5 evolution (bioninja summary) Flashcards
evolution definition
what is evolution in terms of genes
a change in the allele frequency of a populations gene pool over successive generations
what are the 2 proposed theories of evolution?
lamarck – species change via habitual use and disuse (rejected bc no genetic basis)
darwin (and wallace) – species change via natural selection (reinforced by modern genetics)
3 ways genetic variation is maintained in a population
- mutations (gene sequence changes)
- sexual reproduction (new gene combinations)
- gene flow (immigration and emigration)
2 ways population variety is altered
- random chance (genetic drift) - variant just so happens to die in chance event
- directed intervention (natural/artificial selection)
what is speciation?
when populations are isolated and the level of genetic divergence gradually increases (the longer the populations are seperated)
what supports speciation?
continuous variation over geographical range of related pops – gradual divergence
when does speciation occur?
when populations diverge to the extent that they can no longer interbreed and produce fertile, viable offspring
what is a fossil?
the preserved remains or trace of a past organism
what is the fossil record
the totality of all fossils
what does the fossil record show? (law of fossil sucession)
shows that changes have occurred in organisms
– these changes have occurred in a consistent
sequence of development
example of law of fossil succession
ferns always appear before flowering plants
transitional fossils definition
represent intermediary forms within the evolution of a genus and demonstrate species connections
example of transitional fossils
The archaeopteryx links the evolution of birds (wings and feathers) to dinosaurs (jaws and claws)
what is selective breeding? how is it effective?
mating of animals with desired characteristics (artificial selection)
changes happen over fewer generations – phenotype extremes are promoted
example of selective breeding
Large variation in types of dog breeds
what is the “molecular clock”
If a particular gene has a stable mutation rate, the time of evolutionary divergence can be estimated
what are vestigial sturctures
Some species show the presence of FUNCTIONLESS or reduced REMNANTS of organs that were once present in ancestors
example of vestigial structures
whales have a pelvic bone (ancestors were terrestrial)
what are homologous structures
anatomical features that share common basic structure but have different functions
what causes anatomical features to differ
adaptive radiation (organisms adapt to different niches)
Closely related species demonstrate greater homology
example of homologous structure
pentadactyl limb (diff appendages, same bone strcuture)
what can be gleaned from comparing embryonic development + examples
suggests a common evolutionary pathway
- All terrestrial animals have non-functioning gill slits
- Many vertebrate have a primitive tail in early stages
what is biogeography
Biogeography is the distribution of species across an area
- Related species will usually be found in close proximity
- E.g. Monotremes are exclusive to Australia/New Guinea
how can exceptions to biogeography be explained?
continental drift
conditions for natural selection
- genetic variation present
- competition for survival
- environmental selection pressures
- beneficial traits survive and repro = more common
key components to natural selection (ICEAGE)
- Inherited variation
- Competition
- Environmental selection
- Adaptations
- Genotype frequency changes
- Evolution occurs
examples of selection pressures (PANDAS)
- Predator / prey dynamics
- Abiotic factors (e.g. climate)
- Nutrient supply (food source)
- Diseases / pathogens
- Available resources (e.g. light)
- Space requirements (habitat)
what are adaptations
traits that make an individual suited to its environment and way of life
can be structural, behavioural, physiological, biochemical or developmental
how do populations evolve according to environmental conditions
different adaptations based on the functional position of the org in the enviro in its ecological niche
example of adaptation
change in beaks of finches on Daphne Major
how does binomial nomenclature work
proposed by carl linneaus in 1735
two parts
1. genus written first, capitalised
2. species in lower case
what is taxonomy
classifying organisms based
on shared characteristics (or taxa)
more shared taxa = more closely related
taxa order
Kingdom = katy
phylum = perry
class = comes
order = over
family = for
genus = grape
species = soda
3 main domains of life/classification
- eukarya (all eukaryotic)
- archaea (prokaryotic extremophiles)
- eubacteria (pathogenic bacteria)
eukarya vs archaea vs eubacteria 4
histones: present, present, absent
introns: present, present absent
nucleus: present, absent, absent
ribosome: 80s, 70s, 70s
what is natural classfication
involves grouping organisms according to common ancestry (rather than by common characteristics)
* allows for species to be identified by their evolutionary
pathways and enables the prediction of traits within a group
disadvantage of natural classification
taxonomists may need to reclassify groups if new phylogenetic evidence emerges
what is a dichotomous key
involves sequentially dividing organisms into two categories until every organism is individually identified
what is cladistics
classifying organisms into groups of species (clades)
* A clade consists of a single common ancestor and all descendants
what are cladograms
tree diagrams where each branch point represent the
splitting of two new species groups from a common ancestral species
* Each branch point (node) represents a speciation event
* The more nodes between groups, the less related the groups are
homologous vs analogous features
diff structures // similar structures
diff selection pressures // similar
share common ancestry// do not
divergent evolution // convergent evo
eg. pantadactyl limb // fins (whale, shark)
how can molecular evidence be used for cladograms
related species = sequences with more similarities
AA sequences accumulate diffs slower than DNA sequence
