2.0 BIODIVERSITY 2.1 Classification in biology There are millions of organisms on earth. It is impossible to name them easily without putting them into groups. This is called classification. Biologists try to classify living things in a meaningful way. They also look for patterns that may help them to explain the great diversity of life on earth and how organisms are related to each other. In 1753, the Swedish naturalist, Carolus Linnaeus, inverted a system of classification, based on structural similarities, which is still useful today. Living things are first divided into a few kingdoms, e.g. the plant and animal kingdoms. Within each kingdom, the organisms are further classified into several phyla (singular: phylum) or divisions in the case of plants. Each phylum consists of organisms that are basically similar although their similarities may not be obvious at first sight. The phylum is made up of classes and classes of orders. Within each order are the families. In the families of a varying number of genera (singular: genus) and each genus usually has several species. As we go down the scale of classification in this way, we will find that the resemblance between the organisms becomes much closer. For instance, it is easy to distinguish one family from another. It is also easy to separate the different genera but different species may be more difficult to separate. The sub-phylum vertebrata or vertebrates is divided into five classes namely Pisces (fish), Amphibia (amphibians), Reptilia ( reptiles), Aves (birds) and Mammalia ( mammals). 2.2 Binomial system of Naming Species The common name given to an organism may vary in the different parts of the world. This can cause confusion. Linnaeus used Latin, to give two names for each organism. This procedure of naming is called binomial system. The first name refers to the genus to which the organism belongs. It always starts with a capital letter. The second name is the species name and it starts with a small letter. For example, the domestic cat belongs to the genus Felis and the species domestica. Therefore its scientific name is Felis domestica. The dog is called Canis familiaris. 3.1 How do we classify organisms today? Most biologists recognize five kingdoms of living organisms and these are: Prokaryotae – the bacteria Protoctista- A collection of single- celled organisms and some simple multicellular ones like seaweeds. Fungi- the mushrooms, toadstools, moulds etc. Plantae- the green plants Animalia- the animal kingdom In addition there are viruses- the smallest. They are on the borderline between the living and non -living world. 3.2 Example of classification of a lion 3.4 EXAMPLES OF SOME ORGANISMS FROM EACH OF THE FIVE KINGDOMS 3.5 KINGDOM PROTOCTISTA These are single-celled (unicellular) organisms which have a nucleus and it contain chromosomes (DNA). The kingdom is subdivided into PROTOPHYTA (unicellular ‘plants’ which contain chloroplasts for photosynthesis) and PROTOZOA which are unicellular ‘animals’ in that they take in (ingest) and digest solid food. 3.6 Major examples of Protoctista 3.7 Phyla Example Characteristics 3.8 SUBKINGDOM PROTOZOA Highly successful and diverse group of organisms, there are over 50,000 known species, found in all environments where water is present. STRUCTURE OF AN AMOEBA Unicellular No tissues Specialized parts of protoplasm form organelles Amoeba (Class Rhizopoda) moves by constantly changing shape. Its cytoplasm pushes out into pseudopodia (false feet) which are also used for feeding. NUTRITION In amoeba pseudopodia push out and engulf bacteria and other microorganisms. Vorticella, another protozoan feeds by creating a current of water with its cilia which brings food particles to the cell. - They ingest small particles of food, such as bacteria and other small beings. - The food is engulfed with a little of the surrounding water to form a food vacuole. - The food is digested by enzymes which pass in to the vacuole from the surrounding cytoplasm. - The products of digestion are absorbed by the cytoplasm and indigestible materials discharged to the outside. REPRODUCTION Protozoa reproduce by binary fission, where the organism divides into two. The nucleuses divide first, then the rest of the cell, forming two identical daughter cells. Each daughter the feeds and grows to maximum size. . VIRUSES The name ‘virus’ which is Latin for poison was first used in 1852 by a Russian Botanist D.J. Ivanovky who first discovered them although he couldn’t actually see them as they are the smallest. - There are many