Fungi Section 1 CH 22 Fungi Fungi Section

Fungi Section 1 CH 22 Fungi

Fungi Section 1 What Are Fungi? • Fungi are a very diverse group of organisms, but all fungi share three characteristics: – Fungi have threadlike bodies – Fungal cell walls contain chitin – Fungi absorb nutrients from their environment

Fungi Section 1 What Are Fungi? • A fungus body is made of long, slender filaments. The filaments weave more tightly to form reproductive structures, like mushrooms and brackets. • Fungi have cell walls that contain chitin. Chitin is a tough carbohydrate that is also found in the hard outer covering of insects and other organisms. • Fungi obtain energy by breaking down organic and inorganic material in their environment and absorbing the nutrients.

Fungi Section 1 Structure and Function • Most of the body of a fungus is hidden in the ground or in the substance that the fungus feeds on. • The filaments allow the fungus to have a large surface area and to absorb nutrients efficiently.

Fungi Section 1 Visual Concept: Characteristics of Fungi

Fungi Section 1 Structure and Function, continued Body Structure • The threadlike strands of a fungus body are called hyphae (singular, hypha). • In some fungi, these cells do not have walls that separate the cells. Others fungi have partial cell walls, called septa. • Gaps in the septa allow cytoplasm, nutrients, and some organelles to flow through the hyphae.

Fungi Hyphae in Fungi Section 1

Fungi Section 1 Structure and Function, continued Body Structure • Hyphae form a tangled mass, often many meters long, called a mycelium. • In some fungi, hyphae also form rootlike structures, called rhizoids, that hold the fungus in place and absorb nutrients.

Fungi Section 1 Visual Concept: Body Structure of Fungi

Fungi Section 1 Structure and Function, continued Obtaining Nutrients • Fungi release enzymes that break down organic and inorganic matter into nutrients. • Fungi absorb the nutrients across their cell walls.

Fungi Section 1 Structure and Function, continued Obtaining Nutrients • Fungi that absorb nutrients from living hosts are called parasites. • In humans, fungal parasites sometimes cause diseases, such as athlete’s foot and ringworm.

Fungi Section 1 Reproduction Sexual Reproduction • Sexual reproduction occurs when hyphae from one fungus fuse with hyphae from a fungus of the opposite mating type. • The fused hyphae then form a reproductive structure, such as the mushroom. • Inside the structure, nuclei from the two mating types fuse. • These diploid nuclei undergo meiosis and produce haploid spores that are released.

Fungi Section 1 Reproduction, continued Asexual Reproduction • In fungi, asexual reproduction occurs when specialized hyphae produce haploid spores by mitosis. • The fungi that develop from these spores are genetically identical to the parent. • Fungi that do not have an observed sexual stage are grouped together and called imperfect fungi.

Fungi Section 1 Groups of Fungi • • Chytrid Fungi Zygote Fungi Club Fungi Sac Fungi

Fungi Section 1 Chytrid Fungi • The chytrids are a group of aquatic fungi that provide clues about the evolution of fungi. • Chytrids were once classified with protists because the two groups share two important characteristics. – Like protists, many chytrids are unicellular – Like protists, chytrids produce spores and gametes that have flagella.

Fungi Section 1 Chytrid Fungi, continued • Chytrids are now classified with fungi because chytrids have several important fungal characteristics. – Chytrids have chitin in their cell walls. – Chytrids digest food outside their bodies. – Most chytrids produce hyphae that form rhizoids. – The sexual reproductive structures of chytrids contain spores.

Fungi Section 1 Chytrid Fungi, continued • Most chytrids are aquatic, although some live in moist places on land. • They are mainly saprobes, which feed on dead algae or plants. • Some chytrids are parasites that feed on protists, plants, animals, or even other fungi.

Fungi Section 1 Zygote Fungi • Zygote fungi are named for sexual reproductive structures that produce zygotes inside a tough capsule. • Sexual reproduction in zygote fungi begins when hyphae from two mating types come together. • In fungi, different mating types are not referred to as male and female, because they are physically identical. Instead, they are called “+” and “-. ” • Asexual reproduction is more common than sexual reproduction in zygote fungi.

Fungi Section 1 Sac Fungi • Sac fungi are characterized by an ascus, a saclike sexual reproductive structure that produces spores. • The word ascus means “sac. ” • Sexual reproduction in sac fungi is similar to sexual reproduction in zygote fungi.

Fungi Section 1 Club Fungi • Club fungi are characterized by a basidium, a clublike sexual reproductive structure that produces spores. • Sexual reproduction of club fungi is very similar to that of sac fungi. • Hyphae from two mating types fuse and produce a dikaryotic reproductive structure called a basidiocarp. • A mushroom is one example of a basidiocarp.

Fungi Section 1 Club Fungi, continued • Basidiocarps often form at the outer edges of the large mycelial mats that club fungi produce. The mycelia grow out from a central starting point and form an expanding ring of hyphae. • When the fungus reproduces sexually, a ring of mushrooms appears. • The largest known organism on the planet is a club fungus in Oregon that is 3. 5 miles across.

Fungi Fungal Partnerships Section 1 • Fungi form mutualistic symbiotic associations to form lichens and mycorrhizae. • In a mutualistic relationship, both members benefit. • A lichen is an association between a fungus and a photosynthetic partner, such as a cyanobacterium, a green alga, or both. • The photosynthetic partner provides carbohydrates to the fungus. The fungus provides a protected environment, vitamins, and minerals. • Lichens can survive in extreme environments, such as on volcanic rock and arctic tundra. • Lichens can be damaged by chemicals in their environment and serve as indicators of air pollution.

Fungi Section 1 Fungal Partnerships, continued • A mycorrhiza is an association between fungi and the roots of nearly all plants. • The fungal hyphae grow inside or around the plant root and out into the soil. • The hyphae transfer phosphorus and other minerals from the soil to the roots of the plant. • The plant supplies carbohydrates to the fungus.

Fungi Section 1 Summary • Fungi have threadlike bodies, their cell walls are made of chitin, and they absorb nutrients from their environment. • A typical fungal body is made of filaments that allow the fungus to have a large surface area and to absorb nutrients efficiently. • In sexual reproduction in fungi, spores are produced by meiosis. In asexual reproduction in fungi, spores are produced by mitosis.

Fungi Section 1 Summary continued • The chytrids are a group of aquatic fungi that provide clues about the evolution of fungi. • Zygote fungi are named for sexual reproductive structures that produce zygotes inside a tough capsule. • Sac fungi are characterized by an ascus, a saclike sexual reproductive structure that produces spores.

Fungi Section 1 Summary, continued • Club fungi are characterized by a basidium, a clublike sexual reproductive structure that produces spores. • Fungi form mutualistic symbiotic associations to form lichens and mycorrhizae.