Animal Classification

Classification system- Taxonomy Invertebrates Vs Vertebrates Phyla Agricultural Importance of Invertebrates

and Vertebrates Characteristics of Invertebrates. Incomplete and Complete Metamorphosis

Since there is such a variety of living things, it is important that we are able to put them into groups.

This is known as classification and the area of study is called taxonomy.

The method used today classifies organisms into one of five different Kingdoms, based upon similarities in their structures.

The five Kingdoms are Monera, Fungi, Protista, Plantae and Animalia.

Kingdoms are further classified in Phyla (Phylum in singular), then into Classes, then Orders (sometimes), then Families (sometimes) and then the organism is given a Genus and Species Name.

Animals are classified into two main

groups, Invertebrates and Vertebrates. Invertebrates (slugs and insects) do not

have a backbone, while vertebrates

(Humans, birds and mammals) do. The animal kingdom is further divided into

20 phyla, of which the following are of

agricultural importance:

This Kingdom includes many unicellular free-living animals called protozoans (one cell).

It was previously considered a phylum to the animal kingdom, but has recently been placed in a Kingdom of their own along with Algae.

Most of them live in water, either seawater, fresh water or soil borne water.

They are nearly all microscopic. The various species of Protozoans move in a

number of ways:• Pseudopodia (False feet)• Cilia (Small moving hairs)• Tails

Reproduction of protozoans occurs by means of binary fission or mitosis.

Amoeba is one of the most common protozoans and moves by means of pseudopodia.

One of the most agriculturally important species of Protozoans is Babesia.

This protozoan causes Red-water Fever, a disease that affects 100,000 cattle a year.

The phylum Platyhelminthes are dorso-ventrally flattened and have a definite anterior and posterior end giving them bilateral symmetry. 

Some flatworms are parasites, while others are free-living carnivores or scavengers. 

Examples of parasitic flatworms are flukes and tapeworms.

Flatworms also have only a mouth for both food and wastes. 

Their nervous system is composed of a nerve net and sometimes light-sensitive eyespots at the anterior end. 

The phylum is classified into three main groups or classes:• Class Turbellaria (Free living)• Class Trematoda (Parasitic Flukes)• Class Cestoda (Parasitic Tapeworms)

All platyhelminths are hermaphrodites (are both male and female) and can, if required, can fertilise themselves.

The most important agricultural species of platyhelminths is the Liver Fluke or Fasciola hepatica.

The life cycle of the liver fluke is very important in finding ways of controlling the disease.

The Life cycle is complicated and the fluke must lay huge amounts of eggs to survive.

The lifecycle takes place in the cow, on grass and in a secondary host (the mud snail).

The Liver fluke lives in the ducts of the liver. The fluke lays eggs in the bile ducts (20,000

or so a day) The eggs pass in the faeces and hatch two

weeks later in water and form a ciliated Miracidium.

The Miracidium enters the foot of the mud snail and changes into a Sporocyst.

Still inside the snail, the Sporocyst changes into a Redia.

The Redia then produce very small tadpole shaped Cercaria.

For every Miracidium that enters the

snail, 10,000 Cercaria can be produced. The Cercaria then leaves the snail and

goes onto grass. There it becomes encysted (forms a shell)

and waits to be eaten by a sheep or cow. If eaten, the stomach acids dissolve the

cyst and the liver fluke moves to the liver

and restarts the cycle.

Understanding the lifecycle of the liver fluke allows us control the spread in the following ways:

1. Dosing any animals to kill the adult fluke

2. Spraying molluscicides to kill the snail.3. Draining land (the snail only lives in

water) 4. Fencing flooded areas5. Don’t graze wet lands after August

The phylum Nematoda are the roundworms. 

Roundworms are cylindrical in shape, tapered at both ends, and vary in length from being microscopic to  20 inches long. 

Unlike flatworms, roundworms have a complete gut. 

This means that they have a one-way digestive tract with a gut that begins with a  mouth and ends with an anus.

Therefore, they are usually able to digest food. 

However, roundworms have no blood or heart.

Most roundworms are parasites and are found in all habitats.

They have separate sexes generally and reproduce sexually. 

The roundworm Trichinella, causes the disease called trichinosis. 

People get trichinosis from eating infected, undercooked pork. 

