APS121 Evolution Flashcards
Defintion: Biodiversity
Is the variety of life, in all its manifestations. It encompasses all forms, levels and combinations of natural variation.
Defintion: Taxonomy
The science of the classification of organisms
Defintion: Phylogeny
The study of evolutionary relationships
What are the Phanerozoic time periods?
Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene.
(Camels often sit down carefully perhaps their joints creek permanently nowadays)
Reasons Why the fossil records is incomplete:
- Only of a few of the organisms to ever live will end up being fossilised and therefore studied.
- Entire species/taxa may not be at all preserved
What will limit chances of fossilisation?
- Low preservation potential
- Inhabit small geographical areas
- Small populations
- Only lived for a short period of time
How is fossilisation biased?
- Certain environments more likely to preserve organisms- ie marine> terrestrial, terrestrial lowland> terrestrial highland
- Aquatic animals or those who end up on aquatic environments better preserved
- Recalcitrant organisms more readily preserved
Defintion: Recalcitrant Organisms
Organisms with hard features like exoskeletons, bones, teeth.
Better preserved by fossilisation
Types of environmental change through time:
Temporarily Variable- Diurnal, Seasonl
Milankovitch Cycles- Relate to the earth rotating around sun, eg Icehouse or Greenhouse
Examples of long term environmental change:
- solar luminosity (getting brighter)
- decrease in tides as we move away from the moon
- continental drift
- evolving biota
Examples of short term environmental change:
- tsunamis
- super erosions
- mass extinctions
Order of Taxonomy
Kingdom, Phylum, Class, Order, Family, Genus, Species
Kinky pigs can only fly going sideways
Process: Cladistic Analysis
- Create a data matrix of character states for taxa under consideration
- Use a computer package to analyse the data and create a cladogram
(Dark spot means character is present, light spot means character is absent)
Defintion: Analogous
Similarity due to convergent evolution
aka homoplasy
Defintion: Homologous
Similarity due to common ancestry
Defintion: Symplesiomorphies
Shared ancestral characters (trait appeared in original ancestor)
Definition: Synapomorphies
Shared derived characters (trait appeared in most recent ancestor)
Definition: Autopomorphies
A derived character unique to a single taxon
Definition: Monophyletic Group
Contains the latest common ancestor plus all, and only all, of its descendants (Perfect group)
Definition: Paraphyletic Group
Diagnosed by plesiomorphs, doesn’t include all the descendants of a common ancestor (something was missed out)
Definition: Plesiomorphs
Homologous traits which are not unique to a group
Definition: Polyphyletic Group
A group where the most recent common ancestor is assigned to another group and not itself, due to convergence or non homologous characters assumed to have been absent. (added something wrong)
The eight system kingdom:
Bacteria, Archaea, Archaeozoa, Protista, Chromista, Animalia, Fungi, Plantae
The three domains:
Domain Bacteria, Domain Archaea, Domain Eukarya
Prokaryote and Eukaryote differences:
P: 1-10um, E: 10-100um in size
P: cell wall of peptides and sugars, E: cellulose and chitin
P: no membrane bound organelles E: membrane bound Mitochondria and Chloroplast
P: anaerobic E: aerobic
What do Prokaryotes split into
- Eubacteria
- Archaebacteria (less numerous and diverse, inhabit extreme environments)
> 3800 Ma
- Progress retarded by continued bombardment of large objects
- This releases energy sufficient enough to boil of oceans and the atmosphere
< 3800 Ma
- Meteorite bombardment decreases as they incorporate with different planets
- The planet begins to cool so oceans and the atmosphere condense out.
- Organic compounds begin synthesising an accumulating
Uses for the moon as a dead planet
- Can identify and date rock collisions from heavy bombardment
- This is because it is dead so nothing decomposes or changes
What formed the early atmosphere?
