Transcript Species

Classification and
Heredity
Classification: means placing objects into similar
groups or categories.
Taxonomy: is the science of classifying organisms.
Species
• A species is a group of similar organisms that are
capable of naturally interbreeding with each other to
produce fertile offspring e.g.
Domestic dogs
Cats
Humans
Orang-utan
Species
Variation within species:
While members of a species have many features in common
the individual members of any species show many
differences between each other e.g. Humans differ in
features such as – hair colour, skin colour, height etc.
Variation within a Species
Acquired Variation
Inherited Variation
Acquired variations: are not inherited but are learned or
developed during life e.g. ability to walk, speak a language
etc.
Species
Inherited Variations: are controlled by genes.
Inherited Variations
Heredity (genetic inheritance): is the passing on of
features from parents to offspring by means of genes
e.g.:
humans – inherit genes controlling features such
as number of fingers, production of nails, ability
to form tears etc.
Inherited Variations
Genes:
• A gene is a section of DNA that causes production of a
protein.
• control cell because many of the enzymes they produce
control cell activities.
• units of heredity.
Inherited Variations
Gene Expression:
•Gene expression is the precise way in which the genetic
information in a gene is decoded in the cell and used to
make a protein. (i.e. the way in which genes work)
• It is the expression of genes that produces the
characteristics or traits that are inherited.
•
Characteristics = Heredity + Environment
Inherited Variations
Chromosomes:
• composed of 60% protein and 40% DNA
• Protein responsible for holding DNA in a tightly packed
configuration so it can fit into nucleus.
• Genes arranged along DNA of a chromosome in linear
order some close together and others far apart.
• As a result , genes only comprise 3% of the DNA in
human cells the rest of the DNA is said to be non-coding.