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| Descriptives of protists: |
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Definition
small, but there are many
thrive almost everywhere
They have an astonishing genetic diversity
Prokaryotes are divided into two domains: bacteria and archaea |
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| a gel like substance coating a prokaryote that keeps it from drying out |
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| allow prokaryotes to exchange DNA |
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| allow them to stick to their substrate or other individuals in a colony |
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| Most motile bacteria propel themselves by flagella that are structurally and functionally different from eukaryotic flagella |
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| In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli |
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| Prokaryotic cells usually lack complex compartmentalization |
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| Some prokaryotes do have specialized membranes that perform metabolic functions |
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The prokaryotic genome has less DNA than the eukaryotic genome
Most of the genome consists of a circular chromosome |
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Definition
| Some species of bacteria also have smaller rings of DNA called plasmids |
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Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours
Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries |
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Prokaryotes reproduce by binary fission, and offspring cells are generally identical
Mutation rates during binary fission are low, but because of rapid reproduction, mutations can accumulate rapidly in a population
High diversity from mutations allows for rapid evolution |
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| Three factors contribute to this genetic diversity of prokaryotes |
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Definition
Rapid reproduction
Mutation
Genetic recombination |
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| Additional diversity arises from genetic recombination |
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| Prokaryotic DNA from different individuals can be brought together by transformation, transduction, and conjugation |
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| A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment |
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Definition
| is the movement of genes between bacteria by bacteriophages |
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Conjugation is the process where genetic material is transferred between bacterial cells
Sex pili allow cells to connect and pull together for DNA transfer
A piece of DNA called the F factor is required for the production of sex pili
The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome |
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Definition
Cells containing the F plasmid function as DNA donors during conjugation
Cells without the F factor function as DNA recipients during conjugation
The F factor is transferable during conjugation |
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R plasmids carry genes for antibiotic resistance
Antibiotics select for bacteria with genes that are resistant to the antibiotics |
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| Prokaryotic metabolism varies with respect to O2: |
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Definition
Obligate aerobes require O2 for cellular respiration
Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration
Facultative anaerobes can survive with or without O2 |
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| In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3) |
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| In some prokaryotic species, metabolic cooperation occurs in surface-coating colonies called |
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| eukarya, prokatyote, and archae characterisitics |
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| Some archaea live in extreme environments and are called extremophiles |
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Definition
Extreme halophiles live in highly saline environments
Extreme thermophiles thrive in very hot environments |
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Methanogens live in swamps and marshes and produce methane as a waste product
Methanogens are strict anaerobes and are poisoned by O2 |
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photoautotrophs that generate O2
Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis |
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Gram-positive bacteria include
Actinomycetes, which decompose soil
Bacillus anthracis, the cause of anthrax
Clostridium botulinum, the cause of botulism
Some Staphylococcus and Streptococcus, which can be pathogenic
Mycoplasms, the smallest known cells |
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Definition
Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems
Chemoheterotrophic prokaryotes function as decomposers, breaking down corpses, dead vegetation, and waste products
Nitrogen-fixing prokaryotes add usable nitrogen to the environment |
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Term
| Symbiosis is an ecological relationship in which two species live in close contact: a larger host and smaller symbiont |
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Definition
| Prokaryotes often form symbiotic relationships with larger organisms |
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| , both symbiotic organisms benefit |
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| one organism benefits while neither harming nor helping the other in any significant way |
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| an organism called a parasite harms but does not kill its host |
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| parasites that cause diesease |
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| the evolutionary history of a species or group of related species |
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| The two-part scientific name of a species |
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| A taxonomic unit at any level of hierarchy is called |
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| a branch from which more than two groups emerge |
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| Homology is similarity due to shared ancestry |
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| Analogy is similarity due to convergent evolution |
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| A valid clade is monophyletic |
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| signifying that it consists of the ancestor species and all its descendants |
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| A paraphyletic grouping consists of |
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Definition
| an ancestral species and some, but not all, of the descendants |
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| A polyphyletic grouping consists of |
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Definition
| various species that lack a common ancestor |
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Term
| A shared ancestral character is a character that |
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Definition
| originated in an ancestor of the taxon |
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| A shared derived character is |
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Definition
| an evolutionary novelty unique to a particular clade |
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Term
| In some trees, the length of a branch can reflect the number of genetic changes that have taken place in a particular DNA sequence in that lineage |
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Definition
| In other trees, branch length can represent chronological time, and branching points can be determined from the fossil record |
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Term
| Maximum parsimony assumes that |
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Definition
the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely
The principle of maximum likelihood states that, given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events |
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| Phylogenetic bracketing allows us |
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Definition
| to predict features of an ancestor from features of its descendents |
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| are found in a single copy in the genome and are homologous between species |
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| result from gene duplication, so are found in more than one copy in the genome |
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uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change
In orthologous genes, nucleotide substitutions are proportional to the time since they last shared a common ancestor
In paralogous genes, nucleotide substitutions are proportional to the time since the genes became duplicated |
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| Difficulties with Molecular Clocks |
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Definition
The molecular clock does not run as smoothly as neutral theory predicts
Irregularities result from natural selection in which some DNA changes are favored over others
Estimates of evolutionary divergences older than the fossil record have a high degree of uncertainty
The use of multiple genes may improve estimates |
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Definition
| is the movement of genes from one genome to another |
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