Presentation on theme: " There will be no grades given out until this Friday. Please do not ask! HW-Read 11-1 and do the section review on page 273, questions 1-10 due Wed."— Presentation transcript:
There will be no grades given out until this Friday. Please do not ask! HW-Read 11-1 and do the section review on page 273, questions 1-10 due Wed. Use spiral notebook.
A protist is a member of the Kingdom Protista. All protists are eukaryotes, which means that their cells have a nucleus. They are less complex than other eukaryotic organisms. Protista are related more by how they differ than how they are similar. Some scientists think that Kingdom Protista should be divided into several kingdoms
Protists are very diverse and have few traits in common. Some protists control their own movement, others cannot
Some protists produce their own food. They are producers. Some eat other organisms. Some eat decaying matter.
The protists that must get their food from their environment are heterotrophs. Many heterotrophs eat small living organisms, such as bacteria, yeast or other protists. Some are decomposers and eat decaying matter.
Some protists get energy in more than one way. Slime molds get energy by engulfing both small organisms and particles of organic matter.
Some heterotrophs are parasites. An organism that a parasite invades is called a host. Parasites cause harm to their host. They may invade fungi, plants or animals.
During the mid 1800’s, a parasitic protist wiped out most of the potatoes in Ireland. Many people died of starvation.
Like all living things, Protist reproduce. Some reproduce sexually. Most reproduce asexually, by binary fission, like Euglena.
Binary fission is reproduction in which one single-celled organism splits into two single-celled organisms. Some single-celled protists use multiple fission to make more than two offspring from one parent. Each new cell is a single-celled protist.
Sexual reproduction requires two parents. Member of the genus Paramecium sometimes reproduce sexually by a process called conjugation.
During conjugation two individuals join together and exchange genetic material by using a small second nucleus. Then they divide to produce four protists that have new combinations of genetic material.
Many protists can reproduce sexually and asexually. In some protist producers, the kind of reproduction alternates by generation. A parent will reproduce asexually, and its offspring will reproduce sexually. Other protists reproduce asexually until environmental conditions become stresssful, lack of water or food, and then they will use sexual reproduction.
Some protists have complex reproductive cycles. These protists may change forms many times, such as the Plasmodium Vivax, which causes malaria.
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.
Protists are organized into three groups Producers Heterotrophs that can move Heterotrophs that cannot move
Red algae Green algae Brown algae Diatoms Dinoflagellates Euglenoids
Many protists are producers which use the sun’s energy to make food through photosynthesis. These protist producers are known as algae.
All algae have the green pigment chlorophyll, which is used for making food. Most algae have other pigments that give them a color. Most algae live in water.
Some algae are made of many cells. Many-celled algae generally live in shallow water along the shore. You know these algae as seaweeds.
Free floating single- celled algae are called phytoplankton. These algae cannot be seen without a microscope. They float near the water’s surface.
Phytoplankton provide food for most other organisms in the water. They also produce much of the world’s oxygen.
Most of the world’s seaweeds are red algae. Red algae live in tropical oceans, attached to rocks or other algae. Red algae are usually less than 1 m in length.
The green algae are the most diverse group of protist producers. They are green because chlorophyll is the main pigment in their cells. Most live in water or moist soil. Others live in snow, tree trunks and inside other organisms.
Many green algae are single celled. Individual cells of green algae, like Volvox, live in groups called colonies.
Most of the seaweeds found in cool climates are brown algae. They attach to rocks or form large floating beds in ocean waters with only the top part exposed to sunlight. They have chlorophyll and a yellow-brown pigment.
Diatoms are single- celled, found in both salt water and fresh water. They make up a large part of the phytoplankton. The cell walls contain a glasslike substance called silica. The cells are enclosed in a two part shell.
Dinoflagellates are single celled. Most live in salt water, but a few live in fresh water and even snow. They have two whip like strands called flagella. The beating of the flagella causes the cells to spin through the water.
They are single celled protists that live in fresh water They use their flagella to move through the water. Many are producers but some become heterotrophs when there is not enough light to make food. Others do not have chlorophyll and must always get food.
