BIOLOGY: CLASSFICATION OF LIVING THINGS, FORM 1 TO 4

CLASSIFICATION OF LIVING THINGS

Concept of Classification

The Concept of Classification

Have you ever visited a library? How are the books arranged and kept? Are they arranged randomly or systematically? Obviously the books are arranged systematically in the shelves. Science books are kept separately in their respective shelves. Science books are kept separately from social or commercial books. Biology books are separated from physics books or chemistry books. Likewise, in the shop, laboratory or pharmacy items are sorted and placed on the basis of their similarities.

In the world, there are numerous varieties of living organisms.These organisms do vary in size, structure, shape, habitat, mode of feeding and even mode of reproduction. The organisms can be sorted out and placed into different groups based on their similarities. The system of sorting out and placing organisms into different groups on the basis of their similarities and differences is called classification.

The Importance of Classifying Living Things

The following are importance of classification

§     Classification makes the study of living things easy

§     Classification makes communication easy among biologists from different parts of the world

§     It provides good organized system in which a newly identified organism can be easily fitted in future.

§     It makes it easier to identify organisms

§     It can be used to predict characteristics that are present in the members of the same group.

Classification Systems

Types of Classification Systems and Their Differences

There are two types of classification

§     Artificial classification

§     Natural classification

Artificial classification. An artificial classification is based on one or a few easily observable characteristics and usually designed for practical purpose with an emphasis on convenience and simplicity. In this type of classification, unrelated organisms are often placed in the same group while closely related organisms are often placed in different groups.Linnaeus included all

Linnaeus included all worm-like organisms in a single group, the vermes. This included wide a range of animals as from nematodes, earthworms to snakes. This was an artificial classification since it did not consider natural relationships such as the fact that snakes have backbones and earthworms do not have. Thus, snakes have more features in common with vertebrates than with worms.

Bats and birds would be placed in the same group because all have the ability to fly since they posses wings. But bats share many features with mammals. They have features like hair, mammary glands, sweat glands and different types of teeth which are characteristics of mammals. Therefore, bats are more related to mammals than birds.Natural

Natural system of classificationThis type of classification system tries to use natural relationships between organisms. It considers many features in common including internal as well as external features.Similarity of embryology, morphology, anatomy, biochemistry cell, structure and behaviour are all considered relevant. It is based on evolutionary relationship in which organisms belonging to the same group are believed to have a common ancestor.

Characteristic features which show homology are distinguished from those which show analogy. Example the fore limbs of mammals, whales, birds and bats have the same basic pattern and similar bone arrangement, i.e. homologous. This suggests that these organisms are coming from the same ancestor and that can be placed in the same group.

The wings of birds and grasshoppers are analogous. The wings of birds have internal skeletons while the wings of grasshoppers do not have bones but they perform similar function. These organisms cannot be placed in the same group since they are different in many ways.

Merits and Demerits of Each Type of Classification System

Advantages of artificial system of classification

§     It is easy to classify organisms since it is based on few observable characteristics.

§     It does not take much time to classify organisms based on this system (not time consuming).

§     It does not need expertise (even a layman can do).

§     It is relatively stable i.e. not easily changing from time to time.

Disadvantages of artificial system of classification

§     It tends to place closely related organisms into different groups instead of being grouped together e.g. a bat can be placed in a group of birds instead of mammals.

§     Different or unrelated organisms may be placed in the same group e.g. bats placed in a group of birds, worms placed with snakes in the same group

§     The system does not provide enough information about its members.

§     It is difficult to incorporate additional information.

Advantages of natural system of classification

§     Closely related organisms are placed in the same group.

§     It reflects evolutionary relationships.

§     Unrelated organisms cannot be placed in the same group.

§     It makes it easy to incorporate additional information.

Disadvantages of natural system of classification

§     It is difficult since it considers many features.

§     It requires expertise i.e. more knowledge about an organism.

§     It is time consuming.

§     It is relatively unstable i.e. it changes from time to time.

§     It is more expensive since more data are required.

Differences between natural classification and artificial classification

Artificial classification	Natural classification
(i) Considers few features in common	Considers many features in common
(ii) Does not reflect on evolutionary relationships	Reflects on evolutionary relationships
(iii) It is easy to classify	It is difficult to classify
(iv) Not time consuming	It is time consuming
(v) Does not require expertise	Requires expertise
(vi) New information cannot be added	New information can be added.

 

Major Groups of Living Things

The major groups of living things are the kingdoms. Previously, living things were categorized into two main groups; plantae and animalia kingdom. But this classification caused difficulties since some organisms seemed to posses some of the characteristics of both groups. For example, euglena is capable of feeding like an animal and locomote like an animal. Therefore, it is placed in animalia kingdom. But the same euglena has chlorophyll and it is capable of manufacturing its own food. Therefore, it should also be placed in plantae kingdom. Such an organism does not seem to fit exactly in animalia or plantae kingdom. Thus, euglenas are assigned in the major group of their own.

Currently, there are five major groups (kingdoms) of living things.

§     Kingdom monera

§     Kingdom protoctista

§     Kingdom fungi

§     Kingdom plantae

§     Kingdom animalia

 

Ranks of Classification

In the millions of organisms found on earth some are more similar while others are less similar. For example, all human beings resemble each other more closely than they resemble with the chimpanzees. Humans have more resemblance with chimpanzee than cats and dogs, and more like dogs than birds.Therefore when classifying the organisms, groups are established which are called ranks or taxa.

There are seven ranks of classification

§     Kingdom

§     Phylum/division

§     Class

§     Order

§     Family

§     Genus

§     Species

The highest rank of classification is the kingdom. The lowest rank of classification is the species. Every known organism has particular place in each group.

§     Kingdom- this is the highest rank (taxon). It comprises of several related taxa. It comprises of many organisms than any other taxon.

§     Phylum/division– this is the second largest rank of classification. It consists of several closely related classes.

§     Class - members or this group have more characteristics in common than do members of division or phylum.

§     Order- it consists of groups that are more alike than those in a class.

§     Family –this is made up of groups that are more alike than those in the order. Wolves and cats are both in the order Carnivore but wolves are in the family Canidae while cats belong to the family Felidae.

§     Genus – it consists of very similar species but members of different species cannot breed one another.

§     Species – Species can be defined as a group of closely related organisms which are capable of interbreeding and produce fertile offspring.

It is the basic unit of scientific classification. Organisms that need to be placed in the same species must have the following characteristics:

§     Must have many features in common.

§     Must be able to breed one another to produce fertile offspring.

§     Must be distinct and different from other organisms.

N.B: The term division is used by botanists instead of phylum when classifying plants or organisms related to plants.

Classification of some members of animals

	Human	Leopard	Domestic cat
Kingdom	Animalia	Animalia	Animalia
Phylum	Chordata	Chordata	Chordata
Class	Mammalia	Mammalia	Mammalia
Order	Primates	Carnivore	Carnivore
Family	Hominidae	Felidae	Felidae
Genus	Homo	Panthera	Felis
Species	sapiens	padus	catus

 

Scientific naming of living organisms

The scientific process of naming organisms is called nomen-clature. Biological nomenclature is based on the binomial system (double naming system) pioneered by the work of a Swedish naturalist Carl Linnaeus (1707-1778).

Biologists assign scientific names to organisms so as to avoid confusion among themselves since scientists from different countries use different languages. The scientific names are uniform in all languages.

Latin language is used in assigning the scientific name because it is an official language and that this language is no longer subject to changes; it is considered to be a dead language hence names once given remain unchanged.

Rules of binomial nomenclature

§     Scientific names of organisms must be in Latin language and if the names are derived from other languages, they must be latinized.

§     A scientific name of an organism has two parts, genus name and species name.

§     A genus name always starts with a capital letter and a species name follows with a small letter.

§     In typed scripts, a scientific name must be written in italics or underlined if hand written.

§     A specific name is sometimes accompanied with the name of the author who first described and named the organism.

§     When an organism is known by several names, the valid name is the one which was established after the work of Linnaeus.

Example 1

Examples of scientific names

Human being:Homo sapiens

Homo is the generic name and sapiens is the specific name.

