BellringerBellringer

Have you ever hear of a protist before? How many examples of protists can you think of? Why do you suppose protists are not as well known as fungi?

Record your answers in your science journal.

General Characteristics

• A protist is a member of the kingdom Protista. Most protists are single-celled organisms, but some are made of many cells, and others live in colonies.

• Eukaryotic Organisms All protists are eukaryotic, which means that their cells each have a nucleus.

How thy can differ.

Single celled or multi-celled

Autotroph or heterotroph How they move How they reproduce

Producers and Food

Producers Decomposers Parasites Heterotrophs

Protists and Food

• Producing Food Some protists are producers. • Like green plants, these protists make their own food through photosynthesis. They are known as autotrophs.

• Finding Food Some protists must get food from their environment. • These protists are heterotrophs. Heterotrophs are organisms that cannot make their own food.

• Some protists are decomposers. Decomposers get energy by breaking down dead organic material.

• Some protists are parasites. A parasite invades another organism to get the nutrients it needs. The organism that a parasite invades is called a host.

Reproducing

• Asexual Reproduction Most protists reproduce asexually. In asexual reproduction, the offspring come from just one parent.• Fission – where one parent divides into two

identical copies

• Sexual Reproduction Some protists can reproduce sexually. Sexual reproduction requires two parents. • Conjugation – Two individuals join together and

exchange genetic material using a small second nucleus.

Producing More Protists, continued

• Many protists can reproduce asexually and sexually. In some protist producers, the kind of reproduction alternates by generation.

• For example, a parent will reproduce asexually, and its offspring will reproduce sexually.

Reproducing (Cont.)

Complex Reproductive cycles – Some protists have complex reproductive

cycles. These protists may change forms many times. The next slide shows the life cycle of Plasmodium vivax, the protist that causes the disease malaria.

Bellringer

Do you know what algae is? Have you ever seen it? What does it look like? Algae needs a lot of water in order to live. Where do you suppose most algae live?

Record and illustrate your answers in your science journal.

Producers

• Scientist place protists into three groups based on their shared traits: producers, heterotrophs that can move, and heterotrophs that can’t move.

• Many protists are producers. Like plants, protist producers use the sun’s energy to make food through photosynthesis. These protist producers are know as algae.

Producers

• Some algae are made of many cells and generally live in shallow water along the shore. You may know these algae as seaweeds.

• Phytoplankton are the microscopic algae that float near the surface of marine or fresh water.

Producers

• Red Algae Most of the world’s seaweeds are red algae and live in tropical oceans, attached to rocks or to other algae.

• Green Algae The green algae are the most diverse group of protist producers. Most live in water or moist soil. But others live in melting snow, on tree trunks, and inside other organisms.

Producers

• Brown Algae Most of the seaweeds found in cool climates are brown algae. They attach to rocks or form large floating beds in ocean waters.

• Diatoms are single celled. They are found in both salt water and fresh water and make up a large percentage of phytoplankton.

Producers• Dinoflagellates have two whiplike

strands called flagella. The beating of these flagella causes the cells to spin through the water. • Most dinoflagellates live in salt water, but

some live in fresh water or snow.• Euglenoids are single-celled

protists and live in fresh water. • Many euglenoids are producers, but can also

get food as heterotrophs. • Other eugelnoids are full time consumers or

decomposers.

Heterotrophs that move

• Heterotrophic protists that can move are often called protozoans.

• Amoebas and similar amoeba-like protists are soft, jellylike protozoans. They are found in both fresh and salt water, in soil, and as parasites in animals. • Although amoebas look shapeless, they are

highly structured cells.

Heterotrophs that don’t move

• Amoebic Movement Amoebas and amoeba-like protists move with pseudopodia. Pseudopodia means “false feet.” Amoebas and amoeba-like protists use pseudopodia to catch food, too.

• Shelled Amoeba-Like Protists Not all amoeba-like protists look shapeless. Some have an outer shell.

• Zooflagellates Flagellates are protists that wave flagella back and forth to move. Some flagellates live in water. Others live in the bodies of other organisms.

Heterotrophs that don’t move

• Ciliates Ciliates are complex protists. They have hundreds of tiny, hairlike structures known as cilia. Ciliates use their cilia for movement and also for feeding. The best-known genus of ciliates is Paramecium.

Heterotrophs that don’t move

• Some protist heterotrophs are parasites that do not move about. Others can only move at certain phases of their life cycle.

• Spore-Forming Protists Most spore-forming protists are parasites. They absorb nutrients from their hosts. Spore-forming protists have complicated life cycles that usually include two or more hosts.

• Water Molds live in water, moist soil, or other organisms. Some of them are decomposers and thus eat dead matter. But many are parasites.

• Slime Molds can move only at certain phases of their life cycle. Live in cool, moist places in the woods. They use pseudipodia to move around. But when environmental conditions are stressful, they form spores that cannot move.

Heterotrophs that don’t move

Bellringer

Many people love to eat mushrooms. What are mushrooms? There are many different types of edible mushrooms. How many can you name that you’ve eaten? How many mushrooms can you name that are available at your grocery store to eat?

Record your answers in your science journal.

Characteristics of Fungi

• Fungi are eukaryotic heterotrophs that have rigid cell walls and no chlorophyll. They are so different from other organisms that they are placed in their own kingdom.

• Food for Fungi Fungi cannot catch or surround food. Fungi must live on or near their food supply. Most fungi are consumers, but some are decomposers and others are parasites.

Characteristics of Fungi, continued

• Hidden from View Multicellular fungi are made up of chains of cells called hyphae. Most of the hyphae grow together form an underground mass called the mycelium, which makes up the major part of the fungus.

Characteristics of Fungi, continued

• Making More Fungi Reproduction in fungi may be either asexual or sexual.

• In one type of asexual reproduction, the hyphae break apart, and each new piece becomes a new fungus.

Characteristics of Fungi, continued

• Asexual reproduction can also take place by the production of spores. Spores are small reproductive cells that are protected by a thick cell wall. When the growing conditions are right, a spore will grow into a new fungus.

• Sexual reproduction in fungi happens when special structures form to make sex cells. The sex cells join to produce sexual spores that grow into a new fungus.

Kinds of Fungi

• Fungi are classified based on their shape and the way that they reproduce.

• Threadlike Fungi Most threadlike fungi live in the soil and are decomposers. However, some threadlike fungi are parasites. Molds are a threadlike fungi.

• Threadlike fungi can reproduce asexually or sexually.

Kinds of Fungi, continued

• Sac Fungi are the largest group of fungi. Sac fungi include yeasts, powdery mildews, truffles, and morels.

• Sac fungi can reproduce both asexually and sexually during their life cycles. Most of the time, they use asexual reproduction.

Kinds of Fungi, continued

• Club Fungi Mushrooms belong to a group of fungi called club fungi. Club fungi reproduce sexually. During reproduction, they grow special hyphae that form clublike structures.

• Nonmushroom Club Fungi Mushrooms are not the only club fungi. Bracket fungi, puff-balls, smuts, and rusts are also club fungi.

Lichens

• A lichen is a combination of a fungus and an alga that grow together. The alga actually lives inside the protective walls of the fungus.

• Unlike fungi, lichens are producers. The algae produce food through photosynthesis. And unlike algae, the fungi keeps the lichen from drying out. Lichens are found in almost every land environment.