Download Evidence of Evolution

Evidence of Evolution
Evidence of Evolution
• Darwin argued that living things have been
evolving on Earth for millions of years.
• Evidence supporting his theory could be found:
1.
2.
3.
4.
Fossil record
Geographical distribution of living species
Anatomy
Similarity in early development (embryology)
1. The Fossil Record
• Darwin saw fossils as a record of the
history of life on Earth.
• Darwin proposed:
– Earth was millions, rather than thousands, of
years old
– Countless species had come into being, lived
for a time, and then vanished.
2. Geographic distribution of
Living Species
• Species now living on different continents
had each descended from different
ancestors.
• Some animals on each continent were
living under similar ecological conditions
so they were exposed to similar pressures
of natural selection.
Similar, But Unrelated
Species
As a result, Darwin concluded that
because of these similar selection
pressures, different animals
ended up evolving certain features
in common!
3. Anatomy
• Darwin noticed similarities among the
body parts of various animal and plants.
• There are three different types of
structures to help support Darwin's Theory
of Evolution.
1. Homologous Structures
2. Analogous Structures
3. Vestigial Structures
Homologous Structures
• Homologous Structures
– Structures that are similar and have originated
from a common ancestor.
– May look different on the outside, but have
similar structure inside.
– Indicates that organisms may have shared a
recent common ancestor.
Homologous Structures cont’d.
• The limbs of different organisms serve
different functions, but have the same
bone structure inside.
Analogous Structures
• Analogous Structures
– Structures that serve identical
functions, but have different
internal anatomy.
– Ex: wings of birds and insects
• Both allow organisms to fly, but
have different development and
structure.
– Shows a more distant
relationship than
homologous structures.
Identify the following structures as analogy or
homologous. Be able to defend your answer!
Vestigial Structures
• Vestigial – structures that were useful in ancestors but
are no longer used by modern organisms
• Shows relationship between organisms with vestigial
structure and those with a working version.
• Ex: humans have tailbones homologous to tails of other
animals
Vestigial Structures cont’d.
• Some organisms have genes that are conserved.
– Genes that have remained unchanged, but may be “turned off”.
• Ex: whales have genes for hind legs
• Can give clues about early development of a species.
– Ex: whales may have descended from an ancestor who lived on
land
4. Embryology
• Embryology – study of early development
• Many organisms share similarities within the early stages
of development.
• The same groups of embryonic cells develop in the
same order and in similar patterns to produce the tissues
and organs of all vertebrates.
• These common cells and tissues, growing in similar
ways to produce the homologous structures!
• Can indicate a common ancestry among different
species.
Embryology cont’d.
Similarities in Macromolecules
• Similarities within DNA, RNA and proteins of
different species
– Genetic code is universal – all living things share the
same code
– Closely related species have very similar gene
sequences and protein sequences.
• Ex: hemoglobin in humans and gorillas differs by only 1
amino acid
– Can confirm ideas suggested by anatomy and
embryology.