Other examples of organisms with their scientific names

Common name	Scientific name
Earthworm	Lumbricus	terrestris
Cockroach	Periplaneta	americana
Amoeba	Amoeba	proteus
Coffee	Coffea	arabica
Maize	Zea	mays
Bean	Phaseolus	vulgaris
Domestic cat	Felis	catus
Sisal	Agave	sisalana
Ashok tree	Polyanthia	longifolia
Housefly	Musca	domestica
Neem tree	Azadirachta	indica
Flamboyant (Christmas tree)	Delonix	regia
Tropical almond (mkungu)	Terminalia	catapa

 

Viruses

Viruses were discovered by a Russian botanist D. I. Ivanovsky and a Dutchman Beijerink. In 1852 Ivanovsky prepared an infectious extract from tobacco plants that were suffering from mosaic disease. When the extract was passed through a filter able to prevent the passage of bacteria, the filtered fluid was still infectious. 1898 Beijerink gave the name “virus” (in latin means, “poison”) to describe the infectious nature of certain filtered plant fluids.

General and Distinctive Features of Viruses

Characteristics of Viruses

§     They are the smallest living organisms ranging from 20-30nm. On average, they are about 50times smaller than bacteria.

§     Viruses do not have cellular structures, which mean that they lack certain important organelles like nucleus, cytoplasm, golgi bodies, etc.

§     They can only reproduce inside the living cells hence they are parasitic.

§     They have a simple structure consisting of either DNA or RNA but not both, surrounded by a protein or lipoprotein coat.

§     They can be described as living or non-living.

§     They are highly specific to their hosts i.e. each virus recognizes only certain types of cells.

§     Viruses are capable of replicating themselves only when they are inside the host cell.

Viruses as living things

§     They possess genetic material (RNA or DNA).

§     They reproduce when they are in the host cell (replication).

§     They are capable of identifying their hosts and attack them.

§     They can undergo mutation (they mutate) i.e. they undergo different changes in shape.

§     Like other parasites, they are specific to host.

Viruses as non-living things

§     They can crystallize outside the host.

§     They are metabolically inert in isolation.

§     They are non-cellular i.e. they lack cell organelles.

§     They do not perform necessary life processes such as respiration, excretion nutrition etc.

The Structure of Viruses

Generally viruses have a very simple structure consisting of the following:

§     RNA or DNA which may be single stranded or double stranded. They form a structure called core.

§     A protective coat of protein surrounding the core called capsid.

§     A nucleocapsid which is a combined structure of core and capsid.

§     Envelope – an additional layer of lipoprotein layer around the capsid.

§     Capsids are made up of identical repeating units known as capsomeres.

 

Bacteriophage

Bacteriophage is a virus that attacks and kills bacteria. Some of them have head with a tail sheath.

Bacteriophage

Advantages and Disadvantages of Viruses

Advantages of viruses

§     Viruses are used in developing vaccines, for example, vaccines for measles, polio and rubella are made from viruses that have been attenuated (weakened).

§     Viruses are used as biological weapons to kill organisms.

§     They are used as vectors in genetic engineering to transfer genes from one organism to another for improving or treating the defective genes.

§     Bacteriophages are viruses that attack bacteria and hence they help in controlling infections and diseases.

§     Viruses are used as biological weapons in wars and in biological pest control.

Disadvantages of viruses

§     Most viruses cause diseases to both plants and animals. Plant disease such tomato mosaic, cassava mosaic and tobacco mosaic; and animal diseases e.g. measles, small pox, poliomyelitis and yellow fever are caused by viruses.

Kingdom Monera

This kingdom is made up of organisms known as bacteria (singular: bacterium). They are the most ancient and smallest organisms with a cellular structure. They are mainly single celled. Bacteria occupy many environments such as soil, dust, water and in the bodies of plants and animals

Some bacteria are found in hot springs where temperatures are 78ºC or more. Others can withstand very low temperatures. Some are found in very deep cracks in the ocean floor, at very high temperatures, about 360ºC (extreme thermophiles).

 

General and Distinctive Features of the Kingdom Monera

General characteristics of the kingdom monera

§     They are mainly unicellular and very small.

§     They are all prokaryotic (nucleus not bound by membrane)

§     They reproduce by binary fission.

§     Some members of the kingdom are autotrophs while others are heterotrophs

§     They have cell wall made up of protein material and sometimes lipids.

§     Some bacteria form spores during adverse conditions i.e. extreme conditions e.g. high or low temperatures, drought etc. The spores allow them to survive as they have very thick resistant walls.

§     Some are aerobes while others are anaerobes.

§     The genetic material (DNA) is scattered in the cytoplasm and they lack internal membrane bound organelles such as mitochondria, chloroplasts, golgi bodies etc.

General structure of the bacteria

§     Bacteria have strong and rigid cell walls due to the presence of murein. The wall prevents the cell from bursting when it absorbs much water (as a result of osmosis).

§     Bacterial cells are bounded by partially permeable membranes.

§     Bacteria possess capsules which are slimy or gummy.They have flagella which aid motility of the bacteria. Motile bacteria can move in response to a certain stimulus i.e. tactic movement. Flagella can easily be seen by electron microscope.

§     They have small self replicating circle of extra DNA called a plasmid.

General structure of bacterium

Forms of bacteria

Bacterial shape is an important aid to classification. There are four main shapes

Coccus (plural: cocci)

They are spherical in shape and can be of the following types.

§     Micrococcus – exist singly. They cause sore throat.

§     Diplococci - this type of bacteria exist in pairs. The pneumococci (Diplococcus pneumoniae) are the only members. They cause pneumonia.

§     Streptococci – this type of bacteria stick together and form a chain. Most of them infect upper respiratory surface and cause diseases e.g. sore throat.

§     Staphylococci – These bacteria form a grape like bunch. They cause boils, pneumonia, food poisoning and other diseases.

Bacilli (singular: bacillus)

These are rod shaped bacteria. They can be:

§     Single rods, for example, Escherichia coli commonly living in the gut and Salmonella typhiwhich cause typhoid fever.

§     Rods in chain, for example, Azotobacter, a nitrogen-fixing bacteria, and Bacillus anthraciswhich cause the disease anthrax.

§     Bacilli with endospores showing various positions, shapes and sizes of spores. They can be:

§     Central, not swollen e.g. Bacillus anthracis causes anthrax

§     Spherical spore, terminal swollen e.g. Clostridium tetani causes tetanus

§     Sub-terminal, swollen e.g. Clostridium botulism causes botulism.Spores may also be central

Spirilla (singular: spirillum)

These are spiral-shaped bacteria e.g. Treponema pallidum which causes syphilis

Sprrilla

Vibrio

These are comma shaped bacteria, for example Vibrio cholerae.

Vibrio cholerae

The Advantages and Disadvantages of the Kingdom Monera

Outline the advantages and disadvantages of the kingdom monera

Economic Importance of Bacteria

In Agriculture, the bacteria are mostly important for following reasons

§     Nitrogen fixation:Plants cannot trap nitrogen from the atmosphere but bacteria can fix nitrogen and change it into nitrogenous compounds. The phenomenon is called nitrogen fixation. The bacteria, which fix atmospheric nitrogen, are called nitrogen-fixing bacteria. Some of the nitrogen fixing bacteria are found freely in soil are called free-living bacteria, eg. Clostridium and Azotobacter. Some of them are found in root nodules making association with leguminous plants called symbiotic bacteria, eg. Rhizobium.

§     Nitrification:Some bacteria convert ammonium compounds into nitrates in the soil. The process is called nitrification. The bacteria that take part in this process are called nitrifying bacteria, eg. Nitrobacter and Nitrosomonas. Nitrosomonas Nitrobacter Ammonia--------------->Nitrites------------->Nitrates

§     Ammonification:Some bacteria utilize proteins of dead bodies and convert it into amino acids. These amino acids are converted into ammonia by some bacteria. The process is called ammonification and the bacteria involve in the process are called ammonifying bacteria. Then the ammonia reacts with CO2 and H2O and gives ammonium carbonate which is absorbed by plants.

§     Bacteria decompose dead bodies. They convert complex organic compounds into simple inorganic compounds. Therefore they're called natural scavengers.

§     Bacteria make the milk sour and produce flavor. They are responsible for coagulation of milk. E.g. Lacto bacillus.

§     Bacteria convert sugary substances into alcohol, acids, acetones; etc the process is called fermentation.

§     Bacteria also help to produce different types of enzymes like Amylase secreted from Bacillus, Protease from Bacillus, Streptokinase from Streptomyces.

§     Bacteria are useful for vitamin production like Vitamin B (Cabalmin) is secreted from Pseudomonas, Vitamin B (Riboflavin) is secreted from Clostridium.

§     They are important for antibiotic production like Terramycin from Streptomyces rimosus, Streptomycin from S. griseus, Neomycin from S. fradiae.

§     They are also important to produce hydrogen commercially. During the process they ferment carbohydrate and hydrogen gas is produced.

§     Bacteria decompose waste products.

Disadvantage of Bacteria

§     Some of the species cause food poisoning. They secret some toxic chemical substances on out food stuff which cause food poisoning, eg Staphylococcus and Clostridium.

