science B1 edexcel

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Kingdoms

The first rank in this system is called a kingdom. There are five kingdoms, based upon what an organism's cells are like:

  • animalia (all multicellular animals)
  • plantae (all green plants)
  • fungi (moulds, mushrooms, yeast)
  • prokaryotae (bacteria, blue-green algae)
  • protoctista (Amoeba, Paramecium).

 

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Further Division

There are several further ranks before we reach a particular species. In order, these are:

  • kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species.

 

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example

lions have the following classification 

  • kingdom - animal
  • phylum - vertebrate
  • class - mammal
  • order - carnivorous
  • family - cat
  • genus - big cat
  • species - lion.

One way to remember this is by using a daft sentence like this one:
"Kevin plays clarinet oflute - grotty sound!"
All organisms are known by their binomial name which is the genus and species eg Homo sapiens – modern humans

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Kingdom characteristics

The first big division of living things in the classification system is to put them into one of five kingdoms. These are based on what an organism's cells are like. This list shows the names of the kingdoms, the characteristics and examples of the sort of organisms they contain:

  • Animalia: Multicellular, no cell wall or chlorophyll, heterotrophic feeders. Examples: all multicellular animals, including: jellyfish, worms, arthropods, molluscs, echinoderms, fish, amphibia, reptiles, birds and mammals
  • Plantae: Multicellular, have cell walls and chlorophyll, autotrophic feeders.Examples: all green plants, including: algae, ferns and mosses (plants that do not produce seeds), conifers and flowering plants (plants that do produce seeds)

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kingdom characteristics continued

  • Fungi: Multicellular, have cell walls, do not have chlorophyll, saprophytic feeders. Examples: moulds, mushrooms, yeast
  • Protoctista:Usually unicellular, with a nucleus eg amoeba. Examples: amoeba and paramecium
  • Prokaryotes:Unicellular, with no nucleus eg bacteria. Examples: bacteria and blue-green algae
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Classification examples

It can be easy to classify a species. For example, we are Homo sapiens.

 Classification of species:

  • kingdom - animalla 
  • phylum - chordates - animals with supporting rod running the length of the body e.g. backbone.
  • class - mammals - animals that are warm-blooded, have lungs and body hair, produces milk and gives birth to live young
  • order - primates - ape-like animals
  • family - hominids - human-like animals
  • genus - **** - humans
  • species - sapiens - modern humans 


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Classification examples continued

It can also be difficult to classify a certain organism. For example, the single-celled organism called Euglena has some confusing characteristics. It has:

  • chloroplasts, like a plant
  • no cell eall, like an animal
  • a flagellum to swim with, like some bacteria

a fifth kingdom, called protoctista, was made for organisms like Euglena.

viruses:

scientists do not classify a virus as a living thing. this is beacuse:

  • it does not show all seven processes for life
  • when it enters a cell it changes the way a cell works so it can make copies of the virus



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vertebrates

the vertebrates are animals with a backbone. Scientists spearate this groups into smaller groups because of their features:

  • how the animal takes in oxygen - lungs, gills, through the skin
  • thermoregulation - maintains own temperature (homotherms) or temperature varies with surroundings (poikilotherms)
  • reproduction - internal or external fertilisation, lay eggs (oviparous) or gives birth to living young (viviparous)

examples:

  • fish - gills, external fertilisation, oviparous, poikilotherm
  • amphibian - some lungs or gills, external fertilisation, oviparous, poikilotherm e.g frogs
  • reptile - lungs, internal fertilisation, oviparous, poikilotherm
  • birds - lungs, internal fertilisation, oviparous, hemeotherm
  • mammal - lungs, internal fertilisation, vivapaous, hemeotherm e.g. humans

assigning vertebrates to different groups can be difficult as some fall into many categories: e.g. sharks are fish but give birth to live young and use internal fertilisation 

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species

organisms of the same species:

  • have more characteristics in common than they do with organisms of different species
  • can interbreed to produce fertile offspring

sometimes a species may have different kings or breeds that show great variation but the individuals still belong to the same species. different breeds of pedigree dogs are like this.

 Similar species tend to live in similar habitats, and are closely related in evolutionary terms. They are likely to share a relatively recent ancestor. Closely related species living in different types of habitat may have different characteristics. You can use keys to identify organisms according to their features.

A species is defined as organisms that produce fertile offspring but this is sometimes limited as some organisms do not always reproduce sexually, and some hybrids are fertile.

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Species continued

sometimes classification can be complicated by:

  • variation within a specices
  • hybridisation (close related species bredd to produce offspring that have characteristics of both - the hybrids are oftern infertile)
  • ring species - neighbouring populations of species may have slightly differnet characteristics but can still interbreed as part of a chain but the two ends of the chain can't interbreed as they may have similar characteristics
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keys

keys are used to help identify a species. keys can either be branching or a series of paried statements and are based on the physical charateristics of the species.

a key to identify simple farm animals would be:

1. does the animal have four legs - yes - go to statment 2, no - go to statement 4

2. does the animal have a curly tail - yes- pig, no - go to statment 3

3. does the animal have a hoof divided into two parts- yes- cow, no - horse

4. does the animal have webbed feet? - yes - duck, no - human

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