Phylum Anthropoda

Phylum Anthropoda has more species than any other phylum. An arthropod’s body plan is segmented just as annelids.

This is the phylum with more species than any other phylum. Arthropod’s body plan is segmented just as annelids.

They have appendages, which serve a variety of purposes such as gaseous exchange, food gathering, locomotion and direction of stimuli.

Arthropods have an exoskeleton or cubicle that is secreted by the epidermis. Their skeleton is made up of chitin.

Their exoskeleton serves different purposes such as:

• Support
• Attachment for muscles; and
• Protection from physical damage

They have jointed appendages used for various functions such as feeding, locomotion and sensory purposes.

Arthropoda have developed distinct regions of the body, namely the head, thorax and abdomen.

The head possesses sensory receptors such as eyes and antennae as well as feeding appendages. The head is more developed in annelids with a larger brain.

Some classes of the phylum e.g. insects have developed flight which greatly increases opportunities for finding food and escaping from predators.

DISTINCTIVE FEATURES OF PHYLUM ARTHROPODA

They have an exoskeleton made up of a chitin and sometimes-calcareous matter, which may either, be rigid, stiff or flexible.

Each segment in arthropoda typically bears a pair of jointed appendages used for locomotion or feeding or sensory purposes.

CLASS OF PHYLUM ARTHROPODA

1. Class: Crustacean
2. Class: Insecta
3. Class: Chilopoda
4. Class: Diplopoda
5. Class: Arachnida

CLASS CRUSTACEAN

Crustacea is a class of organisms whose bodies are covered by a hard shell called carapace.

DISTINCTIVE CHARACTERISTICS

1. Crustacea are mainly found in marine and fresh water thus they occupy aquatic habitats
2. Their gaseous exchange is by means of gills or through the body membrane
3. Their bodies are divided into two main parts: the head and thorax are fused to form a Cephalothorax the second part is the abdomen
4. They have a pair of compound eyes each on a raised stalk
5. They have two antennae
6. They have four pairs of mouthparts namely maxilla, mandible, labium and labrum
7. They have five pairs of limbs that are modified for swimming

Examples of crustaceans are woodlice, water flea, Cray fish, crabs, lobsters, shrimps and barnacles.

IMPORTANCE OF CRUSTACEANS

1. Human beings use crustaceans as food especially lobsters, shrimps, crabs and crayfish
2. Some of them are used for decorations in the homes especially crabs and crayfish
3. Most crustaceans attract tourists during their visits especially along the beaches

CLASS CHILOPODA

Class Chilopoda is made up of centipedes. The centipede is mainly found on land.

DISTINCTIVE CHARACTERISTICS

1. Centipedes have a clearly defined head while the rest of the segments are similar
2. They have a pair of antennae
3. They have one pair of mouthparts known as mandibles
4. They have simple and compound eyes, although some lack compound eyes
5. They have a pair of legs in each body segment
6. They carry out gaseous exchange by means of tracheoles of the tracheal system
7. They feed on insects and worms
8. They occupy terrestrial habitats
9. They have one pair of poison claws

CLASS DIPLOPODA

Class Diplopoda is made up of millipedes. Millipedes are common in damp places.

DISTINCTIVE CHARACTERISTICS

1. Millipedes have a clearly defined head. All the other body segments are basically similar
2. They have one pair of antennae
3. They have one pair of mouthparts namely, the mandibles
4. They have simple and compound eyes, although some lack compound eyes
5. They have two pairs of legs in each body segment
6. They carry out gaseous exchange through tracheoles of the trachea system
7. They feed on plants
8. They inhabit terrestrial habitats
9. They have a cylindrical body

IMPPORTANCE OF THE CLASS

The millipedes can be useful like earthworms; they help to aerate the soil

CLASS INSECTA

- Insects are the most successful organisms on earth since they possess an exoskeleton, which reduces water loss from the body.

