Chapter 20
Fungi
©Frans Lemmens/Corbis
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-1
Fungi are the closest relatives of animals
Section 20.1
Fungi and animals share many metabolic and chemical features.
For instance, both are heterotrophs and use glycogen to store carbohydrates.
Figure 20.5
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-2
Fungi are a diverse group
Section 20.1
Fungi come in all shapes and sizes. Some are microscopic parasites; others are millions of meters long.
Figure 20.1
(e): ©Ed Young/Corbis
(a): ©Scimat/Science Source; (b): ©Steven P. Lynch/McGraw-Hill Education; (b, micrograph): ©Scenics & Science/Alamy; (c): ©Morley Read/Alamy;
(d): ©WSL Handout/Reuters/Corbis
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-3
Fungi are essential decomposers
Section 20.1
Fungi are the planet’s garbage processors. They break down dead plants and animals, releasing nutrients to be recycled.
Figure 20.1
(a): ©Scimat/Science Source; (b): ©Steven P.Lynch/McGraw-Hill Education;
(b, micrograph): ©Scenics & Science/Alamy
©Emily Keegin/fStop/ Getty Images RF
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-4
Fungi are heterotrophic
Section 20.1
All fungi feed by external digestion. They excrete digestive enzymes and absorb minerals and nutrients.
Figure 20.1
(e): ©Ed Young/Corbis
(a): ©Scimat/Science Source; (b): ©Steven P. Lynch/McGraw-Hill Education; (b, micrograph): ©Scenics & Science/Alamy; (c): ©Morley Read/Alamy;
(d): ©WSL Handout/Reuters/Corbis
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-5
Fungi have unique reproductive cycles
Figure 20.23
Section 20.1
Unlike plants and animals, fungi spend most of their lives in the haploid stage. The diploid stage may be brief.
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-6
Some fungi have a dikaryotic stage
Two haploid cells from different individuals fuse, but the nuclei stay separate. Dikaryotic cells have two genetically unique nuclei.
Section 20.1
Figure 20.2
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-7
In fungi, the diploid stage is very short
In most fungi, the zygote is the only diploid cell; it immediately divides by meiosis. New haploid cells divide by mitosis as the organism grows.
Section 20.1
Figure 20.2
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-8
Hyphae are the underground feeding structures
Section 20.1
Most fungi are composed of threadlike filaments called hyphae that branch toward food sources.
Collectively the hyphae are called the mycelium.
Figure 20.3
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-9
Mushrooms are strictly reproductive structures
Section 20.1
Hyphae above the surface aggregate into a fruiting body, such as this mushroom.
As the mycelium absorbs nutrients, the fruiting body produces spores, which are microscopic reproductive cells.
Figure 20.3
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-10
Spores are sex cells
Section 20.1
Spores can be produced either sexually or asexually.
They are dispersed from fruiting bodies and later germinate into new fungal colonies.
Figure 20.3
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-11
Conidia are asexual spores
Section 20.1
Hyphae produce conidia by mitosis. The fuzz we see on moldy foods consists of conidia.
Figure 20.4
©Steve Gschmeissner/Science Source
©Emily Keegin/fStop/ Getty Images RF
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-12
Fungi are classified by reproductive structures
Section 20.1
Basidiomycota and Ascomycota are the only fungi with a dikaryotic stage in the life cycle.
Biologists are still clarifying the relationships between Chytrids, Zygomycota, and Glomeromycota
Figure 20.5
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-13
Chytrids produce swimming spores
Section 20.2
Chytridiomycetes (chytrids) are thought to resemble the earliest fungi.
They produce motile spores �called zoospores that swim using flagella.
Figure 20.5
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-14
Chytrids are structurally simple
Section 20.2
Some chytrids are single cells. Others have slender hyphae. The structures at the ends of these hyphae produce gametes.
Figure 20.6
(a): ©Biology Pics/Science Source; (b): R. E. Reichle, M. S. Fuller, ‟The Fine Structure of Blastocladiella emersonii Zoospores,” American Journal of Botany, Vol. 54, no. 1,
January 1967, pp. 81 to 92. © 1967 Botanical Society of America. All rights reserved. Used with permission.
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-15
Chytrids are valuable for ecosystems
Section 20.2
Chytrids produce enzymes that break down molecules in animal, plant, and fungal cells. Some live in cow digestive tracts, where they digest cellulose in the grass cows eat.
