Biology Notes DIVERSITY OF ORGANISMS

Diversity of OrganismsThe five kingdom classification system

What is in each kingdom? Prokaryote (Monera )kingdom: simple single-celled organisms that feed by a number of different

methods.Protista (Protoctist) kingdom: complex single-celled organisms and all of the algae (including

multicellular algae) that feed by a number of different methods.Fungus kingdom: multicellular organisms with little cellular differentiation that feed

heterotrophically by absorption.Plant kingdom: multicellular organisms that feed by photosynthesis.Animal kingdom: multicellular organisms that feed heterotrophically by ingestion.

Monera – Bacteria

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Biology Notes DIVERSITY OF ORGANISMS

Bacterial cell - Diagram

Types of bacterial cell Cocci – single, chains, pairs, clusters Rods – single, chains, with or without flagella Spirals – often have flagella

Bacterial shapes

Spore formationOccurs during unfavourable conditions Contents of cell shrinks Tough outer coat formed within the cell This is the endospore

Endospore Resists desiccation Resists high temperatures – hard to kill

When favourable conditions return

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Cell wall Cell or plasma membrane

Nuclear or genetic material Plasmid

Cytoplasm

CapsuleFlagellum

Biology Notes DIVERSITY OF ORGANISMS

Endospore absorbs water Expands Breaks tough outer wall Divides by binary fission

Bacterial endospore

ReproductionUsual method of asexual reproduction is known asbinary fission DNA replicates Cell grows to full size Cell divided across the centre Forms two cells same size each with their own DNA

Mutations and bacteria Favourable mutations are rare Bacteria have a short life cycle – can reproduce about every 20 minutes in favourable conditions Numerous generations can be produced in a very short time – approx 72 in 24 hours Favourable mutations will become the norm very quickly Can give rise to resistant strains of bacteria

Two types of NutritionAutotrophic bacteria – make their own food by Photosynthesis or Chemosynthesis e.g. nitrifying bacteria in soilHeterotrophic bacteria – eat food already made – can be aerobes or anaerobes Saprophytes – free-living Symbiotes – three types : –

Mutualism, Commensalism, ParasitismBacterial nutrition

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Biology Notes DIVERSITY OF ORGANISMS

Factors affecting growth rate Temperature – each has their own optimum Presence or absence of oxygen

– Facultative anaerobes

– Obligate anaerobes e.g. Clostridium botulinum

– Obligate aerobes pH – each has their own optimum External solute concentration – osmosis, jams, Dead Sea bacteria Pressure – some found exclusively at sea depths

Beneficial & Harmful Bacteria

Beneficial Bacteria ProduceStreptomyces sp. (species) AntibioticsLactobacillus sp. Yoghurt or cheeseEscherichia coli Vitimin K in the colonHarmful Bacteria CausesSalmonella typhi TyphoidVibrio cholerae CholeraMycobacterium tuberculosis Pulmonary TB

PathogenA pathogen is an organism that causes a disease.

They are parasitic bacteria that are capable of causing a disease in their host e.g. diphtheria, whooping cough and tetanus (3 in 1) are diseases caused by bacteria.

Antibiotics Are chemicals produced by micro-organisms (m/os) that are toxic to bacteria. antibiotic: substance produced by living micro-organisms (e.g. Penicillium notatum) which destroy or inhibit the growth of other micro-organisms especially bacteria or fungi e.g. penicillin, streptomycin, tetracycline, etc. – has no effect on viruses.

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Biology Notes DIVERSITY OF ORGANISMS

They are naturally occurring chemicals produced by one m/o to prevent the growth of another m/o and thus reduce competition for food, minerals, etc. Consequently there are m/os that can grow in the presence of these antibiotics i.e. they are resistant to the antibiotic.

The gene for this resistance is carried on the plasmids in the bacteria These plasmids can be passed from one bacterium to the next And from one species to another This leads to the development of antibiotic resistant strains of bacteria

How antibiotic resistant strains of bacteria may develop Person given an antibiotic All bacteria (good and bad) killed If there is an antibiotic resistant strain of bacteria present Have no competition Can increase in numbers rapidly Colonise the person If a pathogen arrives it can get the antibiotic resistance from the resident bacteria Antibiotics will now not affect it Effectiveness of antibiotics is being reduced because of this e.g. multiple drug-resistant tuberculosis.

Antibiotic Resistance in Bacteria Intensive farming often involves the addition of small amounts of antibiotics to the food Healthier animals that grow quicker produced Facilitates the development of resistant strains of bacteria Residues of antibiotics in meat consumed by humans Assists the development of more antibiotic resistant bacteria

Growth Curve of bacteria

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Biology Notes DIVERSITY OF ORGANISMS

Explanation of graph Lag phase: bacteria are settling in, adjusting to their new environment, and beginning to produce

the correct enzymes to digest the new food. Back to GraphExponential (Log or Logarithmic) phase: a period of rapid growth – numbers double every time

it replicates, due to abundance of resources. Back to GraphStationary phase: birth rate = death rate due to competition for food, space and the build-up of

toxic wastes. Back to GraphDeath (Decline) phase: numbers decline due to increased competition for food, space and the

build-up of toxic wastes. Back to Graph

Continuous flow production Some microbes are eaten as a protein substitute (animal feed) – single cell protein (SCP) Made in a fermenter Production kept at the exponential phase to produce the maximum quantity Fresh nutrients added to the top and SCP drawn off from the bottom Fermenter cleaned after six months – build up of toxic by-products, etc.

