2Learning Objectives Define the terms: saprophytic & parasitic State the structure & life cycle of RhizopusExplain nutrition in fungi.Outline the structure & reproduction of YeastName 2 Beneficial & 2 Harmful fungiMention that there are Edible and Poisonous fungiIdentify and state functions for the following structures: rhizoid, sporangium, gametangium, zygospore.
4Features of Fungi They do not make their own food They are mostly multi-cellularThey are made up of threads called hyphaeHyphae combine in masses to form a myceliumTheir walls are made of a carbohydrate called chitin
5NutritionAll fungi are heterotrophs i.e. they take in food made by other organismsFungi are either:ParasiticSaprophytic
6Saprophytic fungi Most fungi are saprophytic obtain nutrients from dead materialAs they digest it minerals are released and recycledPlay a vital role in the environment as they are responsible for decayE.g. mushrooms and moulds
7Parasitic 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
8Parasitic Fungi Obligate parasites live on live hosts but do not normally kill themFacultative parasiteskill the host and feed on the remains
9SymbiosisSome fungi e.g. form symbiotic relationships with other organismsA lichen is an organism which is a combination of a fungus and an alga
10Edible and poisonous fungi Some fungi are edible, but many are poisonous if eatenIt is often difficult to distinguish between the edible and poisonous varieties growing in the wild
11Learning Check What is a saprophytic fungi? Give an example of a saprophytic fungiWhat is a parasitic fungi?What is an obligate parasite?What is facultative parasite?Give an example of a parasitic fungi
16They are tubular with no cross walls and are multinucleate They are tubular with no cross walls and are multinucleate. Each nucleus is haploid.Nucleus
17Large numbers of hyphae are called a mycelium The hyphae digest the substrate on which they growsRhizoids provide extra surface area for absorption of the digested materialStolons are arial hyphae which allow Rhizopus to spread sideways
35Review of sexual reproduction Sexual reproduction in Rhizopus can only occur between a plus and a minus strainWhen hyphae from opposite strains grow close together swellings grow on both strains and touch each otherNuclei from both hyphae move into these swellings which are now called progametangiaCross-walls form to produce gametangia
36Review of sexual reproduction The walls of the gametangia dissolve and a number of fertilisations take place producing diploid zygote nucleiA zygospore forms around these nucleiWhen conditions are suitable the zygospore germinates by meiosisA hypha grows out of the zygospore and produces a sporangium at the tipThe sporangium opens releasing many haploid spores which grow into new individuals
37Learning 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?
41Asexual 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.
42Asexual reproduction in yeast This bud can separate from the parent to become a new individual
43Asexual reproduction in yeast This bud can separate from the parent to become a new individualIn some cases the bud does not separate, but can itself bud. In this way long colonies of yeast cells can develop
46Economic importance of fungi Beneficial fungiYeasts can be used to make bread and alcohols such as wine and beerFungi can be used as a source of food e.g. mushroom
47Economic importance of fungi Harmful fungiFungi can attack crops e.g. corn and wheat and cause major financial losses as a resultFungi such as athletes foot and ringworm can infect animalsFungi can spoil food e.g. rhizopus grows on bread
48Learning Check Can you draw the structure of yeast? Describe how yeast reproducesGive an example of how yeast is important economically
49Syllabus: Depth of treatment Saprophytic and parasitic formsRhizopus (Structure and life cycle)NutritionYeast: structure and reproduction (budding).
50Contemporary issues and Technology Mention of edible and poisonous fungi.Economic importance of fungi: examples of any two beneficial and any two harmful fungi.Practical ActivitiesInvestigate the growth of leaf yeasts using agar plates and controls