Fungi C Shevlin Interesting facts about fungi There

Fungi C. Shevlin

Interesting facts about fungi There are more than 60 species of fungi that exhibit the phenomenon of emitting light from their bodies known as bioluminescence. C. Shevlin

People eat mushrooms of all shapes, sizes and colors. Yeasts are used in making bread, wine, beer and solvents. Drugs made from fungi cure diseases and stop the rejection of transplanted hearts and other organs. Fungi are also grown in large vats to produce flavourings for cooking, vitamins and enzymes for removing stains. C. Shevlin

Learning Objectives • • C. Shevlin Define the terms: saprophytic & parasitic State the structure & life cycle of Rhizopus Explain nutrition in fungi. Outline the structure & reproduction of Yeast Name 2 Beneficial & 2 Harmful fungi Mention that there are Edible and Poisonous fungi Identify and state functions for the following structures: rhizoid, sporangium, gametangium, zygospore.

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Features of Fungi • Heterotrophic (Do not make their own food) • No chlorophyll • Mostly multi-cellular • Made up of threads called hyphae • Hyphae combine in masses to form a mycelium • Their walls are made of a carbohydrate called chitin (found in insect bodies) C. Shevlin

Features • They reproduce by means of spores. • They do not ingest food but instead they secrete enzymes onto their food and then absorb the nutrients through their rhizoids. C. Shevlin

Nutrition All fungi are heterotrophs i. e. they take in food made by other organisms. Edible fungi e. g. field mushrooms, truffles Poisonous fungi e. g. death cap Fungi are either: • Parasitic • Saprophytic C. Shevlin

Nutrition 1. Parasites Live off a live host and cause harm. e. g. athletes foot or ringworm. Obligate parasites can only live off a host and not on their own. e. g. smuts and rusts. 2. Saphrophytes Most fungi are saphrophytes and these live off dead material. e. g. ear fungus on dead wood. They are essential for recycling nutrients. C. Shevlin

Parasitic Fungi • Obligate parasites – live on live hosts but do not normally kill them • Facultative parasites – kill the host and feed on the remains C. Shevlin

• Some fungi e. g. form symbiotic relationships with other organisms • A lichen is an organism which is a combination of a fungus and an alga C. Shevlin

Rhizopus C. Shevlin

Bread Mould (Rhizopus) This fungus grows on the starch in bread, vegetable peelings and stored fruits. Digestion takes place outside of the fungus and the nutrients are absorbed. C. Shevlin

Structure Rhizopus • The mould is often called pin mould as it's reproductive • structures look like pins. • Tubes called hyphae form a big mass called a mycelium. • The hyphae digest and absorb the starch in the bread. • A stolon is an aerial hyphae (stands up) which allows the mould to spread more quickly. C. Shevlin

C. Shevlin Rhizopus growing on agar

Structure of Rhizopus C. Shevlin

Rhizopus to Label C. Shevlin

Functions of parts of Rhizopus Part Function Hyphae Mycelium Spread the fungus & absorb nutrients Spread the fungus Sporangium Produces the spores Sporangiophore Holds up the sporangium Stolon Allows fungi to spread Columella Spore release C. Shevlin

Structure of Rhizopus C. Shevlin

Facts about bread mould: 1. Bread mould consists of threadlike structures called Hyphae 2. Hyphae are tubular with no cross walls and are multinucleate. Each nucleus is haploid. C. Shevlin

3. Large numbers of hyphae are called a mycelium 4. The hyphae digest the substrate on which they grows 5. Rhizoids provide extra surface area for absorption of the digested material 6. Stolons are arial hyphae which allow Rhizopus to spread sideways C. Shevlin

Sporangium Spores Columella Apophysis Sporangiophore C. Shevlin

Rhizopus: Sporangia C. Shevlin

Life cycle of Rhizopus Two types of reproduction: 1. Asexual Reproduction 2. Sexual Reproduction C. Shevlin

Asexual reproduction in Rhizopus • Only involves one parent. • Does not involve fertilisation • Offspring are identical to parent 1. Hyphae called sporangiospores grow up into the air. Their tips swell to form sporangium. 2. Cells inside the sporangium produce haploid spores by mitosis. (Sporulation is the process of making spores). 3. In dry conditions the sporangium opens and spores are released. 4. Spores are carried by the wind and if they land on a suitable substrate they C. Shevlin germinate.