§     Some are responsible for human diseases: Cholera: Vibrio cholera, Pneumonia: Staphylococcus pneumoniae, Diarrohea: Escherechia coli, Tuberclosis: Mycobacterium tuberclosis Leprosy: M. leprae, Meningitis: Nisseria meningitides.

§     Some bacteria are responsible for plant diseases. Red stripe in sugarcane, Leaf streak in rice, black rot in cabbage and yellow rot in wheat are caused by Xanthomonas and Pseudomonas.

The Characteristics of Pathogenic and Non-pathogenic Bacteria

Outline the characteristics of pathogenic and non-pathogenic bacteria

Pathogenic bacteria are bacteria that can cause infection. This article deals with human pathogenic bacteria.

Although most bacteria are harmless or often beneficial, several are pathogenic. One of the bacterial diseases with the highest disease burden is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and food borne illnesses, which can be caused by bacteria such as Shigella, Campylobacter, and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy. Pathogenic bacteria are also the cause of high infant mortality rates in developing countries.

Non-pathogenic organisms are those that do not cause disease, harm or death to another organism and is usually used to describe bacteria.It describes a property of a bacterium - its ability to cause disease. Most bacteria are non-pathogenic. It can describe the presence of non-disease causing bacteria that normally reside on the surface of vertebrates and invertebrates as commensals. Some non-pathogenic microorganisms are commensals on and inside the body of animals and are called microbiota. Some of these same non-pathogenic microorganisms have the potential of causing disease, or being pathogenic if they enter the body, multiply and cause symptoms of infection.

Immune comprised individuals are especially vulnerable to bacteria that are typically non-pathogenic but because of a compromised immune system, disease occurs when these bacteria gain access to the body's interior. Genes have been identified that predispose disease and infection with non-pathogenic bacteria by a small number of persons. Non-pathogenic colistrains normally found in the gastrointestinal tract have the ability to stimulate the immune response in humans, though further studies are needed to determine clinical applications.

 

Kingdom Protoctista

General and Distinctive Features of the Kingdom Protoctista

Explain general and distinctive features of the kingdom protoctista

This Kingdom comprises of unicellular and simple multicellular organisms whose cells have organized nucleus and membrane bound organelles. It includes the algae and protozoa.

Algae have chlorophyll hence make their own food through the process of photosynthesis. Protozoa are heterotrophic taking in ready-made food.

Other organisms, which are included in this Kingdom are red algae, Brown algae, Amoeba, Euglena, plasmodium, trypanosome and paramecium.

General features of Kingdom Protoctista

§     Some are autotrophs, for example Euglena while others are multicellular.

§     They are all eukaryotes with most of them having locomotery structure.

§     Most of them live in moist places or in water.

Distinctive features

§     Most are unicellular eukaryotes

§     They reproduce by binary fission

 

 

Phyla of the Kingdom Protoctista

Mention phyla of the kingdom protoctista

The phyla of kingdom protoctists include the following:

§     Euglenophyta e.g. Euglena

§     Rhizopodia e.g. Amoeba

§     Zoomastigma e.g. Trypanosoma

§     Apicomplexa e.g. Plasmodium

§     Oomycota e.g. White root

§     Chlorophyta e.g. Spyrogyra

§     Cilliaphora e.g. Paramecium

§     Rhodophyta e.g. Red algae

Structure of Amoeba and Paramecium

Describe structure of amoeba and paramecium

Amoeba belong to phylum Rhizopoda, organisms with the following extra features:

§     They are eukaryotes

§     Unicellular

§     Parasitic

§     They move using pseudopodia

Pseudopodia are projection of the cytoplasm that extend and pull the amoeba forward or engulf food particles.

 

The Advantages and Disadvantages of Amoeba, Euglena Paramecium and Plasmodiu

Explain the advantages and disadvantages of amoeba, euglena paramecium and plasmodium

Advantages of Paramecium: Are eaten by small water animals

Disadvantages of Paramecium: Causes diseases of bulanterdium eoli destroying the lining of intestines

Osmoregulation:Paramecium has two contractile vacuoles and each is associated with permanent system of collecting channels, which empty, into the main vacuole.

Feeding: Paramecium feed on bacteria. These are obtained from the surrounding water by the beating of the cilia-lining o the oral grove.

Reproduction:Paramecium reproduces both asexually and sexually. The asexual method is more common and it is binary fission. Sexual method is called conjugation.

Movement in paramecium is caused by cilia beating. This movement is called cilliary movement.

 

 

 

 

 

 

CLASSIFICATION OF LIVING THINGS

✔  Msomi Bora Diterbitkan July 03, 2018

 TAGS

 

                                              

TOPIC 1: CLASSIFICATION OF LIVING THINGS

Kingdom Fungi

Member of the kingdom Fungi include fairly familiar organisms such as mushrooms, toadstools and bracket fungi. There are also less obvious but very important members such as mold, which grow on bread, ripe fruits and other food.

The General and Distinctive Features of the Kingdom Fungi

Explain the general and distinctive features of the kingdom Fungi

General features of kingdom fungi

§     Fungi are found in damp or wet places

§     They have eukaryotic cells with a rigid protective wall made of chiti

§     They are heterotrophs, some are saprophytic where others are parasitic

§     They store food as glycogen

§     They reproduce using spore

§     They are non-mobile

Distinctive features of kingdom fungi

§     They have chitin in their cell wall

§     They have septate

The Phyla of the Kingdom Fungi

State the phyla of the Kingdom Fungi

Phyla of the kingdom fungi

§     Ascomycota

§     Zygomycota

§     Basidiomycota

Ascomycota

Ascomycota are also called sae fungi. They produce spore in sae-like cell called asei. These spores are called ascopores. Examples of Ascomycota are bakers’ yeast, cup fungi and ring worm fungi.

Characteristics of phyla Ascomycota

§     Their cell wall is not made by chitin but cetin polysaccharide component of phosphoric acid

§     Have granulated cytoplasm

§     Store food in form of glycogen

§     Reproduce asexually by budding and sexually by means of ascospores.

Distinctive features

§     Reproduce sexually by means of ascospores

(i) Reproduce sexually by means of ascospores

The Structure of Mosses

Describe the structure of mosses

Mosses are small, soft plants called bryophytes, that are typically 1–10 cm (0.4–4 in) tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems. At certain times mosses produce spore capsules which may appear as beak-like capsules borne aloft on thin stalks.

Advantage and Disadvantages of Mosses

Outline advantage and disadvantages of Mosses

On the advantage side, it can help to hold the bonsai soilin place and prevent it from washing out of the container. Moss can increase the water retention capability of the soil by slowing evaporation.

On the disadvantage side, a thick carpet of moss can reduce the diffusion of gases into the soil and to the roots, which can result in root rotor poor drainage conditions. Moss can grow up onto the surface roots and trunk of your bonsai, and soften their bark, promoting its decay.

Division Filicinophyta (Pteridophyta)

General and Distinctive Features of the Division Filicinophyta

Explain general and distinctive features of the division Filicinophyta

This division was formerly called Pteridophyta. The division Filicinpphyta includes a group of primitive vascular plants. The adult plant body in these plants is a sporophyte. It shows differentiation into true roots, stems and leaves. The stem is mostly herbaceous. Leaves may be smaller or larger. Vascular tissues are present in all the vegetative parts of the plant body.

Characteristics of division Filicinophyta

Members of this kingdom include horsetails, ferns and mosses.

§     Reproduction involves production of spores inside special structures called sporangiawhich occur on the underside of the leaves called sporophylls. Sprangia may sometimesbe found in groups called sori.

§     The plants may be homosporous - producing only one type of spore or heterosporous -producing two different types of spores; smaller microspores and larger megaspores.

§     They are seedless vascular plants, which contain vascular tissues but do not produceseeds.

The Structure of Ferns

Describe the structure of Ferns

Ferns are intermediate in complexity between the more primitive bryophytes (mosses, liverworts, and hornworts) and the more advanced seed plants. Like bryophytes, ferns reproduce sexually by making spores rather than seeds. Most ferns produce spores on the underside or margin of their leaves. Like seed plants, ferns have stems with a vascular system for efficient transport of water and food. Ferns also have leaves, known technically as megaphylls, with a complex system of branched veins.

In general, ferns consist of the following structures:

Fronds

The frond is the "leaf" of a fern. It is divided into two main parts, the stipe (leaf stalk or petiole)and the blade (the leafy expanded portion of the frond).

Rhizomes

Rhizomes would be comparable to "stems" in the flowering plants. Fronds arise from therhizome. In some epiphytic ferns (ferns that grow on trees) and in terrestrial creeping ferns therhizome roams widely and is quite visible.