Digestion occurs in a food vacuole. Oxygen passes through the cell membrane. The food vacuole joins with the cell membrane to release waste. They have an eyespot and respond to light.
Photosynthesis takes place in chloroplasts, which contain chlorophyll. Most euglenoids have two flagella, short and long. They can’t see but they have eyespots sense light. A contractile vacuole holds excess water and removes it from the cell.
Some heterotrophic protists have special traits that allow them to move and are known as protozoans. Those that can move are usually single- celled consumers or parasites. Some examples are: Amoebas Shelled amoeba-like protists Zooflagellates Ciliates
Amoebas are jellylike protozoans, found in both salt and fresh water, in soil and as parasites in animals. They look shapeless but are highly structured. They have vacuoles to get rid of excess water.
Many amoebas eat bacteria and small protists, but some are parasites that get food by invading other organisms. Certain amoebas live in human intestines and cause dysentery which causes internal bleeding.
Amoebas and amoeba-like protists move with pseudopodia, which means “false feet”. To move the amoeba stretches a pseudopod out from the cell and then the cells flows into the pseudopod.
Pseudopodias are also used to catch food. When it sense a food source, it moves toward the food and surrounds it, forming a food vacuole. Enzymes move into the vacuole to digest the food and the digested food passes into the amoeba.
Amoebas reverse the process to get rid of wastes. A waste-filled vacuole is moved to the edge of the cell and released.
Amoeba proteus can sense light and tends to move away from it. Just before it reproduces, it rounds up into a ball with tiny pseudopodia extensions. Over the next 15 minutes or so, it splits and becomes two. Image below shows one amoeba in the final stages of splitting. Look carefully and you can see the clear channel between the two new amoebas.
Not all amoeba-like protists look shapeless, some have an outer shell. Radiolarian shells look like glass ornaments. Foraminiferans have snail-like shells. They move by poking pseudopods out the pores in the shell.
Zooflagellates are protists that wave flagella back and forth to move. Some live in water. Others live in the bodies of other organisms.
Some zooflagellates are parasites that cause disease. Giardia lamblia can live in the digestive tract of many vertebrates., causing severe stomach cramps.
Some zooflagellates live in mutualism with other organisms, each helping the other live. The zooflagellate that lives in the gut of termites digests the cell walls of the wood that termites eat and in return the termite gives the protist food and a place to live.
Ciliates are complex protists. They have hundreds of tiny hair- like structures known as cilia which they use for both moving and feeding. The best known ciliate is Paramecium.
The cell of a paramecium has two kinds of nuclei. A large nucleus called a macronucleus controls the function of the cell. A smaller nucleus, the micronucleus, passes genes to another paramecium during sexual reproduction.
The stentor moves using cilia. It creates a whirlpools to suck in food and is sometimes called the trumpet cell. It is large enough that it can sometimes be seen without the microscope. It forms a ball in order to look larger. Digestion occurs in a food vacuole. Oxygen is diffused or released through the cell membrane. Food vacuoles join with the cell membrane to release waste.
When stentors are traveling, they are not in the typical trumpet shape, but contract into a more oval shape. The cilia on the trumpet bell closes up, and the cilia on the body are used for locomotion.
Stentors have a rather complex reproductive cycle. Here a stentor undergoing division. They use a micronucelus for reproduction.
Not all protists heterotrophs can move. Some of these protists are parasites that do not move. Others can move only at certain phases in their life cycle. Some examples are: Spore-forming Protists Water Molds Slime Molds
Many spore-forming protists are parasites. They absorb nutrients from their hosts. They have no cilia or flaglella to move. They have complicated life cycles that involve two hosts like the protist, P. Vivax that causes malaria.
Water molds are also heterotrophic protists that can’t move. Most water molds are small and single- celled. Many live in water, moist soil or other organisms, but some are decomposers Many are parasites.
Slime molds are heterotrophic protists that can move only at certain phases of their life cycle. They look like thin, colorful shapeless globs of slime. They live in cool moist places in the woods.
Some live as a giant cell that has many nuclei and a single cytoplasm at one stage of life. As long as food and water are available, it will grow. Others live as single cells which can come together when times are stressful.
