T8 - Tree of life Flashcards
What are the 7 properties of life that all living organisms share?
- cellular organization (made up of 1 or more cells)
- energy and metabolism (able to extract energy from their environment - photosynthesis, foods)
- Reproduction (able to reproduce to form new generations)
- Heredity and evolution (have genes/alleles, can change because of mutations)
- Growth and development (we grow and go through different stages - insects go through metamorphosis)
- Regulation and homeostasis (maintaining the right equilibrium state - blood pH, temperature, blood nutrients)
- Response to stimuli (signaling molecules or responding to heat and changes in temperature)
Why are viruses not considered organisms?
- No cellular organization
- No internal metabolism
- No growth or development
They depend on the host to reproduce
What is a fossil?
Preserved remnant or impression of an organism that lived in the past
Organisms that lived a long time ago
What is a stromatolite?
Layered rock that results from the activities of photosynthetic prokaryotes that bind thin films of sediment together (bacteria)
What element is on Earth life based on?
Carbon
- highly abundant on earth and in atmosphere
What are the 4 necessary steps from organic molecules to protocells?
1) Abiotic synthesis of small organic molecules - monomers; amino acids, nitrogenous bases
2) Polymerization of small molecules into macromolecules - polyers; proteins, nucleic acids
3) Packaging of these molecules into protocells (vesicles) - precursors of cells with only some components
4) The origin of inheritance through the transmission of self-replicating molecules
- DNA can be replicated when cells divide (forming of gametes)
- transmission of some info needs cells that can ‘copy’ themselves
What are protocells?
Does not contain genetic info (DNA)
Droplet with membranes (bilayer of fatty acids) that maintained an internal chemistry different from that of the environment
Not living organisms - not cells but have many properties of life
What is primordial/prebiotic soup?
Hypothetical set of conditions that led to the transition from the abiotic world to the biotic world
As long as you have the three basic building blocks; water, monomers, energy (to create bonds between all the smaller ones)
Especially in the presence of water
What was Stanley Millers experiement?
The artificial synthesis of organic matter under conditions that mimicked the early Earths atmosphere (methane, ammonia, hydrogen) and lighting (energy)
- Found that under these conditions, there was a synthesis of formaldehyde, hydrogen cyanide, amino acids and hydrocarbons from abiotic molecules
- ∴ the building blocks came from the reactions of all the gases
How do protocells exhibit some properties of life?
- Vesicles can divide spontaneously (reprod)
- Replication reactions inside vesicle (Internal metabolism)
- Vesicles can increase in size (growth)
- Membranes can eb selectively permeable (regulation)
- Membranes can perform metabolic reactions using external molecules (response to env.)
Why do we sometimes say it is an RNA world?
First organisms were thought to have RNA, not DNA
RNA probably came before both DNA and proteins
Why does the question exist asking which came first, enzymes or nucleic acids? What is the answer?
Because proteins (enzymes) are synthesized from DNA and RNA
but DNA and RNA are synthesized through enzymatic reactions
RNA molecules are able to function as enzymes and catalysts (ribozymes)
- ribozymes can then copy other RNA molecules and self replicate
∴ RNA most likely came first
What is inheritance?
The passing of RNA of a splitting vesicle to daughter vesicles
- Some error in RNA replication and some variation (mutations) in replication rate allows for evolution through NS
What can the relative and absolute age of fossils inform us on?
The evolutionary history of organisms
- many fossils belong to species that no longer exist and went extinct
- some fossils ressemble organisms that still exist today
- organisms can undergo very rapid morphological changes
What is biostratigraphy vs radiometric dating?
Biostratigraphy = determination of relative age via sedimentary rocks
- imprecise/inaccurate
- placing a fossil on top of one another where the most recent (youngest) is at the top and the oldest is at the bottom
Radiometric dating = determination of absolute age via magmatic rocks
- precise and accurate
What is faunal succession?
Specific vertical sequence of fossilized flora and fauna that can be identified reliably over wide horizontal distances
How do we define biozones?
With the help fo specific fossil composition
- intervals of time of geological strata
What kinds of species are good biomarkers?
Species that have very specific ecological requirements, that lived for a very short geological period
Biomarkers = diagnostic species (helps put a date on sediments)
How does radiometric dating occur?