The rhizome contains the conducting tissues (xylem and phloem) and the strengthening tissues (sclerenchyma fibres). The conducting tissue, known as the vascular bundle, carries the water, minerals, and nutrients throughout the plant.

Roots

Roots are formed from the rhizomes or sometimes from the stipe. The roots usually do not divide once they grow from the rhizome. Tree fern roots grow down from the crown and help thicken and strengthen the trunk. The roots anchor the plant to the ground and absorb water and minerals.

Sporangia

The sporangia are the reproductive structures of the ferns and fern allies. They produce the dust like spores that are the "seeds" by which ferns are propagated. Several sporangia grouped together are called a sorus. Most ferns have their sporangia on the underside of the frond, arranged in an organized pattern usually associated with veins in the pinnule (leaf). Many times(but not always) the ferns provide a protective covering for the sorus called an indusium

Spores

The "seeds" of the ferns and fern allies are called spores. Normally they are formed in groups of four. Spores contain oil droplets and sometimes chlorophyll in their nucleus.

Advantages and Disadvantages of Ferns

Outline advantages and disadvantages of ferns

Advantages of ferns

§     Some ferns are edible and hence serve as a source of food.

§     They provide nutrients to the soil to improve soil fertility.

§     They cover the soil and prevent soil erosion.

§     They are used as decoration materials.

Disadvantages of ferns

§     They harbour dangerous organisms like snakes and insects.

Some ferns are poisonous when eaten.

 

Kingdom Plantae

1.              Division Coniferophyta (Conifers)

 

General and Distinctive Features of the Division Coniferophyta

Explain general and distinctive features of the division coniferophyta

Division Coniferophyta or the conifers belong to Kingdom Plantae. These plants are gymnosperms (non-flowering). They are non-flowering but seed bearing plants. They have vascular tissues. They are woody plants majority being evergreen trees. Few varieties are shrubs

General and distinctive features of the Division Coniferophyta

General characteristics

§     They have secondary growth whose thickening can be observed in cross section of a stem revealing annual rings. Secondary Growth is the result of growth Lateral Meristems (Vascular Cambium & Cork Cambium).

§     Most of the members of Coniferophyta live in cool climates

§     They form evergreen forests. They keep their leaves year-round.

§     They have a large amount of internodal elongation which allows them to grow faster than the other higher plants.

§     They are Xeromorphic, a characteristic that help to protect them from excessive loss of water and therefore adapt survival in extreme habitats.

§     Most are large trees while a few are shrubs and other small plants.

§     Most of them have hard barks which protect inner softwood.

 

Distinctive characteristics

§     Conifers are non-flowering but seed producing plants.

§     They have seeds born in cones shaped structures rather than in fruits.

§     They are gymnosperms which mean naked-seed plants because they produce seeds in cones rather than inside an embryo.

§     The leaves are needle-shaped and have a thick cuticle for protection and to decrease water loss.

 

The Structure of Pinus

Describe the structure of pinus

Pines are evergreen, coniferous resinous trees growing 3-80 m tall. The bark of most pines is thick and scaly. They have needle like leaves.

Pines are among the most well- known coniferous trees in the world. They thrive in temperate mountainous regions, but can also survive in tropical spots in the northern hemisphere. Pines live relatively long time than other coniferous plants. They may live between 100 and 1,000 years

§     The Stem:The bark of most pines is thick and scaly, but some species have thin, flaking bark. The branches are produced in regular whorls appearing like a ring of branches arising from the same point.

§     Leaves:A cross-section of pine stem has several concentric rings with distinct borders between each ring. The center of the stem is called pith. These rings are called annual rings because they grow seasonally and they help a plant to undergo secondary thickening. Generally adult pines have needle-shaped leaves which are green and photosynthetic. The leaves are in bundles or clusters. The leaves (cotyledons) on seedlings are borne in a whorl of 4–24. Juvenile leaves, which follow immediately after seedlings, have single, green leaves arranged spirally on the shoot. They also have non- photosynthetic scale leaves, similar to bud scales. They are arranged spirally like the juvenile leaves.

§     Cones:A cone is an organ of pines that contains the reproductive structures. The woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous. Explain the advantages and disadvantages of the Division Coniferophyta The advantages and disadvantages of the Division Coniferophyta

The Advantages and Disadvantages of the Division Coniferophyta

Explain the advantages and disadvantages of the division coniferophyta

Advantages of Conifers

i.                  Conifers are very important for our economy because of their softwood, which is used for paper and timber, as well as cedar which many people use for their homes because of its beauty and resistance to insects. They have a large economic use as softwood in furniture. In temperate and tropical regions, they are fast-growing softwoods that will allow harvesting in close succession.

ii.                  Decoration and ceremony Many pine species make attractive ornamentals. They are planted in parks and larger gardens. Some varieties are suitable for smaller spaces. Pines are also commercially grown and harvested for Christmas trees.

iii.                  As medicine, Pines and cypress are rich in vitamin; their branches cones and oils can be extracted and used as nutrient supplements.

iv.                  Due to its soft texture conifers are widely used to manufacture Play wood.

v.                  As other higher plants conifers are source of heat energy, used as firewood and charcoal.

vi.                  Thick forests of conifers form green belts that modify the climate.

vii.                  Conifers form a large arena for Biological research Ecological studies.

viii.                  Food uses: Some species have large seeds, called pine nuts that are harvested and sold for cooking and baking. The soft, moist, white inner bark (cambium) found clinging to the woody outer bark is edible and very high in vitamins A and C. It can be eaten raw in slices as a snack or dried and ground up into a powder for use as bread flour. Also White Pines are rich in Vitamin A and C; flour can be made from the Pine tree's inner bark. By chewing bark of pine you can eliminate bad breath. Pines can reduce the pain of skin infections by applying warm pine sap.

 

2.              Division Angiospermophyta (Flowering Plants)

General and Distinctive Features of the Division Angiospermophyta

Explain general and distinctive features of the division angiospermophyta

Angiosperms are flowering plants under kingdom Plantae and division Angiospermophyta. This group of plants is sometimes called Magnoliophyta. Angiosperms are the most abundant land plants. Like gymnosperms, angiosperms are seed-producing plants but they are distinguished from gymnosperms by their characteristic of producing flowers. These plants produce fruits that contain seeds instead of cones like it is in gymnosperms. The term angiosperm means a plant that produces seeds within fruits.

Angiosperms life cycle:The ovary has ovules that contain mega-sporocyte. Mega-sporophyte has four haploid megaspores; three megaspores disintegrate and the remaining one divides by mitotic divisions to produce eight nuclei in an embryo sac. The three nuclei are organized into the egg whereby one cell is the egg cell; the two others are egg helpers. Although these three cells look are similar, only the egg cell continues to develop to an embryo sac. The embryo sac at this stage is the female gametophyte or mega-gametophyte.

Pollination and fertilization:The pollen from the anther is transported to the stigma of a flower. In the stigma pollen tube emerges. The mature male gametophyte therefore is a germinated pollen grain, pollen tube and three sperm nuclei. The pollen tube grows downward toward the ovary through the style and penetrates the embryo sac. After discharging its contents one of the sperm nuclei fuses with the egg nucleus and form a zygote, the other sperm fuses with the polar cell of the ovary, forming the endosperm nucleus. This is what is known as double fertilization. Fertilization in angiosperms begins very soon after pollination.

Note: In gymnosperms, fertilization can occur up to a year after pollination.

Double fertilization:Double fertilization is a distinctive characteristic of the angiosperms and results in a polyploid endosperm tissue. In double fertilization each ovule receives a pollen tube that delivers two sperm cells to the embryo sac. One sperm fertilizes the egg cell to form the diploid zygote, while the other sperm fertilizes the central polar cell to form triploid endosperm. After double fertilization, the ovule develops into a seed and the ovary into a fruit.

General features of angiosperms

They bear flowers which are reproductive structures. Fertilization takes place between male and female flower by pollination that includes insect pollination, wind pollination and animal pollination.

§     Angiosperms have underground root as well as aerial shoot system.

§     Angiosperms have very well-developed conducting tissues. These tissues include the xylem and the phloem arranged in form of vascular bundles.

§     They have root that helps absorption of water and minerals from the soil.

§     Most of them have leaves that carry out photosynthesis, so they are autotrophs.

§     They have alternation of generation, Sporophyte generation alternate with gametophyte generation. The sporophyte is the dominant, diploid stage and is the more visible form of the plant, with the leaves, stems, roots, and flowers. Gametophyte generation is reduced and it is found within the ovary and anther.

