Biology WJEC Unit 2

• The 2 group of plants are flowering and non-flowering
• The 2 animal groups are vertebrae and invertebrate
• Vertebrates have a backbone and invertebrates do not.
• Scientific names are used to avoid confusion by having one universal name everyone can understand.
• organisms can be classified by either physical features or phylogenetic relationships.
• The 7 levels of classification are...

  kingdom, phylum, class, order, family, genus, and species
• Adaptations mean that organisms are more suited to their environment, which will help them to survive and reproduce as they will be able to outcompete other individuals
• Animals compete for, mates, space, food and water.
• Plants compete for light, water, minerals, and space.
• The 2 types of competition in the ecosystem are Interspecific competition and intraspecific competition.
• Interspecific competition is where organisms of different species compete for resources (e.g. food, water, shelter)
• What is a chromosome?

  A structure found inside the nucleus of a cell. A chromosome is made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes.
• What are gametes?

  Gamete are sex cells (sperm or eggs)
• What is a dominant allele? 


  A version of a gene where only one copy is needed for it to be expressed.
• What is a recessive allele? 


  A version of a gene where two copies are needed for it to be expressed
• What is meant when an organism is homozygous?

  When an organism has two copies of the same allele (two recessive or two dominant)
• What is meant when an organism is heterozygous?

  When an organism has two different versions of the same gene (one dominant and one recessive)
• What is the genotype?

  The genes present for a trait
• What is the phenotype?

  The visible characteristic/ the observable physical properties of an organism
• What is the F1 generation?

  The offspring produced when 2 organisms are bred together
• What is the F2 generation?

  The offspring produced when two offspring (F1 generation organisms) are bred together
• What is selfing?

  When gametes from the same parent fuse (e.g. when pollen from a plant lands on the stigma of that same plant)
• How are dominant alleles represented in a punnett square?

  They are represented using uppercase letters
• How are recessive alleles represented in a punnett square?

  They use the lowercase version of the same letter as the dominant allele
• What is genetic engineering?

  Altering the genome of an organism
• What is a transgenic organism?

  An organism that contains foreign DNA
• Give 2 advantages of genetically modified crops

  • Better crop yields
  • Food will last longer and taste better
• Give 2 disadvantages of genetically modified crops

  • The new genes can easily spread to other plants in the environment
  • We don’t know what long term effects GM crops cause on health
• What are the two types of variation? (higher)

  ● Continuous

  ● Discontinuous
• What is continuous variation? (higher)

  ● Variation that cannot be categorised

  ● Produces a continuous range (e.g. height, weight)
• What is discontinuous variation? (higher)

  Variation that can be categorised into distinct groups e.g. eye colour, blood group
• What are the two causes of variation within a species?

  ● Genetics

  ● Environment
• What is genetic variation?

  ● Variation in the genotypes of organisms of the same species due to the presence of different alleles

  ● Creates differences in phenotypes
• What is environmental variation?

  ● Variations in phenotype that are acquired during the lifespan of an organism

  ● Due to environmental factors e.g. diet, lifestyle, climate, exposure to light etc.
• Illustrate how variation may be due to the interaction of genes and the environment

  An individual’s genes may make them predisposed to being tall. However, lack of nourishment during childhood may stunt growth.
• What creates genetic variation in a species?

  ● Sexual reproduction

  ● Spontaneous mutations
• How does sexual reproduction create variation?

  ● Meiosis produces genetically different gametes (haploid)

  ● During fertilisation, one gamete from each parent fuses to form a zygote (diploid)

  ● Genetic information from both parents is mixed to form a unique individual
• Why does asexual reproduction not create genetic variation?

  It involves mitosis which produces genetically identical daughter cells known as clones.
• What is a mutation?

  A random change to the base sequence in DNA which results in genetic variants
• How may a gene mutation affect an organism’s phenotype? (3)

  ● Neutral mutation does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype.

  ● Mutation may cause a minor change in an organism’s phenotype e.g. change in eye colour.

  ● Mutation may completely change the sequence of amino acids. This may result in a non-functional protein. Severe changes to phenotype.