5.3 Flashcards
what is the binomial system of nomenclature
the formal system by which all living species are classified (taxonomy)
- originally grouped all organisms into two kingdoms – vegetable (plants) and animal
who invented the binomial system of nomenclature
developed by a Swedish botanist named Carolus Linnaeus in 1735
what is the value of the binomial naming system
- It allows for the identification and comparison of organisms based on recognised characteristics
- It allows all organisms to be named according to a globally recognised scheme
- It can show how closely related organisms are, allowing for the prediction of evolutionary links
- It makes it easier to collect, sort and group information about organisms
how to write binomial names
Genus is written first and is capitalised (e.g. Homo)
Species follows and is written in lower case (e.g. Homo sapiens)
binomial writing conventions
- When typing the scientific name, it should be presented in italics
- When hand writing the scientific name, it is customary to underline
three domains
Eukarya, Archaea, Eubacteria
Eukarya
eukaryotic organisms that contain a membrane-bound nucleus (includes protist, plants, fungi and animals)
Archaea
prokaryotic cells lacking a nucleus and consist of the extremophiles (e.g. methanogens, thermophiles, etc.)
Eubacteria
prokaryotic cells lacking a nucleus and consist of the common pathogenic forms (e.g. E. coli, S. aureus, etc.)
taxonomy
Taxonomy is the science involved with classifying groups of organisms on the basis of shared characteristics
hierarchy of taxa
Organisms are grouped according to a series of hierarchical taxa – the more taxa organisms share, the more similar they are
The taxa used are kingdom, phylum, class, order, family, genus and species (genus + species = scientific name)
taxa mnemonic
(domain) King -- kingdom Philip -- phylum Came -- class Over -- order For -- family Grape -- genus Soda -- species
Eukarya
All plant and animal species belong to the same domain (Eukarya) as they are composed of eukaryotic cells
Eukarya kingdoms
Beyond this point plants and animals differ in their classification as they belong to different kingdoms (Plantae vs Animalia)
classification schemes
artificial classification, natural classification and phylogenic classification
Artificial classification
involves arbitrarily selecting unifying characteristics first and then grouping organisms accordingly
Artificial classification advantage
The advantage of artificial classification is that such schemes are easy to develop and relatively stable (unlikely to change)
Artificial classification disadvantage
The disadvantage is that they do not generally show evolutionary relationships and for this reason are not commonly used
- For example, if organisms were classified according to the presence of fins then whales would be grouped with fish
- If organisms were classified based on the presence of shells then snails would be grouped with turtles and not with squid
Natural classification
involves grouping organisms based on similarities first and then identifying shared characteristics
Natural classification advantage
- According to a natural classification system, all members of a particular group would have shared a common ancestor
- This means that natural classification schemes can be used to predict characteristics shared by species within a group
Natural classification disadvantage
A disadvantage of such schemes is that they are highly mutable and tend to change as new information is discovered
- Taxonomists will reclassify groups of species when new evidence arises to compromise the traditional classification scheme
phylogenetic classification
is now being used to differentiate organisms based on genetics
phylogenetic classification explanation
Organisms who share a greater level of homology in their DNA or amino acid sequences are expected to be more closely related
taxonomic levels according to natural selection
According to natural classification, each taxonomic level includes all species that would have evolved from a common ancestor
- Species of the same genus would have a common genus ancestor and be more closely related than species of the same order
- Hence, organisms that share a lower taxa must share all higher taxa (e.g. if the same order then must also be the same class)
why different species may be separated
Groups of species may be separated into different genera if new evidence suggests they evolved from different ancestral species
example of species being separated
Species originally classified as figworts have been reclassified into different genera based on DNA sequence comparisons
why different species may be grouped
Alternatively, different species may be grouped into a shared taxon if new evidence suggests more recent common ancestry
example of species being grouped
The Homininae sub-family was created to include gorillas and chimpanzees when it was deduced that they share more common ancestry with humans than with other great apes (e.g. orang-utan)
phyla in the kingdom Plantae (4 main)
The kingdom Plantae contains 12 phyla – which includes bryophytes, filicinophytes, coniferophytes and angiospermophytes
Bryophytes
- Has no vascularisation (i.e. lacks xylem and phloem)
- Has no ‘true’ leaves, roots or stems (are anchored by a root-like structure called a rhizoid)