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Spores being released from Sporangium C. Shevlin

Sexual Reproduction • Involves two parents • Involves fertilisations and offspring are not identical to parents. Rhizopus doesn't have a male or female but we call them + or -. Both look identical but sexual reproduction needs a plus and a minus strain to happen. C. Shevlin

Steps in Sexual Reproduction 1. Hyphae from opposite strains grow close together. 2. Swellings form opposite each other. 3. The swellings touch. 4. Nuclei (gametes) move into each swelling. 5. Cross walls form and form gametangia. 6. The walls dissolve. 7. Many fertilisations happen to make diploid zygote nuclei. C. Shevlin

Sexual Reproduction 8. A tough walled black zygospore forms around the nuclei. 9. Zygospore germinates by meiosis when conditions are right. 10. A haploid hyphae grows out and makes a sporangiophore with a sporangium This produce new haploid spores which can grow. C. Shevlin

C. Shevlin

Sexual reproduction • Sexual reproduction in Rhizopus can only occur between a plus and a minus strain. C. Shevlin + Strain - Strain

Sexual reproduction • When hyphae from opposite strains grow close together swellings grow on both strains and touch each other. C. Shevlin + Strain - Strain

Sexual reproduction • Nuclei from both hyphae move into these swellings which are now called progametangia. C. Shevlin + Strain - Strain

Sexual reproduction • Cross-walls form to produce gametangia. C. Shevlin + Strain - Strain

Sexual reproduction • The walls of the gametangia dissolve and a number of fertilisations take place producing diploid zygote nuclei. C. Shevlin + Strain - Strain

Sexual reproduction • A zygospore forms around these nuclei. • When conditions are suitable the zygospore germinates by meiosis. C. Shevlin + Strain - Strain

Sexual reproduction • A zygospore forms around these nuclei. • When conditions are suitable the zygospore germinates by meiosis. C. Shevlin + Strain - Strain

Sexual reproduction • A hypha grows out of the zygospore and produces a sporangium at the tip. • The sporangium opens releasing many haploid spores which grow into new individuals. C. Shevlin

C. Shevlin

Review of sexual reproduction • Sexual reproduction in Rhizopus can only occur between a plus and a minus strain • When hyphae from opposite strains grow close together swellings grow on both strains and touch each other • Nuclei from both hyphae move into these swellings which are now called progametangia • Cross-walls form to produce gametangia C. Shevlin

Review of sexual reproduction • The walls of the gametangia dissolve and a number of fertilisations take place producing diploid zygote nuclei • A zygospore forms around these nuclei • When conditions are suitable the zygospore germinates by meiosis • A hypha grows out of the zygospore and produces a sporangium at the tip • The sporangium opens releasing many haploid spores which grow into new individuals C. Shevlin

Yeast The yeast fungus consists of single cells rather than hyphae C. Shevlin

Structure of yeast C. Shevlin

Yeast • • • Another name for yeast is Saccharomyces. They can be round or oval in shape. They can usually only be seen with an electron microscope. Yeast have thin walls made of chitin. They have a thick cytoplasm with many food storage vacuoles. C. Shevlin

Respiration in Yeast Respiration • Yeasts respire anaerobically (without Oxygen) and break down glucose to produce ethanol (alcohol) and Carbon Dioxide. • Glucose 2 Ethanol + 2 Carbon dioxide. • This process is called fermentation. • Fermentation is a type of anaerobic respiration C. Shevlin

Reproduction in Yeast C. Shevlin

Reproduction in Yeast Asexual Reproduction This is done by budding. The parent cell divides by Mitosis and the new nucleus and cytoplasm enter the new cell. If the buds don't separate they form a colony C. Shevlin

Asexual reproduction in yeast • Asexual reproduction in yeast occurs by budding. • The nucleus of the parent cell divides by mitosis. One of the daughter nuclei enters a small developing bud on the outside of the yeast cell. C. Shevlin

Asexual reproduction in yeast • This bud can separate from the parent to become a new individual C. Shevlin

Asexual reproduction in yeast • This bud can separate from the parent to become a new individual • In some cases the bud does not separate, but can itself bud. In this way long colonies of yeast cells can develop C. Shevlin

Budding C. Shevlin

Budding C. Shevlin

C. Shevlin

Economic importance of fungi Beneficial fungi • Making bread and alcohol e. g. wine and beer. • Fungi can be used as a source of food e. g. mushroom C. Shevlin

Economic importance of fungi Harmful fungi • Fungi can attack crops e. g. corn and wheat and cause major financial losses as a result • Fungi such as athletes foot and ringworm can infect animals • Fungi can spoil food e. g. rhizopus grows on bread C. Shevlin

Decomposition Certain species of fungi and bacteria are decomposers. Over time, without decomposition, so much nitrogen would be locked up in leaves and other tissues that there would not be enough nitrogen available for the plant to make new leaves, stems and wood. The surface of the ground would also be buried by dead leaves and wood lying forever where they fell. C. Shevlin

Experiment to grow leaf yeast Sterile means that all microorganisms are destroyed. i. e. there is nothing living. For this experiment we Ash or Ivy leaves. We cut them into circles and stick them face up to the inside of the dish lid. The yeast spores drop off the leaves onto the agar. They start to grow and form pink colonies. Important to keep the bench sterile we wash our hands, the desk and all equipment with disinfectant. We also put the tweezers etc. through a bunsen flame. This is Saccharomyces roseus. C. Shevlin

What have you learned? C. Shevlin

Contemporary issues and Technology • Mention of edible and poisonous fungi. • Economic importance of fungi: examples of any two beneficial and any two harmful fungi. Practical Activities • C. Shevlin Investigate the growth of leaf yeasts using agar plates and controls

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