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BIOL2201 Final pt. 1
Tim's Content
| Question | Answer |
|---|---|
| What is macroevolution? | evolution above the species level; includes patterns or origination, extinction and diversification of higher taxa; restricted to the evolution of great phenotypic changes ofr the origin of characteristics |
| What are the properties of life? | homeostasis; structural organisation (ability to maintain distinct parts and the connections between them); metabolism; response (to external environment or stimuli); growth; reproduction |
| What are the 3 things natural selection needs? | variation; fitness differences; heritability |
| Does the evolutionary theory explain the origins of life? | no, it falls short; it only explains the evolution of life since it came about; doesn't explain how it was created in the first place |
| What is LUCA? | the Last Universal Common Ancestor; it is not a single organism or the first life-form or the only life-form; but it is the only one that left descendants (monophyletic); it is many organisms |
| What is abiogenesis? | where life is created from the non-living |
| What is the Prebiotic Soup hypthesis? | the idea that the earth was a lump of gases and energy with life forms evolving from that; lack of O2; atmospheric gases (nitrogen, ammonia, methane); energy sources (UV light, lightning, volcanic eruptions) |
| How was the Prebiotic Soup hypothesis tested? | the Miller-Urey experiment in the 1950s; set up an environment similar to what we expected earth to look like and tested to see if any amino acids were produced; found in 2008 that there was a lot of amino acids produced (building blocks of life) |
| Where else could we get amino acids and molecules forming? | extraterrestrial origins (meteorites have carbon-rich compounds, amphiphilic lipids, AA, nucleotides); hydrothermal vents have conditions that are ideal for life to exist (e.g. extreme temps., low alkaline, existing for long periods of time) |
| How can ice and clay help concentrate molecules? | clay and ice are filled with areas where agents could possibly concentrate and have a potential to grow and become more complex |
| What is a protocell? | one of the first kinds of cells; made of simple fatty acids that self-assemble; have hydrophilic heads and hydrophobic tails |
| What is a micelle? | a star shaped cell that has simple fatty acids; has the ability to line up in cells and be incorporated into a layer; can go back and forth from the amino acid chain to the layer |
| How do protocell's grow and evolve? | eventually, the outer layer will get really big because micelle's keep adding to it; creates a pocket and buds off to create a sphere; cycle repeats |
| Why were phospholipids selected for in the cellular membrane instead of just normal fatty acids? | experiment done found that a protocell with fatty acids and a few phospholipids were less likely to 'let go' of fatty acids compared to one without phospholipids; therefore the cells with phospholipids didn't split off and just kept growing |
| What is a hypercycle? | an abstract model of organisation of self-replicating molecules in a cyclic structure; when an increase in the rate that A replicates it selectively favoured but also increases B's rate of replication, little benefit goes back to A |
| Why did a hypercycle driven the evolution of an encapsulated cell? | it promoted molecular mutualism as substrates contribute in a positive way to the replication of the other whilst receiving equal benefits; creates a positive feedback loop |
| What are the costs of becoming an encapsulated cell? | building a membrane requires resources; resources must now be brought across the membrane instead of straight into the substrate |
| What are the benefits of becoming an encapsulated cell? | accelerated reproduction; control of microenvironment within cell (chemical gradients etc.); membrane used as defensive mechanism; partitioning of various functions to increase efficiency |
| What is the general theory of RNA world? | the idea that self-replicating RNA came first and then diverged to proteins and DNA; this is because RNA can both store information and undergo processes to help cells form (enzymatic role) |
| What support is their for RNA world? | many proteins contain RNA co-factors (the site that chemical reaction is occurring); to make DNA you have to go through RNA; large ribosome is a catalytic site and composed of RNA, not DNA; 'prebiotic soup' experiments ingredients necessary to make RNA |
| How do we know that RNA can be affected by and withstand natural selection? | Spiegelman et al. experiment started with RNA primer of 4000bp; after 75 transfers, selection favoured RNA strands ~200bp in length; means selection chose what it needs to copy and stay true but doesn't keep the 4000bp |
| If we started with RNA, why is DNA more used today? | RNA works better in earlier, acidic conditions; base of DNA is more stable in present alkaline conditions; double-stranded means less chance of de-stabilisation by other molecules; lower mutation rates with double-strand which allow for longer strands |
| What are the likely properties of LUCA? | replicating cellular organism; DNA used for genetic storage; no nucleus; prokaryotic cell, still very simple; existed for about a billion years before eukaryotic cells start to exist |