Uses changes in the isotope composition of organisms during their transition state to fossils, and magmatic rocks
What is an isotope? What is a stable isotope vs an unstable one?
Isotope = elements with the same number of protons but different number of neutrons
Unstable isotope (parent) 14C decays into daughter isotope 14N at a constant known rate
Stable isotope 12C in the fossil remains constant until the fossil is discovered
WHat is the isotopic half life?
Amount of time it takes for 50% of the parent isotope (14C) to decay into its daughter isotope (14N)
Why is the fossil record incomplete?
Many fossils were destroyed over time without yet being discovered
There is a bias towards species that existed for long evolutionary times and those with hard shells/skeletons
- was found that for some periods of time, there are no fossils perhaps due to erosion (erosion = no sediments)
What can discontinuity in the fossil record indicate?
Can reflect important geologicalm ecological and evolutionary events
- plate tectonics, erosion, decrease in rate of sedimentation
- changes in climate/habitat, retreat of seas and glaciers (changes in sea levels may lead to migration of species)
- species colonization, phenotypic evolution, extinction
What were the different lifestyles like on the Burgess Shale?
Burgess shale was a paelontological site containing sediments with large diversity of fossilized animals
Benthic = living on the sediments
Endobenthic = living in the sediments
Nektonic = swimming freely
What was the Cambrian explosion? What arose from it?
Many animal phyla today appeared around the same time (535-525 mya) increasing the morphological diversity
- Soft bodied to hard shells organisms demonstrated new defensive adaptations, transition from grazers/suspension feeders to predators and new body plans and prey/predator relationships
What are adaptive radiations?
Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities (roles/niches)
What formed due to the evolutionary success of bilateral symmetry?
- Anterior sensing organs (development of a nervous system/reproductive system)
- Anterior predation appendages (prey capturing/feeding)
- Posterior appendages for movement (swimming, crawling, flying) -> feathers
What can cause mass extinctions?
Changes in temperature, massive volcanic eruptions, meteorites
- all lead to a cascade of dramatic ecological events
- always followed by new adaptive radiations and many new families and genera
What happens once the number of species or members or a taxonomic level reach an asymptote (apparent maximum)?
Chances that you will find a new species are high, but low that we will discover a new class (something of a higher/superior class to a species)
What suggests that all living organisms might share a common ancestor?
All living organisms synthesize and use only L optical isomers of amino acids (out of the 2 configs of molecules L or D)
- LUCA (Last Universal Common Ancestor) contained a genetic code which we can hypothesize based off this that all living organisms share a common genetic code
- LUCA was not necessarily the first living organism - the latest organism that is ancestral to all existing organisms we know today
Where did LUCA likely live? What might this mean?
Likely living near deep-sea vents that are deprived of oxygen but rich in CO2 and H2
This means that LUCA was living in anaerobic conditions - using cellular respiration but in the absence of oxygen
What is phagocytosis?
The ability to trap something from outside and eat
It develops the membrane so it can do folding in the cell (developing a nuclear envelope)
How did eukaryotes evolve? What structures differ between them?
Evolved from prokaryotes within the Archaea branch
Differs in a presence of;
- cytoskeleton = help give structure
- endomembrane system = transportation of vesicles (golgi appartus, ER)
- Nucleus
What is serial endosymbiosis?
Prokaryotic cells engulfed by an ancestral archaea cell
- bacteria trapped inside, once its inside it becomes a eukaryote which gave rise to the mitochondria
What is a mitochondrion or plastid?
Organelles possesing a circular DNA, their own transcription/translation proteins, ribosomes/membrane proteins similar to bacteria
- Can do aerobic respiration for the cell further adding metabolic systems inside which increases the chance of capturing/using oxygen for glucose
What are the benefits of a mitochondrion?
Cell gains a new metabolic system (aerobic respiration)W
What is the colonial hypothesis?
Colonies form through the cooperation of unicellular organisms of the same species
- Cells fail to separate (or separate and then rejoin)
- specialization can occur (where some have different functions - 2 cells that can communicate and work together for transport for example)
What is the symbiosis hypothesis?
Cells from different species establish a mutually benefical and long term association (not likely)
- requires both genomes to merge into a unique one
