Transcript What Are Fungi?

Lesson Overview
Fungi
Lesson Overview
21.4 Fungi
Lesson Overview
Fungi
What Are Fungi?
Many fungi grow from the ground, but fungi aren’t plants.
Instead of carrying out photosynthesis, fungi produce enzymes that
digest food outside their bodies. Then they absorb the small molecules
released by the enzymes.
Many fungi feed by absorbing nutrients from decaying matter in the
soil. Others live as parasites, absorbing nutrients from their hosts.
Lesson Overview
Fungi
What Are Fungi?
The cell walls of fungi are composed of chitin, a polymer made of modified
sugars that is also found in the external skeletons of insects.
The presence of chitin is one of several features that show fungi are more
closely related to animals than to plants.
Lesson Overview
Fungi
Structure and Function
Yeasts are tiny fungi that live most of their lives as single cells.
Mushrooms and other fungi, on the other hand, grow much larger. Their
bodies are made up of cells that form long, slender branching filaments
called hyphae.
Lesson Overview
Fungi
Reproduction
Fungi can reproduce asexually, primarily by releasing spores that are
adapted to travel through air and water.
Breaking off a hypha or budding off a cell can also serve as asexual
reproduction.
Lesson Overview
Fungi
Reproduction
Most fungi can also reproduce sexually. The life cycle of the bread mold
Rhizopus stolonifer is shown.
Lesson Overview
Fungi
Diversity of Fungi
More than 100,000 species of fungi are known. Biologists have placed
fungi into several distinct groups.
The major groups of fungi differ from one another in their reproductive
structures.
Lesson Overview
Fungi
Diversity of Fungi
Lesson Overview
Fungi
Decomposition
Many fungi feed by releasing digestive enzymes that break down
leaves, fruit, and other organic material into simple molecules.
These molecules then diffuse into the fungus.
Many organisms remove important trace elements and nutrients
from the soil. Fungi recycle these essential elements and nutrients.
If these materials were not returned, the soil would quickly be
depleted.
Lesson Overview
Fungi
Plant Diseases
A number of parasitic fungi cause diseases that threaten food crops.
Corn smut, for example, destroys corn kernels.
Some mildews, which infect a wide variety of plants, are also fungi.
Lesson Overview
Fungi
Animal Diseases
Fungal diseases also affect insects, frogs, and mammals.
Lesson Overview
Fungi
Animal Diseases
Parasitic fungi can also infect humans.
Lesson Overview
Fungi
Lichens
Lichens are extremely resistant to drought and cold. Therefore, they can
grow in places where few other organisms can survive—on dry bare
rock in deserts and on the tops of mountains.
Lesson Overview
Fungi
Lichens
Lichens are often the first organisms to enter barren environments,
gradually breaking down the rocks on which they grow. In this way,
lichens help in the early stages of soil formation.
Lichens are also remarkably sensitive to air pollution: They are among
the first organisms to be affected when air quality deteriorates.
Lesson Overview
Fungi
Mycorrhizae
The presence of mycorrhizae is essential for the growth of many plants.
The seeds of orchids, for example, cannot germinate in the absence of
mycorrhizal fungi. Many trees are unable to survive without fungal
symbionts.