Key unit competency: To be able to classify animals into their main groups based on their external features.
After studying this unit, I should be able to:
• State the characteristics of all animals.
• Identify the common features of chordates.
• Explain the economic importance of arthropods to humans.
• State other phyla of kingdom Animalia and give examples of each.
• Distinguish different groups of animals using observable features.
• Appreciate the existence of animal diversity and the need for classification
In Senior 1, you learnt about biodiversity and classification of organisms in the
environment. Can you recall the five kingdom system of classification and the main
features of each Kingdom?
Now, look at the picture below. Which animals can you see? Write down their
Fig. 1.1: Animal diversity
With a friend think about how the features can be used to classify the animals. Try putting the animals into various groups. Do you now have an idea of what you will learn in this topic?
1.1 General characteristics of animals
There are many species of animals living on land (about 6.5 million), in water (about 2.2 million) and approximately 10,500 species in the air. However, only a few of these animals are clearly understood. It is therefore important to study and describe the characteristics of the main groups of the animal kingdom. This study enables us to be familiar with our environment as we interact with these animals in our day to day lives. How are animals different from other organisms and from each other?
Activity 1.1: To identify the main characteristics of kingdom Animalia Requirements
Obtain the following for collection of specimen:
• Specimen bottles
• Pair of forceps
• Sweep nets
1. With the guidance of your teacher, go to the school field and collect animal specimen of different types.
• For crawling animals use a pooter.
• Use a sweep net to collect hopping
animals such as grasshoppers.
Caution: Some animals are harmful in some ways. Care should be taken when making collections.
2. Put on gloves and use a pair of forceps to transfer the collected animals into specimen bottles.
3. Carry the collected animals to the Biology laboratory.
4. Observe the animals collected and note down their external features.
Caution! Some animals can bite or sting. Be careful when handling them.
5. Your teacher will also show you pictures and photographs of different animals.
• Can you identify the animals?
6. Keenly observe the animals you collected and do the following:
• Count the number of legs and wings (if present) in each animal.
• How many wings does each animal have?
• Touch the outer covering of each animal. Describe it.
7. Discuss with your classmate the external features you observed.
(a) Do all animals have the same number of legs and wings?
(b) What are the features used to classify animals?
(c) What is the meaning of the following terms?
I have discovered that…….
The main features used to classify animals include:
• Presence or absence of appendages (An appendage is a projection from the body of an organism), their type and number.
• The body form; whether segmented or unsegmented.
• Presence of skeleton and its type; exoskeleton or endoskeleton.
• Type of body symmetry; whether bilateral or radial.
The facts Animals have the following general
1. They are multicellular organisms.
2. They have eukaryotic cells.
3. Their cells are differentiated into tissues and organs.
4. They are all heterotrophic, meaning they depend on other organisms for food.
5. Their cells lack cell walls, cell sap and chloroplasts. They only have cell membranes and this makes their cell to be irregular in shape.
6. Most animals are able to move the whole body from one place to another (locomote).
7. Reproduction in most animals takes place through fusion of gametes.
8. They respond to external stimuli.
- Discussion corner
1. Look up the meaning of the following words; backbone, notochord, exoskeleton and endoskeleton from reference materials provided.
2. Write the meaning of the words in your notebook.
3. Share your findings with classmates.
4. Did you all get the meanings right? I have discovered that …. The term ‘chordata’ comes from theord chorda which means chord. Organisms in this phylum, at one time in their life have a chord-like structure called notochord. The facts We differ from other organisms because we have a backbone that enables us to stand upright. The main characteristics of organisms in phylum Chordata are:
1. Presence of a chord like structure called notochord. The notochord supports the body in lower
chordates while in higher chordates (vertebrates) it is present only during embronic stages. It is replaced by a vertebral column.
2. Presence of a vertebral column which forms part of an internal skeleton. Vertebral column is a bony structure made up of vertebrae. It protects the spinal cord.
3. Presence of a nervous system with a brain which is connected to a hollow nerve tube or a single tubular nerve cord. The nerve tube runs along the back and forms a brain anteriorly.4. Bilateral symmetry: this means that the body can be divided along one plane into two equal halves that are roughly mirror images of each other.Look at these pictures below. Can you state all the similarities and differences among the organisms.