- volcanic outgassing of H2O, N2, CO2, CH4, NH3, H2, H2S
- Eventually this condenses into oceans and the earth becomes hospitable
Definition: Panspermia
The idea that life was seeded on earth by a comet or meteorite
Approaches to solving the Origin of Life
- Analyse living prokaryotes and attempt to reconstruct their common ancestor
- Compare duplicated genes, potentially enabling us to look back and estimate earliest components of genetic machinery
- Reconstruct conditions of previous earth and simulate experimentally to see what is produced
Chemicals required to simulate primitive earth conditions:
- All important amino acids
- Purines and Pyrimidines (ACGU)
- Sugars
- Porphyrins for B12 and chlorophyll
- Complex tar like complexes
Fundamental similarities between Prokaryotes and Eukaryotes
- Both Transmit info into a triplet code in DNA and translating it into proteins through RNA
- In living organisms all amino acids are laevo-rotatory and nucleic acids all the sugars are dextro-rotatory
What does LUCA stand for?
Last Universal Common Ancestor
Energy sources for life
- Sun
- Radioactivity
- Electric Discharges (Lightening)
- Volcanic
Evidence that RNA came before DNA
- Self splicing RNA (RNA that reproduces independently)
- Thymine was not produced in the early atmosphere experiments
What initiated the development of metabolic pathways?
RNA continuously replicates in the ocean and eventually competition begins, this encourages mutations and eventually the chemicals run out.
This encourages the development of metabolic pathways
Name 2 forerunners of photosynthetic pigments
- Cytochromes
- Porphyrins
Must be synthesised
DEFINITION: Obligate Anaerobes
Poisoned by O2, live exclusively by fermentation or anaerobic respiration
DEFINITION: Aerotolerant Organisms
Cannot use 02 for growth but will tolerate it’s presence, live by fermentation
DEFINITION: Facultative Anaerobes
Use 02 if present but can but can also live by fermentation in anaerobic conditions
DEFINITION: Obligate Anaerobes
Can only live using 02 for cellular respiration
Fossil Stromatolites
- Living mounds covered in cyanobacteria that photosynthesise and release 02 bubbles
- Anaerobic bacteria live underneath the outer layer and remain in areas with no other life
- After storms the outer layer is covered in sediment and the bacteria travel to the outside again but produces layered appearances
Carbonaceous Matter
Can be identified chemically as the produce of ancient life, by comparing the ratio of carbon isotopes you can see if life was present in a rock (more c12= definite life)
Early O2 Sinks
- Volcanic gases from the early atmosphere readily combine with 02 forming gases and water
- Dissolved Iron scavenged O2 to form BIFs (banded iron formation from rust)
- Micro organisms carrying out aerobic respiration, some early organisms would’ve been faculative
Pyritic Conglomerates
Pebbles which are only formed in anaerobic conditions, known as fools gold
Advantages for Sexual Reproduction
- Allows advantageous mutations to combine within offspring
- Sex can shed harmful mutation by mating lots, unlike asexual organisms who keep adding until they become extinct
Main theories for why sex evolved
- A method to speed up evolution
- A method to fend off disease/ parasites
- A way to repair genes
(all unlikely due as won’t improve survival in the moment) - Most likely a historical accident
evolved after eukaryotes
Shared Characteristics of Metazoans
- Multicellular body formed from different cells
- Ability to manufacture collagen
- Reproductive cycle with gametes produced from meiosis
- A nervous system comprised of neutrons (except sponges)
Advances in understanding metazoans
- New fossils
- Phylogenic analysis of anatomical & molecular data
- Molecular clock studies
- Molecular genetics of animal development
Ediacaran Period
Late precambrian
Ediacaran Biota were large organisms with a quilt like structure
Were dominant at this time
Suggestions on how Ediacaran Biota fed
- Compartments contained unicellular photosynthetic algae ( unlikely due to water depth and light penetration)
- Took in a substance through a cell wall
- Chemosymbiosis where they utilised sulphide oxidising bacteria from deep sea vents
Interpretations of Ediacaran
- Simple ancestors of several modern phyla, not popular due to great anatomical differences
- Diploblastic animals showing a range in variation not seen in living examples
