Diversity of Organisms.docx

Diversity of Organisms Classification helps us to organise the complex and diverse range of life on earth, grouping them in many ways, such as shape, size, or colour. The ‘Five Kingdom system of Classification’ is the preferred method of classification. Kingdom 1 – Monera (Bacteria) Examples - Esche...

Diversity of Organisms Classification helps us to organise the complex and diverse range of life on earth, grouping them in many ways, such as shape, size, or colour. The ‘Five Kingdom system of Classification’ is the preferred method of classification. Kingdom 1 – Monera (Bacteria) Examples - Escherchia coli - Treponema pallidum - Staphylococcus aureus - Cyanobacteria Characteristics - They are all unicellular - They do not have a nucleus - They have no membrane-bound organelles - They have three main shapes: rods, spheres and, spirals Kingdom 2 – Protista (Protoctista) Examples - Amoeba - Paramoecium - Euglena - Algae Characteristics - They have DNA in a membrane-bound organelle called the nucleus - They have other membrane-bound organelles - They are mostly unicellular - Mostly aquatic Kingdom 3 – Fungi - Mushrooms - Rhizopus - Athlete’s Foot - Mould - Yeast Characteristics - A cell wall made of chitin - The cells have a large permanent vacuole - Their cells have no chloroplasts - They are all heterotrophic Kingdom 4 – Plantae (Plants) Examples - Ferns - Spruce Trees - Daffodils - Roses Characteristics - They have cell walls made of cellulose - They contain a large permanent vacuole - They contain chloroplasts Kingdom 5 – Animalia (Animals) Examples - Lizards - Birds - Mammals - Insects - Frogs Characteristics - They are multicellular - They have no cell wall - They have no chloroplasts - They have no large permanent vacuole - They are either vertebrates (have a backbone) or invertebrates (have no backbone) Distribution of bacteria and fungi in nature - Bacteria are the most numerous organisms on earth and are found everywhere in the biosphere, even in very extreme conditions such as acid, hot volcanic pools and inside the heart of nuclear reactors. Each person has a higher number of bacteria living inside them, and outside them, than there are cells in the body itself. - Fungi are found all around the world, and grow in a wide range of habitats, including deserts. Most grow in terrestrial environments, but several species live only in aquatic habitats. Most fungi live in soil or dead matter, and in symbiotic relationships with plants, animals, or other fungi. Fungi, along with bacteria that are found in soil, are the primary decomposers of organic matter in terrestrial ecosystems. The decomposition of dead organisms returns nutrient to the soil, and the environment. Monera (Bacteria) Structure of Bacterial Cell (1) - Cell Wall: Made of sugars and protein. Its purpose is to protect the bacteria from mechanical damage and osmotic rupture - Plasmid: Found in the cytoplasm. Contain genetic information. Plasmids replicate inside a bacterium - Nucleoid: Contains the genomic DNA - Ribosomes: Protein synthesis Sometimes Present - Flagellum: Allow the bacteria to move - Slime capsule: Protects the bacteria from phagocytic white blood cells Bacteria are classified as prokaryotes for the following reasons; - They do not have a nuclear membrane - They do not have membrane-bound organelles Bacterial Shapes - Spheres (cocci): Can occur singularly or in various groupings - Rods (bacilli): Occur singularly or in various groups. Some have flagella - Spirals (spirillum): Some are tightly coiled while others are only slightly coiled. Some have flagella (2) Reproduction in Bacteria Asexual reproduction by a process called binary fission. In binary fission, the genetic material and plasmids replicate and then move to either side of the midline of the bacteria. The bacteria then pinches in its cell membrane and the cell wall grows across the middle, producing two identical cells. Under ideal conditions, such species such as E.coli, can reproduce every 20 minutes. However, such rates of multiplication are difficult to sustain. (3) Bacterial Growth Phases 1. Lag phase – In the lag phase, the bacteria are adjusting to their surroundings and preparing to undergo reproduction 2. Log phase – Reproduction begins in the log phase, and since resources ae plentiful, it is possible for the population to grow exponentially 3. Stationary phase – Competition occurs in the stationary phase as resources are now in limited supply, and death rate equals reproductive rate. Conditions