Distinctive features of angiosperms

§     The most obvious distinguishing feature of angiosperms is the possession of reproductive structures called flowers.

§     They bear seeds enclosed in a carpel (the fruit). The seeds are the fertilized ovules.

§     They have endosperm produced after fertilization and before the zygote undergo its first division. Endosperm has nourishing function, it nourishes the embryo.

§     They have double fertilization whereby each ovule receives a pollen tube that delivers two sperm cells to the embryo sac. One sperm fertilizes the egg cell to form the diploid zygote, while the other sperm fertilizes the central polar cell to form triploid endosperm.

§     Their haploid gametophyte is confined inside the ovary (female) or anther (male) of the flower, unlike the free- living gametophytes of most other plants.

§     They have conducting tissues phloem and xylem. Unlike gymnosperms which have xylem tracheid angiosperms has xylem vessels.

 

The Classes of the Division Angiospermophyta and their Distinctive Features

Outline the classes of the division angiospermophyta and their distinctive features

Division Angiosperms is divided into two classes which are Monocotyledonae and Dicotyledonae. These two classes are distinguished from each other by their morphology and anatomy.

Features of Class Monocotyledonae

§     Monocots have one cotyledon (or one seed leaf)

§     Monocots have broad leaves with parallel venation.

§     Monocots have fibrous root systems.

§     The floral parts in monocots occur in threes, or multiple of three. PMonocots lack cambium secondary growth.

§     Monocots have scattered vascular bundles in their stems.Typical example of monocot is a maize plant.

Features of Class Dicotyledonae

§     Dicots have two cotyledons (or two seed leaves).

§     Dicots have net venation.

§     Dicots have tap root system

§     Dicots floral parts occur in fours and fives and multiple of four or five.

§     Dicots have cambium secondary growth.

§     Dicots have vascular bundles arranged into a ring. A Typical example of dicot is a bean plant.

 

The Structure of Representative Plants Under Each Class (Monocotyledonae and Dicotyledonae)

Describe the structure of representative plants under each class (Monocotyledonae and Dicotyledonae)

Structure ofMonocotyledonae and Dicotyledonae plants

 

Advantages and Disadvantages of Division Angiospermophyta

Explain advantages and disadvantages of division dngiospermophyta

Advantages of Angiosperms

§     Agriculture. Agriculture depends on angiosperms. Angiosperms provide human food. Example; plants belonging to grass family (grains), are the most important food stocks. They include rice, maize, wheat, barley, millet, sugar cane and sorghum. Legume provides beans, several varieties of nuts and soy. Also of potatoes, tomatoes, and peppers, pumpkins, melons and varieties of vegetables to include cabbage and lettuce. Many fruits oranges, lemons and grapefruits are angiosperms.

§     Livestock. Plants belonging to grass family are the world number one feeds of livestock. Many types of grassland in Africa are either grazed by cattle or wild animals. Also almost all feeds consumed by human are also used by domestic animals as food.

§     Wood. Angiosperms provide different varieties of wood for furniture, paper and building materials. Carpentry and masonry depends largely on angiosperms for both soft and hard wood.

§     Textile. Different varieties of fibers including cotton, flax, and hemp are important raw materials for textile industry. Cotton is the word first class material for clothes.

§     Medicine. Many organic drugs are coming from angiosperm herbs. They are either industrial made or can be utilized in its raw form. Today it is believed that herbs form the best medicine when used in their fresh form than when industrial made.

§     Floriculture. Flowers from angiosperms have great social significance as they are used in different kinds of ceremony. Roses for instance are the most sold flowers and they are highly purchased and used in wedding and burial ceremonies.

§     Forestry. Forestry is the field of study whose base depends on both angiosperms and gymnosperms. Many forests form green belts that habit different varieties of plants.

§     Ecology. Angiosperms provide a wide range of habitats for different species of organisms. They also serve as primary producers of energy.

§     Climate. Angiosperms are used to modify climate. Green belts are established in order to absorb carbon and reduce global warming.

§     Tourism. Many sites of tourism are plants oriented. Ecotourism for instance depends largely on different plant species that host different kinds of land animals.

Disadvantages of Angiosperms

§     Toxins. Some plants are poisonous when eaten by human and other animals. They cause death to human and other living organisms. Some cassava varieties are a good example. They have cyanide acid that inhibits cellular respiration.

§     Drugs. Some angiosperm varieties are drugs that can be abused when taken. Examples are marijuana, cocaine, tobacco and some caffeine varieties.

§     Weeds. Some angiosperm varieties are bad weeds; they reduce crop yields. Some weeds are parasites. Example, Cuscuta kilimanjari is parasitic to coffee plantations.

 

 

 

 

 

 

BIOLOGY: FORM FOUR: Topic 3 - CLASSIFICATION OF LIVING THINGS

✔  Msomi Bora Diterbitkan July 05, 2018

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TOPIC 3: CLASSIFICATION OF LIVING THINGS

Kingdom Animalia

The word 'animal' is derived from the Latin word animalis which means 'having breath'. The Kingdom Animalia is characterized by eukaryotic and heterotrophic organisms. They are multicellular and lack cell wall. They depend directly or indirectly of plants for their food. Food is ingested and digested in their internal cavity and food reserves are stored as glycogen or fat. Nutrition is holozoic, i.e, by ingestion of food. Animals follow a definite growth pattern, the adults have a definite shape and size. Higher forms of animals exhibit well developed sensory and neuromotor mechanism. Most of the organisms are capable of locomotion. Reproduction is by copulation of male and female which is followed by development in embryonic stages.

 

General and Distinctive Features of the Kingdom Animalia

Explain general and distinctive features of the kingdom animalia

Distinguishing characteristics of the Kingdom Animalia include:

§     Cell type - Eukaryotes

§     No cell wall

§     Nutrion - Heterotrophic, ingestion

§     Body form - Muticellular,(invertebrate/ vertebrate)

§     Nervous system - primitive to advanced sensory systems

§     Reproduction - All sexual, some also asexual

§     Locomotion - Ability to move at some point and time throughlife cycle

General characteristics of the Kingdom Animalia are as follows:

§     Animals are eukaryotic, multicellular and heterotrophic organisms.

§     They have multiple cells with mitochondria and they depend on other organisms for food.

§     Habitat - Most of the animals inhabit seas, fewer are seen in fresh water and even fewer on land.

§     There are around 9 to 10 million animal species that inhabit the earth. Only 800,000 species are identified.

§     Biologists recognize 36 phyla in the animals kingdom.

§     Size - The sizes of animals ranges from a few celled organism like the mesozoans to animals weighing many tons like the blue whale.

§     Animal bodies - Bodies of animals are made of cells organized into tissues which perform specific functions. in most animals tissue are organized into complex organs, which form organ systems.

§     Cell structure - The animal cell contains organelles like the nucleus, mitochondria, Golgi complex, ribosomes, endoplasmic reticulum, lysosomes, vacuoles, centrioles, cytoskeleton.

§     Animals are made up of many organ systems, that aids in performing specific functions that are necessary for the survival of the organism.

§     Organ systems are skeletal system, muscular system, digestive system, respiratory system, circulatory system, excretory system, reproductive system, immune system and the endocrine system.

§     Body symmetry - Most of the animals are bilaterally symmetrical, while primitive animals are asymmetrical and cnidarians and echinoderms are radially symmetrical.

§     Locomotion - Most animals have the ability to move, they show rapid movement when compared to plants and other organisms.

§     Respiration - It is a gaseous exchange of taking in oxygen and giving out carbon dioxide. This process takes place in organs of respiration like the lungs, gills, book gills and book lungs and some animals skin is also used for respiration.

§     Digestion - Animals ingest food, and digestion takes place in the internal cavity like the digestive system in animals, in primitive animals vacuoles are for digestion.

§     Nervous system - Sensory mechanism and the coordination of the organ systems is carried on by the nervous system. In animals the nervous system comprises of nerve ganglions, or brain, spinal cords and nerves.

§     Circulatory system - The distribution of nutrients, exchange of gases and removal of wastes takes place in the circulatory system. This system comprises of the heart, blood vessels and the blood.

§     Excretory system - Removal of wastes from kidneys.

§     Skeletal system - support and protection is provided by the skeletal system.

§     Reproductive system - Most animals reproduce sexually, by the fusion of haploid cells like the eggs and the sperms.

§     Glands of the endocrine system help in control and coordination of the body system.

