Lesson 1.8 Classifying plants

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Introduction to lesson

Not only is there a wide variety of animals that need classification, but there is also a wide variety of plants. In this lesson, you will look at the classification of plants. You will learn more about making biological drawings and you will end the lesson looking at keys which help us to identify a particular specimen.This will then bring the chapter to an end.

 Review past lesson

Before starting the lesson, revise the following:

  1.  the seven characteristics of living organisms (and the definitions of these terms)
  2. the classification system from kingdom to species
  3. the characteristics of the five classes of vertebrates
  4. the characteristics of the phylum Arthropods and the four classes of arthropods - insects, crustaceans, arachnids, and myriapods

 Preparing for the lesson

 As you begin to work with the material, ask yourself the following questions:

  1.  Why do you think plants are called producers?
  2. What is the process whereby plants are able to make their own food?
  3. What are the 'ingredients' needed in this process?
  4. What is the product of this process?
  5. What part of the plant generally performs this process?

 Classifying plants

 Read section 1.6 'Classifying plants' in your Coursebook on p.12.

Add the following terms and definitions to your biology reference book. (If you have already written the term and definition in your book, revise the term and its definition, making sure you understand the term and can use it correctly).

Definitions

chlorophyll - a green, light-absorbing pigment found inside chloroplasts in plant cells

cellulose - a polysaccharide carbohydrate which forms fibres and is found in the cell walls of plant cells

photosynthesis - the process by which plants manufacture carbohydrates from raw materials using energy from light

spores - a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavorable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa.

sporangia - (in ferns and lower plants) a receptacle in which asexual spores are formed.

fronds - a leaf of a fern or cycad, usually consisting of multiple leaflets. A large, fan-like leaf of a palm tree. A leaf-like structure such as the thallus of a lichen or a seaweed.

flower - the seed-bearing part of a plant, consisting of reproductive organs (stamens and carpels) that are typically surrounded by a brightly colored corolla (petals) and a green calyx (sepals).

moncotyledon - a flowering plant with an embryo that bears a single cotyledon (seed leaf). Monocotyledons constitute the smaller of the two great divisions of flowering plants, and typically have elongated stalkless leaves with parallel veins (e.g., grasses, lilies, palms).

dicotyledon - The dicotyledons, also known as dicots (or more rarely dicotyls), were one of the two groups into which all the flowering plants or angiosperms were formerly divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons.

Formula

Record the following formula in your biology reference book

magnification = length in drawing/ length of real object.

Learning Activity 1

Copy and complete the following table:

 Monocotyledonous plantsDicotyledonous plants
 Number of cotyledons in seed    
 Leaf shape    
 Leaf veins    
 Root system    
Flowers (petal arrangements)    

Practical investigation 1: Making a biological drawing of a flower

Read Activity 1.1 'Making biological drawings' on p.13 of the Coursebook.

Read Activity 2,1 'Calculating magnification' on p.14 of the Coursebook. Answer questions A1 and A2 in your exercise book.

Choose a good specimen of a flower where all the parts are clearly seen.

  1. Make a biological drawing of the flower. Use a blank sheet of paper to make your drawing. Make sure your drawing is at least half the size of an A4 sheet of paper.
  2. Label the parts of the flower.
  3. Evaluate your biological drawing using the checklist on the CD-ROM.
  4. Calculate the magnification of your drawing.

Practical investigation 2: Dissect a flower

Using the same flower from the above practical investigation, dissect the flower to investigate the different parts as follows:

  1. Spread newspaper on your desk and place the flower on it.
  2. Examine and count the petals. Record the number and colour of the petals. Remove the petals.
  3. Find the stamen. Look at the end of the stamen with a hand lens. Make a biological drawing of what you observe.
  4. Touch the end of the pistil. What does the pistil feel like? Make a biological drawing of the pistil.
  5. Locate the ovary. Split the ovary open with your fingernail. Are there eggs inside? If so, how many? Make a biological drawing of the cross section of the ovary.
  6. Using the checklist on CD-ROM, evaluate your biological drawings. Where do you need to improve?

Practical investigation 3: Studying a fern plant

Find a fern growing in the garden. Look on the underneath of a leaf to find the spores. See if you can identify the rhizome without too much damage to the plant.

Make a biological drawing of the underside of one leaflet of the frond, showing the sporangia. Evaluate your drawing.

 Keys

 Read section 1.7 'Keys' in your Coursebook on p. 15-16. Make sure you are able to identify all five animals on page 15 using the key.

Learning Activity 2

Complete Exercise 1.2 'Using keys' in the Workbook on p. 5-6. This exercise will give you practice at working with keys.

Learning Activity 3

Complete worksheet 1.3

Learning Activity 4

Make a key to identify the four flowers in figure 1.23 on p.16 of the Coursebook. Follow the instructions under the heading 'Constructing keys' on p.16 of the Coursebook. Test your key on your family members and friends to see that it works.

Mark your work. Answers to worksheet can be found here: Worksheet answers. The answers to the workbook exercise can be found here: Workbook exercise.

Common misunderstandings and misconceptions

  • An important tip in using keys is not to look at all the organisms at once and try to match them against the descriptions given. Rather take one organism at a time and work systematically through the key until you can identify it.
  • If you are required to write a key in the exam, be careful of using subjective terms such as 'long' or 'dark'.

Closing the lesson

  • What new things did you learn in this learn?
  • What did you already know?
  • How did you manage with the biological drawings? Where do you need to improve?
  • How did you manage the calculating the magnification? Do you need extra practice? (Perhaps you could work out the magnification of all the drawings you did in this lesson?)
  • Could you use the keys to identify the animals?
  • Were you able to draw a key for the four flowers on p.16
  • Is there anything that you are feeling unsure about? Ask your parents or teacher to help you.