1. Fungi

2. 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.

4. Features of Fungi They do not make their own food
They are mostly multi-cellular
They are made up of threads called hyphae
Hyphae combine in masses to form a mycelium
Their walls are made of a carbohydrate called chitin

5. Nutrition
All fungi are heterotrophs i.e. they take in food made by other organisms
Fungi are either:
Parasitic
Saprophytic

6. Saprophytic fungi Most fungi are saprophytic
obtain nutrients from dead material
As they digest it minerals are released and recycled
Play a vital role in the environment as they are responsible for decay
E.g. mushrooms and moulds

7. Parasitic Fungi Absorb their food from live hosts
They get their food mostly from plants although some fungal parasites live on animals e.g. athlete’s foot

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

9. Symbiosis
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

10. Edible and poisonous fungi
Some fungi are edible, but many are poisonous if eaten
It is often difficult to distinguish between the edible and poisonous varieties growing in the wild

11. Learning Check What is a saprophytic fungi?
Give an example of a saprophytic fungi
What is a parasitic fungi?
What is an obligate parasite?
What is facultative parasite?
Give an example of a parasitic fungi

12. Rhizopus

13. Rhizopus growing on agar

14. Structure of Rhizopus

15. Consists of threadlike structures called Hyphae

16. They are tubular with no cross walls and are multinucleate
They are tubular with no cross walls and are multinucleate. Each nucleus is haploid.
Nucleus

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

18. Structure of Rhizopus

19. Sporangium
Spores
Columella
Apophysis
Sporangiophore

20. Learning Check Can you draw and label the structure of Rhizopus?
What is a hypha?
What is a mycelium?
What is the function of a rhizoid?
What is a stolon?

21. Life cycle of Rhizopus

22. Asexual reproduction
Sporangiophores grow up from the substrate after a number of days
Cells within the sporangium divide by mitosis to produce spores (haploid)

23. Asexual reproduction
Cells within the sporangium divide by mitosis to produce spores (haploid)

24. Asexual reproduction
The sporangium dries out in the right conditions and opens releasing many spores.
Each spore will grow into a new hypha and mycelium if it lands on a suitable substrate

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

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

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

29. Sexual reproduction Cross-walls form to produce gametangia. + Strain

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

31. 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.

32. 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.

33. 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.

35. 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

36. 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

37. Learning Check How does Rhizopus reproduce? What is a prometangia?
How is a gametangia formed?
How is a zygospore formed?
What is produced at the tip of a hypha?

38. Yeast

39. Structure of yeast

40. Reproduction in Yeast

41. 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.

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

43. 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

44. Budding

45. Budding

46. Economic importance of fungi
Beneficial fungi
Yeasts can be used to make bread and alcohols such as wine and beer
Fungi can be used as a source of food e.g. mushroom

47. 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

48. Learning Check Can you draw the structure of yeast?
Describe how yeast reproduces
Give an example of how yeast is important economically

49. Syllabus: Depth of treatment
Saprophytic and parasitic forms
Rhizopus (Structure and life cycle)
Nutrition
Yeast: structure and reproduction (budding).

50. 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