- Insects are the largest group of arthropods

- They occupy every habitat an earth in such places as air, soil and water. However they mainly inhabit terrestrial habitats

Examples of insects include grasshoppers, houseflies, butterflies, bees and termites.

1. Insets have three body parts namely the head, thorax and abdomen
2. They have one pair of antennae
3. They have a pair of compound eyes. In some cases simple eyes are also present
4. They have three pairs of walking legs per segment of the thorax
5. Most insects have one or two pairs of wings on the second or third segment o the thorax. Some insects have no wings
6. They breath by means of air holes called spiracles and carry out gaseous exchange through the tracheoles of the tracheal system
7. They undergo complete or incomplete metamorphosis with a larva stage
8. They mainly occupy terrestrial habitats

IMPORTANCE OF INSECTS

1. Most insects are naturally useful in pollination e.g. bees and flies
2. Other insects e.g. bees are able to make various substances like honey and wax that are consumed by humans and wax is used for making candles
3. Some insects like termites and earthworms help to turn the soil over and so keep it lose and aerated
4. Most insects are vectors of several species of disease causing organisms e.g. mosquito is the vector for plasmodium that causes malaria in humans. Flies are vectors for filarial worms that cause river blindness in humans

DISADVANTAGES OF INSECTS

Many insects transmit diseases to people by transmitting contaminated material by means of their appendages e.g. houseflies transmit cholera by carrying contaminated stool to whatever can be consumed by human beings.

CLASS ARACHNIDA

Arachnida are terrestrial arthropods. Examples of arachnids are spiders, ticks, scorpions and mites.

DISTINCTIVE CHARACTERISTICS

1. Arachnids have two body parts. The head and thorax are fused to form cephalothorax or prosoma, the abdomen is referred to as opithosoma.
2. They do not have mouthparts. However they have one pair of appendages for sensing prey and another pair for capturing the prey
3. This pair of appendages is known as chelicerae. Thus they have a carnivorous mode of feeding
4. They have simple eyes
5. They have four pairs of walking legs
6. They carry out gaseous exchange by the lung book or trachea
7. A lung book consists of folds of ectoderm with slit like opening on the surface of the abdomen
8. Arachnids do not have wings
9. They inhabit terrestrial habitats

ECONOMIC IMPORTANCE OF ARTHROPODA

Arthropoda are of great economic importance in many ways. Some of them include the following:

1. They cause damage to crops and forestry, locusts and some larvae e.g. feed on crops
2. They spread diseases to humans and other domestic animals e.g. female anopheles spreads malaria, while tsetse flies spread sleeping sickness
3. They are source of food e.g. green grasshoppers, termites, crabs and shrimps
4. They cause damage to household materials e.g. cockroaches damage furniture
5. Some members aid pollination e.g. bees, butterflies and lady birds

PHYLUM CHORDATA

Phylum chordata is found in the kingom Animalia. Members found on phylum chordata are fish, frog, lizard, birds, rats etc.

General Distinctive Characteristics of Phylum Chordata are:

1. They have a notochord in the embryonic stage. If they notochord persists throughout the life span, it may be surrounded by a vertebral column as in lungfish or it may both be surrounded by a vertebral column as in some chordata
2. Their nerve cord is hollow and placed dorsally to the gut
3. They have gill slits at least during the embryonic stage
4. They have tail which is behind the anus

They phylum chordata consists of six classes which are class Chondrichthyes, Class Osteichthyes, Class Amphibia, Class Reptilia, Class Aves and Class Mammalia

Distinctive features of Class Chondrichthyes

1. The skeleton is made up of cartilage
2. The body is covered with placoid scales
3. The caudal fin has tow lobes that differ in size
4. Each pair of gills is in a separate compartment
5. The mouth and two nostrils are ventrally placed
6. Males have Copulatory structures called claspers

Example of Specimen found on Class Chondrichthyes

Distinctive Features of Class Osteichthyes

1. The skeleton is made up of bones
2. The body is covered with ganoid scales
3. The mouth is terminally placed and nostrils are forced on the dorsal surface
4. All pairs of gills are found in common chamber and the chambers are covered by an operculum
5. The caudal fin has loves of the same size

Class Amphibia

Amphibia are found in a number of habitats example in trees, freshwater and damp places but never in salt water.

