Characteristics & 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
• Sensitivity

  The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses
• Growth

  A permanent increase in size and dry mass by an increase in cell number or cell size or both
• Reproduction

  The processes that make more of the same kind of organism
• 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
• Mrs Gren

  Movement

  Respiration

  Sensitivity

  Growth

  Reproduction

  Excretion

  Nutrition
• Species


  A group of organisms that can reproduce to produce fertile offspring
• Species can be classified by the features that they share 

  e.g. all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas)
• The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Linnaeus's system of classification

  A) Kingdom

  B) Phylum

  C) Class

  D) Order

  E) Family

  F) Genus

  G) Species

  
• Dichotomous Keys


  These are 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
• • In order to successfully navigate a dichotomous key:

  1. You need to pick a single organism to start with, or you may be presented with an unfamiliar one as part of an exam questions
  2. Follow the statements from the beginning. Each statement or question you should be able to answer using the information provided in the question or an image given as part of the question.
  3. Eventually there will be no more statements or questions left and you will have the name of the organism
  4. You then pick another organism and start at the beginning of the key again, repeating until all organisms are named

  
• 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
• Using DNA to Classify Organisms

  Organisms share features due to descending from a common ancestor

  • Ex. All mammals have bodies covered in hair, feed young from mammary glands, and have external ears
• Originally, organisms were classified using:

  • Morphology
  • The overall form and shape of the organism
  • Ex. If they have wings of legs
  • Anatomy
  • The detailed body structure determined by dissection
• Microscopes, knowledge of biochemistry, and eventually DNA sequencing allowed us to classify organisms using a more scientific approach.

  The studies of DNA sequences of different species show that the more similar the base sequences in DNA of the two species, the more closely the species are.

  This means that base sequences in mammal's DNA are more closely related to other mammals

  
• • These sequences show that Brachinus armiger and Brachinus hirsutus are more closely related than any other species in the list as their DNA sequences are identical except for the last but one base.
  • As DNA base sequences are used to code for amino acid sequences in proteins, the similarities in amino acid sequences can also be used to determine how closely related organisms are

  
• 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
• Main features of all plants:

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

  A) nucleus

  B) cell membrane

  C) mitochondria

  D) ribosomes

  E) cytoplasm

  
• A typical plant cell

  A) cell membrane

  B) chloroplasts

  C) cell wall

  D) ribosomes

  E) nucleus

  F) mitochondria

  G) cytoplasm

  H) permanent vacuole

  
• Vertebrates Table

  
• Vertebrate classification

  
• Arthropod table

  
• Arthropod classification

  
• Main features of all fungi (e.g. moulds, mushrooms, yeast)

  • usually multicellular
  • cells have nuclei and cell walls not made from cellulose
  • do not photosynthesize but feed by saprophytic (on dead or decaying material) or parasitic (on live material) nutrition
• Saprophytic

  Feeding on dead or decaying material
• Parasitic

  Feeding on live material
• A typical fungal cell

  A) nucleus

  B) cell membrane

  C) ribosomes

  D) cell wall

  E) chitin

  F) mitochondrion

  G) cytoplasm

  
• Main features of all Protoctists (e.g. Amoeba, Paramecium, Plasmodium)

  • most are unicellular but some are multicellular
  • all have a nucleus, some may have cell walls and chloroplasts
  • meaning some protoctists photosynthesise and some feed on organic substances made by other living things
• Two examples of protoctist cells

  A) food vauoles

  B) nucleus

  C) ribosomes

  D) cell membrane

  E) mitochondrion

  F) cytoplasm

  G) contractive vacuole

  H) water

  I) nucleus

  J) ribosomes

  
• Main features of all Prokaryotes (bacteria, blue-green algae)

  • often unicellular
  • cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria
• A typical bacterial cell

  A) cell membrane

  B) cell wall

  C) peptidoglycan

  D) cytoplasm

  E) circular loop of dna

  F) plasmid

  G) ribosomes

  
• At least some parts of any plant are green, caused by the presence of the pigment chlorophyll which absorbs energy from sunlight for the process of photosynthesis