Figure 20.6
(a): ©Biology Pics/Science Source; (b): R. E. Reichle, M. S. Fuller, ‟The Fine Structure of Blastocladiella emersonii Zoospores,” American Journal of Botany, Vol. 54, no. 1,
January 1967, pp. 81 to 92. © 1967 Botanical Society of America. All rights reserved. Used with permission.
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-16
Some chytrids are parasites
Section 20.2
These chytrids feed on keratin protein in frog skin. The frog loses its ability to breathe through its skin, and dies.
World frog populations have been declining for years due to a chytrid epidemic.
Figure 20.7
(chytrid): ©Lee Berger, James Cook University; (frog): ©Dr. Janalee Caldwell
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-17
Zygomycetes are fast growing and prolific
Section 20.3
Zygomycetes fungi include molds that grow on bread, fruit, and vegetables. They are common in the soil where they feed on decaying plants and animals.
Figure 20.8
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-18
Zygomycetes produce zygospores
Section 20.3
This group of fungi produce a distinctive structure when 2 hyphae fuse to form a diploid zygote.
Figure 20.5, 20.8
©Ed Reschke
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-19
Zygomycetes reproduce sexually
Section 20.3
Hyphae fuse to form a diploid zygospore with a spiny coat, which produces haploid spores.
Figure 20.8
©Ed Reschke
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-20
Zygomycetes reproduce asexually
Section 20.3
Each hypha produces spore sacs by mitosis. All spores are genetically identical.
Figure 20.8
©Ed Reschke
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-21
Zygomycetes disperse spores in unusual ways
Section 20.3
Figure 20.9
These hyphae penetrate the fly’s exoskeleton and produce spores inside the fly’s body as it dies.
These hyphae release spores in grass, which multiply inside the cow and germinate in cow dung.
(a): ©Dwight Kuhn; (b): ©Andrew Syred/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-22
Glomeromycetes produce large, asexual spores
This group of fungi do not have a sexual life cycle, which makes them difficult to place in the family tree.
Figure 20.5
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-23
Glomeromycetes spores are unusually large
Section 20.4
Some are hundreds of nanometers in diameter, and can be seen by the naked eye.
Figure 20.10
©Joseph B. Morton
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-24
Glomeromycetes colonize plant roots
Section 20.4
Glomeromycetes only live in association with plant roots. A fungus-plant root combination is called a mycorrhiza.
The fungus exchanges minerals and nutrients with the plant root at structures called arbuscules.
Figure 20.10
©Joseph B. Morton
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-25
Mycorrhiza are mutually beneficial
Section 20.4
Hyphae absorb water and nutrients from the soil and share them with the plant. The plant produces sugars that the fungus uses for energy.
Figure 20.10
©Joseph B. Morton
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-26
Ascomycetes produce spores in sacs
Section 20.5
Ascomycetes is the largest group of fungi, containing more than 50,000 species. The red bread mold below is a valuable model organism.
Figure 20.5
©Steven P. Lynch/McGraw-Hill Education
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-27
Ascomycetes have varying lifestyles
Section 20.5
Some decompose organic matter. Others live in symbiosis with other organisms, either as parasites or mutualists.
The fungus shown here is carnivorous. It is devouring a worm.
Figure 20.11
©Photo Researchers/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-28
Some ascomycetes benefit humans
Section 20.5
Ascomycetes that humans use include edible fungi, yeasts used for fermenting alcohol, and fungi that produce medicines. These truffles and morels are considered delicacies.
Figure 20.13
(a): ©DEA/G. Cozzi/Getty Images; (b): ©Robert Marien/Corbis RF
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-29
Some ascomycetes are pests
Section 20.5
A few species cause diseases in plants and animals.
Others grow on our food and homes. Their spores can make it difficult to breathe.
Figure 20.12
©Julie Dermansky/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-30
Ascomycetes form dikaryotic cells
Section 20.5
Separate haploid hyphae fuse, forming a dikaryotic cell. The nuclei eventually fuse, forming a diploid zygote.
Figure 20.14
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-31
Ascomycetes spores are in an ascus
Section 20.5
The zygote produces sets of eight haploid spores inside an elongated sac called an ascus. Many asci together form a fruiting body.
Figure 20.14
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-32
Ascomycetes reproduce asexually
Section 20.5
During asexual reproduction, a hypha produces identical haploid spores, each of which germinates into a haploid hypha.