Distinctive Features of Class Amphibia

1. Their skin is always moist example frogs
2. Their life cycle involves larva form called tadpole
3. They have gills which are present in the early stages of the development of the tadpole
4. They have a heart which has three chambers
5. There is gaseous exchange by gills in the tadpole and in the adult it takes place in the lungs, skin and the mouth lining

Structure of Amphibians

The body of toad or frog consists of a head and trunk only. The skin is dry and warty in toads and smooth and shiny in frogs. On the head are pair of nostrils and lower eyelids, which are almost immovable.

The fore limbs of toads and frogs are short. They have 4 digits on each hand, as the thumb is missing. The hind limbs are much longer than the front ones and the feet are very large. A thin web of skin, which is particularly well developed in frogs, joins the toes. Adult toads are mainly land animals and usually enter water only to breed.

Importance of Amphibians

1. They are ecologically important
2. They are used in research specimen
3. Some amphibians are eaten as food
4. Some amphibians have unique features. Example abnormally big sizes attract tourists
5. They have typical characteristics of larger animals hence they are among the most preferred specimens for biological studies

Class Reptilia

Reptilia have different habitats like aquatic areas and others live in terrestrial areas. Examples of reptiles are snakes, lizards, tortoise, etc.

Distinctive features of Class Reptilia

1. They have a dry skin covered with horny scales
2. With exception of crocodiles, they have a heart, which is divided into two atria and two partially divided ventricle chambers. Reptiles vary greatly in size.

Structure of a Snake

The body of a snake is long, cylindrical and without a neck. A protective layer of overlapping horny scales, which are under of its body, covers the tail of a snake; they are large and transversely elongated.

Movement of snake I also helped by their lower ends to the ventral snake.

Importance of Class Reptilia

1. Reptiles act as attractive features e.g. colour of snake
2. Reptiles are used as a source of food for other species example birds feed on snakes
3. Reptiles are used in decorations in houses

Disadvantages of Class Reptilia

1. Can cause death to human beings example snake

Class Aves

Members of this class vary in size, form and habitat. Some birds are large example Ostrich while others are relatively small example sunbird.

Distinctive features of Birds

1. The body is covered with feathers
2. The anterior pair of limbs is modified into wings
3. The mouth is modified into a beak or bill

Structure of Bird

Most birds have a comparatively small lightly built body. The body is covered with feathers. Feathers occur in rows. The overlapping of the feathers covers the bare spaces in between. They possess wings.

Importance of Birds

1. Flesh of several species is used as food for human beings example chicken, duck
2. The feathers of birds are used for decorations
3. Birds are also used for the pollination of seeds and fruit dispersal
4. Some birds like Ostriches are attractive to tourists
5. Some species of birds are used for biological control

Class Mammalia

Members of this class vary in size, form and habitat. Some mammals are very large example the whale and the African elephant while others are relatively small example mouse and rats. The mammal’s heart has four chambers. The body temperature of mammals is constant (homoeothermic). Most mammals live in land and others live in water.

Distinctive features of Class Mammalia

1. Their body is covered with hairs
2. They have mammary glands
3. They have teeth of different types and shapes
4. They have diaphragm
5. Their red blood cells have no nucleus
6. They have sweat glands. The body temperature of mammals is constant

Importance of Mammals

1. Most mammals serve as source of food for human beings example cows, sheeps
2. Mammals help in production of manure example manure from cows, goats
3. The bones of mammals are used for production of animal charcoal
4. Most wild animals in national parks and game reserves attract tourists
5. Some domestic mammals such as cows and donkeys are trained to perform human duties such as cultivation of crops