Ch. 20 Sec. 1 Protists

I. What Is a Protist? Protists are eukaryotes that are not members of the Plant, Animal, or Fungi kingdoms.

A. May include more than 200,000 species B. Most are unicellular

II. Evolution of Protists The first eukaryotic organisms on Earth Mitochondria and chloroplasts in eukaryotic cells may have descended from prokaryotes that lived inside larger cells Chloroplast Plants and plantlike protists

III. Classification of Protists A. Classified by how they obtain nutrition Heterotrophs - animal-like protists Photosynthesizers – plantlike protists Decomposers and parasites - funguslike protists

Animallike Protists: Protozoans Ch. 20 Sec. 2 Animallike Protists: Protozoans

Animal-like protists are classified by their means of movement There are four phyla of animal-like protists: zooflagellates sarcodines ciliates Sporozoans Animal-like protists are classified by their means of movement 7

I. Zooflagellates Animal-like protists (heterotrophs) Swim using flagella Long, whiplike projections Allow a cell to move Most have one or two flagella Some species have many Fluorescence photomicrographs of chonaoflagellates 8

C. Most reproduce asexually 1. Mitosis 2. Cytokinesis D. Some may reproduce sexually 1. Gametes form through meiosis 2. Gametes fuse 9

II. Sarcodines Pseudopods - temporary cytoplasmic projections used for feeding or movement 10

A. Amoebas Flexible, active cells Thick pseudopods a. Extend out of the central mass of the cell Amoeboid movement a. Cytoplasm streams into the pseudopod b. The rest of the cell follows 11

Structures of an Amoeba Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey. Fig. 20-4 Page 500 Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey. 12

4. Amoebas surround food and engulf it a. Food vacuole - small cavity in the cytoplasm that temporarily stores food b. Food digested c. Nutrients passed to cell d. Waste stays in vacuole until released outside the cell 5. Amoebas reproduce by mitosis and cytokinesis 13

B . Other sarcodines Foraminiferans Heliozoans (“sun animals”) 14

III. Ciliates Ciliates use cilia for feeding and movement 1. Short hairlike projections 2. Propel a cell B. Paramecia 1. Cilia a. Grouped into rows and bundles b. Beat in a regular pattern 15

Structures of a Paramecium Ciliates use hairlike projections called cilia for feeding and movement. Ciliates, including this paramecium, are covered with short, hairlike cilia that propel them through the water. Cilia also line the organism’s gullet and move its food—usually bacteria—to the organism’s interior. There, the food particles are engulfed, forming food vacuoles. The contractile vacuoles collect and remove excess water, thereby helping to achieve homeostasis, a stable internal environment. Fig. 20-5 Page 501 Ciliates use hairlike projections called cilia for feeding and movement. Ciliates, including this paramecium, are covered with short, hairlike cilia that propel them through the water. Cilia also line the organism’s gullet and move its food—usually bacteria—to the organism’s interior. There, the food particles are engulfed, forming food vacuoles. The contractile vacuoles collect and remove excess water, thereby helping to achieve homeostasis, a stable internal environment. 16

C. Internal Anatomy Trichocysts Bottle-shaped structures Below the surface of the cell membrane Used for defense 17

2. Paramecia possess two types of nuclei: Macronucleus keeps multiple copies of most genes for its day-to-day existence Micronucleus contains a “reserve copy” 18

b. Traps the particles and forces them into food vacuoles 3. Gullet a. Cilia sweep food in b. Traps the particles and forces them into food vacuoles c. The food vacuoles fuse with lysosomes i. contain digestive enzymes 4. Anal pore a. After digestion, the waste material empties through the anal pore 19

5. Contractile vacuoles - cavities in the cytoplasm a. Specialized to collect water b. In fresh water: osmosis c. Excess collected in vacuoles d. Contract, pumping water out e. Maintain homeostasis 20

D. Conjugation Reproduction is usually asexual by mitosis and cytokinesis Conjugation - When placed under stress 21

Two paramecia attach themselves to each other. Meiosis produces four haploid micronuclei, three of which disintegrate. The remaining micronucleus in each cell divides again. Macronucleus Micronucleus MEIOSIS During conjugation, two paramecia attach themselves to each other and exchange genetic information. The process is not reproduction because no new individuals are formed. Conjugation is a sexual process, however, and it results in an increase in genetic diversity. See Fig. 20-6 Page 502 During conjugation, two paramecia attach themselves to each other and exchange genetic information. The process is not reproduction because no new individuals are formed. Conjugation is a sexual process, however, and it results in an increase in genetic diversity. 22

