What is classification?
naming and organising organisms into groups based on characteristics
What is the taxonomic hierarchy?
domain: archaea, eubacteria and eukaryotae
kingdom: plantae, animalia, fungi, protoctista, prokaryotae
phylum: same body plan
class: same general traits
order:
family
genus:
species
What is the trend in terms of ease and classification?
- higher levels easier to classify e.g. two phyla in animals (chordata with backbone and arthropoda with exoskeleton)
- as you descend it becomes harder due to fewer differences
What is the biological and phylogenetic definition of a species?
What are the issues with biological one?
biological: freely interbreed to produce fertile offspring ->
phylogenetic: organisms that are similar in anatomy, biochemistry, appearance, and physiology.
issues = asexual reproduction, fossils
What was early classification like?
- appearance, anatomy and niche dependent
- plant or animal -> water, land, air
- similarities often led to incorrect groupings e.g. fins, wings.
What changed in the modern classification techniques?
- electron microscopes caused adaptations
- showed organisms with plant AND animal features e.g. Euglena
- fungi were originally classified as plants but don’t photosynthesise and they digest organic matter
-> led to 5 kingdoms. still based on observable features but at the microscopic level.
What is the binomial naming system?
- genus + species. Genus as capital for first letter and the rest lowercase. e.g. Homo sapiens
- Latin as universal language; can be understood better; avoids confusion often caused by common names;
What are the features of prokaryotae?
- plasmids + non linear DNA
- no membrane bound organelles
- smaller ribosomes
- free living or parasitic
- uni cellular
What are the features of protoctista?
- eukaryotic
- MOSTLY unicellular
- some feed using extracellular enzymes
- autotrophic or heterotrophic
- mostly free-living
- wide variety of forms
What are the features of fungi?
- eukaryotic
- chitin
- free living or saprophytic
- multinucleate cytoplasm
- unicellular or mycelium with hyphae
What are the features of plantae?
- autotrophic
- eukaryotic
- multicellular
- cellulose
-chlorophyll
What are the features of animalia?
- eukaryotic
- multicellular
- heterotrophic
- able to move around
How did the 3 domain system come about?
- ribosomal RNA gene research
- divided Prokaryotae into 2 groups as Bacteria are fundamentally different from Archaea and Eukaryotae
- bacteria have diff cell membrane structure, RNA synthesis enzymes, DNA replication mechanisms, flagella structure.
- archaea and eukaryota have similar RNA synthesis enzymes, DNA replication
- fits phylogeny better
What is phylogeny?
- study of evolutionary relationships.
- classification reflects phylogeny
What is artificial vs natural classification?
artificial: few characteristics, doesn’t reflect evolutionary relationships, limited info, stable
natural: many characteristics, reflects relationships, lots of useful info, may change -> can use to find out more about an endangered species.
What does monophyletic mean? What can we use to learn more about phylogeny
- any two living species have a common ancestor
- can use phylogenetic trees -> root is the very bottom. where two species meet is a node.
What is convergent evolution?
- unrelated species evolve similar traits due to adapting to a similar niche
What is homology?
grouping of organisms based on features that they share e.g. pentadactyl limb
How can biological molecules be used as evidence of evolution?
- help determine how closely related species are as we assume earliest organisms had identical versions
1) cytochrome C: similar/same amino acid sequence = CLOSELY RELATED. Differences = EVOLVED SEPARATELY LONG TIME AGO
2) DNA: changes due to mutations. more similar base sequence = evolved separately recently. More differences = less closely related.
What is standard deviation? What does it indicate?
- spread from the mean
- LOW: greater reliability
HIGH: lower reliability - anomalous data usually outside 2SD from mean.
When do we use the correlation coefficient? What does it indicate?
- tells us whether two sets of data are correlated or not
- d.o.f = n-2
- ranking must be done the same way for both variables
- compare to table of critical values (ignore sign)
- if GREATER than critical value for pairs of measurements at p = 0.05 = REJECT null hypothesis = strong correlation. Significant difference.
- if LESS than critical value = no significant correlation, results due to chance.
When do we use the students/unpaired t-test? What is degrees of freedom? How do we analyse the results?
- two means to test for significance
- degrees of freedom = (n1 + n2) -2 : n being number of data sets
- can use a table of t values to assess whether our calculated one indicates a significant diff. use 5% probability level.
- calc value GREATER = significant. 95% sure data is not due to chance
- calc value LESS = insignificant
How did Darwin and Wallace contribute to the theory of natural selection?
- INDEPENDENTLY
- Darwin: voyage and collected specimens and info, esp from Galapagos Islands
- Wallace: collected specimens from South America and South East Asia.
What was the deduction from this observation:
-offspring generally appear similar to their parents
characteristics are passed on
