Life Science 2017 Viruses Bacteria and Protists Viruses

Life Science 2017 Viruses, Bacteria and Protists

Viruses • Viruses are tiny, nonliving particles that enter and then reproduce inside living cells. – Require a host to obtain energy and reproduce – Act like parasites or organisms that live on or in a host and cause it harm • Almost all destroy their host cell

Viruses vary widely in shape: – Influenza virus • Spherical – Tobacco mosaic virus • Rod shaped – Bacteriophage • Complex, robotlike shapes • “Bacteria eaters” – Much smaller than cells (cannot be seen with our Microscopes)

How Viruses Multiply 1. Virus enters the host cell 2. Virus’s genetic material takes over cell’s functions 3. Cell is instructed to produce virus’s proteins and genetic material (DNA) 4. New virus is created

Virus Structure • Virus surface proteins must match certain host cell membranes – Like a “lock and key” – Reason why the common cold virus infects cells in the nose and throat – the area where this illness is mostly found in humans

Usefulness of Viruses • Gene therapy allows scientists to treat certain diseases – Virus acts as “messenger” of reparative DNA • A vaccine is a substance introduced in the body to help produce chemicals that destroy specific viruses. – Often made from weakened or dead viruses – Host cells now recognize the virus as a threat and know how to fight it

Amoeba Sisters Virus Video

Bacteria • Many bacteria are harmless or even good for you. – Examples: • Yogurt • Coat your skin • Inside nose **There are more organisms inside your mouth than there are people on Earth.

Cell Structures • First discovered in 1600 s by Anton von Leeuwenhoek • Bacteria are prokaryotes whose genetic material is not contained in a nucleus Contain: Cell membrane Cell wall Ribosomes Flagellum DNA Cytoplasm

Food • Autotrophic – Some conduct photosynthesis – Some use chemical substances to make food • Heterotrophic – Examples of foods: • Milk • Meat • Decaying plant matter

Role of Bacteria in Nature • Oxygen and food production – Autotrophic bacteria help keep atmospheric oxygen levels stable • Health maintenance – Break down food to create new food ie. making cheese and yogurt – Pasteurization removes harmful bacteria through intense heating – Digestive bacteria help keep you healthy • Medicine production – Can be used in the production of insulin • Environmental cleanup and recycling – Decomposers break down chemicals in oil spills

Protists Euglenoid Amoeba Slime Mold

What Are the Characteristics of Animal-Like Protists? • Protists are eukaryotes that cannot be classified as animals, plants, or fungi. – This kingdom is very diverse • • Most are unicellular Some are multicellular Some heterotrophs while others are autotrophs All live in moist locations 3 categories of protists: 1) Animal-like – protozoans 2) Plant-like – algae 3) Fungi-like

Animal-like Protists • • Heterotrophs Most can move to get food Unicellular Called protozoans

Protozoan Movement and Life 4 Groups: • with Pseudopods – temporary bulges of the cell that form around food (false foot) • with Flagella – Called flagellates who have long whip-like tales • with Cilia – Hair-like projections that beat in waves to move • Parasites – Not classified by movement but instead by how they obtain energy from other organisms

Pseudopods • Cytoplasm moves towards side of cell where food is located and rest of the cell follows and surrounds food Example: Amoeba

Flagellates • Some are harmful and some are beneficial – One breaks down food in intestine of termite – Giardia, found in fresh water, causes hiker’s disease

Ciliates • Cilia help organism move and sweep food into the cell Example: Paramecium

Parasites • Feed on cells and body fluids of their hosts Example: Plasmodium (causes malaria and is transmitted By mosquitoes)

Plant-Like Protists • • Commonly called algae Autotrophs Unicellular or multicellular Use pigments to capture light energy – Green, yellow, red, brown, orange or black

Types of Algae • • • Euglenoids Dinoflagellates Diatoms Red algae Brown algae

Fungus-Like Protists • Heterotrophs • Cell walls • Use spores to reproduce – Spores are tiny cells that can grow into a new organism. Examples: Slime molds Water molds Downy mildews