The two cells exchange one micronucleus from each pair. The macronuclei disintegrate, and each cell forms a new macronucleus from its micronucleus. During conjugation, two paramecia attach themselves to each other and exchange genetic information. The process is not reproduction because no new individuals are formed. Conjugation is a sexual process, however, and it results in an increase in genetic diversity. 23

Conjugation is not a form of reproduction Conjugation is not a form of reproduction. In large populations, conjugation helps produce and maintain genetic diversity. Genetically identical paramecia form During conjugation, two paramecia attach themselves to each other and exchange genetic information. The process is not reproduction because no new individuals are formed. Conjugation is a sexual process, however, and it results in an increase in genetic diversity. 24

IV. Sporozoans Immobile Parasitic 1. Worms 2. Fish 3. Birds 4. Humans 25

Sporozoans reproduce by sporozoites. Many sporozoans have complex life cycles that involve more than one host. Sporozoans reproduce by sporozoites. A sporozoite can attach itself to a host cell, penetrate it, and then live within it as a parasite. 26

V. Animal-like Protists and Disease Some animal-like protists cause serious diseases, including malaria and African sleeping sickness. 27

A. Malaria Malaria is one of the world’s most serious infectious diseases, killing as many as 2 million people each year. The sporozoan Plasmodium, which causes malaria, is carried by the female Anopheles mosquito. 28

Malarial Infection Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. Fig. 20-7 Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. 29

A female Anopheles mosquito bites a human infected with malaria and picks up Plasmodium gamete cells. Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. 30

The sexual phase of the Plasmodium life cycle takes place inside the mosquito. Gametes fuse to form zygotes, meioses occurs, and sporozoites are produced and migrate to salivary gland. Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. 31

Infected mosquito bites another human, injecting saliva that contains Plasmodium sporozoites. Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Plasmodium sporozoites 32

Sporozoites infect liver cells and multiply asexually. Plasmodium sporozoites Liver Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. 33

Infected liver cells burst, releasing Plasmodium cells called merozoites that infect red blood cells. Plasmodium sporozoites Liver Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. Merozoites Liver cells burst 34

Merozoites reproduce asexually inside red blood cells. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. Red blood cells 35

Infected red blood cells burst, releasing merozoites that infect other red blood cells. Some cells release gametes that can infect mosquitoes. Merozoites Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies. Red blood cells 36

B. Other Diseases Caused by Protists African sleeping sickness Amebic dysentery Giardia 37

VI. Ecology of Animal-like Protists A. Many animal-like protists are essential to the living world Some live symbiotically within other organisms Some recycle nutrients from dead organic matter Some live in water, where they are eaten by tiny animals, which in turn serve as food for larger animals 38

B. ex: Trichonympha 1. Lives in the digestive systems of termites 2. Breaks down cellulose 3. Allows termites to digest wood 39

20–1 The Kingdom Protista The kingdom Protista is a diverse group. Protists are eukaryotes that are not members of the kingdoms Plantae, Animalia, or Fungi. Most protists are unicellular. Earth’s first eukaryotes were protists. One way protists are classified is according to how they obtain nutrition. Thus, many protists that are heterotrophic are called animallike protists. Protists that produce their own food by photosynthesis are called plantlike protists. Protists that obtain their food by external digestion are called funguslike protists.

20–2 Animallike Protists: Protozoans Animallike protists are called protozoans. Protozoans are heterotrophs. There are four phyla of animallike protists. They are classified according to how they move. • Protists that swim using flagella are classified in the phylum Zoomastigina. They are called zooflagellates. Flagella are long, whiplike projections that allow a cell to move. • Members of the phylum Sarcodina move by using pseudopods. Sarcodines also use pseudopods for feeding. Pseudopods are temporary projections of cytoplasm. Sarcodines called amoebas have thick pseudopods. An ameoba moves by first extending its psuedopod. The cell’s cytoplasm flows into the pseudopod. The rest of the cell then follows. This type of movement is called amoeboid movement.

• Members of the phylum Ciliophora, known as ciliates, use cilia for feeding and movement. Cilia are short, hairlike projections similar to flagella. Some of the best-known ciliates belong to the genus Paramecium. The cilia of a paramecium are organized into evenly spaced rows and bundles. Just under the cell membrane, a paramecium has small defense structures called trichocysts. When a paramecium is in danger, the trichocysts release stiff projections that protect the cell.

• Members of the phylum Sporozoa do not move on their own • Members of the phylum Sporozoa do not move on their own. They are parasites that reproduce by means of sporozoites. Some animallike protists cause serious diseases. For example, Plasmodium is a sporozoan that causes malaria. Trypanosoma is a zooflagellate. It causes African sleeping sickness. Some animallike protists are helpful. Trichonympha lives in the digestive system of termites. This protist helps termites digest wood.