Variation and Evolution

• Are individuals in a population identical

  No, just usually similar
• What is variation


  Differences in the characteristics of individuals in a population
• What is a population?


  a group of individuals of the same species living in the same area at the same time
• What is a species?


  Used in the classification of living organisms, referring to related organisms capable of interbreeding and producing fertile offspring.
• What are causes of variation

  genetic, environmental or both
• Why do children look like their parents, but not identical to one of them

  They get half their inherited features from each parent
• What contains genetic information needed for an individual

  Sperm and egg cell (half each)
• What do sperm and egg cells contain

  Half of genetic information needed forindividual
• What are sperm and egg cells?

  haploid
• What does haploid mean

  A sex cell (gamete) that contains half the normal number of chromosomes (1 set)
• What is formed when sperm and egg cell join during fertilisation

  A new cell (zygote) which contains ALL the genetic information needed for an individual
• What are zygotes


  diploid
• What does diploid mean?

  Contains 2 sets of chromosomes (the normal amount)
• What is a genetic variation


  difference in DNA among individuals (inherited from parents)
• Examples of genetic variation

  Blood group, skin colour, eye colour.
• Examples of environmental factors that affect the characteristics of an organism


  climate, diet, accidents, culture and lifestyle
• examples of environmental variation


  Accent, body weight, scar, flower colour in hydrangeas
• Explain flower colour in hydrangeas

  plants that produce blue flowers in acidic soil and pink flowers in alkaline soil)
• Examples of genetic and environmental factors combined


  the weight of a dog is caused partly by its genes - inherited - and partly by what it eats - environmental
• What are the two types of variation that organisms within a species show

  Continuous and discontinuous
• What is continuous variation?


  A characteristic that can take any value within a range
• example of continuous variation


  height and weight
• What is a 'height range'

  from that of the shortest person in the world to that of the tallest person
• What is the typical shape of a characteristic of continuous variation graph

  Bell shaped
• What is the bell-shaped curve?

  Symmetrical curve that takes shape of bell

  (Increases at kncreasing rate at start, then levels of around middle, then falls back down, decreasing at a decreasing rate)
• What is discontinuous variation?

  A characteristic of any species with only a limited number of possible values
• Example of discontinuous variation


  Gender, eye colour, blood group
• Why is blood group discontinuous variation

  Human beings have one of four blood groups, A, B, AB or O. There are no values in between (intermediate values)
• What is another word for 'values in between'

  Intermediate vakues
• What type of reproduction only requires one parent

  asexual reproduction
• Why are offering produced by asexual reproduction genetically identical to the parent

  Because there is no fusion of gametes. Genetic material does not mix. All genes are inherited from the one parent
• What are asexual offspring called

  Clones (of their parent)
• What does not happen in asexual reproduction

  Fusion of gametes (mixing of genetic material
• Examples of organisms that use asexual reproduction

  Bacteria

  Fungi produce spores

  Some plants eg strawberries use runners

  Tubers in potatoes and bulbs in doffodils
• What process does asexual reproduction use to create clones of parent cell

  Mitosis
• What is mitosis


  A type of cell division which produces daughter cells identical to the parent.
• What do the offspring of asexual reproduction not show?

  Genetic variation
• What does sexual reproduction require?

  two parents, a male and a female, each of which produce gametes.
• What is fertilization?

  fusion of the nucleus of a male gamete with the nucleus of a female gamete.
• In humans, what does each gamete contain?

  23 chromosomes-half the number of chromosomes in a normal cell.