are no longer ideal due to the build up of waste materials 4. Death or decline phase – Toxic waste is so concentrated that the death rate exceeds reproductive rate (4) Endospores When a bacterium is exposed to harmful conditions, it responds by forming a resistant structure called an endospore. The process of endospore formation; - The DNA replicates and the new DNA moves to one end of the cell - A thick, resistant wall then surrounds the new DNA - The contents of the endospore shrink as water is removed and its metabolism stops - The original cell bursts, releasing the endospore (5) Temperatures more than 120oC are required to kill endospores. Endospores can remain viable for centuries, becoming active only when suitable conditions are encountered. Nutrition Bacteria can be divided into two main groups; 1. Autotrophic – make their own food a. Photosynthetic – Have the ability to make their own food by photosynthesis, using sunlight as their source of energy b. Chemosynthetic – Obtain their energy from other chemical reactions and not light 2. Heterotrophic – obtain their food from other organisms a. Saprophytic organisms – live by digesting dead organic material and this causes the material to decay. In the process, valuable nutrients are returned to the environment and made available for use by other organisms b. Parasitic bacteria – Live in or on another species and cause them harm. They are responsible for many human, animal, and plant diseases Factors affecting growth - Temperature: Most mammalian bacteria function best at around 35 – 40oC. Cultures must be kept at this temperature to ensure maximum growth - pH: Most bacteria function best at around pH 7. Bacterial enzymes are denatured in an unsuitable pH - Oxygen concentration: Most bacteria are anaerobic, so keeping oxygen out of their environment is important - Availability of nutrients: An excess of nutrients must be kept available at all times to supply all the materials for growth and reproduction - Availability of water: Water is essential for bacterial growth. If water is removed by drying or osmosis, the bacteria will die - Waste materials: Waste materials must be removed to prevent a build up of toxic substances that would otherwise inhibit growth Antibiotics Antibiotics are substances made by microorganisms that kill microorganisms. The ability to kill microorganism allows antibiotics to be used to control pathogenic (disease causing) organisms, such as tuberculosis and thrush. Most antibiotics work by inhibiting cell wall synthesis during cell division e.g., penicillin. Antibiotic Resistance Antibiotic Resistant means not killed by antibiotics. There are three main causes of antibiotic resistance; - Overuse: Taking antibiotics for the common cold or flu. Antibiotics do not kill viruses. - Failure to complete the course: If a person stops taking an antibiotic before the course is finished, it gives resistant bacteria the chance to multiply. This means that infection can re-occur and will be much harder to treat as the bacteria are now more resistant to the antibiotic. - Antibiotic residues in food: Antibiotics are given to farm animals to treat infection and to make them gain weight faster. If this is done too close to slaughter, traces of the antibiotic will remain in the meat and be passed on in the food chain. Economic Importance of Bacteria Beneficial Bacteria - Production of yoghurt and cheese using Lactobacillus - Manufacture of antibiotics e.g., penicillin - Bacteria are used to bread down dead plants and animals which leads to nutrient recycling in soil Harmful Bacteria - Bacteria can cause human disease e.g., TB, meningitis, typhoid, pneumonia - Food spoilage e.g., Lactobacilli causes milk to turn sour Bioprocessing Bioprocessing is the use of organisms or their products to make useful substances. There are two standard processes to do this; 1. Batch Process A fixed amount of nutrients and microorganisms are added to the bioreactor at the start. Air is added if needed and waste gases are removed. Growth is allowed up to a certain point, the bioreactor is emptied, and the product is extracted. The bioreactor is cleaned and sterilised. Used for antibiotics. (6) 2. Continuous process Nutrients are continuously added to the bioreactor. Once the bioreactor is set up, spent medium and products are continuously removed. This is a quicker process because there is no need to empty the bioreactor regularly. It also allows for a continuous yield of product. By adjusting the nutrients added, the