 

The major Phyla of the Kingdom Animalia

Mention the major phyta of the kingdom animalia

Kingdom Animalia has approximately 36 sub-divisions known as 'phyla'. Each phyla share particular properties structurally and functionally which together separate it from other phyla. Below are the most common phyla classified under traditional biological methodology

§     Phylum Porifera- They are primitive organisms, most of them are salt-water sponges. They do not have organs or nerve cells or muscle cells. Approximately, 8,000 species exist today. Example:Sycon, Euspongia, Spongilla.Phylum Coelentrata (Cnidaria)- This group is composed of jelly-fish and other lower aquatic animals. Approximately, 15,000 species exist today.Example:Aurelia, Adamsia.

§     Phylum Platyhelminthes- This group consists of flat worms. They inhabit both marine and fresh water habitats and they are mostly endoparasites found in animals. Example:Taenia, Fascicola.

§     Phylum Aschelmeinthes- It is a group of round worms, most of them are parasites. This phylum consists of about 80,000 parasitic worms.

§     Phylum Annelida- They are present in aquatic, terrestrial and are free-living or parasitic in nature. This phylum comprises of segmented worms. Example: Earthworm, Leech etc.Phylum Arthropoda- This is the largest phylum which consists of insects. There are over 1 million species of insects existing today. Example: Locusts, Butterfly, Scorpion, Prawn.

§     Phylum Mollusca- It is the second largest phylum. They are terrestrial and aquatic. Example:Pila, Octopus.

§     Phylum Echinodermata- This consists of sea stars and sea urchins. There are about 6,000 species. Example:Asteria,Ophiura.

§     Phylum Chordata- Animals of this phylum have a characteristic feature of presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. Within this phylum advanced group called vertebrates which include fish, amphibians, reptiles, birds and mammals.

 

Phylum Platyhelminthes

Etymology: From the Greek platy for flat and helminthes for worms, Hence Flat Worms

The General and Distinctive Features of the Phylum Platyhelminthes

Explain the general and distinctive features of the phylum platyhelminthes

Characteristics of Platyhelminthes include:

§     Bilaterally symmetrical.

§     Body having 3 layers of tissues with organs and organelles.

§     Body contains no internal cavity.

§     Possesses a blind gut (i.e. it has a mouth but no anus)

§     Has Protonephridial excretory organs instead of an anus.

§     Has normally a nervous system of longitudinal fibres rather than a net.

§     Generally dorsoventrally flattened.

§     Reproduction mostly sexual as hermaphrodites.

§     Mostly they feed on animals and other smaller life forms.

§     Some species occur in all major habitats, including many as parasites of other animals.

The Structure of Organism under the Phylum Platyheminthes

Describe the structure of organisms under the phylum latyhelminthes

Platyhelminthes are mostly worm like creatures that are dorsoventrally flattened, meaning they look like a ribbon, this is why they are called names such as Tapeworm, Flatworm, Fluke and Planarian

The Platyhelminthes are a successful phylum with around 25,000 known species divided into four classes. Most Platyhelminthes are parasites on other animals, only the Turbellarians are mostly non-parasitic. A few species are commensalists living in harmony, or mutual benefit with another, normally larger organism. Most species feed on animal material either as parasites or as scavengers, a very few species feed on algae. Although a few of the free living marine and terrestrial species are very beautiful, most species are not particularly attractive to the human mind.

Platyhelminthes live nearly everywhere, on land, in both fresh and marine waters as well as inside other animals. Most of the free living species are marine with only a small number inhabiting fresh water and very few being terrestrial. Parasitic species normally move between different habitats as they change life cycle stages and hosts. A number of parasitic species are of importance to mankind because they infect either our bodies or the bodies of our livestock. A few species can be fatal to humans if not treated, but nearly all species can be treated with modern medicines. Schistosomiasis (Bilharzia) is the most important platyhelminth disease of humans, causing much suffering and some death, over 200 million people are infected with the causative agent in tropical countries.

While they remain fairly morphologically simple the Platyhelminthes show several advance in body structure over the simple radial phyla that came before them. They have a definite congregation of of sensory organs(a few have light sensing organs) and nervous tissues at one end of their body giving them a distinct head and tail. They also have distinct upper and lower (dorsal and ventral) body surfaces. They have a number of organs and even the beginnings of organ systems and a more distinct 3rd layer of cells in their body plan. The evolution of this connective tissue, called parenchyma, the cells of which serve as storage reservoirs as well as protecting the internal organs, is a major step forward toward the more complex body plans of higher animals, such as humans.

However they still no anus, instead they have only a blind ending gut, or no gut at all. Those species with a gut must therefore excrete there digestive waste products through their mouths.

Planarian Anatomy

 

Phylum Aschelminthes (Nematoda)

General and Distinctive Features of the Phylum Aschelminthes

Explain general and distinctive features of the phylum aschelminthes

Characteristics of Phylum Aschelminthes are:

§     Mostly parasitic (in animals and plants), a few free living called as flukes.

§     Body is long, cylindrical, fusiform (pointed at both the ends).

§     Body wall is composed of cuticle, epidermis and musculature.

§     Presence of a false body pseudocoelom not lined by epithelium.

§     Digestive system is complete.

§     Respiration by simple diffusion.

§     Nervous system consists of a nerve ring and many longitudinal nerve cords.

§     Only sexual reproduction. Sexes are separate with sexual dimorphism. Males are usually shorter than females

The Structure of Organisms under the Phylum Aschelminthes

Describe the structure of organisms under the phylum aschelminthes

The Phylum Nematoda (roundworms or nematodes) includes harmless, soil-dwelling roundworms (nematodes) that eat decaying organic material or small soil animals. The phylum also includes plant parasites that infect the roots of plants. These parasitic nematodes decrease the productivity of many human crops. The phylum includes several human parasites (see below).

Like the Phylum Platyhelminthes, the Phylum Nematoda consists of bilaterally symmetrical animals that have the organ system level of organization.

The Phylum Nematoda differs from the Phylum Platyhelminthes in two significant ways. First, roundworms have a complete digestive system. This means that there are two opening to the digestive system. The mouth at the anterior ingests or swallows food, and the anus at the posterior releases digestive waste. A complete digestive system is much more efficient than a cul-de-sac gut. The complete digestive system allows continuous processing of food. A roundworm can eat continuously, food digestion can occur continuously, and waste material can be released continuously. Animals with a cul-de-sac gut must wait until a meal has been digested, release digestive waste from the mouth, and only then swallow the next meal.

The second significant difference between the Phylum Nematoda and the Phylum Platyhelminthes is that the roundworms have a fluid filled body cavity. The presence of this structure allows space and cushioning for organs, provides the roundworm with a hydraulic skeleton, and aids in the distribution of food from the digestive tract to the other cells of the worm.

Several human parasites are roundworms. Many people in tropical countries are infected with hookworm. Immature stages of this parasitic worm burrow through the skin, travel through the blood vessels to the lungs, enter the air spaces of the lungs and crawl into the esophagus. The immature stage is then swallowed. The worm attaches to the intestine with hooks and matures into an adult. Fertilized eggs are released with feces, and the zygotes develop into immature stages on soil. When people walk barefoot over the soil, they become infected. The mature hookworm drinks blood and lymph juices. They cause anemia due to blood loss.

The human roundworm is common where human feces is used as plant fertilizer. People ingest eggs when they eat plant material. The immature stages travel through the human body in blood vessels. Mature human roundworms live in the intestine where they produced eggs that are released with feces.

People can become accidentally infected with the trichina worm by eating undercooked port. The muscle of pork may contain immature stages of trichina worm. When people ingest the larval stage, it matures in the intestine where the adult worms reproduced. Immature stages migrate from the intestine to muscle tissue. There the larva forms a cyst. Since humans aren’t generally eaten, the cysts become coated with calcium carbonate. This causes muscle stiffness. We call this condition trichinosis.

The Advantages and Disadvantages of Roundworms

Outline the advantages and disadvantages of roundworms

Roundworm parasites affect most species of animals and plants, making them important agricultural pests. There are also several species of roundworms that live in humans, some nasty, some not. Here are a few...

§     Trichinella spiralisis alsoa parasite that has been around for a while, since it has probably been responsible for several cultures long-standing dietary laws.Trichinellacan be found around the world, more in temperate zones than the tropics, mostly in various animals that eat meat, from rats to bears. Humans most common exposure comes from pork, and pigs commonly pick it up from eating rats. These worms can live as juveniles in muscle and other tissues while adults occupy support tissues and the lymphatic system. A new host becomes infected by eating tissue containing juveniles. Juveniles become adults and mate in the new hosts intestines, then females bore out of the intestines, which can cause a wide range of serious symptoms, settle someplace and begin to release juveniles, which migrate all over the body, causing damage as they go, until they mostly coil up in muscle tissues and "wait" for the host to be eaten by a new host.

