CSEC Biology General

• All living things are made up of CELLS. Thus, there are two types of organisms: UNICELLULAR and MULTICELLULAR
• Unicellular organisms


  Only made of one cell, usually have simple structures and do not rely on a transport system for their nutrients, instead move dissolved gases and nutrients around by the process of diffusion, do not rely on sexual reproduction to continue their species, instead reproducing by splitting in two
• Multicellular organisms


  Require a more complex structure and specialized systems may be necessary to enable the organism to digest and transport food, escape predators, seek shelter and find a sexual mate to continue the species
• Characteristics of living organisms

  • Growth
  • Respiration
  • Irritability
  • Movement
  • Nutrition
  • Excretion
  • Reproduction
• Metabolism


  The chemical processes that occur in the body
• Locomotion


  The ability of an organism to move from one location to another
• Species


  Members have very similar physical and biological characteristics and are able to interbreed and produce viable, fertile offspring
• Artificial classification involves categorising by certain features of anatomy
• Anatomical/physical features to separate organisms


  • Number of dorsal fins
  • Presence of whiskers
  • Shape of tailfins
  • Striped tailfins
• Using artificial classification can be problematic for identifying organisms of the same species
• Reasons artificial classification can be problematic


  • Organisms inherit different genetic traits from parents
  • Maturity causes changes in appearance
  • Males and females of a species may look different
• Natural or modern classification


  Based on an organism's DNA base sequences and evolutionary descent, structured as a hierarchy with each level called a TAXON

  
• Binomial name


  Genus and species
• Examples of genuses


  • Canis
  • Equus
  • Citrus
  • Homo
• Five kingdoms


  • Plantae
  • Animalia
  • Fungi
  • Prokaryota or Monera
  • Protista

  
• Viruses are not classed under any kingdom because they are not considered living organisms
• Eukaryotic cells


  Can be both unicellular and multicellular, DNA found in a nucleus in chromosomes, larger in size

  
• Prokaryotic cells


  Only unicellular, no nucleus, DNA in loose threads, smaller in size

  
• An ecosystem is a system of living and non-living factors that interact with each other
• Components of an ecosystem

  • Biotic (organisms)
  • Abiotic (physical features)
• Population


  A group of one species within a particular habitat
• Community


  All the populations of different species in a particular habitat
• Niche


  An organism's role in its environment, including its behaviour, interactions, how it meets its needs, and how it reproduces
• Habitat


  The place where an organism lives, can be classified as terrestrial or aquatic
• Categories of organisms in a food chain


  • Autotrophs (producers)
  • Heterotrophs (consumers)
  • Decomposers
• Decomposers are not to be confused with carrion feeders or detritivores
• Energy moves from organism to organism in a food chain in a unidirectional flow, as it cannot be directly returned to an organism or the Sun

  
• Trophic level


  Each stage in the food chain, where energy decreases through each successive level
• Most food chains are limited to four to six trophic level links because there would be too little energy available to sustain life on higher trophic levels
• Components of a food web


  • Autotroph (algae)
  • Herbivore (tadpole)
  • Carnivore (frog)
  • Omnivore (small fish)
  • Tertiary consumer (kingfisher)
  • Predator/prey (frog and snail)

  
• Types of ecological pyramids


  • Pyramid of numbers
  • Pyramid of biomass
  • Pyramid of energy

  
• In a predator-prey relationship, the number of predators is almost always less than the number of prey
• Advantages of biological controls


  • Targets a specific pest
  • Does not result in air and land pollution
  • Is a long-term solution and less manual labour is required

  
• Disadvantages of biological controls


  • Can result in disruptions in the food web
  • Takes a long time to work properly
  • Research is expensive
• Types of symbiotic relationships


  • Parasitism
  • Commensalism
  • Mutualism
• Advantages of Biological Controls


  • Targets a specific pest
  • Does not result in air and land pollution, such as pesticides
  • Is a long-term solution and less manual labour is required in the long run

  
• Disadvantages of Biological Controls


  • Can result in disruptions in the food web if the control becomes a predator
  • Takes a long time to work properly, unlike using chemical control
  • Research is expensive
• Section


  1. Predator pop. high because prey pop. is high

  2. Prey pop. decreases because predator pop. is too high; food is depleted

  3. Prey is allowed to reproduce since predator pop. is low. Predator pop. then increases once again
• Symbiosis


  Relationships where at least one organism benefits
• Types of symbiotic relationships


  • Parasitism
  • Commensalism
  • Mutualism