growth rate can be kept at a level which gives the maximum yield of product. Used for single-celled proteins. Fungi Fungi are complex organisms that form a variety of different structures. They are classed as Eukaryotic organisms for the following reasons: - They have a membrane-bound nucleus - They have membrane-bound organelles e.g., mitochondria Most Fungi are saprophytic, meaning they obtain their nourishment by breaking down plant and animal material. For example, Rhizopus. Some Fungi are parasitic, meaning they cause harm to the organism which they feed off and live on. For example, Athlete’s Foot. Some fungi are extremely poisonous e.g., The destroying Angel (Amanita phalloides). Far more fungi, such as the field mushroom (Psalliota campestris), are edible and completely harmless. Nutrition Fungi normally exist as microscopically thin threads called hypha that permeate through the substance they grow on. This substance is called the substrate. A collection of hyphae is called a mycelium. Fungi obtain their nourishment by extracellular digestion. This involves three steps: 1. The cells of the hyphae exude digestive enzymes 2. These enzymes break down any dead plant materials around them 3. The products of this digestion are then absorbed by the hyphae, but they are also available to any plants whose roots are in the area to use as nutrients. Rhizopus The black bread mould, Rhizopus, is a mould that commonly appears on stale bread and rotting fruit. It is a haploid (n). This means that it only has one set of chromosomes. Structure - Stolon: Aerial hyphae growing horizontally. They spread over the surface, turning downward at intervals, to create rhizoids - Rhizoids: Branched hyphae which penetrate the food source anchoring the fungus. Rhizoid release digestive enzymes into food and absorb digested food. - Sporangiophore: These are hyphae that arise unbranched from rhizoid tufts. They enlarge at the tip to form spherical sporangia. - Sporangium: The swelling at the tip of sporangiophore containing spores. - Columella: A cross wall which pushes up into sporangium from below. They separate spores from the sporangiophore. - Spores: Small, black, light, asexual reproductive structures. Spores can be transported by wind (7) Asexual Reproduction Asexual reproduction is the most common type of reproduction in Rhizopus. The tip of the sporangiophore swells to form a columella and this is cut off from the sporangiophore by a structure called the apophysis. The columella produces numerous haploid spores by mitosis, and these are held in the sporangium. When mature, the wall of the sporangium turns black. The sporangium dries out and bursts, releasing hundreds of spores that are carried by wind. When these spores land on a suitable substrate, they germinate, producing a hypha that grows through the substrate forming a new product. Sexual Reproduction Sexual reproduction occurs when hyphae of two different strains of Rhizopus grow side by side. There is no structural difference between the strains, so one is designated plus and the other minus. The process of sexual reproduction is as follows - Swellings, called progametangia, form from each hypha, opposite each other - Once they meet, the tips of each progametangia are cut off from the stalk and are now gametangia - The walls separating the two gametangia break down and fertilisation occurs when the nuclei from each of the gametangia fuse to form diploid zygotes - The wall thickens and forms a resistant zygospore - The zygospore is able to withstand adverse conditions. The zygospore will now be disperses and will germinate once it finds suitable conditions - The zygote divides by meiosis and a haploid sporangiophore grows vertically upwards - A sporangium forms at the top and asexual reproduction begins, spreading the fungus through the substrate (8) Yeast Yeast (Saccharomyces cerevisiae) is a unicellular fungus. Nutrition The most common yeast is baker’s yeast (Saccharomyces cerevisiae). However, there are many other types. For example, Thrush (Candida albicans), a parasite, is a common infection of the mouth and vagina. Baker’s yeast is a saprophyte, obtaining its minerals and requirements from sugar-rich solutions e.g., rotting fruit. Respiration Yeast obtains its energy by anaerobic respiration of sugars. Yeast breaks down glucose according to the equation C6H12O6 = 2 C2H5OH + 2 CO2 Glucose Ethanol Carbon Dioxide It produces an enzyme called zymase which is used to speed up the reaction. The reaction produces only a small