Figure 20.14
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-33
Basidiomycetes spores are shaped like clubs
Section 20.5
Basidiomycetes include mushrooms and other fungi.
Figures 20.5, 20.16
©Cultura RM Exclusive/Rolf Ritter/Getty Images
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-34
Basidiomycetes disperse spores in many ways
Section 20.6
The putrid odor of the stinkhorn’s slimy spore mass attracts flies,
which carry the spores on their feet.
Raindrops splash the spore-laden “eggs” out of a bird’s nest fungus.
Puffballs disperse spores in the wind.
Figure 20.15
(a): ©RF Company/Alamy RF; (b): ©George McCarthy/Corbis; (c): ©imageBROKER/
Alamy RF; (d): ©Steven P. Lynch/McGraw-Hill Education
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-35
Basidiomycetes play roles in human life
Section 20.6
Mushrooms are sometimes edible, although they can also be poisonous or can induce hallucinations.
Figure 20.15
(a): ©RF Company/Alamy RF; (b): ©George McCarthy/Corbis; (c): ©imageBROKER/
Alamy RF; (d): ©Steven P. Lynch/McGraw-Hill Education
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-36
Basidiomycetes reproduce sexually
Section 20.6
Most of the life cycle is devoted to sexual reproduction.
Haploid hyphae grow from spores and fuse, forming a dikaryotic cell. Mitosis of the dikaryotic cell produces a dikaryotic mycelium.
Figure 20.16
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-37
Mushrooms are reproductive structures
Section 20.6
The dikaryotic mycelium grows into a mushroom.
The mushroom cap contains gills on which club-shaped cells called basidia form.
Figure 20.16
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-38
The zygote grows in the basidium
Section 20.6
Within each basidium, the two haploid nuclei fuse into a diploid zygote.
The zygote then divides by meiosis, forming four haploid, genetically unique basidiospores.
Figure 20.16
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-39
Fungi interact with other organisms
Section 20.7
Fungi form symbiotic relationships, in which both the fungi and the other organism benefit.
Figure 20.17, 20.20
©Dr. Elizabeth Arnold
(b): ©William H. Mullins/Science Source;
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-40
Endophytes live inside plant tissues
Section 20.7
These fungi do not trigger disease symptoms or otherwise harm plants. Some produce substances that help defend plants against herbivores.
All plants harbor endophytes.
Figure 20.17
©Dr. Elizabeth Arnold
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-41
Mycorrhizal fungi exchange material with roots
Section 20.7
Most land plants form mycorrhizae with fungi. Some plants cannot live without their fungi.
Figures 20.10, 20.18
Glomeromycetes form the most common types of mycorrhizae.
©Joseph B. Morton
©Dr. Elizabeth Arnold(a): ©R Henrik Nilsson; (b): ©Biology Pics/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-42
Ectomycorrhizae wrap around the roots
Section 20.7
Basidiomycetes and ascomycetes form ectomycorrhizae, in which the fungal hyphae wrap around the root but do not penetrate root cells.
Figure 20.18
©Dr. Elizabeth Arnold(a): ©R Henrik Nilsson; (b): ©Biology Pics/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-43
Some ants cultivate fungi
Section 20.7
Leaf-cutter ants build underground chambers and fill them with leaves.
Basidiomycetes use the leaves as a food source. Ants eat the growing hyphae.
Bacteria coating the ants secretes a toxin that protects the basidiomycetes.
Figure 20.19
©Gail Shumway/Photographer’s Choice/Getty Images
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-44
Lichens are dual organisms
Section 20.7
Lichens are fungi with green algae or cyanobacteria living among their hyphae.
The fungi absorb minerals and water while the algal cells produce sugars by photosynthesis.
Figure 20.20
©Eye of Science/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-45
Lichens are ecologically important
Section 20.7
They secrete acids that break down rock, which starts to develop into soil.
Many harbor nitrogen-fixing bacteria needed by plants.
Animals such as caribou eat lichens.
Figure 20.20
(b): ©William H. Mullins/Science Source;
(c): ©Eye of Science/Science Source
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-46
Investigating life: �The battle for position in cacao tree leaves
Section 20.8
Cacao trees are often attacked by harmful parasites, and they also harbor many endophytes.
Figure 20.21
©Robert van der Hilst/Corbis
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-47
Investigating life: �Endophytes protect trees from disease
Section 20.8
When cacao trees were inoculated with a pathogenic water mold, trees with endophytes were damaged less than those without.
Figure 20.22
©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.
20-48