5.3 Classification of biodiversity Flashcards
Convention for naming living organisms
Convention for naming living organisms
- The accepted convention of using one common system for the naming of living organisms is an essential basis for scientific research.
- The convention always follows the Genus species (both in italics) format.
Define species
A group of organisms in the same genus that is able to interbreed to produce fertile offspring.
Define genus
A group of species that share common characteristics but may not be able to interbreed.
What is the difference between genus and species?
- A genus is a group of species that share characteristics.
- For example, the -genus Macropus, or ‘big foot’, is a genus of kangaroos that all have big hind legs.
- The species name is specific to that organism and may refer to a specific trait of that particular organism.
- For example, Macropus rufus is a red kangaroo.
What are the rules that scientists follow when it comes to naming a species with these scientific names?
- Genus name starts with a capital (upper case) letter.
- Species name starts with a lowercase letter.
- Genus name is always written before the species name.
- The complete name, i.e. genus and species should be word processed in italics or underlined when handwritten.
- Genus and species names are often written using Latin or classical Greek because they are unchanging languages. However, there are many other sources of binomial names.
Universality of the binomial system of names for species
- The binomial system of names for species is universal (used by all) and has been agreed upon and developed at a series of congresses.
- Each time a new species is discovered, it is given a scientific name using the binomial system.
Abbreviation of genus names
- The genus name is often abbreviated once it has been used in a text.
- So, from this point onwards, we would use M. rufus rather than having to use the complete name, Macropus rufus.
Classification of species into subspecies
- Some species may be classified into subspecies.
- Organisms placed in the same species and subspecies are able to interbreed to have fertile offspring. For example, there are two subspecies of the eastern grey kangaroo ( Macropus giganteus), the Macropus giganteus giganteus and the Macropus giganteus tasmaniensis, also known as the Tasmanian eastern grey kangaroo.
- These two subspecies of kangaroo are able to interbreed to have fertile young. However, they do not often interbreed in nature because they are geographically isolated.
- Macropus giganteus giganteus is endemic in mainland Australia, whereas the Macropus giganteus tasmaniensis is endemic on the island of Tasmania.
- Neither subspecies of the grey kangaroo are able to interbreed with the red kangaroo ( M. rufus ) because it is classified as a different species.
What are organisms that are placedin the same species and subspecies able to do?
Interbreed to have fertile offspring
What are Allium sativum and Allium cepa?
Two different species of the same genus
Both of these organisms are called Allium so they belong to the same genus. They have different species names: sativa and cepa, so they are two different species.
What is the correct way of writing the scientific name of asparagus?
Asparagus officinalis (in italics)
Two kangaroos have the following scientific names respectively: M. giganteus giganteus and M. giganteus tasmaniensis.
What do you know about these two types of kangaroo?
They are two subspecies of the same species.
What does the genus combine?
- Organisms that resemble each other in one or more characteristics.
- For example, the big hind legs in the kangaroo genus Macropus.
What can the genera (plural of genus) be grouped into?
Families
What can families be grouped into?
Orders
Groupings beyond genus
- The genera (plural of genus) can be grouped into families, and families can be grouped into orders.
- Each of the groupings is called a taxon (plural taxa).
- As we go up each level, to the level of a domain, each higher level includes a larger group of organisms.
- In other words, there is a hierarchy of taxa.
The more taxa organisms share, ___
The more they have in common.
When are organisms able to interbreed to produce fertile offspring?
When they share the same taxa down to the species level.
Diagram showing biological classification
What are the principal taxa for classifying eukaryotes?
Kingdom , phylum , class , order , family , genus, and species
What is the highest level of classification?
A domain
How were organisms classified before DNA sequences could be used to classify organisms?
They were divided into prokaryotes (Latin: Prokaryota ) also known as monera, organisms without a nucleus, and eukaryotes (Latin: Eukaryota ), those with a nucleus.
What did Carol Woese discover in 1977 and what did this change?
