Protists and Fungi. What are fungi? What are fungi?

Protists and Fungi What are fungi? What are fungi? Did you know that the world’s largest organism is not a whale or other animal? It is a fungus in Or...
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Protists and Fungi What are fungi? What are fungi? Did you know that the world’s largest organism is not a whale or other animal? It is a fungus in Oregon that measures nearly 9 km2. Fungi are eukaryotes. Scientists estimate that more than 1.5 million different species of fungi exist.

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Fungi form long, threadlike structures that grow into large tangles. The structures are usually underground. These structures, which absorb minerals and water from the ground, are called hyphae (HI fee). The hyphae create a network called a mycelium (mi SEE lee um), shown here. Fungi are heterotrophs, which means they cannot make their own food. Some fungi are Fruiting body parasites. These fungi get Hyphae their nutrients from living organisms. Most fungi get their food by releasing chemicals that break down dead matter. Mycelium The fungi then absorb the nutrients.

Types of Fungi Scientists group fungi based on how they look and how they reproduce. Fungi can reproduce sexually or asexually. Almost all fungi reproduce asexually by producing spores. Spores are small reproductive cells with a strong outer covering. The spores can grow into new fungi. There are four groups of fungi:

• club fungi • sac fungi • zygote fungi • imperfect fungi The classification of fungi and funguslike protists often changes as scientists learn more about them. Technology and discoveries might lead to more changes in the classification of some imperfect fungi.

Club Fungi

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When you read the title of this lesson, you might have thought about mushrooms. Mushrooms are a type of club fungi. Their reproductive structures have a clublike shape. The part of a mushroom that grows above ground is called a basidiocarp (bus SIH dee oh karp). Inside the basidiocarp are the basidia (buh SIH dee uh; singular, basidium), reproductive structures that produce sexual spores. Most of a club fungus is a network of hyphae that grows underground and absorbs nutrients. Many club fungi are named for their shapes and characteristics. Puff-balls, stinkhorns, and birds’ nest fungi belong to this group. There is even a club fungus that glows in the dark because of a chemical reaction in its basidiocarp.

Sac Fungi Did you know that bread and diaper rash have something in common? A type of sac fungus causes bread dough to rise. A different sac fungus causes a rash to develop on damp skin. Sac fungi can cause diseases in plants and animals. Humans eat some sac fungi, such as truffles and morels. Sac fungi are named for their reproductive structures. The ascus (AS kuhs) is the reproductive structure where spores develop on sac fungi. The ascus often looks like the bottom of a tiny bag or sack. The spores of a sac fungus are called ascospores (AS kuh sporz). Sac fungi can reproduce sexually or asexually. Many yeasts are sac fungi. The gas released by the yeast during cellular respiration causes bread dough to rise.

Zygote Fungi Bread mold is caused by another type of fungus called a zygote fungus. Zygote fungi grow in moist areas, such as a damp basement or a bathroom shower. The hyphae of a zygote fungus grow over the surface of a material, such as bread. There, the hyphae dissolve the material and adsorb the nutrients. When this fungus undergoes sexual reproduction, tiny stalks called zygosporangia (ZI guh spor AN jee uh) form. The zygosporangia release spores called zygospores. New zygote fungi can grow from zygospores.

Imperfect Fungi Athlete’s foot and blue cheese are two things that can be caused by imperfect fungi. The moist environments near a shower and in a sweaty shoe are perfect places for the imperfect fungus that causes athlete’s foot to grow. The blue color in blue cheese comes from colonies of imperfect fungi that are added during the cheese-making process. These fungi are called imperfect because scientists have not observed a sexual, or “perfect,” reproductive stage in their life cycle. Because fungi are classified by the shape of their reproductive structures, these types of fungi do not fit other categories.

The Importance of Fungi

Decomposers Fungi are important because they are eaten by people. Fungi are also important because of the things they eat. Fungi are necessary to the environment because they break down dead plant and animal matter. Without fungi and other organisms, dead plants and animals would pile up year after year. Fungi also help break down pollution in soil. Without fungi, this pollution would build up in the environment. When fungi break down dead matter, they help put nutrients back into soil. Plants need these nutrients to grow. Fungi help keep soil fertile.

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Fungi are important to humans. Chocolate, carbonated soda, cheese, bread, and medicines are made using fungi. Some fungi are used as a substitute for meat because they are high in protein and low in cholesterol. Other fungi are used in making antibiotics.

Fungi and Plant Roots Many fungi and plants help each other as they grow together. Recall that the hyphae of a fungus take in minerals and water underground. The roots of a plant and the hyphae of a fungus weave together to form a structure called a mycorrhiza (mi kuh RI zuh), as shown below.


Mycorrhizae Minerals

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Mychorrhizae can exchange molecules. As fungi break down decaying matter in soil, they make nutrients more available to plants. They also increase the amount of water that plants can absorb because they increase the surface area of the roots. Fungi do not use light energy to make their own food. The fungi in mycorrhiza take in some of the sugars from plants. Plant produce these sugars through photosynthesis. The plants receive more nutrients and water because of the fungi. The fungi continue to grow using the sugars from the plants. So, both a plant and a fungus benefit in this relationship. Scientists suspect that most plants can benefit from mychorrhizae.

Health and Medicine Fungi, like protists, can be harmful to humans. A small number of people die every year from eating poisonous mushrooms or spoiled food containing harmful fungi.

Effects of Fungi You do not have to eat fungi for them to make you sick or uncomfortable. Some fungi can cause allergies, athlete’s foot rashes, diaper rashes, pneumonia, and thrush. Thrush is a yeast infection that grows in the mouth. It is most common in infants and in people with weak immune systems. While some fungi are harmful, others are used to make important medicines. Antibiotics, such as penicillin, are made from fungi. An accident resulted in the discovery of penicillin. Alexander Fleming was studying bacteria in 1928 when spores of the Pennicillium fungus contaminated his experiment and killed the bacteria. After further study, this fungus was used to make an important antibiotic called penicillin, which is still useful today.

Bacterial Resistance Over time, bacteria have become resistant to many antibiotics. The antibiotics no longer work to kill the bacteria. New antibiotics need to be developed to treat the same diseases. As new fungi are discovered and studied, scientists might find new sources of antibiotics and medicines.

What are lichens?

Green algae and photosynthetic bacteria are autotrophs. This means that they can make their own food using photosynthesis. Lichens are beneficial to both organisms, just as mycorrhizae are. In lichens, the fungus provides water and minerals, while the bacterium or alga provide the sugars and oxygen made from photosynthesis.

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You have read about plants and fungi that live together and benefit each other. A lichen (LI kun) is a structure formed when fungi and some other photosynthetic organisms grow together. Usually, a lichen consists of a sac fungus or a club fungus that lives in a partnership with either a green alga or a photosynthetic bacterium. The fungus hyphae grow in a layer around the algal cells.

The Importance of Lichens Lichens are found in many harsh environments. They might be found on a steep, rocky cliff near the ocean. The fungi can absorb water, help break down the rocks, and get minerals for the algae of bacterium. The algae can make food for the fungi through photosynthesis. The diagram below shows how lichens form. Once lichens have settled into an area, it becomes a better environment for other organisms. Many animals that live in harsh environments survive by eating lichens. Plants benefit from lichens because the fungi help break down the rocks and form soil. Plants can grow in the soil, providing a source of food for other organisms. Fungal hyphae

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Algal cell

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