5.3 - Classification and Biodiversity Flashcards
5.3.U2 When species are discovered they are given scientific names using the binomial system
Species – A group of organisms which can interbreed and produce viable (fertile) offspring
Genus – A group of similar species
An organism is given a genus and species name
Eg. Saccharomyces cerevisiae (Yeast)
Panthera leo
Panthera tigris
Binomial nomenclature
2 named naming system
The binomial system was developed by Carolus Linnaeus, a Swedish botanist and taxonomist
It is based on the physical traits of species
Carl Linnaeus originally published Systema Naturae in 1758 in which he gave binomial names for all species known at that time
The IBC (International Botanical Congress) of Vienna in 1905 voted to accept his naming convention
Since then both the IBC and ICZ (International Congress of Zoology) have been the bodies that oversee the international efforts to maintain consistent naming conventions and use of taxon
Periodically the congresses meet to discuss issues affecting classificatio
5.3.U7 Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species.
Historically classification systems have been revised repeatedly based on emerging evidence.
Previously in the second half of the 20th century all living organisms were classified in five kingdoms.
This included prokaryotes being placed in one kingdom and eukaryotes were split-up into the remaining four kingdoms.
Recent evidence from genetic studies of ribosomal RNA has shown that “prokaryotes” are far more diverse than anyone had suspected.
ribosomal RNA is found in all organisms and evolves slowly so is a good way to track evolution over long time periods.
5.3.U4 All organisms are classified into three domains.
Revision of the classification system lead to a new level of taxon called domains
The Prokaryotae are now divided into two domains, the Bacteria and the Archaea
Bacteria and the Archaea are as different from each other as either is from the Eukaryota, the third domain.
No one of these groups is ancestral to the others, and each shares certain features with the others as well as having unique characteristics of its own.
Features and examples of each domain:
Archaea: Halobacterium sp. (lives in water with high salt concentrations) No nuclear membrane
RNA and biochemistry distinct from bacteria
Bacteria (Eubacteria): Staphylococcus aureus (above) can cause skin infections and respiratory disease. No nuclear membrane
Eukaryota: Includes several kingdoms including fungi, animals and plants. nuclear membrane
5.3.U3 Taxonomists classify species using a hierarchy of taxa.
Taxonomy is the practice and science of organizing organisms into levels of classification
As we move from kingdom to phylum, all the way to species, organisms share more and more characteristics
This system allows us to group organisms while also assigning unique species names and is very helpful in identifying and naming new species
5.3.A1 Classification of one plant and one animal species from domain to species level.
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Eukaryota
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo
Sapiens
Eukaryota
Plantae
Spermatophyta
Eudicotyledons
Magnoliidae
Ranunculales
Ranunculus
Acris
5.3.A2 Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.
Bryophytes (mosses, hornworts and liverworts)
No roots, but structures similar to root hairs called rhizoids
Mosses have simple leaves and stems
Liverworts have a flattened thallus
No vascular tissue
Spores produced in capsules, which develop at the end of a stalk
Filicinophytes (ferns)
Roots present
Short non-woody stems.
Leaves usually divided into pairs of leaflets
Vascular tissue
Spores produced in sporangia on the underside of the leaves
Coniferophytes (conifer shrubs and trees)
Roots, present
Woody stems
Leaves usually narrow with a thick waxy cuticle
Yes
Seeds develop from ovules in female cones. Male cones produce pollen.
Angiospermophytes (flowering plants)
Leaves and roots variable in structure
Stems maybe woody (shrubs and trees)
Yes
Seeds develop from ovules in ovaries, inside flowers. Seeds are dispersed by fruits which develop from the ovaries.
A summary of key features that can be used to distinguish between the vertebrate classes
Mammals
4 Pentadactyl limbs
Lungs with alveoli
Internal fertilization
Give birth to live young
Mammary glands secrete milk
Hairs growing from the skin
Teeth including living tissue
birds
4 Pentadactyl limbs, 2 limbs modified as wings
Lungs with parabronchial tubes
Internal fertilization
Hard shells around the eggs
Feathers growing from skin
Beak but no teeth
reptiles
4 Pentadactyl limbs
Lungs with extensive folding
Internal fertilization
Soft shells around eggs
Dry scaly impermeable skin
Simple teeth – no living tissue
amphibians
4 Pentadactyl limbs
Simple lungs with small internal folds and moist surfaces
External fertilization in water
Protective jelly around eggs
Larval stage lives in water
Soft moist permeable skin
fish
Fins
Gills
External fertilization in most species
Scales grow from the skin
with a single gill slit
Swim bladder for buoyancy
A summary of key features that can be used to distinguish between animal phyla
porifera
(sponges)
None
None
No mouth or anus
Porous
attached to rocks
Filter feeder
cnidaria
(corals, jellyfish)
Radial
None
Mouth but no anus
Stinging cells
Tentacles
platylhelmintha
(flatworms)
Bilateral
None
Mouth but no anus
Flattened body
annelida
(earthworms, leeches)
Bilateral
Very segmented
Mouth and anus
bristles often present
Mollusca
(oyster, snails, octopus)
Bilateral
Non-visible segmentation
Mouth and anus
Most have shell made of CaCO3
Arthropoda
(ant, scorpion, crab)
Bilateral
Segmented
Mouth and anus
Exoskeleton
jointed appendages
Chordata
(fish, birds, mammals)
Bilateral
Segmented
Mouth and anus
notochord
hollow dorsal nerve cord
(some have ) pharyngeal slits
5.3.U6 In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.
Natural classification groups together species that share a common ancestor from which they evolved. This is called the Darwinian principle of common descent
It is expected that members of a group share important attributes or ‘homologous’ traits that are inherited from common ancestors. For example Lions share more traits with Jaguars than with Clouded Leopards.
Grouping together birds, bats and bees because they fly would be an artificial classification as they do not share a common ancestor and evolved the ability to fly independently.
Plants and fungi were once classified together because they both possessed shared characteristics such as cell walls. It is now known that this is an artificial grouping as their cell walls have a different molecular makeup and they evolved separately.
Natural classification is not straightforward as convergent evolution can make distantly related organisms appear similar and adaptive radiation can make similar organisms appear very different from each other.
5.3.U8 Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.
Natural classification is very helpful when dealing with new species:
Dichotomous keys can be used to help identify the species. The keys can place a specimen with the most closely related species, genus, family or phyla using natural classification. To what level of classification a specimen can be placed depends on how unique it is.