different types of viruses. - Viruses vary in shape and size. - Some live in the cells of animals or plants and there are even viruses that infect bacteria. - Viruses are much smaller than bacteria cells. - Viruses are less than 0.0005mm in diameter and 0.001mm in length. - Virus structure can only be seen with electron microscope at magnification of about 30,000. STRUCTURE - The structure of a virus is very simple and is not cells. - They all have a central core of DNA or RNA surrounded by protein coat. - The protein coat is made up of regularly packed protein units called capsomeres, each containing many protein molecules and the protein is coat is known as capsid. - They do not have a nucleus, cytoplasm, cell organelles or cell membrane. The DNA or RNA in the centre acts as the nuclear material. - Virus is the only one which has RNA acting as the genetic material. - In all other organisms DNA acts as the genetic material. NUTRITION - Viruses do not feed, respire, excrete, grow or respond to their environment. - The only characteristic of living things they have is reproduction and they can only do this parasitically. REPRODUCTION - Viruses reproduce by entering the host cell and taking over the host’s genetic machinery to make more virus particles. - If a virus reaches near a suitable host cell it sticks to the cell membrane of the host cell. - In some case the whole virus will enter the host cell. - In others only the RNA particle enters in to the cytoplasm of the host cell. - In the case where it enters the host cell, the protein coat breaks and releases the genetic material in to the host cell cytoplasm. - The genetic material directs the host cell to make more genetic material for the virus and to form new protein coat surrounding each of the newly formed RNA or DNA. - After many virus particles have been formed, the host cell dies and the particles are released to infect more cells. BACTERIOPHAGE VIRUS - In bacteriophage virus (a virus which attacks bacteria) the virus attach to the bacterial wall. - After attaching to the bacterial wall the bacteriophage virus injects its DNA or RNA in to the bacterial cytoplasm. - The DNA of the virus takes control of the bacterial cell and makes it produce virus proteins and DNA, instead of bacterial proteins and destroy the bacterial cell wall and comes out and may attack more cells. Some examples of diseases in humans which are caused by viruses are: Influenza ( the flu) ; common cold; small pox; measles; mumps; rubella ( German measles); poliomyelitis (polio) ; Yellow fever etc. Types of viruses BACTERIA - Are very small single celled organisms. Most bacteria are between 0.0005mm and 0.002mm in diameter and they rarely exceed 0.01mm in length. STRUCTURE - There are three distinct shapes of bacteria, rods (bacilli), spheres (cocci) and spirals (spirilla), but they all have similar internal structures. STRUCTURE OF BACTERIA Generalized diagram of a bacterium Types of bacteria - All bacteria are surrounded by a cell wall that protects the bacterium and keeps the shape of the cell. Bacteria cell wall contain neither chitin nor cellulose, instead they are composed of complex chemicals made up of polysaccharides and proteins. Some species have another layer out side the cell wall, called a capsule or slime layer. - Underneath the cell wall is the cell membrane. The middle of the cell is of cytoplasm. Bacterium has no nucleus. Its genetic material (DNA) is a single chromosome or nucleoid, loose in the cytoplasm, forming a circular loop. Some bacteria can swim and are propelled through water corkscrew like movements of structures called flagella. Many bacteria do not have flagella and cannot move by themselves. Other structures present in the cytoplasm are plasmids. Plasmids are circular rings of DNA carrying genes which give the bacteria protection against antibiotics (antibiotic resistance), or allow it to use a wider range of nutrients. Not all bacteria contain plasmids. NUTRITION - Few species of bacteria contain chlorophyll like pigment for photosynthesis. - Most bacteria are saprophytic. - Saprophytic bacteria produce and release enzymes which digest food outside the cell and then the products of digestion are absorbed in to the bacterial cell. - Some bacteria are aerobic while others are anaerobic. REPRODUCTION - Bacteria reproduce asexually by binary fission. - Bacteria cell simply divide in to two cells and each of them develop in to individual bacteria. THE PROCESS OF BINARY FISSION - First of all a cell grows until it has doubled its