- Reproduce by releasing spores from sporangia (reproductive stalks)
Filicinophytes
- Has vascularisation (i.e xylem and phloem)
- Have leaves, roots and stems (leaves are pinnate – consisting of large fronds divided into leaflets)
- Reproduce by releasing spores from clusters called sori on the underside of the leaves
Coniferophytes
- Has vascularisation
- Have leaves, roots and stems (stems are woody and leaves are waxy and needle-like)
- Reproduce by non-motile gametes (seeds) which are found in cones
Angiospermophytes
- Has vascularisation
- Have leaves, roots and stems (individual species may be highly variable in structure)
- Reproduce by seeds produced in ovules within flowers (seeds may develop in fruits)
Bryophytes example
Examples include mosses and liverworts
Filicinophytes example
Examples include ferns
Coniferophytes example
Examples include pine trees and conifers
Angiospermophytes example
Examples include all flowering plants and grasses
kingdom Animalia two main groups
invertebrates (no backbone) and vertebrates (most chordata)
Animalia phyla
porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata
Porifera
- No body symmetry (asymmetrical)
- No mouth or anus (have pores to facilitate the circulation of material)
- May have silica or calcium carbonate based spicules for structural support
Examples include sea sponges
Cnidaria
- Have radial symmetry
- Have a mouth but no anus (single entrance body cavity)
- May have tentacles with stinging cells for capturing and disabling prey
Examples include jellyfish, sea anemones and coral
Platyhelmintha
- Have bilateral symmetry
- Have a mouth but no anus (single entrance body cavity)
- Have a flattened body shape to increase SA:Vol ratio and may be parasitic
Examples include tapeworms and planaria
Annelida
- Have bilateral symmetry
- Have a separate mouth and anus
- Body composed of ringed segments with specialisation of segments
Examples include earthworms and leeches
Mollusca
- Have bilaterial symmetry
- Have a separate mouth and anus
- Body composed of a visceral mass, a muscular foot and a mantle (may produce shell)
Examples include snails, slugs, octopi, squid and bivalves (e.g. clams)
Arthropoda
- Have bilateral symmetry
- Have a separate mouth and anus
- Have jointed body sections / appendages and have a hard exoskeleton (chitin)
Examples include insects, crustaceans, spiders, scorpions and centipedes
Chordata
- Have bilateral symmetry
- Have a separate mouth and anus
- Have a notochord and a hollow, dorsal nerve tube for at least some period of their life cycle
Examples include mammals, birds, reptiles, amphibians and fish (also invertebrate sea squirts)
Vertebrate Classes
birds, mammals, amphibians, reptiles and fish
Chordates
animals that possess certain key features in an embryonic state that may persist into adulthood
- These features include a notochord, hollow dorsal neural tube, pharyngeal slits and a post-anal tail
Fish
- Covered in scales made out of bony plates in the skin
- Reproduce via external fertilisation (egg and sperm released into the environment)
- Breathe through gills that are covered with an operculum
- Does not maintain a constant internal body temperature (ectothermic)
Amphibian
- Moist skin, permeable to gases and water
- Reproduce via external fertilisation (usually spend larval state in water, adult state on land)
- Can breathe through skin but also possess simple lungs
- Do not maintain a constant internal body temperature (ectothermic)
Reptiles
- Covered in scales made out of keratin
- Reproduce via internal fertilisation and females lay eggs with soft shells
- Breathe through lungs that have extensive folding (increases SA:Vol ratio)
- Do not maintain a constant internal body temperature (ectothermic)
Birds
- Covered in feathers (made out of keratin)
- Reproduce via internal fertilisation and females lay eggs with hard shells
- Breathe through lungs with parabronchial tubes
- Maintain a constant internal body temperature (endothermic)
Mammals
- Skin has follicles which produce hair made out of keratin
- Reproduce via internal fertilisation and females feed young with milk from mammary glands
- Breathe through lungs with alveoli
- Maintain a constant internal body temperature (endothermic)
dichotomous key
A dichotomous key is a method of identification whereby groups of organisms are divided into two categories repeatedly
how dichotomous keys are represented
- As a branching flowchart (diagrammatic representation)
- As a series of paired statements laid out in a numbered sequence (descriptive representation)
archea and eukaryotes
The archaeal cells were found to possess certain features that were more in common with eukaryotic cells than eubacteria
- This included certain structural features (e.g. cell wall composition) and the presence of histone-like proteins in DNA
- Based on these discoveries it was concluded that eukaryotes and archaea share more recent common ancestry than eubacteria
Animal Classification
Red Fox (Vulpes vulpes) D: Eukarya K: Animalia P: Chordata C: Mammalia O: Carnivora F: Canidae G: Vulpes S: Vulpes vulpes
Plant Classification
Common Sunflower (Helianthus annuus) D: Eukaryote K: Plantae P: Magnoliophyta C: Magnoliopsida O: Asterales F: Asteraceae G: Helianthus S: Helianthus annuus
