1. Fungi
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2. 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.
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3. People eat mushrooms of all shapes, sizes and colors
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.
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4. Learning Objectives 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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6. 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)
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7. 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.
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8. 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
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9. Nutrition 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.
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10. Parasitic Fungi Obligate parasites
live on live hosts but do not normally kill them
Facultative parasites
kill the host and feed on the remains
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11. 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
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12. Rhizopus
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13. 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.
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14. Rhizopus
Structure
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.
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15. Rhizopus growing on agar
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16. Structure of Rhizopus
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17. Rhizopus to Label
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18. Functions of parts of Rhizopus
Hyphae
Spread the fungus & absorb nutrients
Mycelium
Spread the fungus
Sporangium
Produces the spores
Sporangiophore
Holds up the sporangium
Stolon
Allows fungi to spread
Columella
Spore release
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19. Structure of Rhizopus
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20. Facts about bread mould: 1
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.
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21. 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
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22. Columella Sporangiophore
Sporangium
Spores
Columella
Apophysis
Sporangiophore
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23. Rhizopus: Sporangia
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24. Life cycle of Rhizopus Two types of reproduction: 1
Life cycle of Rhizopus Two types of reproduction: 1. Asexual Reproduction 2. Sexual Reproduction
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25. Asexual reproduction in Rhizopus
Only involves one parent.
Does not involve fertilisation
Offspring are identical to parent
Hyphae called sporangiospores grow up into the air. Their tips swell to form sporangium.
Cells inside the sporangium produce haploid spores by mitosis. (Sporulation is the process of making spores).
In dry conditions the sporangium opens and spores are released.
Spores are carried by the wind and if they land on a suitable substrate they germinate.
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27. Spores being released from Sporangium
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28. 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.
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29. 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.
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30. 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.
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32. Sexual reproduction
+ Strain
- Strain
Sexual reproduction in Rhizopus can only occur between a plus and a minus strain.
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33. Sexual reproduction
+ Strain
- Strain
When hyphae from opposite strains grow close together swellings grow on both strains and touch each other.
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34. Sexual reproduction
+ Strain
- Strain
Nuclei from both hyphae move into these swellings which are now called progametangia.
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35. Sexual reproduction Cross-walls form to produce gametangia. + Strain
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36. Sexual reproduction
+ Strain
- Strain
The walls of the gametangia dissolve and a number of fertilisations take place producing diploid zygote nuclei.
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37. Sexual reproduction A zygospore forms around these nuclei.
+ Strain
- Strain
A zygospore forms around these nuclei.
When conditions are suitable the zygospore germinates by meiosis.
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38. Sexual reproduction A zygospore forms around these nuclei.
+ Strain
- Strain
A zygospore forms around these nuclei.
When conditions are suitable the zygospore germinates by meiosis.
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39. 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.
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41. 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
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42. 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
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43. Yeast The yeast fungus consists of single cells rather than hyphae
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44. Structure of yeast
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45. 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.
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46. 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
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47. Reproduction in Yeast
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48. 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
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49. 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.
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50. Asexual reproduction in yeast
This bud can separate from the parent to become a new individual
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51. 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
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52. Budding
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53. Budding
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55. 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
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56. 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
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57. 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.
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58. 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.
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59. What have you learned?
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60. 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
Investigate the growth of leaf yeasts using agar plates and controls
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61. 2011 Paper > Section C > Question 15 > Part c
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