Unit 2 Flashcards
history of organizing life
Carlus Linnaeus (sweden) established modern taxonomy (bionomial nomenclature)
taxonomy
naming and classifying organisms
phylogeny
the evolutionary relationships among organisms or their genes
What are the 5 hypotheses portrayed in the phylogenetic tree?
1- morphology 2- paleontology 3- behavior 4- development 5- molecular
morphology
anatomy, external structures, more in common (closer evolutionary relationship)
limitations of morphology
difficult to compare distantly related species and some variation caused by environment
ex- leopard frogs N and Central America
paleontology
includes when are where organisms lived (ancestral vs derived traits)
limitations of paleontology
fossil record- few and fragmented
behavior
active morphology
cultural vs inherited traits (bird and frog calls)
developmental patterns
sea squirts and vertebrae both have notochord
molecular data
DNA often used to construct phylogenetic trees
- mutations accumulate over time
- fewer differences= more closely related
what are photogenically analyses important for?
studying the transmission of viruses
how to (not) read a phylogenetic tree
time is read from root to tip
nodes are speciation events
relatedness = most recent common ancestor
Basic principle of molecular clock
Average rate at which a given gene or protein accumulates changes- used to gauge time of particular split in phylogeny
What does the molecular clock help with?
Dating evolutionary events
-rates constant so they can be used to predict divergence times
What is an example of what a molecular clock can help with?
Timing of when HIV first entered human pop from chimp
What is 16s rRNA? What does it code for?
- Small ribosomal subunit
- useful for comparing bacteria (common among all)
Biological species concept
Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups
Limitations of biological species concept
Not asexual/ limited to certain point
Morphological species concept
Appearance
Limitations of morphological species concept
Young, look alike, cryptic species
Group of organisms that can mate with one another and produce fertile offspring
Species
Divergence of biological lineages and the emergence of reproductive isolation
Speciation
Clade
Include all species linked by descent from a common ancestor
Monophyletic
Clade
Polyphyletic
Missing common ancestor
Paraphyletic
Missing some descendants
Taxon
Any species or group that we designate or name
How are new species formed?
Reproductive isolation between species
Reproductive isolation
No longer exchange genes
Reproductive isolation only affects
Sexually reproducing organisms
Allopatric
Populations separated by physical barrier
Examples of allopatric speciation
Continents drift, sea level changes, glaciers, climate changes
(Ozarks vs eastern highlands- fish)
Sympatric speciation
No physical isolation
Pre zygotic isolating mechanisms
Before fertilization occurs
3 examples of prezygotic isolating mechanisms
- mechanical
- behavior
- temporal
Mechanical isolation
Differences in size and shape of reproductive organs makes mating impossible
Behavior isolation
Individuals reject to fail to recognize potential mating partners
Temporal isolation
Mating periods do not overlap
Post zygotic isolating mechanisms
Reduce fitness of hybrid offspring
Examples of post zygotic isolating mechanisms
- low hybrid fitness
- zygotes or adult offspring have lower fitness or hybrids are infertile
Similarities between eukaryotic and bacterial cells
- have cytoplasm
- have plasma membranes
- need to divide to produce more cells
- carry DNA on chromosomes
- copy DNA
Three differences antibiotics exploit
- ribosomes
- prokaryotes have circular DNA
- cell wall
Explain ribosomal difference
- prokaryotes have smaller ribosomes than eukaryotes (70s)
- both have rRNA and proteins =subunits of ribosome
- antibiotics bind to pockets in subunits of ribosomes
Describe difference of prokaryotes shape of DNA
- need DNA gyrase
- –uncoils DNA during replication and prevents “knots”
- –halts DNA replication, kills cell
Describe the difference of the cell wall
Made of peptidoglycan in bacteria
–use to break bacteria into two groups (gram + and -)
How do bacteria form communities?
Aggregate into bio films
How do bacteria reproduce?
Asexually - binary fission
Bacteria 2 locations of DNA
- bacterial chromosome (circular DNA)
- plasmids (DNA connected to chromosome)
Survival strategies of bacteria
- bacteria aggregate into bio films, surrounded by protective slime
- endospores
Endospores
- Produced by bacillus when nutrients are depleted
- resistant to desiccation, heat, and chemicals
- resistant to harsh conditions (anthrax)
Shapes of bacteria
Spirilla (spirals)
Bacilli (rods)
Cocci (sphere)
Size of bacteria
Human hair (100 um)- eukaryotes (60 um) - prokaryotes (1 um) - viruses (0.1 um)
Arrangement of bacterial cells- pairs
Diplococci and diplobacilli
Arrangement of bacterial cells- clusters
Staphylococci
Arrangement of bacterial cells- chains
Streptococci, streptobacilli
Principle of gram stain
Separate bacteria into 2 groups via differential stain
Explain gram stain
Gram +: peptidoglycan = thick and outside (purple)
Gram -: peptidoglycan = think and covered by another layer (pink)
How do we currently define a “species” of bacteria?
- no widely accepted concept
- sequence common 16s rRNA and define cut offs of 95-97%
- operational taxonomic units (otu)
What are the four phyla common the gut?
- actinobacteria
- bacterioidetes
- proteobacteria
- firmicutes