length. - The chromosome is then copied in a process called replication. - The two copies separate to opposite ends of the cell and the cell membrane folds inwards to form double layer across the middle of the cell. - Two new cell walls are then made in between the two membranes. - Plasmids also replicate themselves. - Each daughter cell receives copies of the plasmids too. - The two daughter cells then separate and grow until they are ready to divide again. - Under good conditions this process can happen very quickly. - Bacteria can divide in to two every twenty minutes. - During unfavorable conditions bacteria undergo multiple fission. - The nuclear strand divides in a number of fragments and each of them is surrounded by a bit of cytoplasm and produces cell walls and develops in to bacteria during favorable conditions. - Bacteria can be killed by high temperatures (50 °C and above), but some can produce spores which are resistant. FUNGI . - Familiar organisms are mushrooms, toad stools, puff balls and the bracket fungi, which normally grow on the tree trunks. - The mould fungi which grow on bread, cheese, fruits and other foods are known as rhizopus. STRUCTURE OF ANY FUNGI - The basic unit of a fungus is a hypha. Hypha is not a cell, they are microscopic threads. The branching hyphae spread through the material on which the fungus grows and absorb food from it. The net work of hyphae that grow over or through the food material is called mycelium. In some species of fungi there are incomplete cross walls dividing the hyphae in to cell like regions, but the cytoplasm is free to flow through the pores in this walls. The hyphal wall is made up cellulose or chitin or both. Cytoplasm fills the tips of growing hyphae, but in older regions there may be central vacuole. Many very small nuclei are present in the cytoplasm. NUTRITION - Fungi are either saprophytic or parasitic. - Saprophytic fungus secretes enzymes in to the organic matter which digest it to liquid products. - The digested food are then absorbed back in to the hyphae and used for energy or for the production of new protoplasm or hyphal walls. - Parasitic fungi are the principal disease causing organisms in plants. REPRODUCTION a. ASEXUAL REPRODUCTION - After establishment of mycelium long hyphae stolons grow out from the mycelium. - At first it grows in to the air and then bends over and touch the food material again. - A stolon is a horizontal stem which may lie on the surface of the soil. - After touching the food material the stolon make a number of branching hyphae which may penetrate in to the material and may absorb nutrients. - At the same time some vertical hyphae grow out and their ends become swollen. - The swelling is known as sporangium. - In the sporangium each nucleus will be surrounded by a little bit of cytoplasm and becomes a spore. - Spores are single celled and dispersed in air currents or by other methods. - When the spores are mature the sporangium wall breaks open, liberating the spores. - When a spore lands on a suitable organic matter it germinates to produce mycelium. b. SEXUAL REPRODUCTION - Two short hyphal branches grow out and meet each other. - Where they meet, the ends swell and are cut off from the rest of the mycelium by cross walls. - The nuclei within the swollen body divide repeatedly. - The walls between the two swollen hyphae break down and the contents mix and a zygospore forms. - In the zygospore the nuclei pair up and fuse and the cytoplasm mix. - The zygospore becomes thickened. - Connecting hyphae shrivel (shrink), leaving the zygospore to germinate into a new hyphae. ALGAE - Range in size and shape from unicellular types like diatoms to the sea weeds, which include some of the largest living plants. Algae are generally either marine or fresh water plants, though some live in the soil, on the barks of trees or in unusual habitats like hot springs, salty lakes etc. STRUCTURE OF SPIROGYRA - In green algae like spirogyra, chlorophyll is the only pigment present. Spirogyra is common on the surface of ponds, where it forms a tangled mass of threads with air bubbles in between. It feels slimy to touch. The plant is a filament, many cells long, but only one cell thick. The wall of cellulose. A large vacuole filled with the cell the cell sap occupies much of the cell and most of the cytoplasm is pressed against the cell wall. One or more chloroplasts are embedded in the cytoplasm. NUTRITION - Produce their own food by photosynthesis. REPRODUCTION - Vegetative reproduction is common in spirogyra and