Download Sources of Evidence for Evolution

Sources of Evidence for
Evolution
1. Fossils
• Sedimentary rock with fossils shows the kinds of species
that were alive in past.
• This history of life captured in rock is called the fossil
record.
Evidence from the Fossil Record
• Fossils in young layers of rock are more similar to species
alive today as opposed to fossils found in older layers of
rock. (eg. evolution of the modern camel)
• Fossils appear in chronological order in rock layers.
• Not all organisms appear in the fossil record at the same
time. (eg. fish are the 1st vertebrates that appear)
Evidence from Transitional Fossils
• These fossils show intermediary
links between groups of organisms.
• Have helped scientists the process
• of evolution and relationships between groups of
organisms.
• Link the past with the present.
• Allow scientists to identify vestigial structures
(structures that are the reduced form of structures in
an organism’s ancestors)
• See Fig 8.7 on pg 335
2. Biogeography
• Defined as the study of the past and present
geographical distribution of organisms.
Evidence
• Geographically close environments are more likely to
be populated with related species.
• Animals found on islands often closely resemble
organisms on the closest continent.
• Fossils of the same species can be found on the
coastlines of neighbouring continents.
• Closely related species are almost never found in
exactly the same location or habitat.
3. Anatomy
• Homologous structures have similar structural
elements and origin but may (or may not) have a
different function. (eg. hair in mammals)
• Organisms that share a common ancestor will show
homologous structures. (see Fig 8.9)
• Functional similarity in anatomy does not mean that
those species are closely related. (eg. wings in
insects, birds, bats and pterosaurs all serve the same
function but show no structural similarities)
Homologous Structures
Analogous Structures
– Analogous structures have similar
functions even there the
organisms do not share any
common evolutionary origin
– Some species of different origins
have similar physical structures
(convergent evolution)
– Example1: the wings of bats and
insects
– Example 2: the eyes of
vertebrates, molluscs (like squid
and octopus) and insects
4. Embryology
• The study of early pre-birth stages of an organsim’s
development.
• The similarities between embryos in related groups
(eg. vertebrates) provide evidence for a common
ancestral origin.
• See Fig 338
5. DNA
• Evolutionary relationships between species are
reflected in their DNA.
• Scientists can determine how related 2 organisms by
comparing the similarities in their DNA.
• Similar patterns in 2 organisms DNA must have been
inherited from a common ancestor.
• Gene sequences have determined that dogs are
related to bears and that whales and dolphins are
related to ungulates (i.e. cows and deer)
Read pg 339 and answer the ?
HW
• pg 340 #1, 2, 5-7, 11, 15