4. Classification Flashcards
Why classify living organisms?
Need to be able to distinguish one type of organism from another.
Classification is the organisation of organisms into groups – this makes it easier to study them
The concept of SPECIES
Organisms are similar to one another but different from members of other species.
Capable of successfully breeding to produce living fertile young (belong to the same gene pool).
They are different species and here’s why……
The zygote from which the mule develops is formed is produced when the egg of a female horse (n=32) is fertilized by the sperm of a male donkey (n=31).
This means the diploid mule zygote has 63 chromosomes – an odd number.
Mitosis can occur and the mule can grow
In meiosis I – homologous pairs of chromosomes come together to form bivalents – this cannot happen in mules
Mules cannot successfully reproduce in other words they are infertile (there are occasional exceptions – can you find out why?)
This means the offspring of the horse and donkey is infertile and therefore the horse and donkey are different species.
Naming species (aka Nomenclature)
Binomial system – all organisms are given a Latin name with 2 parts. The first name is given a capital letter, the second a lower case letter. The two words are written in italics or are underlined.
Felix tigris (Felix tigris)
Felix = Genus name
tigris = specific name
Taxonomy
the science of classification
It involves naming organisms and organising them into defined groups.
Phylogeny
the study of the evolutionary history of groups of organisms
This is Natural classification:
This is Natural classification:
Based on the evolutionary historyof organisms (aka phylogenetics)
Groups of organisms with shared features derived from a common ancestor.
Arranges groups into a hierarchy in which groups are put into larger groups with no overlap.
Grouped according to homologous characteristics eg: pentadactyl limb
What is a tetrapod?
What is an amnion?
What is an homologous characteristic?
Which is the oldest group of animals that have been on the planet for longest?
Which are most closely related – amphibians & mammals or Crocodiles(reptiles) & mammals?
What homologous characteristic do ostriches and hawks share?
An animal with 4 limbs
A fluid filled sac in which a foetus develops.
Homologous characteristics are characteristics that an organism possesses as a result of evolution from a common ancestor.
Lungfish
Crocodiles and mammals
feathers
The variety of colours displayed by catfish is important in courtship. Give two ways in which courtship increases the probability of successful mating.
- Attracts / recognises same species;
Attracts mate of the same species = two marks. - Attracts / recognises mate / opposite sex;
- Indication of sexual maturity / fertility / synchronises mating;
Allow ‘ready to mate’. - Stimulates release of gametes;
- Form pair bond;
A scientist carried out breeding experiments with catfish from different populations.Describe how the results could show that the catfish belong to the same species
If Fertile offspring produced the catfish were from the same species (1)
Explain which of these levels of classification could not be
(i) a genus;…………………………………………………………………………………………..
……………………………………………………………………………………………………….
(ii) a phylum………………………………………………………………………………………….
…………………………………………………………………………………………………….
) Taxon A - there is more than one level/taxon below it / genus only has species /only has one level / taxon above it; (1)
(ii) Taxon C - there is more than one level/taxon above it / phylum onlyhas kingdom / only has one level taxon above it; (1)
