and reproduce than individuals without this feature.

        digestive system

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      4. The group of organs that are involved in the breakdown of food in the body, which includes the stomach and intestines.

        ventral

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      6. The lower surface (the belly) of an animal.

        organic matter

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      8. The decomposed remains of living organisms and their waste products.

        species

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      10. (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.

        chemicals

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      12. Everything is made up of chemicals. All matter (anything made of atoms) can be called chemicals. They can be in any form – liquid, solid or gas. Chemicals can be a pure substance or a mixture.

        saliva

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      14. A watery fluid produced by the salivary glands in the mouth. It is made up of water, mucus, amylase, lipase and sodium bicarbonate.

        blood vessel

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      16. Any of the vessels, as arteries, veins, or capillaries, through which the blood circulates.