Week 1 Flashcards
What are some of the primary mechanisms that generate diversity in the tree of life
Natural selection
- Phenotypic variability within populations created by genetic mutations
-Environmental, spatial and temporal heterogeneity (diversity)
What are some of the secondary mechanisms that generate diversity in the tree of life
-Complexity in structures
-Interactions
-Complex reproductive systems
- Colonization of novel habitats
-Hybridization and polyploidy
Key attributes to diversity of life
-Genetic variation
-morphological diversity
-ecological niches
-behavioural adaptations
-physiological diversity (functions of structures)
-reproductive strategies
-genomic complexity
Progression of our understanding of the tree of life
Aristotles ladder of life –> Whittakers 5 kingdoms based on morphology –> Universal tree of life, based on rRNA
What can increase a cells complexity?
Membranes and the organization that they provide
What is the best piece of evidence that advocates for a common ancestor between species?
A common genetic code - emphasizes the importance of rRNA in phylogenetic sequencing
- RNA is largely believed to be the initial genetic material
What are the 3 fundamental characteristics of life?
- Is able to grow (if not in size than in population)
- is able to reproduce
- is able to pass on characteristics to the next generation
The stages that produced the first simple cells on earth
- The abiotic synthesis of small organic molecules such as amino acids and nitrogenous bases
- The joining of these small molecules into macromolecules (proteins and nucleic acids)
- The packaging of these molecules into protocells (droplets with membranes that maintained an internal chemistry, different from that of their surroundings
- The origin of self-replicating molecules that eventually made inheritance possible
The impact of the oxygen revolution
Doomed many prokaryotic species
SAQW DIVERSE ADAPTATIONS TO THE CHANGING ATMOSPHERE SUCH AS CELLULAR RESPIRATION
- selected for mitochondria
Define a virus
a genome that replicates itself inside of a host cell by directing the machinery of the host cell to synthesize viral nucleic acids and proteins
Sorting Homology from Analogy
Convergent evolution: analogy
Common ancestry: homology
viral replication cycle
the viruses enters the cell and is uncoated, releasing viral DNA and capsid proteins
host enzymes replicate the viral genome
host enzymes transcribe the viral genome into viral mRNA, which host ribosomes use to make more capsid proteins
viral genomes and capsid proteins self-assemble into new virus particles, which exit the cell
Definition of a species
Biological species: reproductive isolation, gene flow
Ecological species - niche differences
Morphological Species - differences in structure
Prokaryotic species: share 97% DNA they are of the same species
Why are viruses important in the functioning of soils and oceans
Viruses are acting on the bacteria all the time, killing them and releasing their contents
- makes their contents available to other organisms
Are viruses considered living?
On the border:
they contain heritable material
not personally affected by temperature
rely on a host to function
could have been the first living organism on Earth
Prions
proteins as infectious agents
act very slowly, have a long incubation period
Viral transmission
animal vectors, bodily fluids, air, hand contact
How do prokaryotes accomplish variation
Short generation times and large populations
- Genetic Recombination
-Transformation
-Transduction- Conjugation and plasmids
vertical Transmission of viruses
inherits from parent
Horizontal Transmission of viruses
Very common in plants, the plant is infected from an external source of the virus (animal eating it)
How does being so small impact prokaryotes
Intimate contact with their surroundings makes them highly sensitive to their environment
Rapid Reproduction
High rate of living do the a high SA:Volume
Rely heavily on water availability
Describe the boom and bust life cycle of prokaryotes
since they have limited mobility spatial and temporal heterogeneity in nutrients and environment is critical to prokaryotic activity
The environment they are in selects for their survival: boom and bust life cycle - when things are good they flourish and if not they quickly cease
Since it is hard to phagocytosize due to the rigid cell walls, how do prokaryotes get nutrients
secrete exoenzymes that can degrade organic matter and take up the nutrients by active transport across the membrane
Heterotroph vs Autotroph vs Chemotroph vs Phototroph
Energy from light: prototrophs
Energy from chemical: chemotrophs
Only need CO2: autotrophs
Require at least one organic nutrient to make organic compounds: heterotrophs
Metabolic Cooperation
Cooperation between prokaryotic cells allows them to use environmental resources they could not use as individual cells
Can take place between specialized cells of a filament - a cell cannot do two processes at once, and so by having filamentous chains and can carry out both photosynthesis and nitrogen fixation (done by heterocyst’s)
Metabolic cooperation between species often occurs in surface-floating colonies called biofilms
Reasons for prokaryotic success
Long evolutionary time
Particular aspects of their biology:
Small size
Rapid generation time
Capacity for prolonged dormancy
Diverse energy and nutritional capabilities
Diverse mechanisms to generate genetic variability