§     Hookworms infecta variety of mammals, with species in cows, dogs, cats, and others, as well as humans. Hookworms are fairly host-specific - worms of non-human hosts cant live long in a human. You definitely dont want to catch one of the hookworms specific to humans, though. They have a very unusual habit for worms that live in the intestine: instead of living on all of the food around them, they bite through the intestinal lining and live on blood. Serious infections occur when bacteria from the intestines get into the surrounding tissues and/or the blood, and heavy infections can produce enough blood loss to cause anemia. Its no wonder that one genus is called

§     Necator, or "killer"! Hookworm eggs pass in feces, and juveniles live for a while in the soil if its nice and wet. The worms get into the next host either by latching on and boring through their skin, or sticking to paws and getting licked off. If they come in through the skin, they get into the blood and migrate to the intestines, usually by way of the lungs, sometimes causing tissue damage as they go.Hookworms for non-human hosts that penetrate human skin by mistake can wander under the skin, unable to penetrate further, but the body reaction to them can cause a condition sometimes called creeping eruption.

§     Ascaris is an impressively large worm, up to 50 centimeters long and about as thick as a pencil, that lives in human intestines, with maybe as much as a quarter of the worlds population infected. They are taken in as accidentally-swallowed eggs, hatch in the intestine, and the juveniles bore out, get into the blood, wander the body (where they can cause problems), emerge in the lungs, grow there for a while (and possibly cause problems), then migrate up to be swallowed and get back to the intestines again, where they mate. Females find males by touch (its dark in an intestine) and crawl into the males hooked tail for mating; sometimes they mistake the opening of the ducts from the liver or pancreas for a males tail and get caught, blocking the flow of digestive juices. A heavy infection can produce aknot of worms that blocks movement of materials through the intestine. Females that cant find males have been known to migrate up or down the canal, reaching the nose or anus in some cases - quite a surprise for the host! Females lay eggs that pass in feces. The eggs can remain infective in the environment for years, long after that fecal material has been broken down. Dirty hands in the mouth explains why children are the most common hosts for these worms.

§     Filarial worms are a group of roundworms that commonly use biting insects to get juveniles from host to host, then the adults live in the fluid systems - blood or lymph systems - of the final host. There are several filarial worms that infect humans, including Wuchereria,which can block fluid drainage through the lymph system, causing gross swelling of tissues and a form of elephantiasis.

§     Onchocerca causes a disease called river blindness when juvenile worms enter and gradually damage the eyes (the "river" part is due to the biting fly carriers being tied to rivers for breeding, restricting the geographical range of the disease).

§     Heartworms are filarial parasites of dogs and cats. The juvenile worms are carried by mosquitos, and the adults settle in the chambers and major vessels of the heart. Heartworms do not generally infect humans.

§     Dracunculus medinensis, also called guinea worms, have been known and written about for centuries (although often called "serpents" in modern translations), including passages from Ancient Greek scholars and from the Bible. Adult worms can be as long as a meter, although they are very thin. As adults, they live in the tissues under the skin, usually somewhere at and below the hips, where they may be visible as a white line. After mating, a female produces huge numbers of eggs that hatch inside her and begin to migrate out into the surrounding tissue, often causing an allergic reaction with inflammation and ulceration of the skin (some ancient texts call them the "fiery serpents" from their effects on the skin). When the skin breaks, many many tiny juvenile worms may emerge. An opening remains in the skin through which the female will continue to release young. To continue their life cycle, the juvenile worms must get into open water and infect a tiny crustacean; for this reason, worms are most active when the skin is wet.Ancient treatments, still used in some places, involve cutting a thin slot in a stick, wetting the skin so the worm sticks out, catching the writhing worm in the sticks slot, then winding it slowly out from under the skin. The medical symbol, the caduceus,of a snake or snakes wrapped around a pole,most likely is taken from one of the few effective devices ancient doctors had, a worm-removal stick (worm, snake; remember, in ancient classification schemes not much distinction was made among long wriggly things). Worms infect the next host when water containing infected crustaceans is drunk; the juveniles leave their carriers in the intestine, bore out of the intestine and migrate to their position under the skin. Humans are affected both by their allergic reactions to the released juveniles, infections from bacteria that enter through the broken skin, and worms that stall in deeper tissues, where they may cause serious damage. Because there is a fairly simple preventative measure - physically filtering drinking water -this parasite is very close to being eliminated.

 

Phylum Annelida

General and Distinctive Features of the Phylum Annelida

Explain general and distrinctive features of the phylum annelida

Characteristics of Annelida:

§     Bilaterally symmetrical and vermiform.

§     Body has more than two cell layers, tissues and organs.

§     Body cavity is a true coelom, often divided by internal septa.

§     Body possesses a through gut with mouth and anus.

§     Body possesses 3 separate sections, a prosomium, a trunk and a pygidium.

§     Has a nervous system with an anterior nerve ring, ganglia and a ventral nerve chord.

§     Has a true closed circulatory system.

§     Has no true respiratory organs.

§     Reproduction normally sexual and gonochoristic or hermaphoditic.

§     Feed a wide range of material.

§     Live in most environments.

Structure of Organism under the Phylum Annelida (Earthworm)

Describe structure of organism under the phylum annelida (Earthworm)

The Annelida are a medium sized phylum of more than 9,000 species of worms. Most species prefer aquatic environments, but there are also a number of well know terrestrial species. Only a few species of annelids are commonly known to human beings, these include the delightful Rain, Dew or Earthworms that work so hard to make our soils healthy, the Ragworms and Lugworms used by marine fishermen and the much smaller Tubifex or Red worms used by aquarists to feed their fish. In many countries people are still familiar with Medicinal leeches, and people who live closer to nature are naturally more familiar with a much wider range of Annelids than those who live in cities.

Annelids range in size from the Giant Earthworms, of which Michrochaetus rappi (Michrochaetus michrochaetus) is the largest, this magnificent animal has an average length of 1.36 m (54 ins) and a record breaking specimen has been recorded that measured 6.7 metres (22 ft) in length, it was 2cm (0.8 ins) in diametre. Larger worms have been reported but not scientifically proven. The smallest Annelid known to science is Chaetogaster annandalai which is full grown at 0.5 mm (0.02 ins).

Annelids have two main modes of existence, they either live rather quietly in holes or they live more active lives. The basic Annelid body plan is one of a head followed by a long thin body of numerous similar segments ending in a small tail. The head consists of a mouth (prostomium) and sometimes a peristomium, and the tail is more correctly called a pygidium, as it is not really a tail. Annelids are coelomate animals meaning they have a true coelom within their body. They have sets chaetae attached to each body segment, and these can be simple and small as in the Earthworms or complex and varied as in many Polychaetes. The head is often reduced and difficult to distinguish in the hole living species, but may be easily recognised, with eyes and other sensory devices in those species living a more active life.

Annelids are coelomate animals (meaning they have a true coelom, even if this is reduced secondarily). They normally have long thin bodies composed of a series of identical segments. These segments lie between the head, comprised of a prostomium, a mouth and sometimes a peristomium, and a tail called a pygidium. Growth occurs both laterally, by enlargement of the segments during the juvenile stages, and through the addition of new segments. New segments are produced by the foremost section of the pygidium. In some species they are produced throughout the animals life but in many species production stops once a certain set number of segments has been achieved.

Advantages and Disadvantages of Lumbricus (Earthworm)

Explain advantages and disadvantages of lumbricus (Earthworm)

Despite the amazing and delicate beauty of polychaetes such as the Fan Worms, and the huge (really beyond estimation) economic debt owed by mankind to the Oligochaete Earthworms for their work in soil creation and maintenance many people still fail to appreciate their true wonder and beauty.

The earthworms, of which there are many species, are exceedingly important in soil creation, particularly in temperate areas. Without them, agriculture and perhaps the whole of human society as we know it would never have evolved. Like so much of the unnoticed invertebrate world earthworms are essential to our very existence. In marine environments the numerous species of Polychaetes play a fundamentally important role in the maintenance of food chains and the whole ecological balance of the seas, thus supporting the seemingly endless stocks of fish we like to eat.

One of the strangest ways that humans relate to Annelids is in the hobby of 'Worm Charming'. This involves enticing earthworms from their holes (catching them), originally it was a means of acquiring worms for bait, but now-a-days it is a sport. The world record as far as I know is held by Tom Shufflebotham who charmed 511 worms from their underground hideouts from an area of 3 square metres in only 30 minutes during the 1980 Annual Worm Charming Championships held in Cheshire UK. The rules specify that the worms must be brought to the surface without using refreshment, stimulation, drugs or digging. Tom used a method called twanging which involves sticking a 4-pronged pitchfork into the ground and twanging it.

