Bio 51 Exam 3

protocells

droplets wit membranes that maintain an internal chemistry different from that of their surrounding.

stromatolites

layered rocks that form when certain prokarytoes bind thin films of sediment together.

endosymbioosis

when a prokaryote cell engulfs another small cell.

serial endosymbiosis

suggests that the mitochondria evolved before plastids through a sequence of endosymbiotic events

plastids

double membrane organelles in plant and algae cells. these are responsible for many things like photosynthesis, pigment synthesis, and nutrient storage.

phylogeny

evolutionary history of a species or group of species

taxon

named group at any level of hierarchy

phylogenetic tree

evolutionary history of a group of organisms can be represented with this

branch point

represents a the common ancestor of two evolutionary lineages diverging from it.

evolutionary lineage

sequence of ancestral organisms leading to a particular descendant taxon

sister taxa

groups of organisms that share an immediate common ancestor

rooted phylogenetic tree

a branch point (often farthest to the left) represents the most recent common ancestor.

basal taxon

lineage that diverges from all other members of its group early in the history of the group

homology

phenotypic and genetic similarities due to shared ancestry

analogy

similarities between organisms due to convergent evolution

cladistics

common ancestry is used to classify organisms

clades

groups that contain ancestral species and all of its descendants

monophyletic group

consists of one ancestral species and all of its descendants

parapyletic group

contains an ancestral species and only SOME of its descendants

polyphyletic

most recent common ancestor of the members is not part of the group

shared ancestral character

characteristic that originated from an ancestor of the taxon

shared derived character

a character shared by all of the group but not found in their ancestors. evolutionary novelty unique to the clade

outgroup

species/group of species from an evolutionary lineage that is closely related but not part of the group of species being examined

ingroup

group of species being examined

orthologous genes

homology is the result of a speciation event and occurs between genes found in different species.

paralogous genes

homology results from gene duplication, thus multiple copies of these gens have diverged from one another within a species.

molecular clock

approach for measuring the absolute time of evolutionary change based on the observation that some genes and regions of genomes appear to evolve at a constant rate.

horizontal gene transfer

process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable elements and plasmids, and viral infections.

prokaryotes

single celled organisms that make up the domains bacteria and archae. They can also survive in a large range of environment

peptidoglycan

what most bacterial cell walls are made of
polymer composed of modified sugars cross-linked by short polypeptides

gram stain

technique used to categorize bacteria by observing differences in cell wall composition

gram positive

relatively simple wall composed of a thick layer of peptidoglycan

gram negative

walls have less peptidoglycan and are structurally more complex
outer membrane contains lipopolysaccharides

capsule

sticky outer layer of polysaccharide protein that covers the cell wall of many prokaryotes.
is also called a slime layer if it is not well defined
this layer protects against dehydration and some can protect against attacks to the immune system

endospores

developing resistant cells during times where there is minimal water or nutrients.

fimbriae

hairlike appendage that some prokaryotes use to stick to their substrate

pili

appendages that pull two cells prior to DNA transfer from one cell to the other

taxis

directed movement towards or away from a stimulus
move towards oxygen/nutrients (positive)
move away from toxic substance (negative)

nucleoid

where prokaryotes have their chromosomes

plasmids

smaller rings of independently replicating DNA molecules that prokaryotic cells have (most carry only few genes)

transformation

where genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings.

transduction

phages (bacteriophages) carry prokaryotic genes from one host cell to another.

conjugation

DNA is transferred between two prokaryotic cells (usually the same species) that are temporarily joined. always one way (bacteria)

F factor

piece of DNA responsible for for the ability to form pili and donate DNA during conjugation.

F plasmid

F factor in plasmid form

R plasmid

similar to F plasmid and often carry resistance genes (code for enzymes that specifically destroy/hinder effectiveness of certain antibiotics).

obligate aerobes

must use O2 for cellular respiration and cannot grow without it

obligate anaerobes

poisoned by O2
some will live exclusively on fermentation while others will extract chemical energy by anaerobic respiration

facultative anaerobes

use O2 if it is present but can also carry out fermentation or anaerobic respiration if there is no oxygen present

nitrogen fixation

some cyanobacteria and methanogens use this method to convert atmospheric nitrogen into ammonia. This ammonia is used in amino acids and other organic molecules

heterocysts

specialized cell in a filamentous chain that performs nitrogen fixation

biofilims

metabolic cooperation among cells of one or more prokaryotic species ocurring in surface coating colonies

extremophiles

first prokaryotes in domain Archaea that live in extreme environments.

extreme halophiles

live in highly saline environments

extreme thermophiles

live in high temperature environments

methanogens

archaea that lives in a moderate environment. releases methane as by-product of how they obtain energy

exotoxins

proteins secreted by certain bacteria and other organisms that are poisonous.

endotoxins

lipopolysaccharide components of the outer membrane of gram-negative bacteria. released only when the bacteria die and their cell walls break down.