Unicellular Organisms

Most living organisms are composed of millions of cells Most living organisms are composed of millions of cells. They are multicellular. Some living organisms are unicellular which means that they only consist of one cell. This means that this single cell will be able to show all the characteristics of a living organism. Examples of unicellular organisms which show animal characteristics include 1. amoeba 2. paramecium

Amoeba Cell Membrane Nucleus Contractile Vacuole Pseudopod Pseudopodia Food being engulfed Food vacuole Cytoplasm

amoeba

Cilia Food Vacuoles Oral Groove Cell Mouth Micronucleus Macronucleus Contractile Vacuole

Some unicellular organisms show plant like features. Eg pleurococcus

Euglena show plant and animal features. Cell membrane Food store / reserve Nucleus Light detector Contractile Vacuole Eyespot Second Flagellum Chloroplast Flagellum

Euglena has chloroplasts which is typical of a plant. Typical animal features include flagellum (for movement), lack of cell wall. The eyespot and light detector work together to detect direction and intensity of light. What to do 1. Collect textbook . Copy diagrams and tables of pleurococcus and paramecium. from textbook page 1. Copy diagram of euglena page 5 and make up a similar table for this organism. 2. If available view pondwater under microscope. Add a drop of glycerine to slow organisms down. 3. View bioviewers of unicellular organisms.

Adaptations of Unicellular Organisms 1.2.3: Explain how various structures of unicellular organism help that organism survive. Essential Question: How do adaptations in unicellular organisms enable them to survive in their environments?

Contractile Vacuole Vacuoles store materials such as water, salts, proteins, and carbohydrates. In unicellular organisms like paramecium, they contain a vacuole called a contractile vacuole. By contracting rhythmically, this specialized vacuole pumps excess water out of the cell. This allows the cell to maintain homeostasis or balance.

Cilia Ciliates, like the paramecium, use hairlike projections called cilia for feeding and movment. Cilia propel them through the water. They also line the organism’s gullet and move its food to the organisms interior. The food particles are engulfed, forming food vacuoles. The contractile vacuoles collect & remove excess water, which helps to achieve homeostasis.

Flagella Some prokaryotic cells use flagella to propel themselves. Flagella are whiplike structures that are used for movement. Some eukaryotic cells have flagella as well. Sponges carry out basic functions, such as feeding and circulation, by moving water through their bodies. Choanocytes use flagella to move water through pores in the wall of the sponge and out through the osculum. As water moves through the sponge, food particles are filtered from the water, and wastes are removed from the sponge.

Pseudopods Some eukaryotic organisms move by temporary cytoplasmic projections called pseudopods. Pseudopods are used for feeding and movement. An ameoba is a type of organism that uses pseudopods. These can also be called “false feet.” The amoeba moves by first extending a pseudopod away from its body. The cytoplasm then streams into the pseudopod. This is a slow but effective way to move from place to place.

Eyespots Plantlike protists, like algae, possess a structure called an eyespot. This is used to help the algae find sunlight to power the process of photosynthesis. Flatworms have an eyespot that can detect changes in the amount of light in their environment.