When environmental conditions are stressful slime molds grow stalk- like structures with rounded knobs at the top, containing spores. Spore are small reproductive cells covered by a thick cell wall. The spores can survive for a long time without water or nutrients.
A person who studies fungi.
Most fungi are consumers that they get their nutrients by secreting digestive juices on their surroundings and absorbing the food. Many are decomposers and others are parasites.
Some live in mutualism, called mycorrhiza, with other organisms. Fungi grow on or in the roots of a plant which provides nutrients to fungus. The fungus helps the root absorb minerals and protects the plant from disease.
Many celled fungi are made up of chains of cells called hyphae. Hyphae are threadlike fungal filaments. These filaments are made of cells that have openings in their cell walls. These openings allow cytoplasm to move freely between cells.
Most of the hyphae that make up a fungus grows together to form a twisted mass called the mycelium. The mycelium makes up the major part of the fungus but most of it is hidden underneath the ground.
Reproduction may be sexual or asexual. Asexual reproduction occurs in two ways. The hyphae may break apart and each becomes a new fungus or spores are produced and spread.
Fungi are classified based on their shape and the way that they reproduce. There are four main groups of fungi: Threadlike fungi Sac fungi Club fungi Imperfect fungi
Most threadlike fungi live in the soil and are decomposers. Some threadlike fungi are parasites. A black bread mold is an example of something that belongs to this group.
Threadlike fungi can reproduce asexually. Parts of the hyphae grow into the air and form spore cases at the tip, called sporangia. When they break open they are released into the air.
Threadlike Fungi reproduce sexually when a hypha from one individual joins with a hypha from another individual. The hyphae grow into specialized sporangia that can survive times of cold or little water. When conditions improve, they will grow into a new fungi.
Sac Fungi area the largest group of fungi which includes yeasts, mildew, They can reproduce both sexually and asexually. When they reproduce sexually they form a sac called an ascus. Spores develop within the sac.
Yeasts are single- celled sac fungi. When they reproduce asexually, they use a process called budding. In budding a new cell pinches off from an existing cell.
Yeast are used to make breads and alcohols. Yeasts use sugar as food and produce carbon dioxide gas and alcohol as waste. Trapped bubbles of carbon dioxide cause the bread to rise.
Yeast is also used to make antibiotics
Some yeasts, such as truffles and morels, are prized as human foods.
Some sac fungi are parasites and cause Dutch elm disease which is harmful to the tree.
The umbrella-shaped mushrooms are the most familiar fungi. The group gets its name from structures that the fungi grow during reproduction. Club fungi reproduce sexually by growing special hyphae that form clublike structures.
These clublike structures are called basidia from the Greek word for clubs. Sexual spores develop on the basidia.
The most familiar mushrooms are known as gill fungi. The basidia of these mushrooms develop in structures called gills, under the mushroom cap. Some are sold in grocery stores, while others are very poisionous.
Mushrooms are not the only club fungi. Bracket fungi grow outward from wood and from small shelves. Smuts and rusts are plant parasites that attach corn and wheat.
The imperfect fungi group includes all of the species that do not fit. They do not reproduce sexually. Most are parasites that causes diseases in plants and animals. One common human disease is athlete’s foot.
Peniciliium is the fungi that is the source of the antibiotic Penicillin. Other imperfect fungi produce some cheeses, soy sauce and the citric acid used in cola drinks.
A lichen is a combination of a fungus and an alga that grow together. The alga lives inside the protective wall of the fungus. The merging of the two is so complete that scientists give lichens their own scientific name.
Unlike fungi, lichen are producers. The algae produces food through photosynthesis. Lichens keep the algae from drying out. Lichens can be found in almost any environment.
Because lichens need only air, light and minerals to grow, they can grow on rocks. As lichens grow, the changes they make to their surroundings allow other organisms to live there also. They break down the rock and as they die, they form soil from the decaying matter.
Lichens absorb water and minerals from the air. As a result, they are easily affected by air pollution. The presence or absence of lichens is a good indication of the quality of the surrounding air.