Cells – Chapter Summary

Cells – Chapter Summary

A living thing is called an organism, e.g. a dog is an organism, so is a daffodil. The characteristics of living things are:

  • Feeding -living things need food to get energy.
  • Movement – living things move either their whole body (animals) or parts of the body (plants).
  • Respiration – process by which organisms obtain their energy.
  • Sensitivity – organisms are able to respond to changes in their surroundings.
  • Excretion – living things get rid of wastes they have made in their bodies which would be harmful.
  • Reproduction – living things are able to make more of their own kind.
  • Growth – living things get bigger.

There are many types of animals. They are important in agriculture as food; in medicine because they cause disease; in the fishing industry and as a source of pleasure and recreation. There are many types of plants. Plants form the first link in all food chains and are in important source of oxygen. A food chain is a feeding relationship between organisms. Plants are important in agriculture, industry, medicine and as a source of pleasure, e.g. gardening. Plants differ from animals in a number of ways, e.g. feeding and  movement.

CaptureAll living things are made of cells which are the building blocks of organisms.  To study cells we use the light microscope.

  • Eyepiece – allows you to view the object to be magnified.
  • Objective lens – magnifies the specimen.
  • Course focus – lowers and raises the microscope to focus the object.
  • Fine focus – allows accurate focusing at high power.
  • Stage – holds the glass slide in position.
  • Light source – bulb or mirror allow the object to be illuminated.

Exp: Preparing a slide involves the following steps.

  1. A drop of water is placed in the centre of a clean dry slide.
  2. A small piece of onion skin is peeled off and placed flat on the slide in the water using a forceps.
  3. A drop of Iodine is put on the specimen.
  4. A coverslip is lowered carefully at angle to cover the specimen and avoid air bubbles getting trapped.
  5. The onion is examined first at low power and then at higher powers.

cell

All cells consist of the following parts:

  • Cytoplasm contains dissolved substances, jelly-like
  • Cell Membrane controls the entry and exit of substances in/out of the cell
  • Nucleus controls the activities of the cell
  • Vacuoles store food, large in plants small in animals
  • Cell Wall give strength to the cell, plants only.
  • Chloroplasts help plants make their food, plants only

Plant cells differ from animal cells in the following ways: large vacuoles, cell walls and chloroplasts. . Groups of similar cells with a special function form a tissue. e.g.  muscle. Several tissues grouped together form organs, e.g. heart. When a group of organs work together to perform a function they make up a system, e.g. the circulatory system

Growth results from cells dividing.

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About the Author

Daithí Mac an Aircinn

Daithí has been teaching science, biology, chemistry and physics to Junior & Leaving Certificate students for the last 30 years.
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