5.3 Classification of biodiversity
Essential idea: Species are named and classified using an internationally agreed system.
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5.3.U1 The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.
5.3.U1 The binomial system of names for species is universal among biologists and has been agreed and developed at a series of congresses.
Be able to:
Outline the role of botanical and zoological congresses in the naming of plants and animals.
The binomial system of nomenclature is the formal system by which all living species are classified (taxonomy). It was initially developed by a Swedish botanist named Carolus Linnaeus in 1735.
Normal two naming system of classifying species.
Currently, many scientists and specialists meet in a series of International Congresses of Zoology which meet in different cities every 4 years
They meet to discuss their findings regarding genetics, animal behavior and classification
A main topic is the binomial nomenclature system and decisions regarding the classification of new organisms or the reclassification of old ones because of new evidence regarding ancestry.
The binomial system of nomenclature provides value because:
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
5.3.U2 When species are discovered they are given scientific names using the binomial system
5.3.U2 When species are discovered they are given scientific names using the binomial system
Be able to:
Define binomial nomenclature.
State three rules of binomial nomenclature formatting.
A formal two naming system of classifying species. The first name in the binomial naming system is called the genus and is always capitalized. The second name starts with a small letter and is called the species.
The binomial system allows for scientists across cultures, regions and languages to communicate effectively with regards to specific organisms.
species = the natural basic grouping of organisms
a group of organisms with similar characteristics
which can interbreed
and produce fertile offspring
genus = every species is classified into a genus
a group of similar species
binomial nomenclature
first name = genus, written in italics, if in type, or underlined if not, with the first letter in upper case
second name = species, written in italics, if in type, or underlined if not, all letters in lower case
5.3.U3 Taxonomists classify species using a hierarchy of taxa.
5.3.U3 Taxonomists classify species using a hierarchy of taxa.
Be able to:
Define taxon and taxonomist.
List the hierarchy of taxa, from largest to smallest.
Taxonomy is the science involved with classifying groups of organisms on the basis of shared characteristics. 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)
A taxon means a group of something
Scientists arrange or organize species in to a hierarchical set of groups in order to organize organisms into specific similar groups based on similar characteristics
As one goes higher up on a classification chart, the greater the number of species are included into the group
5.3.U4 All organisms are classified into three domains.
5.3.U4 All organisms are classified into three domains.
Be able to:
State the two groups of prokaryotes.
List the three domains of life.
Outline differences between the three domains of life.
Draw a tree diagram to illustrate the evolutionary relationship between organisms of the three domains.
Currently, all living organisms are classified into three domains. Archaea, eubacteria and eukaryote should be used for the three domains:
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.)
Members of these domains should be referred to as archaeans, bacteria and eukaryotes.
The Archaea and Bacteria domains are prokaryotes. These are organisms that do not have a membrane bound nucleus and their DNA is not associated with proteins.
The Bacteria domain consists of Eubacteria and archaebacteria are classified as Archaeans.
The Eukarya domain includes eukaryotes, or organisms that have a membrane bound nucleus. This domain is further subdivided into the kingdoms Protista, Fungi, Plantae, and Animalia
Groups organisms primarily based on differences in ribosomal RNA structure. Ribosomal RNA is a molecular building block for ribosomes.
5.3.U5 The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species.
5.3.U5 The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species.
Be able to:
List the four kingdoms of eukaryotes.
List the hierarchy of taxa, from largest to smallest.
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.
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.
Be able to:
Define natural classification.
List two difficulties in determining the natural classification of species.
For natural classification, it is assumed that all members of that group shared a common ancestor at some point in their history. This can be seen in their structure. Unnatural or artificial classification for example would be birds and flies. They both can fly; however flight evolved separately, and they are classified separately
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.
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.
Be able to:
List two situations in which the reclassification of a species may be necessary.
Outline an example of a species (or group of species) which were reclassified when new evidence was discovered
Sometimes new evidence is found that shows scientists that members of a particular group do not share a common ancestor as once originally thought. Sometimes other species that were once thought to be a lot different, are found to be more similar; sharing a common ancestor. This switching of classification is an ongoing process as new discoveries or better methods of classification are found.
5.3.U8 Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.
5.3.U8 Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.
Be able to:
Explain two specific advantages of natural classification.
Historically, there have been two main classification schemes used to identify living organisms – artificial and natural classification. Both use prominent features as the basis for classification, however differ in the way these characteristics are established
Artificial classification involves arbitrarily selecting unifying characteristics first and then grouping organisms accordingly
Natural classification involves grouping organisms based on similarities first and then identifying shared characteristics.
phylogenetic classification –A third type of classification is now being used to differentiate organisms based on genetics.
Natural classification is very useful for research into biodiversity. It is easier for the identification of new species that do not obviously fit into a specific classification (Kingdom --> Phylum --> Class à etc.)
A dichotomous key could be used to put an organism into a classification that fits that organism the best
This would not work as well for artificial classification (eg. Colour of flower petals)
Since organism evolved from a common ancestor, new species would share similar characteristics (likely internal), allowing for easier identification and classification. For example the pentadactyl limb, or mammary glands in mammals
List characteristics observed in this new species which was recently found in the Cambodian rainforest.
