What is a species?
- They are capable of breeding to produce living, fertile offspring.
What system is used for identifying organisms?
- Binomial system
- Organisms are defied by two names
What are the features of the binomial system?
- It is a universal system based upon Latin or Greek names
- The first name, called the generic name, denotes the genu sto which the organisms belongs.
- The second name, called the specific name, denotes the species to which the organism belongs to.
What are some rules that are applied to the use of the binomial system in scientific writing?
- In italics or if handwritten underlined
- First letter of the generic name is in upper case but the specific name is in lower case
- If the specific name is not known , it can be written as ‘sp’
Why is courtship behaviour important?
- recognise members of their own species
- identify a mate that is capable of breeding and that is sexually mature
- form a pair bond that will lead to successful mating and raising of offspring
- synchronise mating so that it takes place when there is the maximum probability of the sperm and egg meeting
- become able to breed by bringing a member of the opposite sex into a physiological state that allows breeding to occur.
What is classification?
The grouping of organisms
What is taxonomy?
The theory and practice of biological classification
What are the two main forms of classification?
Artificial classification and Phylogenetic classification
What is meant by artificial classification?
- Where organisms are divided according to differences the are useful at the time
- These differences are called analogous characteristics where they have the same function but do not have the same evolutionary origins.
What is meant by phylogenetic classification?
- Based on the evolutionary relationships between organisms and their ancestors
- Classifies species into groups using shared features derived from their ancestors.
- Arranges the groups into a hierarchy, in which the groups are contained within larger composite groups with no overlap
- Relationships in a phylogenetic classification are partly based on homologous characteristics.
What are homologous characteristics?
Characteristics that have similar evolutionary origins regardless of their functions
What is a taxon?
- Each group within a phylogenetic biological classification
What are the different taxonomic ranks?
- Domain -> Bacteria, Archaea and Eukarya
- Kingdoms -> Protoctista, Fungi, Plantae and Animalia
- Phyla -> eg Chordata
- Classes -> Mammalia
- Orders -> Carnivora
- Families -> Felidae
- Genera -> Felix
- Species -> tigris
What is phylogeny?
- The hierarchical order of taxonomic ranks is based upon the supposed evolutionary line of descent of the group members.
- This evolutionary relationship is called phylogeny.
How is the phylogenetic relationship of different species represented ?
- Usually represented by a tree-like diagram called a phylogenetic tree.
- The oldest species is at the base of the trees while the most recent ones are represented by the ends of the branches.
- The closer the branches, the closer the evolutionary relationships.
What are some difficulties involved in defining species?
- Species are not fixed forever but change and evolve over time.
- Within a species there can be considerable variation among individuals.
- Many species are extinct and most of these have left no fossil record.
- Some species rarely reproduce sexually.
- Members of different populations of the same species may be isolated and so never meet and therefore never got the opportunity to interbreed.
- Some types of organism are sterile.
What is meant by biodiversity?
The general term used to describe variety in the living world.
What is meant by species diversity?
- The number of different species and the number of individuals of each species within any one community
What is meant by genetic diversity?
- The variety of genes possessed by the individuals that make up a population of a species.
What is meant by ecosystem diversity?
- The range of different habitats, from a small local habitat to the whole of the Earth.
What is species richness?
It is the number of different species in a particular area at a given time (community).
Why is species richness not a good way to measure diversity?
- Because two communities may have the same number of species but the proportions of the community made up of each species may differ.
What is the equation for the index of diversity?
d = N(N-1) / sum of n(n-1)
where:
d = index of diversity
N = total number of organisms of all species
n = total number of organisms of each species
the higher the value d, the greater the species diversity
How does biodiversity reflect how well an ecosystem is likely to function?
- The higher the species diversity index, the more stable an ecosystem usually is and the less it is affected by change.
- If there is a change in the environment it is more likely that there is one species which is able to tolerate the change in a community with a high diversity index than in a community with a low diversity index.
- Therefore at least one of the species is likely to survive. `
