Life - patterns in evolution Flashcards
What does it mean to say that a species is dimorphic?
Females and males of the species have prominent differences in physical characteristics
What are cryptic species?
Species that are morphologically indistinguishable, yet do not inter breed
What is the lineage species concept
The idea that the history of a species can be seen as starting and ending with a speciation event (or extinction)
What happens, in terms of genetics, to populations that are isolated over time
They may acquire new fixed alleles at many different loci
Offspring between isolated groups is likely to be functionally inferior
What is allopatric speciation?
Speciation caused by geographical/physical isolation
What is the dominant mode of speciation in most oranisms?
Allopatric
What is sympatric speciation?
Reproductive isolation of populations inhabiting the same regions
Speciation is usually a gradual process. Give an exception
Polyploidy (chromosome duplication)
In only a couple of generations, complete reproductive isolation may occur
Give four example of prezygotic reproductive barriers
Mechanical isolation, temporal isolation, behavioural isolation and habitat isolation
What is low hybrid zygote viability?
Hybrid zygotes failing to develop/mature normally
What is low hybrid adult viability?
Hybrid offspring has low survivorship rate
What is hybrid infertility?
Hybrid offspring, like mules,
which are sterile
What is reinforcement?
When natural selection favours traits that strengthen prezygotic barriers, driving isolated populations apart further
What is speciation?
The process by which one species splits into two or more daughter species, which thereafter evolve as distinct lineages
How does the biological species concept distinguish species?
On the basis of reproductive isolation
How does the morphological species concept distinguish species?
On the basis of physical characteristics
Give 4 factors that influence rates of speciation
Dispersal ability, type of pollination, sexual selection and specialised diets
birds which are sexually dimorphic have _ rates of speciation than monomorphic species
Higher
For wind-pollinated plants, speciation rates are _ than those for animal-pollinated plants
Lower
Why can a high diversity of host plants lead to higher rates of speciation for herbivorous bugs?
They usually only specialise on a few closely related plants.
There are lots of opportunities for exploitation
Why do animals with complex sexual selection behaviours have higher speciation rates?
Sophisticated discrimination of partners can have a large impact on which individuals are successful
Why do species with lower dispersal ability have higher rates of speciation?
Even a a small physical barrier can have a large impact
What is evolutionary radiation?
When a large number of daughter species descend from a single ancestor
When is evolutionary radiation adpative?
When daughter species have a diverse array of characteristics used to exploit many different environments
What do multicellular eukaryotes and unicellular prokaryotes have in common?
They use the process of glycolysis
They have plasma membranes and ribosomes
They use DNA as genetic material - transcription, translation, replication processes
give an example of a type of universal gene
The genes that code for structural components of ribosomes
Read this
Prokaryotic cells lack a cytoskeleton and a nucleus
What process do prokaryotic cells use to divide?
Binary fission
Many prokaryotic cells have only one main chromosome, making them _
Haploids
Eukaryotic cells have a most common ancestor with _
Archaea
Last common ancestor of the three domains lived
2 to 3 billion years ago
The bacteria in your intestinal tract _
outnumber all of the humans that have ever lived
Why are multicellular colonies of prokaryotes not considered to be a multicellular organism?
They are fully viable as individuals
Prokaryotes adhere to one another after binary fission, forming associations in _
the form of chains
Dental plaque is _
A biofilm
What are the oldest fossils ever discovered?
Stromatolites - layers of fossilized biofilms
How do microbes form biofilms?
They bind to a surface and then secrete a sticky polysaccharide substance which traps other cells
The cell wall of almost all bacteria contain _
Peptidoglycan
What determines whether a cell is gram-positive or gram-negative?
Whether or not they retain dye during the chemical treatment
Gram-negative cells have a _ peptidoglycan layer
Thin
Gram-positive cells have a _ peptidoglycan layer
Thick. 5 times as much
gram- _ prokaryotes have a _ space between an inner and outer membrane
negative
periplasmic
Why are cell walls a good target against pathogenic bacteria?
Because there is no counterpart in eukaryotes. Less collateral damage
Give an example of bacteria communicating chemically
Quorum sensing - detecting population density by chemical means
Give an example of bacteria communicating physically
Bioluminescence
Prokaryotes display _ metabolic diversity than eukaryotes
Greater
What is the difference in the motion of flagella between prok and euk
Pro have rotation around the base
Euk more of a whip like action
What is the typic generation time scale for bacterial cells?
Days to hours
What are obligate anaerobes?
Cells that live only through anaerobic metabolism. Molecular oxygen is poisonous to them
Which kinds of prokaryotes perform cellular respiration?
Obligate aerobes and facultative anaerobes
What are obligate aerobes?
Cells that cannot survive with out oxygen for extended periods. They use cellular respiration
What are aerotolerant anaerobes?
Oxygen is not poisonous to these cells but they do not perform cellular respiration
What are facultative anaerobes?
Cells that switch between anaerobic and aerobic modes
What are photoautotraphs?
Cells that perform photosynthesis - using light as an energy and CO2 as a carbon source