 

Phylum Arthropoda

General and Distinctive Features of the Phylum Arthropoda

Explain general and distinctive features of the phylum arthropoda

Phylum Anthropoda has more species than any other phylum. An 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 the 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.

Classes of the Phylum Arthropoda

Mention classes of the phylum arthropoda

Classes of the Phylum Arthropoda include:

§     Class: Crustacean

§     Class: Insecta

§     Class: Chilopoda

§     Class: Diplopoda

§     Class: Arachnida

Examples of Organisms under each Class of the Phylum Artropoda

Cite examples of organisms under each class of the phylum artropoda

Examples of Organisms under each Class of the Phylum Artropoda include:

§     Class Crustacean:Crustacea is a class of organisms whose bodies are covered by a hard shell called carapace.Examples of crustaceans are woodlice, water flea, Cray fish, crabs, lobsters, shrimps and barnacles.

§     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.

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

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

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

Distinctive Features of each Class of the Phylum Arthropoda

Explain distinctive features of each class of the phylum arthropoda

Distinctive features of Class Crutacean

§     Crustacea are mainly found in marine and fresh water thus they occupy aquatic habitats

§     Their gaseous exchange is by means of gills or through the body membrane

§     Their bodies are divided into two main parts: the head and thorax are fused to form a Cephalothorax the second part is the abdomen

§     They have a pair of compound eyes each on a raised stalk

§     They have two antennae

§     They have four pairs of mouthparts namely maxilla, mandible, labium and labrum

§     They have five pairs of limbs that are modified for swimming

Distinctive features of Class Insecta

§     Insets have three body parts namely the head, thorax and abdomen

§     They have one pair of antennae

§     They have a pair of compound eyes. In some cases simple eyes are also present

§     They have three pairs of walking legs per segment of the thorax

§     Most insects have one or two pairs of wings on the second or third segment o the thorax. Some insects have no wings

§     They breath by means of air holes called spiracles and carry out gaseous exchange through the tracheoles of the tracheal system

§     They undergo complete or incomplete metamorphosis with a larva stage

§     They mainly occupy terrestrial habitats

Distinctive features of Class Chilopoda

§     Centipedes have a clearly defined head while the rest of the segments are similar

§     They have a pair of antennae

§     They have one pair of mouthparts known as mandibles

§     They have simple and compound eyes, although some lack compound eyes

§     They have a pair of legs in each body segment

§     They carry out gaseous exchange by means of tracheoles of the tracheal system

§     They feed on insects and worms

§     They occupy terrestrial habitats

§     They have one pair of poison claws

Distinctive features of Class Diplopoda

§     Millipedes have a clearly defined head. All the other body segments are basically similar

§     They have one pair of antennae

§     They have one pair of mouthparts namely, the mandibles

§     They have simple and compound eyes, although some lack compound eyes

§     They have two pairs of legs in each body segment

§     They carry out gaseous exchange through tracheoles of the trachea system

§     They feed on plants

§     They inhabit terrestrial habitats

§     They have a cylindrical body

Distinctive features of Class Arachnida

§     Arachnids have two body parts. The head and thorax are fused to form cephalothorax or prosoma, the abdomen is referred to as opithosoma.

§     They do not have mouthparts. However they have one pair of appendages for sensing prey and another pair for capturing the prey

§     This pair of appendages is known as chelicerae. Thus they have a carnivorous mode of feeding

§     They have simple eyes

§     They have four pairs of walking legs

§     They carry out gaseous exchange by the lung book or trachea

§     A lung book consists of folds of ectoderm with slit like opening on the surface of the abdomen

§     Arachnids do not have wings

§     They inhabit terrestrial habitats

Structures of Representative Organisms under each Class of Phylum Arthropoda

Describe structures of representative organisms under each class

Structures of Representative Organisms

The Advantages and Disadvantages of the Organisms under each Class of Phylum Arthropoda

Explain the advantages and disadvantages of the organisms under each class of phylum arthropoda

IMPORTANCE OF CRUSTACEANS

§     Human beings use crustaceans as food especially lobsters, shrimps, crabs and crayfish

§     Some of them are used for decorations in the homes especially crabs and crayfish

§     Most crustaceans attract tourists during their visits especially along the beaches

IMPORTANCE OF THE CLASS DIPLOPODA

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

IMPORTANCE OF INSECTS

§     Most insects are naturally useful in pollination e.g. bees and flies

§     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

§     Some insects like termites and earthworms help to turn the soil over and so keep it lose and aerated

§     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.

IMPORTANCE OF ARTHROPODA

§     They cause damage to crops and forestry, locusts and some larvae e.g. feed on crops

§     They spread diseases to humans and other domestic animals e.g. female anopheles spreads malaria, while tsetse flies spread sleeping sickness

§     They are source of food e.g. green grasshoppers, termites, crabs and shrimps

§     They cause damage to household materials e.g. cockroaches damage furniture

§     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 and Distinctive Characteristics Features of the Phylum Chordata

Explain general and distinctive characteristics features of the phylum chordata

General Distinctive Characteristics of Phylum Chordata are:

§     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

§     Their nerve cord is hollow and placed dorsally to the gut

§     They have gill slits at least during the embryonic stage

§     They have tail which is behind the anus

Classes of the Phylum Chordate

Mention classes of the phylum chordate

The phylum chordata consists of six classes which are

§     Class Chondrichthyes

§     Class Osteichthyes

§     Class Amphibia

§     Class Reptilia

§     Class Aves and

§     Class Mammalia

Distinctive Features of Each Class of the Phylum Chordata

Explain distinctive features of each class of the phylum chordata

Distinctive features of Class Chondrichthyes

§     The skeleton is made up of cartilage

§     The body is covered with placoid scales

§     The caudal fin has tow lobes that differ in size

§     Each pair of gills is in a separate compartment

§     The mouth and two nostrils are ventrally placed

§     Males have Copulatory structures called claspers

Distinctive Features of Class Osteichthyes

§     The skeleton is made up of bones

§     The body is covered with ganoid scales

§     The mouth is terminally placed and nostrils are forced on the dorsal surface

§     All pairs of gills are found in common chamber and the chambers are covered by an operculum

§     The caudal fin has loves of the same size

Distinctive Features of Class Amphibia

§     Their skin is always moist example frogs

§     Their life cycle involves larva form called tadpole

§     They have gills which are present in the early stages of the development of the tadpole

§     They have a heart which has three chambers

§     There is gaseous exchange by gills in the tadpole and in the adult it takes place in the lungs, skin and the mouth lining

Distinctive features of Birds

§     The body is covered with feathers

§     The anterior pair of limbs is modified into wings

§     The mouth is modified into a beak or bill

Distinctive features of Class Mammalia

§     Their body is covered with hairs

§     They have mammary glands

§     They have teeth of different types and shapes

§     They have diaphragm

§     Their red blood cells have no nucleus

§     They have sweat glands. The body temperature of mammals is constant

Structure of Representative Organisms in each Class of Phylum Chordata

Describe structure of representative organisms in each class of phylum chordata

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.

Example of Specimen found on Class Chondrichthyes

Example of Specimen found on Class Chondrichthyes

Example of Specimen found on Class Aves

Example of Specimen found on Class Mammalia

Example of Specimen found on Class Reptilia

The advantages and disadvantages of Organisms under each Class of Phylum Chordata

Outline the advantages and disadvantages of organisms under each class of phylum chordata

Importance of Amphibians

§     They are ecologically important

§     They are used in research specimen

§     Some amphibians are eaten as food

§     Some amphibians have unique features. Example abnormally big sizes attract tourists

§     They have typical characteristics of larger animals hence they are among the most preferred specimens for biological studies

Importance of Class Reptilia

§     Reptiles act as attractive features e.g. colour of snake

§     Reptiles are used as a source of food for other species example birds feed on snakes

§     Reptiles are used in decorations in houses

Disadvantages of Class Reptilia

§     Can cause death to human beings, for example a snake

Importance of Birds

§     Flesh of several species is used as food for human beings example chicken, duck

§     The feathers of birds are used for decorations

§     Birds are also used for the pollination of seeds and fruit dispersal

§     Some birds like Ostriches are attractive to tourists

§     Some species of birds are used for biological control

Importance of Mammals

§     Most mammals serve as source of food for human beings example cows, sheeps

§     Mammals help in production of manure example manure from cows, goats

§     The bones of mammals are used for production of animal charcoal

§     Most wild animals in national parks and game reserves attract tourists

§     Some domestic mammals such as cows and donkeys are trained to perform human duties such as cultivation of crops