Organisms n environment and variation

• What is the definition of a species?

  A group of organisms that can interbreed
• What is the first part of a binomial name?

  Genus
• What is the second part of a binomial name?

  Species
• What is the binomial name for polar bears?

  Ursus maritimus
• What is the definition of a population?

  A group of organisms of one species
• What is a community in ecological terms?

  All populations of different species in an ecosystem
• What is an ecosystem?

  A unit containing organisms and their environment
• What is a habitat?

  The place where an organism lives
• What is a niche?

  The role of an organism in an ecosystem
• What does a niche include?

  • Its habitat
  • Adaptations to the environment
  • Interactions with other organisms
  • Interactions with the physical environment
  • Features of its life cycle
• Why is no ecosystem entirely self-contained?

  Organisms from one ecosystem interact with others
• How does a habitat differ from an ecosystem?

  • Habitat: Place where an organism lives
  • Ecosystem: Interacting community of organisms and environment
• What is biodiversity?

  The range and variety of different species
• What factors does biodiversity consider?

  • Species richness
  • Variation within each species
  • Species distribution
  • Population size
• Why is biodiversity important?

  It ensures stability of ecosystems
• What do different species depend on each other for?

  • Food
  • Shelter
  • Maintenance of the physical environment
• What happens if births exceed deaths in a population?

  The population will increase
• What happens if deaths exceed births in a population?

  The population will decrease
• What factors might affect a population of plants?

  • Competition
  • Light
  • Water
  • Soil nutrients
  • Space
  • Disease
  • Herbivore numbers
• What are abiotic factors?

  Non-living factors within an environment
• What are biotic factors?

  Living factors in the environment
• How do births and deaths affect population size?

  Births increase, deaths decrease population size
• What abiotic factors can affect a population?

  Light intensity, temperature, soil pH
• What biotic factors can affect a population?

  Predator numbers, competition, availability of food
• What is variation in biology?

  Differences between individuals of the same species
• What are the two types of variation?

  • Continuous Variation
  • Discontinuous Variation
• What does continuous variation result in?

  A range of phenotypes between two extremes
• What type of distribution does continuous variation usually give?

  A normal distribution curve
• How does discontinuous variation differ from continuous variation?

  It results in a limited number of phenotypes
• What is genetic variation controlled by?

  Genes
• What causes variation in organisms?

  Genes and the environment
• What is environmental variation?

  The influence of the environment on phenotype
• How does continuous variation like human height occur?

  It is influenced by both genes and the environment
• How does discontinuous variation like blood groups occur?

  It is usually only influenced by genes
• What are the three causes of genetic variation?

  Random fertilisation, meiosis, mutation
• What happens during random fertilisation?

  Any two gametes can fuse together
• What is meiosis?

  A type of cell division that produces gametes
• What do gametes produced by meiosis have?

  Genetic differences
• What is a mutation?

  A change in a gene that can be inherited
• What can mutations form?

  New alleles