All these worms reproduce by laying thousands of eggs, which become encysted in the grass and wait to be ingested.

The most important agricultural species are:• Lungworms (Causes Hoose)• Hairworms (Worms in school children)• Potato eelworm• Stomach worms

Trichinella gets into muscles and leaves calcium deposits which effect muscle contraction. 

Trichinosis can affect the heart.  Another roundworm, Ascaris, parasitizes

human lungs. The Filaria worm attacks the lymphatic

system causing great swelling. This condition is called elephantiasis. Hookworms and pinworms are also

roundworms which parasitize humans.

The phylum Annelida are the segmented worms and are abundant in all habitats.

Segmentation gives worms more flexibility in movement.

If one segment is damaged, it isn't usually fatal to the animal because their organs are duplicated in other segments. 

Annelids have a A tube within-a-tube body plan known as a coelom which is fully lined and contains the body organs. 

The coelom runs from the mouth to the anus.

Annelids have bilateral symmetry and a well-developed brain.

Earthworms belong to this phylum. 

Each segment of the earthworm has setae or external bristles made of chitin.  These bristles allow the earthworm to move and to burrow into soil.  

Earthworms have a head and a central nervous system. 

Earthworms respire through their moist skin as they dig through the soil and help loosen it.

They have a closed circulatory system in which blood is pumped by five pairs of hearts. 

Most earthworms feed on decomposing vegetation causing it to decompose faster.

Earthworms bring the nutrients from the subsoil to the top soil, thereby helping plants to grow. 

Undigested materials or castings are deposited outside burrows.

1. They eat their way through the soil and mix the ingested material with mucus in their guts. This helps to improve soil crumb structure.

2. Depositing soil in different places and mixing horizons.

3. Improve drainage of heavy clay soils4. Introduces more air into the soil.5. When they die the further increase the

amount of organic matter.

The molluscs include slugs, snails, squid,

mussels, clams and octopus.

These animals generally have a foot,

which excretes a slimy mucus.

They also have a rasping tongue.

The most important mollusc is the mud

snail (Lymnaea truncatula)

The members of the phylum Arthropoda all have jointed appendages. In fact, the word "arthropod" means jointed leg. 

There are more species of arthropods than any other phylum.

Arthropods have these characteristics: •Hard exoskeleton which is usually

composed of substance called chitin •Go through periodic ecdysis (moulting) as

they shed or moult their exoskeleton •They have specialized body segments

(head,  thorax, cephalothorax, & abdomen) • Jointed appendages such as legs, antenna,

and mouthparts.   •Open circulatory system  (blood is pumped

out of blood vessels into the body) The most important groups of arthropods are as

insects, spiders and crustaceans.

They have three main body parts: Head, thorax and abdomen

They include aphids, lice, fleas, crane-flies and butterflies.

The life cycle of all insects follows this path:

Egg Larvae Pupa Adult The larva is another name for a maggot

and the pupa is a cocoon.

The spider has two main body segments, the cephalothorax and the abdomen.

Some of the diseases spiders cause on the farm are mange (scabies) and mite attack.

Ticks are blood sucking spiders that can attack sheep and spread disease (red water fever)

Mange is again caused by borrowing into the skins and laying eggs.

The animal suffers from a severe allergic reaction and secondary bacterial infection can occur.

A lot of the members of phylum

Arthropoda are Parasites.

Parasites are animals that live at the

expense of other animals.

There are two main classes of parasites:

Endoparasite – inside animals

Ectoparasites – outside animals.

All animals in the phylum Chordata have backbones and are vertebrates.

Examples include fish, birds, amphibians, reptiles and mammals.

The two main agricultural classes are Class Aves (Birds) and Class Mammalia (Mammals).

Only these two classes are said to be homoeothermic – warm blooded – and can regulate their body temperature.

All members of this class have feathers, no teeth but a beak, lightened bones and no bladder

All mammals have the following traits:• Hair• A Placenta• Mammary glands to produce milk

Again they are further classified into sub classes.

Some of the common sub classes are:• Carnivores (Dogs and cats)• Ungulates (Hooved animals)• Odd toed - horse• Even toed – sheep, cattle• Marsupials – kangaroos• Primates – monkeys and humans