consists of part of a filament breaking off and continuing to live as a separate plant. - Occasionally a type of sexual reproduction called conjugation occurs between filaments lying side by side. - First out growths appear on the walls of cells lying opposite one another. - These then meet and where they touch the cell wall disappears so that a conjugation tube joining the two cells is formed. - While this has been going on, the protoplasm in each of the cells forms in to a mass called a gamete. - The gamete of one filament passes through the conjugation tube and joins the gamete of the other filament. - The nuclei unite and the whole mass of protoplasm becomes oval and surrounded by a thick brown wall. - This is called zygospore. - After a short rest, the wall of the zygospore bursts and a new spirogyra filament grows out. ARTHROPODA - Arthropods include an incredibly diverse group of organisms such as insects, crustaceans, spiders, scorpions and centipedes. There are far more species of arthropods than species in all other phyla combined. Members of the phylum have been responsible for the most devastating plagues and famines, man kind has known. Yet other species of arthropods are essential for our existence. STRUCTURE OF AN ARTHROPOD - Arthropods are bilaterally symmetrical, with strongly segmented bodies. Segments affect both external and internal structure. - Some segments are fused to form specialized body regions, the head, thorax and abdomen. The body is covered with an exoskeleton made up of chitin. Primitively, each body segment bears a pair of segmented (jointed) appendages. In all living arthropods, many of these appendages are dramatically modified, or even lost. Arthropods grow by moulting their exoskeleton in a process called ecdysis. Movement of appendages is controlled by a complex muscular system. Cilia are not present. Most arthropods have a pair of compound eyes. Most of the body cavity is open haemocoel or space filled loosely with tissue, sinuses and blood. The circulatory system is open and consists of heart, arteries and the open space of the haemocoel. The gut is complete. Gaseous exchange takes place through the body surface and or by means of gills trachea or book lings. NUTRITION - Arthropods are heterotrophic. - Arthropods have become adapted to a greater range of diets. - Appendages, especially those just and behind the mouth are utilized in many different modes of feeding. REPRODUCTION - Most arthropods are dioecious and have paired reproductive organs (ovaries and testes). - Fertilization is internal in most but not all groups. - Most lay eggs and development often proceeds with some form of metamorphosis. MALARIA Malaria is a serious disease and is caused by a protozoa (single celled organism) called plasmodium. This organism is passed from one person to another by the female anopheles mosquito. THE LIFE CYCLE OF ANOPHELES MOSQUITO The female anopheles mosquito lays eggs on the surface of stagnant water. After about 3 days the eggs hatch into larvae. The larvae live just under the surface of the water, feeding and growing there. They obtain oxygen by spiracle tubes leading to the surface of the water. The larvae live for about three (3) weeks and then form pupae, which also live just under the water surface. Inside the pupae the tissues of the larvae are broken down and reassembled into those of the adult insect. After about three (3) days the pupa case opens and the adult insect emerges. The adult lives on land usually in shady vegetation and in the dark corners of houses. Feeding The egg contain food stores inside it e.g. yolk, to provide nourishment before hatching. The larva filters the water to take in microscopic plankton. The pupa has no active feeding; nourishment comes from food stored within its tissues. The adult is a liquid feeder. The male feeds on plant sap while the female anopheles mosquito only feed on blood. Life cycle of the plasmodium 1. In the gut of the mosquito there are male and female sex cells obtained during feeding on the blood. 2. The gametes fuse to form a zygote. 3. The zygote enters the gut wall. 4. The zygote produces a cyst. The cyst divides to form sporozoites. 5. The sporozoite invades salivary glands of the mosquito. 6. The sporozoites are then injected into the human bloodstream during feeding. 7. Once in the human blood sporozoites invade the liver cells. They then divide and form merozoites. 8. Merozoites divide in the liver to form more merozoites. 