1.Characteristics and Classification of Living Organisms

• • Movement: an action by an organism or part of an organism causing a change of position or place
• • Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism
• • Excretion: the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements
• • Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds, ions and usually need water
• Prokaryotic cells: have no nucleus but do contain DNA in the cytoplasm; they may be single-celled bacteria or part of larger multicellular organisms such as algae
• There are millions of species of organisms on Earth
• • A species is defined as a group of organisms that can reproduce to produce fertile offspring
• Species can be classified into groups by the features that they share 
• • all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas)
• • Organisms were first classified by a Swedish naturalist called Linnaeus in a way that allows the subdivision of living organisms into smaller and more specialised groups
• Linnaeus’s system of classification

  
• Genus name is capitalized and has its first letter followed by an uppercase letter
• Dichotomous Keys

  • used to identify organisms based on a series of questions about their features
• Dichotomous means ‘branching into two’ and it leads the user through to the name of the organism by giving two descriptions at a time and asking them to choose
• • Classification systems aim to reflect evolutionary relationships between species
• Traditional biological classification systems grouped organisms based on the features that they shared.If organisms shared more similar features then they were said to be more closely related
• using the physical features of species (such as colour/shape/size) has many limitations and can often lead to the wrong classification of species
• • Organisms share features because they originally descend from a common ancestor
• morphology 

  the overall form and shape of the organism, e.g. whether it had wings or legs
• anatomy 

  the detailed body structure as determined by dissection
• the more similar the base sequences in the DNA of two species, the more closely related those two species are
• base sequences in a mammal’s DNA are more closely related to all other mammals than to any other vertebrate groups
• the five kingdoms

  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
• Main features of all animals:

  • they are multicellular
  • their cells contain a nucleus but no cell walls or chloroplasts
  • they feed on organic substances made by other living things
• typical animal cell

  
• Main features of all plants:

  • they are multicellular
  • their cells contain a nucleus, chloroplasts and cellulose cell walls
  • they all feed by photosynthesis
• typical plant cell

  
• mammals main featurs:

  • fur/hair on skin
  • placenta
  • young feed on milk from mammary glands
  • external ears
  • endothermic
• mammal examples: horse,dog,squirrel,human
• birds main features:

  • skin covered in feathers
  • two legs,two wings
  • lay hard egg shells on land
  • have a beak
  • endothermic
• bird examples: eagle,parrot,blue tit
• reptiles main features:

  • dry,fixed scales on skin
  • lay eggs on land with rubber shells
• reptile examples: snake,turtle,eguana
• amphibian main features:

  • smooth,moist skin
  • adults usually live on land (have lungs)
  • larvae live in water (have gills)
  • lay eggs,without shells, in water
• examples of amphibians: frogs, toads, salamanders, newts
• fish main features:

  • loose,wet,scales on skin
  • gills to breathe
  • lay eggs,without shells,in water
• fish examples: flounder,grouper,salom
• classification of animals

  vertebrates (animal that have a backbone)

  
• Invertebrates

  • do not possess a backbone
  • One of the morphological characteristics used to classify invertebrates is whether they have legs or not
  • All invertebrates with jointed legs are part of the phylum Arthropods
• myriapods main features:

  • body consists of many segments
  • each segment contains at least 1 pair of joint legs
  • 1 pair of antennae