Lesson 1.2 Characteristics of living things

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Lesson introduction

You  finally ready to start working in depth with the material! This chapter is entitled "Classification". Classification is about dividing things into similar groups where members of a particular group have something in common. You should have noticed during your scanning of the chapter in the last lesson, that there are different levels of classification from kingdom down to species. But did you notice that the first type of classification presented in the chapter is distinguishing between living things and non-living things. Biology is the study of living organisms, but what makes a living organism living? That is what you will explore in this lesson.

Before starting to work through the material, ask yourself the following questions:

  1. Look around the room you are in and identify examples of living things and examples of non-living things.
  2. What would you say are the main differences between living things and non-living things?
  3. How would you define life?
  4. Do you think there is life on other planets? What characteristics would it have to show in order to be classified as life? Would it have to show all the characteristics of life here on earth?
  5. What would you say is the main difference between a plant and an animal?
  6. Would you say that plants can be classified as living organisms? Why or why not?

Characteristics of living things

Read Section 1.1 'Characteristics of living things' on p.2-3 of the Coursebook. Note that there are two boxes of key definitions. The first box on p.2 are the definitions that core students need to learn. The box on p.3 are the definitions that extended students need to learn.

Thinking it through

Answer the following questions to help you think through what you have read.

  1. How did your list of characteristics of living things compare with the coursebook's list?
  2. Think of a plant. How does a plant show all the characteristics of living organisms? Do plants have movement? (Think of the roots and stems), Do plants show sensitivity? Do plants have nutrition?
  3. What is the difference between movement and locomotion? (Use a dictionary to look up the meanings of these two words). Does a plant move? Does a plant have locomotion?
  4. What is the difference between excretion and egestion? (Again, use a dictionary to look up the meanings of the two words)
  5. Does a plant excrete? How?
  6. What is the difference between respiration and breathing and gas exchange?

Take note: Any one living organism does not have to carry out all the processed all the time. So, for example, an animal may not be reproducing at this moment, but as a species they have the capacity to reproduce.

In your biology reference book (index book), add the definitions of the seven characteristics of living organisms (these are the definitions required at extended level):

Definitions of the seven characteristics of living organisms

Movement - an action by an organisms or part of an organism causing a change of position or place.

Respiration - the chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

Sensitivity - the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

Growth - a permanent increase in size and dry mass by an increase in cell number or cell size or both.

Reproduction - the processes that make more of the same kind of organism.

Excretion - removal from organisms of the waste products of metabolism (chemical reactions in cell including respiration), toxic materials and substances in excess of requirements.

Nutrition - taking in of materials for energy, growth, and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water.

In your biology reference book, add the following terms and definitions:

Definitions

organism - a living thing

metabolism (metabolic reactions) - the chemical reactions that take place inside a living organism

stimuli (singular - stimulus) - a change is an organism's surroundings that can be detected by its sense organs.

egestion - the passing out of food that has not been digested, as faeces, through the anus.

breathing - the process of taking air into and expelling it from the lungs.

gas exchange - the entry of oxygen into an organism's body, and the loss of carbon dioxide.

Add any other term in the text that you are not familiar with.

Learning Activity 1

The definitions of the seven characteristics of living organisms is very important. You will be expected to give these definitions in the exam. In this learning activity, you will make either flash cards or a visual aid. Make them well, so that they will last until the exams when you need to revise them again. You can either make the flash cards or the visual aid. It is not necessary to make both, unless you want to.

Flash cards

  1. Make seven cards the same size using stiff card.
  2. Write one characteristic of a living organism on one side of each card.
  3. Write the correct definition (see above) on the other side of the card with the correct term.
  4. You can then test yourself by reading the term and giving the correct definition; or reading the definition and giving the correct term

Visual aid

  1. Make yourself a picture similar to the one on p.2 - a picture of a living organism. You can either draw the living organism or cut out a picture from an old magazine or card.
  2. Write the characteristics of the living organisms around the picture and write the definition of each characteristic next to the correct term.

Learning Activity 2

Some students find it easier to remember lists using a mnemonic. (A mnemonic is a device such as a pattern of letters, ideas, or associations that assists in remembering something). To remember the seven characteristics of living organisms, some students like to use 'MRS GREN' where each letter stands for a characteristic.
M - movement
R - respiration
S - sensitivity
G - growth
R - reproduction
E - excretion
N - nutrition

Try making up your own mnemonic to help you remember the seven characteristics of living organisms.

Learning Activity 4

Answer the following questions in your exercise book:

  1. What is the other feature mentioned in the text that all living organisms have in common?
  2. List five structures found in cells.
  3. Which structure in the cell is involved in making proteins?
  4. What is the function of enzymes in the cell?

Mark your work.

Common misunderstandings and misconceptions

  • Students often only think of animals (mainly mammals) when listing characteristics of living organisms. Remember there are other living organisms that are not animals - plants, fungi and even bacteria are living organisms.
  • Students often get confused between movement and locomotion. They think a plant cannot move - look at the definition of movement. Do you think a plant can move according to this definition? (Think of the roots and stems). Why do you think locomotion is NOT a characteristic of all living organisms?
  • Students also confuse excretion with egestion and therefore don't think that plants excrete. Remember that oxygen is a waste product of photosynthesis and is excreted by the plant.
  • Respiration can sometimes be confused with breathing or gas exchange. Look again at the definition of respiration. How is this different from breathing?

 Closing question

 Why is a car not a living organism when it needs nutrition (fuels) and releases energy through chemical reactions (oxygen and fuel) and can respond to stimuli (driver's foot on the brake pedal) and can move?

 Exam tip

 You need to know these definitions well for the exam - so make sure you understand what the various words mean and then learn the definitions.

 Closing the lesson

  • What new things did you learn in this lesson?
  • What did you already know?
  • Is there anything that you feel unsure about? Ask your parent or teacher to help you.

Looking ahead - preparing for Lesson 1.4 (practical work)

In lesson 1.4, you will be studying fungi. The lesson will include a practical study of bread mold and mushroom

  1. Make bread mold - take a slice of bread and dampen slightly. Put in a dark, dry place until the lesson. It should grow a bread mold which you will study with a hand lens.
  2. Mushroom - purchase mushrooms from the grocery store. Mushroom can be very poisonous so do not pick ones in the garden.