- Entirely separate attempt at multicellular life that failed
- Recent geochemical evidence suggests some are related to animals
Phosphate rich environments on preservation
- Entirely soft tissued organisms that usually rot can be preserved perfectly in phosphate rich environments
Middle Cambrian
- Suddenly many organisms develop preservable parts ie shells, all modern phyla can now be found in the ocean
Known as the Cambrian explosion - Special environments, often anaerobic, meant many soft tissue organisms were preserved
Examples of well persevered sites from the Cambrian explosion
- Burgess Shale
- Emu Bay
- Sirius Passat
- Chenjiang
Triggers for the Cambrian Explosion
- Wilson Cycles (continents breaking apart)
- Series of glaciations
- O2 dramatically increasing
- Evolution of eyes and sight for predators
DEFINITION: Transitional Forms
Used in the fossil record to demonstrate evolutionary links between major groups
DEFINITION: Homologous Character
Traits inherited from a common ancestor, they show that different groups have evolved from common ancestors swell as when they may have diverged
ie the pentadactyl limb
DEFINITION: Vestigal Characters
Structures that exist but have no function, their presence however serves as evidence for evolutionary relationships and change
eg. Whales possess a tail bone but no legs linking them to terrestrial ancestors
3 Conditions for selection
- Variation
- Heritability
- Competition and fitness
DEFINITION: Variation
Within a species, not all individuals are alike, there is variation between parents and offspring
DEFINITION: Discrete Variation
Distinct categories ie black and white peppered moths
DEFINITION: Continuous Variation
A range of morphs ie intensity of banding on snail shells
DEFINITION: Heritability
- Individuals inherit characteristics from parents, the basis for this inheritance is genetic
- ie variation is not random but has a deterministic genetic basis
Competition and Fitness
Due to a finite amount of resources available to members of a species some individuals are successful and others are not.
Consequently not every individual can survive & reproduce
DEFINITION: Ecological Competition
- Consequence of limited resources, these may include food, water, shelter
- There is a direct relationship between amount of resource captured and fitness
DEFINITION: Fitness
- A measure of the reproductive success of an individual
- An individual who passes on copies of 100% of their genes to the next generation has a fitness of 1.0
- To achieve a 1.0 fitness diploid organisms need to produce at least 2 offspring
DEFINITION: Directional Selection
- A systematic change of the characteristics of an organism through time
- Typically in size
eg giraffe neck length
DEFINITION: Stabilising Selection
- Evolution selects an optimum, neither too big or too small
- Removes overly large or small
ie baby size
DEFINITION: Disruptive Selection
- Occurs when multiple forces simulataneouly shape a trait
- Some birds have large & some small beaks within one population
- This is due to different food sources
- Therefore intermediate beaks are a disadvantage
DEFINITION: Altruistic Action
An action of an individual that benefits others rather than itself
Potentially challenges evolutionary ideas
Kin Selection
- Used to explain altruistic behaviour
- Increases the survival and reproduction of other individuals, however these individuals are kin so will possess the same genes
- Highlights it doesn’t matter which individual possesses the gene as long as its passed on
Relatedness equation
r x b > c
r= relatedness of target individual
b= benefit to target
c= cost to giver
DEFINITION: Relatedness
The proportion of genes shared because of common ancestry
With each generation the genes half
DEFINITION: Selfish Genes
Selection will favour genes that spread at the expense of others, the individual plays no role, the outcome for the gene is all that matters
DEFINITION: Green beard Selection
Relatedness is not always required, if altruism gene is linked to an obvious phenotype possessors will spread it by being altruistic
DEFINITION: Sexual Dimorphism
Differences in the size, colouration or behaviour between males and females of the same species
DEFINITION: Intrasexual Selection
Members of the same sex compete with each other to be able to mate with others, eg red stag
DEFINITION: Intersexual Selection
Females choose from a selection of many males