| How did prokaryotic cells survive and reproduce? | horizontal gene transfer; can pass genetic material from one organism to another which increases the complexity of the next individual and enables them to perform more functions |
| What do major transitions need to have in order to be defined as a major transition? pt.1 | individuals give up the ability to reproduce independently, reproduction is now shared (obligate relationship) |
| What do major transitions need to have in order to be defined as a major transition? pt.2 | once individuals aggregate into higher-level groupings, they can utilise economies of scale and efficiencies of specialisation; grouping gives them abilities that they otheriwse wouldn't be able to do themselves |
| What do major transitions need to have in order to be defined as a major transition? pt.3 | organisms develop new and more efficient ways to acquire, process, transmit and store information (e.g. switch from RNA to DNA) |
| How can we explain why major transitions work? | need to explain it by the immediate selective advantage to individuals rather than group-level benefits; selection can only work on the phenotype at the individual level |
| What is parthenogenesis? | a way to police cheaters; it is when a female is able to produce offspring without being fertilised |
| What is genomic imprinting? | differentially expressed alleles; some alleles won't work without being brought in from one parent; a good way to stop cheating |
| What is the Endosymbiosis Theory on the evolution of eukaryotic organelles (mitochondira)? | idea that a prokaryote engulfed a proteobacterium capable of energy production; created a symbiotic relationship; proteobacterium protected in cell, cell now specialised and doesn't have to use as much effort to get its energy |
| What is the Endosymbiosis Theory on the evolution of eukaryotic organelles (chloroplast)? | prokaryote host engulfed a cyanobacterium capable of photosynthesis |
| What support is there for this theory? | mitochondria and chloroplasts have their own genome consisting of circular chromosomes (similar to bacteria); organelle RNA is more closely related to prokaryotes than eukaryotes |
| Did eukaryotes come from Archaea ('informational' genes) or Bacteria ('operational' genes)? | early studies suggested eukaryotes share a common ancestor with both bacteria and archaea; recent sutdy suggests that ancient eukaryotes emerged from Archaea, specifically the Phyla Eocyta (paraphyletic relationship); eukaryotes nested in archaea |
| How did the eukaryotic nucleus form? | endosymbiosis played a role; genes found in organelles migrate to nucleus; 'promiscuous DNA'; humans have 200-600 insertions of mitochondrial DNA into nuclear genome |
| What are apicoplasts? | found in Plasmodium cells (responsible for malaria); enclosed in 4 membranes; arose through secondary symbiosis (engulfed by cell twice) |
| How did the evolution of multicellularity spread? | occurred independently many times in many taxa (dramatic convergent evolution); single organisms can come together via two different routes to become multicellular |
| What is the 'staying together' method of multicellularity? | clonal route; cells in an ancestral lineage remained together after reproduction; more common; cells are clones of one another; reduces genetic conflict (reproductive interests aligned); favoured by natural selection because they are identical |
| What is the 'coming together' method of multicellularity? | formally free-living cells join together during early stages of evolution of multicellularity; not an obligate condition; early on in evolution of multicellularity, cells may have joined together then disbanded |
| What are the benefits of multicellularity? | locomotion (cells can move in unison so travel faster); reproduction (all cells in one spot makes it easier to reprodue); division of labour; predator protection; important (none of the se work without efficient communication) |
| What are two group living benefits? | increased foraging; predation avoidance |
| What are the passive and complex benefits of increased foraging in a group setting (e.g. chimps hunting)? | passive (individual does exactly what it usually does; aggregate impact); complex (more communication and coordination of behaviour, roles within a group, regulated by social rules, cheaters are selected against) |
| What are the passive and complex benefits of predation avoidance in a group setting (e.g. schooling fish)? | passive (individual does exactly what it usually does, aggregaTE impact); complex (flash explosion of schooling fish, hydrodynamics = swim faster, creates confusion and information overload for predators) |
| What makes a group work? | a group only works if the overall fitness effect on an individual is positive; can include benefits like economies of scale or foraging success per individual increasing when in a group |
| What are some costs of group living? | increased visibility to predators; conspecific competiont; reproductive interference; 'cheaters'; increase vulnerability to disease |
| What were the first multicellular animals and what were their characteristics? | sponges (metazoans); no germline (so are they really individual?); little cell differentiation but some communication; no symmetry; benefit from economies of scale; evolved around 635 million years ago |