HINT 1: It is not a worm or a snake
HINT 2: It's scientific name is Ichthyophis cardamomensis
HINT 3: It belongs to the CLASS Amphibia
Why use classification?
Practicality - easy to use and speeds up communication
Information Content - summarization of characteristics about organisms in a species and makes it easy to find
Predictivity - can be used to predict features of other organisms within the group.
A 5.3.1 Classification of one plant and one animal species from domain to species level.
A 5.3.1 Classification of one plant and one animal species from domain to species level.
Be able to:
State the classification of a plant, from domain to species.
State the classification of an animal, from domain to species.
All plant and animal species belong to the same domain (Eukarya) as they are composed of eukaryotic cells. Beyond this point plants and animals differ in their classification as they belong to different kingdoms (Plantae vs Animalia)
A 5.3.2 Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.
A 5.3.2 Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta.
Be able to:
discuss which plant phyla have vascular tissue (other internal details are not required).
State the four major plant phyla.
Outline the differences between the four major plant phyla in regard to external recognition features.
Identify the phyla of plant given external recognition features.
bryophyta: mosses
no roots, only structures called rhizoids, which resemble root hairs
no true leaves or stems, both lacking vascular tissue
maximum height = 0.5 m
reproductive structures: spores produced in capsules at the end of stalks
filicinophyta: ferns
have true roots, leaves and non-woody stems, all containing vascular tissue
maximum height = 15 m
reproductive structures: spores produced in sporangia, usually on the underside of leaves
coniferophyta: conifers
have roots, leaves and wood stems all containing vascular tissue
maximum height = 100 m
reproductive structures:
male cones produce pollen
female cones produce ovules on the underside of scales
seeds develop from fertilized eggs with in ovules
angiospermophyta: flowering plants
have roots, leaves and stems all containing vascular tissue
maximum height = 100 m
reproductive structures:
flowers, containing female pistil and/or male stamen
male stamens produce pollen
female pistils produce ovaries containing eggs
seeds develop from fertilized eggs with in ovules
fruits develop from ovaries to disperse seeds
A 5.3.3 Recognition features of porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata
A 5.3.3 Recognition features of porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata
Be able to:
State seven major animal phyla.
Outline the characteristics of seven major animal phyla.
Identify the phyla of animal given external recognition features
Recognition features expected for the selected animal phyla are those that are most useful in distinguishing the groups from each other and full descriptions of the characteristics of each phylum are not needed.
porifera: sponges
no clear symmetry
attached to a surface
pores through body
no mouth or anus
cnidaria: corals, jellyfish, anemones
radial symmetry
tentacles
stinging cells
mouth, but no anus
playhelminthes: flat worms
bilateral symmetry
unsegmented, flat body
mouth, but no anus
annelida: segmented worms
bilateral symmetry
segmented
mouth and anus
mollusca: slugs, snail, clams, squids
muscular foot and mantle
shell usually present
segmentation not visible
mouth and anus
arthropoda: insects, spiders, crabs, millipedes
bilateral symmetry
exoskeleton
segmentation
jointed appendages
chordata: fish, amphibians, reptiles, birds, mammals
stiff rod-like notochord
bilateral symmetry
internal skeleton
gills or appendages in pairs
segmentation not visible
mouth and anus
A 5.3.4 Recognition of features of birds, mammals, amphibians, reptiles and fish
A 5.3.4 Recognition of features of birds, mammals, amphibians, reptiles and fish
Be able to:
Contrast chordate and vertebrate.
State five major classes of chordata.
Outline the characteristics of five major vertebrate classes.
Identify the vertebrate class of animal given external recognition features.
Fish (Pisces)
Live in fresh water or sea water
Body is covered with slimy scales
Fins and tails are used to swim and balance the body
Breat through gills
Cold-blooded
Lay eggs
Amphibians (Amphibia)
Can live on land and in the water
Have moist and exposed skin
Cold-blooded
Lay eggs
Have webs
Do not have external ears
Reptiles (Reptilia)
Have dry and scaly skin
Most lay eggs
Cold-blooded
Breath through lungs
Have one type of teeth
Teeth are sharp and cone-shaped
Birds (Aves)
Live on land
Covered with feathers
Festhers are waterproof and can trap heat to keep the body warm
Can swim
Can fly
Lay eggs
Warm-blooded
Breathe through lungs
Do not have teeth but use beak to peck
Hard scaly legs and sharp claws
Mammals (Mammalia)
Most live on land
covered with hair or fur
Skin has sweat glands
Warm-blooded
Breathe through lungs
S 5.3.1 Construction of dichotomous keys for use in identifying specimens.
S 5.3.1 Construction of dichotomous keys for use in identifying specimens.
Be able to:
Explain the use of a dichotomous key in the identification of a specimen.
Create a dichotomous key given a sample of known specimens.
A dichotomous key is a key constructed from a series of statements arranged into pairs..
The two descriptions should represent separate choices or characteristics that determine the difference between two organisms.
Both choices are read and compared with the organism to be identified.
If the first characteristic is present in the organism to be identified follow the instructions at the end of the statement. If the characteristic is not present go to the second statement as this should be true.
Once a choice is made, that selection directs you to another pair of descriptive statements.
One statement might identify the organism or lead you further on in the key.
This process is repeated until a successful identification is obtained.
Porifera
Platylhelmintha
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