A.S Biology Unit 2.14.1 Classification

aimee1234's version from 2015-04-11 07:32


Question Answer
What is taxonomy?Taxonomy is the science of classification
What is classification?Classification is the organisation of living organisms into groups. This process is not random.
Why are organisms put into different groups?Makes it easier for scientists to identify and study them.
How many levels of groups (taxonomic groups) are there and what are they?7 levels of groups used to classify organisms. 1.Kingdom 2.Phylum 3.Class 4.Order 5.Family 6.Genus 7.Species
How many groups can each organism belong to at each level in the taxonomic hierarchy?Organisms can only belong to one group at each level in the taxonomic hierarchy - there's no overlap. Similar organisms are first sorted into large groups called Kingdoms, e.g. all animals are in the animal kingdom. Similar groups from that kingdom are then grouped into a phylum. Similar organisms from each phylum are then grouped into a class, and so on down the seven levels of the hierarchy.
What happens as you move down the hierarchy?As you move down the hierarchy, there are more groups at each level but fewer organisms in each group.
What does the hierarchy end with?The hierarchy ends with species - the groups that contain only one type of organism (e.g. humans, dogs, E.coli)
What is a species?A species is a group of similar organisms able to reproduce to give fertile offspring.
Why are species given a scientific name and how is this name created?Species are given a scientific name to distinguish them from similar organisms. This is a two-word name in Latin. The first word is the genus name and the second word is the species name - e.g. humans are homo sapiens.
What does giving organisms a scientific name enable scientists to do?Giving organisms a scientific name enables scientists to communicate about organisms in a standard way that minimises confusion. E.g. americans call a type of bird a cockatoo and australians call them flaming galahs but its the same bird. If the correct scientific name is used there's no confusion. also american and english robin are two different types of bird.
Why do scientists constantly update classification systems?Because of discoveries about new species and new evidence about known organisms (e.g. DNA sequence data).
What is phylogenetics? Details?Phylogenetics is the study of the evolutionary history of groups of organisms. All organisms have evolved from shared common ancestors (relatives). E.g. members of the Hominidae family (great apes and humans) evolved from a common ancestor. First orangutans diverged (evolved to become a different species) from this common ancestor. Next gorillas diverged, then humans, closely followed by bonobos and chimpanzees.Phylogenetics tells us who's related to whom and how closely related they are. Closely related species diverged away from each other most recently. Humand and chimpanzees are very closely related. so their branches are closer together and they diverged very recently whereas humans and orangutans are more distantly related so their branches are further apart
Why do scientists find it difficult to sometimes see which species an organism belongs to, or whether they belong to a new, distinct species.You can't always see their reproductive behaviour (you can't always tell if different organisms can reproduce to give fertile offspring)
Why can't you always see an animals reproductive behaviour?1.They're extinct. 2.They reproduce asexually - they can never reproduce together if they belong to the same species, e.g. bacteria. 3.There are practical and ethical issues involved - you can't see if some organisms reprodce successfully in the wild (due to geography) and you can't study them in alab (because it's unethical), e..g no-one would try to mate humans and chimps.
Other than reproductive behaviour what can scientists now do to classify them?Scientists can now compare the DNA of organisms to see how related they are, e.g. the more DNA they have in common the more closely related they are. But there's no strict cut-off to say how much shared DNA can be used to define a species. E.g. only about 6% of human DNA differs from chimpanzee DNA but we are separate species.

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