amount of energy. Reproduction Asexual reproduction carried out by budding. A bud forms at one end of the and the nucleus and the vacuole of the parent cell split in two. One part of each moves into the bud. The bud is cut off from the parent cell, forming two separate cells. If food is plentiful, buds can form at both ends of a yeast cell, and buds can form on buds. This is known as pseudomycellium. (9) Economic Importance of Fungi Benefits - Yeast used to produce Alcohol - The mould (Penicillium Roquefort) is used to flavour cheese - The mould (Penicillium notatum) led to the production of penicillin Disadvantages - Parasitic fungi can cause disease (Athlete’s Foot, Thrush, Ringworm) - The potato-blight fungus (Phytophthora infestans) led to The Great Famine by causing potatoes to rot Mandatory Practical – Investigate the growth of leaf yeast using agar plants and controls - Obtain an ash leaf by cutting with scissors and tweezers - Put the leaf into a plastic bag and bring it back to the lab - Wash the bench with alcohol and sterilising solution to prevent contamination - Take two sterile nutrient malt agar plates - Seal one plate and label it ‘control’. - Keeping the lid of the Petri dish facing down, attach one leaflet with the upper surface facing up to the lid using petroleum jelly - Replace the lid and seal with the tape again to prevent contamination - Leave the petri dish the right way up for one day at room temperature - Invert the petri dish and leave it at room temperature for three days - Examine both plates - Replicate the experiment to verify results - When finished, soak the petri dishes in sterilising fluid to kill any microorganisms that have grown. Dispose in the rubbish bin - There should be shiny pink colonies on the agar plate containing the leaf, and they should shine form the shape of the leaflet - No colonies should be present on the empty dish Precautions when working with Microorganisms Aseptic technique includes all the steps taken to prevent contamination. This is very important as many microorganisms are pathogenic and can cause serious harm to humans and the environment. Sterile means that there are no microorganisms present. The following procedures should be followed to achieve asepsis; - Flame equipment by passing through a Bunsen flame - Keep all experiments in sealed containers - Minimise all openings in terms of size and duration - After use, soak everything in disinfectant - Dispose of all sterilised material in the waste bin Protista (Amoeba) Amoeba is a free-living eukaryotic organism that feeds on bacteria and other similar organisms in water. Some amoeba species live in fresh-water and some live in the sea. Structure (10) The cell is filled with two different types of cytoplasm: 1. Ectoplasm – A thick jelly-like material that forms a thin layer just inside the cell membrane 2. Endoplasm – A more fluid, jelly-like material that fills the rest of the cell. The cell organelles are suspended in the Endoplasm. The endoplasm is also involved in movement. Osmoregulation Osmoregulation is the process by which cells regulate the concentration of water within the cell. It is carried out as follows: 1. The contractile vacuole eliminates excess water which comes as a by-product of respiration, or which enters the cell by osmosis. 2. Water is actively transported into the contractile vacuole. Many mitochondria surround the contractile vacuole producing the necessary Energy. 3. The vacuole gradually increases in size and when full, moves through the cytoplasm to the surface of the cell where it bursts and expels the water. (11) Movement Movement is achieved by structures called pseudopodia which develop on Amoeba. Environmental conditions determine the direction of Amoeba’s movement. Chemicals released by their prey attract Amoeba, while other conditions repel it. This is known as chemotaxis. Once the pseudopodia appear, the endoplasm flows into them, causing Amoeba to move in that direction. This type of motion is described as amoeboid motion. Feeding Amoeba feed by a process known as phagocytosis. A layer of cell membrane surrounds the food particle, and it is taken into the endoplasm, forming a structure called a food vacuole. One or more lysosomes from the cytoplasm fuse with the food vacuole and supply the digestive enzymes to break down the food. The products are then adsorbed through the membrane into the cytoplasm. Undigested food is left behind as the food vacuole moves to the edge of the cell in a process called egestion. (12) Reproduction