• An adaptation is any structure or
behavioral trait that improves an
• Most adaptations serve one of three
2. prevent an organism from becoming food for another
Jean-Baptise de Lamarck
• Before the 18th century people believed
that earth and living things existed
unchanged since the beginning of time.
• organisms desired to become more
complex and change for the better.
• organisms could produce new or improved
parts to be better adjusted to their
environment.
• Lamarck used his
model to explain how giraffes got such long necks:
• Giraffes started out with short necks, but soon low tree leaves were removed.
• They had to stretch to reach the higher
• Lamarck tried to prove his theory by
cutting off the tails of mice and breeding
them to see if their offspring were born
with tails.
• The experiment failed
• We study his theory because although he
was wrong, he did get people thinking
Thomas Malthus
Said that populations remain quite
stable due to natural checks and
balances such as limited
His ideas were very influential on Charles Darwin.
Populations
Charles Darwin
• His observations on his trip led to the
development of his theory of natural
selection.
Variations in humans
• Blood type
• Ear lobe attached or not
•
Organisms compete for limited resources:
•
Between members of the same species
• The best adapted individuals in the population are considered the most fit because they are able to pass on their traits to more offspring.
• This theory also became known as
'The
Survival of the Fittest'.
Alfred Russell Wallace
• Darwin kept his theory to himself for over 20 years.
• He did not publish his theory until Wallace sent Darwin a paper that had a very similar
conclusion to Darwin.
• Darwin and Wallace presented their work
• In 1859, Darwin
published his book
The Origin of Species
in which he described his theory of natural selection.
• The entire first
• His book said that: all life on earth shared a common ancestor
and that a population could change over time to produce new species.
How do new species get
produced?
• Species- organisms that are capable of interbreeding to
produce fertile offspring.
1. Variation in a species
• Changes in the environment drive the
process of natural selection.
• Variation in a species must be present
before a change in the environment
• Belgian Blue cattle, 1 gene mutated to produce very large muscles
• Evolution is usually a very slow process
caused by the accumulation of inherited
variation
• DNA
Genes
Chromosomes
• Our genes determine our traits
• Sexual reproduction produces far more
variation than asexual reproduction
• Sex can introduce new gene combinations
into a population and is an important
2.
Isolation
• In order for a group of organisms to develop and be distinct from other members of their species they must be isolated so they can adapt to their own habitats in their own way.
• Isolation restricts the gene pool and encourages mutations.
Two types of Isolation:
• Geographic
Isolation: two groups are separated by
changes to habitat. E.g. separating
• part of Taylor Glacier, the Blood Falls, in Antarctica.
• a lake was covered by the glacier about 2
million years ago, trapping the microbes inside.
They evolved
independently of outside life for all that time, and
were discovered due to a few leaks from under the
2. Reproductive Isolation
• Organisms no longer breed naturally. E.g. different mating rituals.
Adaptive Radiation
• The evolution of a group of organisms from a single
ancestral species into several new species, each specialized into its own specific niche.
• This often happens on newly formed islands. E.g. Hawaii or
Galapagos Hawaiian
