Classification Processes Flashcards
3.1.6 Recognise that biological classification can be hierarchical and based on different levels of similarity of physical features, methods of reproduction and molecular sequences.
Describe the classification system for:
a) similarity of physical features
Hence describe the Linean Classfication system.
The Linnaean system of classification consists of a hierarchy of groupings, called taxa(singular, taxon). Taxa range from the kingdom to the species (see Figure below). The kingdom is the largest and most inclusive grouping. It is based on similarities in obvious physical traits. Examples are the plant and animal kingdoms. The species is the smallest and most exclusive grouping. It consists of organisms that are similar enough to produce fertile offspring together. Closely related species are grouped together in a genus.
Describe the classification system for:
a) similarity of physical features
What are the eight levels of classification in the Linean Classification system?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Describe the classification system for:
a) similarity of physical features
What are the rules for writing scientific names according to the method of binomial nomenclature?
This method, called binomial nomenclature, gives each species a unique, two-word Latin name consisting of the genus name and the species name. The rules for writing scientific names:
Capitilise the first letter of the genus name
Do not capitalise the species name
Both names must be underlined
Example: human = Homo sapiens
why is binomial nomenclature important for biological classification?
Binomial Nomenclature is important because it allows people from all over the world to communicate unambiguously about the various plant and animal species. Also, it makes sure that every scientific name is unique.
3.1.7 Describe the classfication system for:
b) methods of reproduction (asexual, sexual - K and r selection)
Describe asexual reproduction.
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. It involves mitosis and therefore only produces offsprings that are genetically identical to parents. An example of asexual reproduction is pathenogenesis which is a process of binary fission in amoeba and involves development of unfertilised egg into a new individual.
3.1.7 Describe the classfication system for:
b) methods of reproduction (asexual, sexual - K and r selection)
Describe sexual reproduction.
Sexual reproduction is a type of reproduction that involves meiosis, complex life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines with another to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). As a result the offsprings are genetically different to the parents and to each other.
3.1.7 Describe the classfication system for:
b) methods of reproduction (asexual, sexual - K and r selection)
What are the characteristics of K-selected species?
Low reproductive rate
Late reproductive age
Small number of offsprings
Requires high level of parental care
Late ages of maturity
Large body sizes
Longer life expectancies
Stable population sizes and density dependent (competition and predation)
3.1.7 Describe the classfication system for:
b) methods of reproduction (asexual, sexual - K and r selection)
What are the characteristics of r-selected species?
High reproductive rate
Early reproductive age
Large number of offsprings
Low parental care
Early ages of maturity
Small body sizes
Short life expectancies
Variable population size and Density-independent (fires, climactic events)
3.1.7 Describe the classification systems for
c) molecular sequences
Describe molecualr phylogeny or cladistics.
Cladistics is an approach to biological classification in which organisms are categorized in groups based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics that are not present in more distant groups and ancestors. The evidence is accumalated through DNA sequencing. DNA inherited is passed on from one generation to subsequent generations. DNA acquired mutations at a constant rate in some genes, meaning that a time frame can be used to determine evolutionary relatedness of different organisms. Sequencing a region of DNA can produce a “barcode” which can be compared to barcodes of other organisms. The more similar these barcodes, the more closely related the two organisms are.
Describe the classification system for:
a) similarity of physical features
What are some limitations of the Linean Classification system?
The major limitation of the Linnaean classification system is that it is based on physical traits. Physical traits may not necessarily be a sign of relatedness and indeed DNA evidence has forced scientists to reconsider many classifications based on the old system. Microscopic organisms like bacteria, fungus, protozoa, etc were not included either in plant kingdom or in animal kingdom.
3.1.7 Describe the classification systems for
c) molecular sequences
What are some assumptions for molecular phylogeny or cladistics?
There are three basic assumptions in cladistics: Any group of organisms are related by descent from a common ancestor. There is a bifurcating (divide into two branches or forks) pattern of cladogenesis. Change in characteristics occurs in lineages over time. Mutations occur at a constant rate over time.
3.1.12 Recognise the need for multiple definitions of a species.
Define species.
A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial.
3.1.12 Recognise the need for multiple definitions of a species.
Define biological species.
A group of organisms that can reproduce naturally and produce fertile offsprings.
3.1.12 Recognise the need for multiple definitions of a species.
Define morphological species.
A group of organisms with the same anatomical structures such as fossils that are clearly distinguished from other organisms.
3.1.12 Recognise the need for multiple definitions of a species.
Define phylogenetic species.
The concept of a species as an irreducible group whose members are descended from a common ancestor and who all possess a combination of certain defining, or derived, traits (determined by genetic analysis).
3.1.12 Recognise the need for multiple definitions of a species.
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The multiple definitions of species is needed to determine most likely when the species diverged and evolved compared to when the common ancestor was around.
3.1.13 Identify one example of an interspecific hybrid that does not produce a fertile offspring.
What are interspecific hybrids? Provide examples.
These result from interbreeding between members of different species. The offspring display traits and characteristics of both parents, but are often sterile, preventing gene flow between the species. Mules, hinnies, and other normally sterile interspecific hybrids cannot produce viable gametes, because differences in chromosome structure prevent appropriate pairing and segregation during meiosis, meiosis is disrupted, and viable sperm and eggs are not formed. Other examples include Liger (Lion and Tiger) and Zonkey (Zebra and Donkey).
3.1.8 Define the term clade.
A clade is a group of organisms that consists of a common ancestor and all its linear descendants.
3.1.9. Recall that common assumptions of cladistics include a common ancestry, bifurcation and physical change.
Recall the three basic assumptions of cladistics.
Relationships represented in diagrams are called cladograms are based on data from morphological characteristics and/or molecular sequences. They represent the evolutionary history of organisms in the same taxonomic group.
The three basic assumptions of cladistics are
1.) Groups of orgranisms are related by descent from a common ancestor
2.) The branching pattern is dichotomous (each branch is called bifurcation)
3.) Physical characteristics of lineages changes over time
3.1.10 Interpret cladograms to infer the evolutionary relatedness between groups of organisms.
Describe cladograms.
Cladograms are a type of phylogenetic tree that represents the evolutionary relationship between organisms. They are constructed by grouping organisms that share derived traits (traits that are different from the group’s ancestor).
3.1.10 Interpret cladograms to infer the evolutionary relatedness between groups of organisms.
Explain phylogenetic trees.
Also represent evolutionary relationships among organisms. Reflect how species and other groups evolved from a series of common ancestors but use similarities in DNA or protien sequence as evidence instead of just physical characteristics. Cladograms show the sequence of divergence whilst phylogenetic trees show the evolutionary history of an organism and the timeline of evolution.
