TXST Dr. Vargas BIO 1321 - Exam 2

characteristics of prokaryotes

- smallest & simplest living things

- single-celled (cannot be seen w/naked eye)

- 3 common shapes: spherical, rod-shaped, spiral-shaped

- they live EVERYWHERE

- reproduce by binary fission

binary fission

- single bacterium replicates DNA then divides in half

- asexual cell division producing identical copies (sometimes w/mutations)

- can occur as often as every 20 minutes

- fast reproduction=fast evolution

conjugation

- exchange of genetic material between prokaryotes without reproduction

plasmid

- small, circular piece of DNA located in the cytoplasm of many bacteria

- separate from main chromosome

differences between bacteria & archaea

1. molecular & structural differences

2. archaea can produce methane

3. some bacteria (autotrophs) can undergo photosynthesis

- archaea = heterotrophs

4. some bacteria are pathogenic

5. bacteria contain peptidoglycan

- gram stains

6. some bacteria produce endospores or biofilms

heterotrophs

organisms that cannot make their own food

autotrophs

organisms that are able to make their own food

pathogens

disease causing agents

peptidoglycan

- layers carbohydrates linked by proteins

- forms a mesh-like layer around bacteria

- some bacteria also have an extra fatty layer covering

gram stains

- tells whether the peptidoglycan is on the outside or covered by the extra fatty layer

- gram positive = purple

- gram negative = pink/red (extra fatty layer)

biofilms

communities of slime-secreting bacteria

endospores

A thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions.

prokaryotes & nutrition

- prokaryotes in digestive system break down carbohydrates into absorbable nutrients and produce certain vitamins (B & K)

- promote immune system function

- killing of pathogenic bacteria

- breakdown of dietary carcinogens

prokaryotes & recycling

- break down complex organic molecules into basic building blocks that all organisms need

- they break down waste products & the dead bodies of plants & animals

prokaryotes & nitrogen fixation

- ~78% of our atmosphere = nitrogen

- all organisms need nitrogen: prokaryotes break down N2 into a useable form of nitrogen

prokaryotes & bioremediation

- some can clean up pollution

- a few human-made substances are biodegradable by certain prokaryotes

bioremediation

stimulating the breakdown of pollutants by living organisms

pathogenic prokaryotes

- some bacteria can cause illness & disease

- spread through: inhalation, insect bites, contaminated food/water, open skin, shared bodily fluids

non-living pathogens

viruses, viroids, prions

virus

- a molecule of DNA or RNA surrounded by a protein coat that holds their genetic material, not a cell

- not alive

- very small

- can & do evolve but do not maintain homeostasis

- require energy or nutrients

- can only reproduce with help

- are PARASITES

- attack all living organisms (prokaryotes, plants, fungi, protists, & animals)

viroids

- infectious particles with only short RNA strands (no protein coat)

- only affect plants

- effects on food supply

prions

- infectious proteins devoid of any genetic material

- extremely resistant to disinfection & sterilization

- 142 amino acids

- resistant to proteolytic enzymes

- survives dry heat

- cannot be destroyed

protists

- any eukaryotic organism that is NOT an animal, plant, or fungi.

- 3 categories: animal-like, plant-like, fungi-like

animal-like protists

move around & hunt for prey like an animal

fungi-like protists

live as heterotrophs & form sheet-like colonies of cells like a fungus

plant-like protists

multicellular & photosynthetic like a plant

areas of diversity among protists

1. single- v. multicellular

2. terrestrial v. aquatic

3. motile v. stationary

4. sexual v. asexual reproduction (binary fission)

5. heterotrophic v. autotrophic (or both=euglena)

heterotrophic protists

absorb nutrients directly through the cell membrane

predatory protists

- ingest food using pseudopods (extension of cell membrane) to surround & engulf prey