9. Some merozoites will be released into the blood stream where they invade red blood cells. In the red blood cells they multiple to form more of the merozoites. 10. Eventually in red blood cells some merozoites develop into female and male sex cells. 11. The sex cells will be taken by another hungry female anopheles mosquito during feeding. 12. The cycle will then repeat as above. Symptoms of malaria Malaria is characterized by periods of intensive fever and intensive shivering, tiredness, aching and vomiting may occur. The disease follows a cyclical pattern. Cold stage Shivering and chattering of the teeth and last for 1-2 hours. It follows the release of parasites into the blood. Hot stage The person feels very hot and the body temperature may rise to about 40℅. There is also a rapid pulse and breathing rate increase, severe headaches, and general discomfort lasting for 3 to 4 hours. Sweating stage There is profuse sweating for 2 to 4 hours. The patient’s temperature falls below normal and feels exhausted. After this, there is a period of relief with no major signs or symptoms until the on set of the next attack. The patient will experience fever 2 to 3 days later depending on the type of malaria. Prevention and control Use of drugs Parasites inside the human body can be killed by the use of drugs such as chloroquinine. This is used to treat malaria and can also be used for prophylaxis i.e. prevent malaria from occurring before visiting malarial areas and those staying in those areas. The drug is taken even after visiting the area for about 4 weeks. Even so, the drugs do not always work to prevent malaria occurring. Some forms of the plasmodium are becoming resistant to the drugs. Use of insectides Residual insecticides can kill adult mosquitoes by spraying on the dark corners of the house. Residual insecticides include DDT or Malathion. DDT is not recommended in most countries but there are still a few poor nations in Africa using it. A residual insecticide is the one which continues to work for several weeks or months. The insecticide will kill the adult mosquito. Other commonly used insect ides are doom, etc. mosquito repellents should be used such as peaceful sleep and mosquito coils. Use of oil Oil can also be sprayed in stagnant water to kill the larva by preventing them from respiring. Draining stagnant waters This will break the life cycle of the mosquito as no breeding site. Irrigation can also help the water to flow continuously and mosquitoes can not lay eggs, wash away larvae or pupae. Keeping the environment clean Getting rid of empty containers which could collect rain water and become a breeding site for the mosquito, even a beer can is enough for a mosquito to breed. Biological control The world health organization (WHO) is also keen on developing methods of biological control. This is whereby one organism is used to reduce the number of the pest organism. In the case of mosquito, gambusia fish can be bred and released into stagnant water. It produces a poisonous chemical substance which kills the larvae. These methods are less harmful to the environment and other organisms than insecticides. Research is also being carried out to produce a vaccine against malaria, although this takes some time. Wearing protective clothing On personal level, people in malarial areas must take precautions not to be bitten. They should wear long sleeves and trousers. Use of mosquito nets People in malarial areas should avoid to be bitten by sleeping under mosquito nets. This prevents the mosquito from picking the parasites and passing it to another person. VERTEBRATES - Are animals which have a vertebral column? Are divided in to five classes, fish, amphibian, reptile, birds and mammals. STRUCTURE STRUCTURE OF A VERTEBRATE - Have internal skeleton of bone or cartilage. They have gill slits, which are later replaced by lungs, except in fish, at some stage during their life time. Have single hollow dorsal nerve cord. Have closed blood system. Have hearts in the ventral position. ( for invertebrates it is dorsal ) Body is bilaterally symmetrical. Body has three regions, head, trunk and tail. Head contains brain, eyes, auditory (hearing) and olfactory (smelling) organs. The trunk encloses heart, digestive, respiratory, excretory and reproductive organs. Trunk has two pairs of limbs or fins. Trunk encloses the body cavity called coelom. NUTRITION - Vertebrates are heterotrophic. - They have well developed digestive tracts. - Have become adapted to a wide range of diets. REPRODUCTION - Vertebrates reproduce sexually. - They have well developed reproductive organs.