- In 1977, while using DNA sequencing information to group organisms, an evolutionary microbiologist called Carl Woese discovered that organisms grouped together into prokaryotes actually had two separate ancestors.
- Thus, there are three lines of living things (and not two).
What did Carl Woese go on to propose?
- He went on to propose the division of organisms into three domains in 1990 namely: Bacteria (which will be referred to as Eubacteria from now on), Archaea, and Eukaryota.
- Although it took a bit of time for biologists to accept his classification, today all organisms are classified into these three domains.
What should you refer to the three domains as?
Bacteria, Archaea and Eukaryota.
What are members of the three domains referred to as?
Bacteria, archaeans, and eukaryotes.
Characteristics of bacteria
- Histones: absent
- Cell membrane: Glycerol-esters of lipids, D-form of glycerol
- Cell wall: Peptidoglycan
Characteristics of archea
- Histones: Present in some species (similar to histones found in Eukaryota )
- Cell membrane: Glycerol-ether lipids, L-form of glycerol
- Cell wall: Not made of peptidoglycan
Characteristics of archea
- Histones: Present in some species (similar to histones found in Eukaryota )
- Cell membrane: Glycerol-ether lipids, L-form of glycerol
- Cell wall: Not made of peptidoglycan
Characteristics of eukaryota
- Histones: Present
- Cell membrane: Glycerol ester lipids, D-form of glycerol
- Cell wall: Not made of peptidoglycan, sometimes absent
Describe the habitats of archea
- Archaea are usually unicellular organisms that lack a nucleus and often live in extreme habitats, such as hot water springs, deep earth sediments, cow intestines and lakes or pools with extremely high salt concentrations.
- However, they may also live in less extreme habitats such as the ocean’s surface, soil and marshlands.
What are eubacteria?
These are the remaining prokaryotic organisms lacking a nucleus and are often considered pathogenic or disease causing.
What does the domain of eukaryotes include?
- The eukaryotes include the remainder of all living organisms whose cells have a membrane-bound nucleus.
- These organisms include protists, fungi, plants and animals.
Diagram showing the phylogenetic tree
Why are viruses not included in this taxonomy?
- They do not have enough features to be considered living organisms.
- For example, they cannot reproduce without a host.
- Taxonomy is concerned with living organisms.
In the hierarchy of taxa, what is in a family?
A group of genera
The individuals in the picture to the left are classified as Canis lupus familiaris, otherwise known as the domestic dog.
The individual in the picture on the right is classified as Canis lupus, the gray wolf.
What do you know about these organisms?
They are all classified under the same family
Organisms in the same genus are also in the same family.
Of the three domains, which is the only one that has been further classified into kingdoms?
Eukaryota
What are the four kingdoms that make up the eukaryotic domain?
Protoctista, Fungi, Plantae, and Animalia
Which kingdom is in the domain of bacteria?
Eubacteria
Which kingdom is in the domain of archaea?
Archaebacteria
Characteristics of eubacteria
Cell structure: Cell walls have peptidoglycan
Number of cells: One
Mode of nutrition: Autotroph or heterotroph
Examples: E. coli , Streptococcus (italics)
Characteristics of archaebacteria
Cell structure: No peptidoglycan in cell walls
Number of cells: One
Mode of nutrition: Autotroph or heterotroph
Examples: Halophiles
Characteristics of Protoctista
Cell structure: Chloroplasts or cell walls made of cellulose
Number of cells: One, several or colonial
Mode of nutrition: Autotroph or heterotroph
Examples: Giant kelp, amoeba
Characteristics of Fungi
Cell structure: Cell walls made of chitin
Number of cells: One or several
Mode of nutrition:
Examples: Yeasts, mushrooms
Characteristics of Plantae
Cell structure: Cell walls of cellulose and contain chloroplasts
Number of cells: Several
Mode of nutrition: Autotroph
Examples: Flowering plants, ferns
Characteristics of Animalia
Cell structure: No cell walls or chloroplasts
Number of cells: Several
Mode of nutrition: Heterotroph
Examples: Insects, fish, worms, humans
What do you need to know about classification for the exam?