in Amoeba Reproduction is by a process called binary fission. - When Amoeba reaches a certain size, it withdraws its pseudopodia and becomes rounder in shape - The nucleus divides in two and the two nuclei move apart - The cytoplasm between the two nuclei divides in two in such a way that a nucleus is enclosed in each half - This results in two identical daughter cells and takes approximately 30 minutes Exam Questions 2014 – HL – Section A – Question 4 4. (a) The living world may be divided into five kingdoms: Monera; Protista; Fungi; Plantae; Animalia. In the case of each of the following pairs of kingdoms give any structural feature of members of the first-named kingdom not found in members of the second kingdom. (i) Fungi and Animalia – Fungi have cell walls made from chitin (ii) Plantae and Fungi – Plants have chloroplasts (iii) Animalia and Monera – Animals have membrane-bound organelles (iv) Protista and Animalia – Protistans have contractile vacuoles (b) In each of the following cases, name an organism that fits the description. (i) A multicellular fungus - Rhizopus (ii) A member of the Protista that catches and consumes smaller organisms - Amoeba (iii) A harmful member of the Monera – Escherchia coli 2013 – HL – Section C – Question 12 (b) (i) Name the kingdom to which bacteria belong - Monera (ii) Draw a large diagram of a bacterial cell to show: 1. The relative positions of the cell wall, cell membrane and capsule. 2. A plasmid. Label each of the above structures. (iii) 1. Under what circumstances does a bacterial cell form an endospore? Under harsh or unfavourable conditions 2. Describe briefly how an endospore forms. - The DNA replicates and the new DNA moves to one end of the cell - A thick, resistant wall then surrounds the new DNA - The contents of the endospore shrink as water is removed and its metabolism stops - The original cell bursts, releasing the endospore (iv) Name two types of heterotrophic nutrition used by bacteria – Parasitic and Saprophytic 2012 – HL – Section B – Question 8 8. (a) (i) Are fungi prokaryotic or eukaryotic? Eukaryotic (ii) Name one structure in plant cells not found in fungi - Chloroplast (b) (i) What is the purpose of using agar when growing fungi or bacteria in the laboratory? Agar acts as a source of nutrients for the growth of microorganisms. It also acts as a medium upon which the microorganisms can attach themselves (ii) Suggest one reason why leaf yeasts are more plentiful in July than in March – There are more leaves on the trees in July. There is also a more suitable temperature in July for growing leaf yeast (iii) Describe how you introduced the leaf yeasts into agar plates – Leaves are attached to the lid of the Petri dish using petroleum jelly with the underside of the leaf facing the agar (iv) What was the precise purpose of a control in this investigation? The control acts as a comparison to show that the leaf yeast came from the leaf and not from the agar (v) How did you recognise the leaf yeasts when they appeared on the agar? The leaf yeast formed small round pink colonies (vi) How did you safely dispose of the plates at the end of the investigation? The plates were immersed in disinfectant for 24 hours and then disposed of in general waste (vii) Using the axes below, draw a graph to show how the number of leaf yeasts varied following their introduction into the plate. 2012 – HL – Section C – Question 14 (c) (i) Answer the following questions in relation to sexual reproduction in the mould Rhizopus. 1. Sexual reproduction in Rhizopus is normally triggered by an adverse environmental stimulus. Suggest one such stimulus – Lack of water 2. Draw diagrams to show the main events of sexual reproduction in Rhizopus. In your diagrams label three structures other than the zygospore. 3. Give two advantages to Rhizopus of zygospore formation - Enables Rhizopus to survive lack of water or substrate - Dispersal of the zygospore to colonise a new habitat (ii) Answer the following questions in relation to asexual reproduction in yeast. 1. What term is used to describe the process of asexual reproduction in yeast? Budding 2. What happens to the new cells formed in the process? New cells break away from the parent cell 3. How does asexual reproduction in Rhizopus differ from that in yeast? Asexual reproduction in Rhizopus is by means of spores References Sciencefacts.com Sciencefacts.com Embibe.com Study.com Examlearn.ie Cs.montana.edu Examlearn.ie Examlearn.ie BYJUS.com Eduinput.com Examlearn.ie Classnotes123.com