| What did the Ediacaran Fauna look like? | was the first appearance of Cnidarians (jellyfish and corals); symmetry (radial, bilateral); no evidence of feeding appratus or appendages; 'simple' organisms; some forms may have persisted |
| What happened in the Cambrian Explosion? | was 542-522 mya; had the appearance of almost all modern classes of marine animals; most dramatic adaptive radiation in the history of life; but the lineages would have had to originate earlier than the Cambrian; increased diversity of bilaterians |
| What were characteristics of early bilaterians? | could now be patterned (front and back, top and bottom); this was useful for coordinating locomotion; had a defined 'head' region which had a concentration of sensory input and effieicent feeding; segmentation |
| What were the potential triggers of the Cambrian Explosion? | combination of genetic and ecological causes |
| What were the genetic reasons for the Cambrian Explosion? | evolution of regulatory genes (Hox) govern differentiation of body parts; changes in Hox genes cause new combinations to appear; morphological changes led to new interactions among organisms (e.g. predation); selective pressure further enhanced diversity |
| What are the potential environmental reasons for the Cambrian Explosion? | increase in atmospheric oxygen levels can enable an increase in the size of a multicellular animal (more oxygen available); could have been the end of 'Snowball Earth' which could have opened up more environments |
| What is significant about multicellularity in plants? | it has evolved independently many times; there was no 'sponge' equivalent (earliest plans have differentiated cells unlike sponges) |
| Why has multicellularity evolved independently in plants so many times? | 'convoy' principle (harder for a predator to find the same number of cells in a group than it is to find the same number uniformly distributed); radical changes (sexual reproduction, yeast clusters, quorum sensing) |
| What are 3 key evolutionary events along plant lineages? | tissue differentiation; vascularisation; reproductive strategy |
| What did the earliest land plants look like? | around 500 mya; had differentiated body patterning (branching, apical growth); tissue organisation; retention of egg |
| What are bryophytes? | include mosses, liverworts; no roots, stems, fruit, leaves or flowers; microphylls instead; require water to reproduce; gametophyte is large; coincides with Cambrian Explosion |
| What are vascular plants? | includes ferns and clubmosses; 425mya; had a vascular system (xylem and roots); allows larger size; slightly drier environments; smaller gametophytes but still needs moist conditions |
| What are gymnosperms? | includes cycads, confiers; 364mya; massive sporophyte (trees); tiny gametophyte (seed); pollen; seeds had dispersal opportunities and protection; sets up complex interactions between plants and animals; stayed same for next 230 my |
| What are angriosperms? | all flowering plants; 130mya; 88% of plant kingdom; most diverse group of plants; huge potential to evolve (complex interactions, MADS genes able to duplicate, replicate and change a lot) |
| Why might plants have fewer body plans than animals? | don't use Hox genes and instead use MADS genes |
| What is the difference between animal multicellularity and plant multicellularity? | animals 'glued' their cells together using adhesion moleculares (good for communication, bad for keeping shape); plants have passive multicellularity, with cells embedded in cell wall (hard for communication, good for keeping shape) |
| What was plants solution for making communication between their cell walls? | the evolution of the plasmodesmata (little channels betweeen cell walls) |
| What were animals' solution to stabilise their tissues and retain shape? | evolution of skeletal structures (spicules in earliest animals, i.e. sponges) |
| What are some body plan innovations in plants? | apical growth and ordered branching pattern; different tissue types with specialised jobs (e.g. water transport in vascular plants); patterning of tissues 9i.e. roots and flower systems) |
| What are some body plan innovations in animals? | body patterning (dorsal/ventral, anterior/posterior); ability to evolve limbs, a head with mouth and sensory organs; segmentations of body |
| What are Hox genes and MADS-box genes? | both homeotic genes; control the pattern of body formation in developing organisms; similar to a 'master swithc' tjat can turn on/off large developmental cascades; small changes can produce drastic change; don't produce the proteins to make the phenotype |
| What problems did both plants and animals have to work through once they moved to land? | fertilisation that was independent of water; hydration (had to minimise water loss either through a waxy cuticle or skin); gravity (create lignin or bone for structure) |
| What are the differences between micro- and macroevolution? | macroevolution is above species scale, micro is at population level; macro over long time scales; micro can be characterised through experimentation; macro requires inference; macro relies in part on microevolutionary insight |
| What did the birth of the 'Modern Synthesis' do? | bridges the gap between micro- and macroevolution by showing that organisms harbour heritable variation (e.g. in form of alleles), which natural selection can act on over any number of generations |