You are expected to know the classification of one animal and one plant species, from domain to species level.
What are the three ways in which classification has been used?
- Unnatural or artificial classification
- Natural classification
- Phylogenic classification
Describe unnatural or artificial classification
-Artificial classification involves arbitrarily selecting unifying characteristics first and then grouping organisms accordingly
-The advantage of artificial classification is that such schemes are easy to develop and relatively stable (unlikely to change)
-The disadvantage is that they do not generally show evolutionary relationships and for this reason are not commonly used
- For example, all organisms with wings would be classified together.
Describe natural classification
Describe natural classification
-This involves grouping organisms based on similarities first and then identifying shared characteristics
-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
-A disadvantage of such schemes is that they are highly mutable and tend to change as new information is discovered
What are the limitations of natural classification?
- When considering other characteristics, this kind of grouping no longer makes sense.
- Whales and porpoises are mammals and have different characteristics than sharks and other types of fish.
Describe phylogenic classification
-A third type of classification – phylogenetic classification – is now being used to differentiate organisms based on genetics
-Organisms that share a greater level of homology in their DNA or amino acid sequences are expected to be more closely related
What advances may be made in the field of taxonomy?
- Sometimes new findings, such as DNA sequence analyses, reveal that some previous classifications were wrong.
- For example, the taxon may contain species that have evolved from different ancestors. In this case, taxonomists may reclassify groups of species according to the new evidence.
Which type of classification is widely accepted?
- Natural classification
- Shared ancestors make it very likely that certain features are also shared, and these can be used to classify a newly discovered organism.
- For example, if a new organism was discovered which had mammary glands, a hairy coat and a placenta, any biologist would not hesitate to classify the organism as a mammal.
- Further classification would then depend on other shared characteristics.
- Another important feature of natural classification is that it allows the prediction of characteristics shared by species within a group.
Classification of human
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primate
Family: Homonidae
Genus: Homo (italics)
Species: sapiens
Classification of garlic
Domain: Eukaryota
Kingdom: Plantae
Phylum: Angiospermophyta
Class: Eudicotidae
Order: Ranunculales
Family: Ranunculacae
Genus: Ranunculus (italics)
Species: acris (italics)
If organisms A, B, and C belong to the same class but to different orders, and if organisms D, E, and F belong to the same order but to different families, which of the following pairs of organisms would be expected to be the most similar?
D and F
Class is a higher taxon of many orders. So if organism D, E and F belong to an order they would share more characteristics than organisms A, B or C that share the same class.
A researcher wants to determine the genetic relationship of several breeds of squirrel. The researcher should compare homologous sequences of this type of biochemical ___
Nucleic acids
Nucleic acids comparison is the best indicator for relatedness. Better than proteins because some mutations at the DNA level do not cause a change in the protein structure. These changes in nucleic acids could indicate that two organisms may not be as related as when one compares the protein structures.
What is dichotomy?
This means splitting into two or a division into two opposing groups.
Why is dichotomy important?
When you are working in the field, it is often essential to be able to classify certain organisms belonging to a particular genus or family.
What can a dichotomous key help you to figure out?
They can help you to quickly identify organisms, such as trees, wildflowers, insects, mammals, reptiles, birds and fish.
How do dichotomous keys work?
- A dichotomous key is a series of paired opposing statements which guide the user to the identity (or allows the classification) of an item or organism.
- Dichotomous keys consist of a series of choices that lead the user to the correct name of an item or organism.
- They may make use of yes or no questions, such as, ‘Does the organism have 6 legs? Yes – go to step 3. No – go to step 2’, but, there are always two opposing choices in each step.
- Dichotomous key field guides rely on visible features to classify organisms.
- Each time you are given a choice of two features, but you should always follow the one that applies: each choice leads to another choice until the organism is narrowed down to its genus and finally to its species.