- some create tiny currents to sweep food particles into mouth-like openings

protists that absorb nutrients

- free-living: decompose organic dead matter

- parasitic: live inside an organism, sometimes harm host

protists & photosynthesis

- autotrophic protists provide about half the energy on Earth

- turn sunlight into fuel

- produce oxygen

- pull carbon dioxide from atmosphere

protists & food

- provide important food source for land & ocean organisms

- plankton are the most important organism on the ocean food chain

protists & commercial uses

- agar=derived from algae (used for a lot of things)

• vegetarian substitute for gelatin

• thickener for jellies, ice creams, & other

desserts

• clarifying agent for brewing

• thickener for toothpaste, paint, cosmetics

• base for vitamin & drug capsules

• culture medium for microbiology research

pathogenic protists

- cause plant & animal disease

- hard to treat illnesses caused by protists because they are eukaryotes--need to find ways to kill them without harming our own cells

- can infect important crops

- some marine protists release toxins (some release a nerve toxin that causes illness or even death in dolphins, seals, sea otters, fish, birds, humans, etc.)

Key features of fungi

- heterotrophic: secrete enzymes breaking down surrounding food molecules to absorb

- have chitin in cell walls

- multicellular (except yeast)

- reproduce using spores (except yeast,

- mycelium body structure (an interwoven

mass of threadlike filaments called hyphae)

- form important relationships with other organisms (endophytes, mycorrhizae, & lichen)

spores

- reproductive cells that grow when they land in a suitable habitat

- often rely on being carried through the

air or water

fruiting bodies

reproductive spore-producing structures such as mushrooms, puffballs, or truffles

endophytes

- live inside plants and take nutrients

- provide benefits to the plant:

increased growth

resistance to drought

protection against pathogens

protection from being eaten by insects &

other animals

mycorrhizae

- live in & around the roots of plants, taking some of the energy the plants make from photosynthesis

- In return, fungi secrete enzymes that break down large nutrients in the soil all around the roots, allowing the plant to absorb them

lichen

- fungi that live with photosynthetic protists or bacteria

- take some of the energy made from photosynthesis

- fungi provides an anchor & protection

- very diverse: grow on a wide variety of materials (soils, tree trunks & branches, leaves, rocks, fences, roofs, walls, & in water, etc.)

- can survive environmental extremes (newly formed volcanic islands, deserts, high altitudes, etc.)

fungi positives

- provide antibiotics, food, yeast for baking & brewing

- act as important decomposers

- create healthier environments through their symbiotic relationships

fungi negatives

- some fungi are parasitic & cause damage to hosts

- mold & mildew can destroy goods

- some fungi are poisonous

- some fungi are pathogenic

fungi & antibiotics

- not all, but many antibiotics are derived from fungi

- 1st antibiotic discovered, penicillin, is produced by a mold

- other medications are derived from fungi

fungi & food

- mushrooms, such as morels & truffles, are eaten by many animals

- certain molds impart flavor to some of the world's most famous cheeses (Roquefort, Gorgonzola, Brie, etc.)

yeast

- Wine is produced when yeasts ferment fruit sugars

- Beer is derived when yeasts ferment sugars in germinating grains (e.g. barley)

- Bread rises when yeasts ferment sugar that has been added to bread dough

fungi & decomposition

- Fungal saprophytes feed on dead organisms: secrete substances that digest the tissues of dead organisms, liberating nutrients that can be reused by plants

parasitic fungi

- fungal parasites cause the majority of plant diseases

- rusts & smuts = parasites that cause considerable damage to grain crops

mold & mildew

- can destroy goods

- some cause wooden structures to rot

- some damage cotton & wool fabrics

poisonous fungi

- Claviceps purpurea produces several toxins

(including LSD): infects rye plants & causes

a disease called ergot

ergot

symptoms of ergot poisoning = vomiting, convulsive twitching, hallucinations, & death

pathogenic fungi

- Athlete's foot, jock itch, & ringworm are caused by fungi that affect skin

- Most vaginal infections are caused by the yeast

Candida albicans

- Valley fever & histoplasmosis are caused by fungi

that affect the lungs

• infection occurs when the victim inhales

spores - can be fatal