| What are some extrinsic properties? | climate change; meteor impact; tectonic shift; oxygen content of air; parasites; predation' phenotypic plasticity |
| What are some intrinsic properties? | sex of offspring; body plan evolution is heavily influenced by our ancestry; food fed to offspring; mechanisms of organ development; living organisms have an evolutionary past that connects them to their ancestors and other lifeforms |
| What is evolvability? | intrinsic ability of a clade to adapt to a variety of selection pressures |
| How can development and evolution be restricted by intrinsic properties? | some adaptive traits cannot develop because their development is impossible (or lethal); development determines ability to adapt slow or fast; development can produce freak changes with little fundamental gene change and high probability of |
| How are the forelimbs of marsupials constrained by intrinsic properties as to what they can change into? | as soon as marsupials are born they have to make journey to pouch; forearm are developed at a very early stage because of this; this developmental constraint leads to lower evolvability of the clade, particularly of the forelimb and shoulder girdle |
| What is an example of extrinsic factors limiting the evolution of an organism? | predation selects for large body sizes, but the evolution of large body sizes is counteracted by arid conditions leading to lack of food |
| What is an example of intrinsic factors limiting the evolution of an organism? | selection for an additional pair of legs in mammals is impossible because embryos with extra legs are unviable |
| What is developmental change? | the raw material for macroevolution' the driver of speciations; the little tweaks in the development of an organism thhat allows it to become extremely different |
| What was Von Baer's take on evolutionary development? | thought general traits developed before specialist traits; traits that appear early in dev. are resistant to change and have greater consequences in magnitude (often fatal); wrong because selection acts from first formation, each stage equally important |
| What is heterochrony? | the time in the developmental process at which a trait is first expressed in a species, relative to when that same trait is first expressed in the ancestor; major mechanism rof macroevolutionary change |
| What are the two main categories for the timing of developmental changes (heterochrony)? | changes that affect the timing of the onset of reprodductive traits; changes that affect the timing of the appearance of non-reproductive traits |
| What is recapitulation? | one type of heterocrhony; a trait that appears earlier in the devel. in descendant, later in devel. in ancestor |
| What are the two ways recapitulation can occur? | acceleration (somatic trait appearing earlier in development, e.g. growth occurs earlier in descendant); hypermorphosis (reproductive trait appearing later in development; e.g. period of growth is extended in descendant)) |
| What is paedomorphosis? | a trait that appears later in development in a descendant; or earlier in development in the ancestor |
| What are the two ways paedomorphosis can occur? | neoteny (somatic trait appearing later in development; e.g. onset of growth delayed, rate decreased); progenesis (reproductive trait appearing earlier in development; i.e. period of growth is stopped prematurely in descendant) |
| What is an extreme example of neoteny? | axolotl; retains almost all of its juvenile features, doesn't go to adult stage; however still reproduces at the same time as ancestor; used as a paedomorph advantage |
| What are the relative frequencies of heterochrony? | theoretically paedomorphosis and recapitulation should occur with roughly equal frequencies, however not always the case; e.g. amphibians show lots of paedormorphosis, recapitulation may have been more frequent in dinosaurs (e.g. T-rex) |
| What are homeotic genes? | genes that determine the identity and positioning of anatomical structures during development, e.g. Hox genes |
| What are Hox genes? | common spelling system for body plans; regulators at the top of developmental cascades; tells cells where they are along embryonic anteroposterior axis |
| What does temporal and spatial collinearity mean in Hox genes? | the more anterior a Hox gene is on its chromosome, the more anterior and the earlier it is expressed in the body; enables Hox genes to give a specific identity to different parts of the body |
| What does it mean when we say that Hox genes are homologous? | Hox works exactly same in arthropods and mammals; are highly conserved; can switch Hox genes from one species and substitue it for another from a different species |
| How are MADS genes different to Hox genes? | not collinear; transcription factor combinations determine phenotypes; but the same mechanisms of combining different expression products to inform the shape of various structures; also highly conserved |
| What are the 3 major processes in differential gene expression (how Hox genes work)? | genetic switches; gene duplication; functionalisation |
| How do genetic switches work in gene expression? | transcription factors can turn genes on or off; can then have genes with multiple different enhancer sequences |
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tkeen40
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