- Dichotomous keys are usually in the form of either concept maps or outlines.
Diagram of a simple dichotomous key in both formats
Dichotomous keys for exam
You must be able to design a simple dichotomous key yourself and use a key to identify a species.
Diagram of a simple dichotomous key
A collection of four organisms is observed and a dichotomous key is applied.
Using the key below, which specimen is an earthworm?
- Segmented body. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .go to 2
Non-Segmented body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .go to 3
- Body has no exoskeleton . . . . . . . . . . . . . . . specimen A
Body has an exoskeleton. . . . . . . . . . . . . . . . . . . . . . . . . . . specimen B
- Jointed appendages present . . . . . . . . . . . . . . . . . . . . . . . . . specimen C
Jointed appendages absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . specimen D
Specimen A
An earthworm is a segmented worm (with bilateral symmetry).
How many species does the kingdom Plantae consist of?
Approximately 400,000
What are the four phyla in the kingdom Plantae?
Bryophytes, filicinophytes, coniferophytes and angiospermophytes.
Bryophyta
-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)
-Examples include mosses and liverworts
Filicinophyta
-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
-Examples include ferns
Coniferophyta
-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
-Examples include pine trees and conifers
Angiospermophyta
-Have 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)
-Examples include all flowering plants and grasses
Summary table of plant phyla recognition features
What types of symmetry do different animals have?
- Some animals have bilateral symmetry where, if a line were drawn down the middle of the animal, both halves would look the same.
- Other animals have radial symmetry, where the animal is symmetrical along multiple planes stemming from the center of the body.
Animals that have no symmetry at all are considered ___
Asymmetrical
How is it determined in which phylum an animal is categorized?
Symmetry and other physical traits
Diagram showing types of symmetry
What are some of the animal phyla?
Porifera, cnidaria, platyhelminthes, annelida, mollusca, arthropoda and chordata.
(However, there are more phyla in the animal kingdom than the seven discussed here.)
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 specialization of segments
-Examples include earthworms and leeches
Mollusca
-Have bilateral symmetry
-Have a separate mouth and anus
-Body is composed of a visceral mass, a muscular foot, and a mantle (may produce a 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)
Table summarizing invertebrate phyla recognition features
.
Which of the organisms, identified by the key below, represent an annelid?
- Shows bilateral symmetry go to 2
Does not show bilateral symmetry Cnidaria
- Has a segmented body go to 3
Does not have a segmented body go to 4
- Has jointed legs I
Does not have jointed legs II
- Has a shell III
Does not have a shell IV
II → 1. Shows bilateral symmetry. 2. Has a segmented body. 3. Does not have jointed legs.
Bilateral symmetry, segmented body and no jointed legs describes an earthworm, which is an annelid.
What are vertebrates?
A subphylum of chordata.
What are Chordata?
- 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
- In some chordates, the neural tube will develop into a spine and the notochord will form a protective backbone
- These chordates are grouped into a sub-phylum (vertebrata) and include birds, mammals, amphibians, reptiles, and fish
Fish
-Covered in scales made out of bony plates in the skin
-Reproduce via external fertilization (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)
Amphibia
-Moist skin, permeable to gases and water
-Reproduce via external fertilization (usually spend larval state in water, adult state on land)
-Can breathe through the skin but also possess simple lungs
-Do not maintain a constant internal body temperature (ectothermic)
Reptilia
-Covered in scales made out of keratin
-Reproduce via internal fertilization 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)
Aves (birds)
-Covered in feathers (made out of keratin)
-Reproduce via internal fertilization and females lay eggs with hard shells
-Breathe through lungs with parabronchial tubes
-Maintain a constant internal body temperature (endothermic)
Mammalia
-Skin has follicles that produce hair made out of keratin
-Reproduce via internal fertilization and females feed young with milk from mammary glands
-Breathe through lungs with alveoli
-Maintain a constant internal body temperature (endothermic)
