Mode of Nutrition

• Hyphae secrete digestive enzymes into the external environment.
• External digestion of complex biomolecules.
• Absorption of the simple soluble products of digestion by diffusion and active transport.
• Distribution of absorbed nutrients through the mycelium.

Reproduction and Life Cycle of Rhizopus

Asexual Reproduction

• Vegetative structure is haploid (n).
• Sporangia form at the tip of sporangiophores.
• The sporangium fills with haploid nuclei and cytoplasm.
• The columnella forms separating the sporangium from the sporangiophore.
• Each nucleus with cytoplasm forms a haploid spore with a tough resistant wall.
• The spores are wind dispersed.
• The spores germinate forming a new haploid mycelium if conditions are suitable.

Sexual Reproduction
Textbook Diagram: sexual reproduction by Rhizopus.

• Mycelia of opposite strain are close.
• Hyphae of opposite strain grow towards each other.
• The touching tips of the hyphae fill with nuclei and cytoplasm – progametangia formed.
• A cross wall forms behind each tip forming gametangia.
• The hypha behind each gametangium is called a suspensor.
• The contents of the gametangia mix.
• The nuclei of opposite strains fuse in pairs – fertilisation.
• The combined gametangia develop into a diploid zygospore.
• The zygospore is thick-walled resistant and dormant.
• In favourable conditions the zygospore germinates by meiosis.
• A haploid sporangiophore with a spore-filled sporangium grows from the zygospore.
• The spores are wind dispersed and germinate forming a new haploid mycelim.

Yeast – a unicellular fungus

Textbook Diagram: the yeast cell.

Reproduction
Textbook Diagram: budding of yeast.

• Asexual reproduction by budding.
• Good growth conditions – cell increasing in size.
• A small bubble-like extension grows from the cell.
• The nucleus undergoes mitosis.
• A daughter nucleus moves into the bud.
• The bud may remain attached and form a small colony by further budding.
• The bud may detach and undergo budding.
• Budding is a very fast method of reproduction.

Economic Importance of Fungi

Beneficial

• Alcohol (ethanol) formation for beer, wine and spirits.
• Carbon dioxide gas formation for baking and fizzy drinks.

Harmful

• Crop diseases, e.g., potato blight.
• Food spoilage.

Edible and Poisonous Fungi

• What are commonly called mushrooms and toadstools are the reproductive organs of certain fungi.
• Scientifically there is no difference between mushrooms and toadstools.
• There are no features that distinguish edible from poisonous fungi.
• The ability to recognise the handful of deadly types is essential.
• Identification of the good edible types is a safe starting point.
• Edible Examples: Field Mushroom, Parasol Mushroom.
• Poisonous Examples: Death Cap, Fly Agaric.

Mandatory Activity

Дата добавления: 2015-11-14