B2a: Classification

We are surrounded by a huge variety of living organisms. Through classifying them according to their similarities and differences, we can better understand the evolutionary and ecological relationships between living organisms. The ability to correctly classify organisms is crucial if we are to identify and maintain global biodiversity. 

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Organisms can be classified into groups according to what?
Shared Characteristics.
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What four species come under arthropods?
Insects, crustaceans, myriapods and arachnids.
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How many legs do insects have?
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What species has over 20 legs?
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How many legs do crustaceans have?
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What species has 8 legs?
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State two things about organisms of the same species.
May show great variation but they have more features in common than they do with other species.
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Why do similar species tend to live in similar types of habitats?
Their characteristics are adapted for the best chance of survival in that habitat.
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What is the variety of life?
The variety of life is a continuous spectrum.
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What does the variety of life make difficult?
It makes it difficult to place organisms into distinct groups.
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What seven categories are living organisms split into? In order.
Kingdom, Phylum, Class, Order, Family, Genus and Species.
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Why are classification systems important?
They help us understand how organisms have evolutionary relationships and ecological relationships.
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What are evolutionary relationships?
How organisms are related.
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What are ecological relationships?
How organisms interact with each other.
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What two types of classification are there?
Natural and Artificial.
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What are natural classification systems based on?
Evolutionary relationships and genetic similarities between organisms.
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What are artificial classification systems based on?
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Explain how the use of DNA sequencing information has led to changes in understanding of classification.
DNA sequencing allows us to see genetic differences between different groups. We might found out that 2 groups aren't actually as closely related as we'd thought - or 2 groups that we thought were very different might turn out to be close relatives.
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Why do systems of classification change over time?
Newly discovered species and DNA sequencing.
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Explain how the use of newly discovered species has led to changes in understanding of classification.
They might not really fit into any of the categories. These could be living species or newly discovered fossils.
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Give an example of newly discovered species being difficult to place in the classification system.
The archaeopteryx fossil has features of two different classes (birds and reptiles) so its hard to know where to place it.
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What do evolutionary trees display?
Common ancestors and evolutionary relationships. The more recent the common ancestor, the more closet related the two species - and the more characteristics they're likely to share.
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What do scientists analyse to find out about the evolutionary relationships between organisms?
Lots of different genes responsible for lots of different characteristics. This involves analysing huge amounts of DNA data and it is only possible thanks to advances in ICT.
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Define the term species.
A species is a group of organisms which are capable of interbreeding to produce fertile offspring.
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Explain the importance of the binomial system.
It is the international basis of naming species.
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Problems of classifying hybrids.
They are usually infertile so they aren't a new species.
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Problems of classifying organisms that only produce asexually.
There is no interbreeding with another organism so they don;t fit the definite of a species.
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How evolution causes problems with classifying.
Organisms change over time, so the way they've been classified might also change. Sometimes a group of organisms will change so much they form a new species - but it can be difficult to tell when this has happened.
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What are hybrids?
Hybrids are formed when you interbreed a male species with a female from a different species. For example, a mule is a cross between a donkey and a horse.
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What is asexual reproduction?
Is where an organism reproduces by making a copy of itself. (e.g. bacteria)
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What do closely related species have?
A relatively recent ancestor however they may have different features if they live in different types of habitats.
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Other cards in this set

Card 2


What four species come under arthropods?


Insects, crustaceans, myriapods and arachnids.

Card 3


How many legs do insects have?


Preview of the front of card 3

Card 4


What species has over 20 legs?


Preview of the front of card 4

Card 5


How many legs do crustaceans have?


Preview of the front of card 5
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