Fungi

What do you think of when you hear the words fungus

and mold?

• The words fungus and mold usually make people think of unpleasant images.

• For example, fungi rot wood, attack plants, spoil food, and give humans athlete’s foot.

• However, ecosystems would collapse without fungi to decompose dead organisms, fallen leaves, and other organic materials, thereby recycling essential chemical elements back into the environment in forms that other organisms can use.

• Humans have been using fungi for centuries.

• For example, we use fungi for food (mushrooms), to make bread rise (yeast), to ferment beer and wine, and to produce antibiotics and other drugs.

What is a Fungus?

• Although there are a few unicellular types of fungi, such as yeast, most fungi are multicellular organisms.

• Multicellular fungi are made up of thread-like cells called hyphae, which develop from spores.

• In many types of fungi, the hyphae are divided by cross walls called septa.

• Hyphae elongate at their tips and branch into a network of filaments called mycelium.

• Fungi have cell walls made up of a carbohydrate called chitin.

HyphaeHyphae are the basic structural units of fungi that grow to

form mycelia – a complex form of filaments.

Fungi: The Earth’s Great Recyclers• Fungi play an extremely very role in our environment as the

major decomposers of organic matter such as dead organisms, trees and leaves, wastes, etc.

• Fungi are heterotrophs who obtain nutrients through extra-cellular digestion, where the food is digested outside of the cells.

• Extracellular digestion occurs when hyphae extend into the cells of a dead organism and release powerful digestive enzymes that break large molecules down into smaller ones.

• The molecules then diffuse into the cells of the fungus.

Fungi Reproduction• Fungi can reproduce either sexually or asexually.• Budding is a form of asexual reproduction in which mitosis

takes place and a new cell grows from the parent cell, eventually pinching off.

• The production of spores is an form of sexual reproduction whereby spores are released into the air, and forming hyphae where they land.

Spores

Budding

Benefits of Spores

• How do you think developing spores helps a fungus species survive?

• Fungal spores are small and extremely lightweight, which allows them to be carried by the wind easily.

• In addition, fungi usually produce billions of spores, many of which are released.

• What advantages do each of these features have?

Symbiotic Relationships

• Recall that as symbiotic relationship is a mutually beneficial relationship between two organisms living in direct contact with each other.

• Over the years, fungi have formed mutual relationships with other organisms to help themselves better adapt to their environment.

Examples: Mycorrhizae & Lichen

Mycorrhizae• A mycorrhizae is a symbiotic relationship in which fungus

lives in close contact with the roots of a plant partner.

• In the relationship, the hyphae of the fungus extend from the roots of the plant to obtain more nutrients for the plant. In return, the fungus receives sugars and amino acids from the plant.

Lichen• A lichen is a symbiotic relationship between a fungus and

green algae.

• In this relationship, the fungus forms a dense web that helps retain moisture for the algae. In return, the algae gives the fungus some of its products from photosynthesis.