5.3 classification

binomial nomenclature

genus species

underlined/italicised

binomial system of names is universal

domains

eubacteria: prokaryotes, unicellular, cell walls made of peptidoglycan, no histones, no/rare introns

archaea: prokaryotes, unicellular, extreme environments, are bacteria, cell walls not made of peptidoglycan, proteins similar to histones bound to dna molecule, some introns

eukarya: eukaryotes, multicellular, have membrane-bound compartments, some have cell walls (not made of peptidoglycan), frequent introns.

6 kingdoms

eubacteria, archaebacteria, protista, animalia, fungi, plantae.

taxonomy

domain, kingdom, phylum, class, order, family, genus, species.

each group is a taxa.

eg. eukarya → animalia → chordata → mammalia → carnivora → canidae → vulpes → vulpes vulpes.

natural classification

natural: look at visibly similar characteristics, then shared characteristics. based on evolutionary lineage.

may fail due to divergent/convergent evolution / adaptive radiation that can make organisms appear superficially similar/different.

all organisms of a genus/higher taxon have a common ancestor.

adv: make it easier to identify a species.

vs artificial classification

artificial: arbitrarily selecting unifying characteristics first then grouping organisms accordingly, not based on evolutionary lineage.

• eg. birds & bats: grouped tgt bcos they fly — not based on evo r/ships, they don’t share a common ancestor that can fly. flying developed independently in these 3 groups after they diverged from the last common ancestor.

• eg. plants & fungi: classified tgt bcos they have cell walls & can’t move. but this is artificial bcos their cell walls evolved separately & are made of diff materials.

reclassification

taxonomists may reclassify species when new evi (dna analysis/molecular evi) show that a taxon contains species that have evolved fr diff common ancestors.

eg. humans classification was controversial: humans assigned to family Hominidae, all other great apeas placed in family Pongidae. new evi showed that chimpanzees & gorillas are closer to humans than to orang-utans → new sub-family Hominidae created to incl gorillas & chimpanzees → only orang utans left in Pongidae.

eg. red pandas: dna sequencing showed that they belonged in their own family, were not bears.

skill: dichotomous key

a series of paired descriptions, where one matches the species & the other doesn’t

plant phyla

bryophyta

filicinophyta

coniferophyta

angiospermophyta

characteristics: vegetative organs, vascular tissue, cambium, pollen, ovules, seeds, fruits, egs, special features

animal phyla

porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda.

characteristics: symmetry, body cavity, segmentation,

vertebrate classes

bony ray finned fishes, amphibians, reptiles, birds, mammals

characteristics: outer covering, lungs/gills, limbs, legs/fins/wings, sperm/egg for int/ext fertilisation, where/how they give birth, constant body temp