Viruses, Bacteria & Protists

Viruses, Bacteria & Protists Quarter 4 Week 2

Viruses: Structure and Reproduction • Structure • --biological particles composed of DNA or RNA and a protein coat • --Protein coat can be all different types of shapes • --Some contain a membrane-like envelope to help it reproduce (chicken pox, influenza, HIV)

Reproduction • —cannot reproduce on their own • inserts virual DNA into a cell, which then takes over the cell’s reproduction and quickly produces • new viruses until the cell dies and breaks open (called the lytic cycle). • some virus DNA will incorporate into the cell’s DNA and will wait to make more viruses until there is some external stimuli (fever, stress, etc.). All of the cell’s offspring will include this viral DNA (called the lysogenic cycle)

Reproduction

Viruses • viruses gain new genetic material through mutations • This ability to inject DNA into a cell is used now as a treatment method. Ex: A person cannot make insulin and has diabetes. Put the gene within a disabled virus and it injects it into the DNA of the sick person. • **Because they do not meet all of the characteristics of lifethey are considered non-living and do not have their own kingdom!!

Bacteria Structure & Reproduction • Archaebacteria • --prokaryotic, so basically DNA and ribosomes within a membrane • --oldest type of bacteria • --live in extreme habitats (early Earth was a toxic place!) • --Reproduction through binary fission (grow and then divide into two cells); this is asexual reproduction.

Bacteria • -Methanogens make methane gases (intestines of humans and cows and bottom of swamps) • -Extreme halophiles live in high salt environments (Great Salt Lake) • -Thermoacidophiles live in extremely hot and acidic places (hot springs)

Eubacteria • --prokaryotic • --have one of three basic shapes • -bacilli or rod-shaped • -spirrilla or spiral • -cocci or spherical (in chains or • clusters) • --uses cell membrane to produce ATP and go through photosynthesis

Bacteria structure

Bacteria • --DNA is a closed loop that floats in cytoplasm with ribosomes • --capsules or endospores form for protection if conditions become to harsh for survival • --pili are found in some bacteria that help it attach to things and transfer some genetic material • --Reproduction is mostly asexual (binary fission); new DNA can be gained through mutations, pili, viral attacks, and taking in DNA from environment

Protists • --eukaryotic, so contain nucleus and other membrane-bound organelles • --can be divided into three groups: • -Animal-like (Protozoas)—heterotrophic, move independently; unicellular • -Plant-like (Algae)—make food through photosynthesis; some can be multicellular • -Fungus-like (slime molds)

Protist • --protists that are motile use many structures to move: • -flagella (one or two long hairs that have a whip motion) • -cilia (many small hairs that beat back and forth rhythmically) • -pseudopodia (extensions of cell; moves like the “Blob”) • --Reproduction is mostly binary fission (asexual) • some can go through can get new DNA through conjugation • plant-like protists have sexual and asexual reproductive stages

Protists

Fungi • --most are microscopic molds or yeasts • --molds and mushrooms produce filaments to absorb their food • -hyphae-filaments • -mycellium—mat of hyphae you can see • -cells of hyphae can be divided or undivided

Fungi • **Remember that fungi are DECOMPOSERS. As the hyphae digest the materials around them, the chemicals that they do not absorb are returned to the soil. They work at every trohpic level and are the most important part of the nitrogen cycle (working at every stage).**

Fungi • --Reproduction--both sexual and asexual • asexually they produce genetically identical spores, bud, or produce new hyphae • sexual reproduction through fusion of hyphae which creates a genetically unique individual.

Fungi

Viruses, Bacteria & Protists