Simple diagram of continuous flow method of microbe production

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Biology Notes DIVERSITY OF ORGANISMS

Batch flow production Usually used when microbes are producing a product that is required e.g. penicillin Fermenter filled with nutrients and culture Stirred and temperature controlled Liquid removed and culture removed by filtration Penicillin crystallised from remaining fluid

Diagram showing batch production of penicillin

FungiTypes of Fungi Parasites – on people and crops e.g. athlete’s foot, Dutch Elm disease, etc. Saprophytes – important in decomposition e.g. Dry rot in timber, mildew on clothes, etc. Fruiting bodies of many saprophytic fungi are edible e.g. mushrooms, but some are highly poisonous or fatal e.g. Death cap.

Mushroom (Agaricus) close up

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Biology Notes DIVERSITY OF ORGANISMS

Mushroom – showing gills

Gill of mushroom showing spores

Structure of Rhizopus

Rhizopus – bread mould

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Biology Notes DIVERSITY OF ORGANISMS

Saprophytic Multicellular Aseptate = no crosswalls dividing the cytoplasm into separate cells - no cells, has nucleii.

Rhizopus – types of hyphae 3 types of hyphae.Stolons: Grow horizontally on surface of substrate Rhizoids: Grow downwards into substrate - anchorage and absorption of food.Sporangiophores: Grow upwards away from substrate - function in reproduction.The three types of hyphae that make up the fungus are collectively called the Mycelium

Rhizopus - nutritionSaprophyte - hyphae secrete enzymes onto the substrate on which they are growing – digestion is external (e.g. starch to sugar, lipids to ?, proteins to ?) – hyphae then absorb soluble products of digestion by diffusion.

ReproductionTwo types Asexual - does not involve the manufacture or union of sex cells or gametes -

involves only one parent and all the offspring are genetically identical Sexual - involves the union of sex cells or gametes,

two parents and results in genetically different offspring

Asexual reproduction usual method in suitable conditions i.e. supply of food, water and a suitable temperature Tip of sporangiophore develops a swelling (sporangium) Diagram Separated from rest of sporangiophore by crosswall (columella) Diagram Spores produced within sporangium by mitosis Sporangium bursts when ripe - spores released in dry conditions and carried by the wind Germinate into new hypha and mycelium

Sexual reproduction plus and minus strains of hyphae growing close together (structurally similar, chemically different - no male or female) short side branches (progametangia) grow towards each other tips swell (gametangia) and produce a haploid (n) gamete tips meet each other – gametes fuse to form a diploid zygote (2n) – develops into the zygospore (2n) resistant to adverse conditions after a time of dormancy meiosis - germination produces one sporangium – forms spores bursts when ripe – spores released germinate into new hypha

Sexual reproduction in Rhizopus

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Beneficial & Harmful Fungi

Yeast – structure SaccharomycesUnicellular fungus – (e.g. on fruit skins - apple and grape) ovoid or spherical cells found singly or in groups thin cell wall, granular cytoplasm, nucleus and large storage vacuoles

Yeast – reproduction Asexually by budding – usual method modified mitotic division bulge (bud) forms on side of cell Enlarges and fills with cytoplasm nucleus divides in two by mitosis and one goes into the bud the bud may remain attached to the parent and undergo further budding to form a colony or separate from the parent and form a new colony itself

Economic importanceBrewing industry - yeast respire anaerobically producing ethanol + carbon dioxide C6H12O6 Energy + 2C2H5OH + 2CO2 Baking industry - the CO2 produced by yeast causes the dough to rise - the heat evaporates the

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Biology Notes DIVERSITY OF ORGANISMS

ethanol

Precautions when working with micro-organismsAssume that all are hazardous until otherwise proven.

Asepsisor aseptic techniques – methods used to prevent microbes entering an area. These include: -Sterilisation of working area, all equipment, instruments and materials – before and after useFlaming of containers, needles and loops during useContainment methods and safe disposal of unwanted materials after use

Containment methods Work in laboratories with negative pressure outside – microbes drawn back into lab Use laminar airflow cabinets – microbes kept behind a flow of filtered air Use of protective clothing and masks

All materials are sterilised before disposal or re-use

SterileThis refers to a substance that is free from all types of microbes – the substance may have been

treated to kill all the microbes.

Sterilising is the killing of all microbes e.g. by moist heat (120°C for 20 minutes) using an autoclave.

Protista – Amoeba Protista e.g. Amoeba

Plant and Animal Kingdoms

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Cell membrane

CytoplasmEctoplasm

Endoplasm

Mitochondrion

Ribosome

Biology Notes DIVERSITY OF ORGANISMS

Plant Kingdom Vs Animal Kingdom Multicellular Photosynthetic Cells with cell walls Include a large number of phyla e.g. Bryophyta, Pteridophyta, Spermatophyta

Multicellular Heterotrophic Cells without cell walls Include a large number of phyla e.g. Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda

Prokaryotic nature of bacteria No membrane-bound nucleus or organelles Circular piece of DNA (the chromosome) attached to cell membrane known as the nucleoid This chromosome does not contain proteins Ribosomes, food storage granules and enzymes found in cytoplasm Cytoplasm surrounded by plasma or cell membrane Cell membrane surrounded by cell wall made of peptoglycan Cell wall may be surrounded by a capsule Some may have flagellaA diagram of a bacterium

Eukaryotic nature of fungi More advanced cellular structure Contain many membrane-bound cellular organelles, including a nucleus May have developed as a result of a number of prokaryotic cells coming together Chloroplasts and mitochondria contain their own DNA

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