Biology Chapter 8: Microscopic Organisms

Microscopic organism

an organism too small to be seen by an unaided human eye

Biogenesis

the formation of new living organisms

Urey-Miller experiment

one of early experiments to attempt to recreate atmosphere of early Earth resulting in organic polymers

Prokaryotes

the first groups of life to evolve on Earth; have relatively small, simple celled organisms; found everywhere there is life, including many places where no other life can survive

Bacteria

unicellular, found everywhere, some cause disease, but most are beneficial

Archaea

unicellular, often found in extreme conditions such as anoxic, extreme heat, or extreme salinity

Cell wall

provides protection in a range of environments in prokaryotes

Capsule

provides protection and allows prokaryotic cell to stick to surfaces

Flagella

propel prokaryotic cells

Endospore

a thick-shelled protective container in prokaryotic cells for harsh conditions

Binary fission

a process by which most prokaryotes reproduce asexually by splitting in half, which can result in a huge population of prokaryoties in a short period of time

Cocci

prokaryotic cells with a spherical shape that may be found alone, in chains, or clustered

Spiral

curved shaped prokaryotes mostly occur singly

Bacilli

rod-shaped prokaryotic cells that may be found singly or in chains

Biofilms

organized colonies of one or several species attached to a surface, such as rocks or living tissue

Methanogens

archaea which emit methane gas as a waste product of their metabolism; frequently found in the thick anaerobic mud at the bottom of a swamp or bog

Halophies

archaea that thrive in very salty environments

Thermophiles

archaea which can live in areas with temperatures above boiling

Probiotic bacteria

helpful bacteria which convert milk into yogurt through lactic acid fermentation

Sex pilus

a hollow extension used by a donor cell to form a physical connection to a recipient cell during conjugation

Conjugation

a donor cell transfers a chromosome copy through a mating bridge

Endomembrane system

a unique feature of eukaryotic cells which consists of interconnected internal membranes and membrane-enclosed organelles

Endosymbiosis

when one species lives inside another host species

Protist

used to describe all eukaryotes that do not belong to the plant, animal, or fungus kingdoms

Protozoans

protists that obtain nutrients primarily by eating

Amoebas

single-celled protists with great flexibility in their body form

Slime molds

protists that resemble fungi in appearance and lifestyle

Algae

photosynthetic protists able to produce their own food from sunlight

Colony

loose physical association of individual free-living cells

Virus

a nonliving parasite which has no cells and cannot reproduce on its own

Retrovirus

a virus with an RNA genome that is converted to DNA which targets cells of the immune system and spreads by sexual contact or by sharing blood products

Protease inhibitors

interfere with viral proteases so no more proteins form

AZT

inhibits reverse transcriptase by mimicking thymine, making DNA production stop

Emerging virus

a virus that has rapidly come to the attention of scientists

Pathogen

any agent that cuases disease

Living pathogen

bacteria, fungi, or protists that causes disease

Non-living pathogen

a virus which causes disease

Prion

an infection, misshapen version of a normal brain protein

Viroids

small, circular RNA molecules that can infect plants