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 the 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.
– Fish are the 1st vertebrates that
appeared
– Amphibians appeared later
meaning that they evolved from
ancestral fish
Evidence from Transitional Fossils
• These fossils show intermediary links between
groups of organisms.
• Have helped scientists develop 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
Whale Evolution
• https://www.youtube.co
m/watch?v=I2C-3PjNGok
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.
Homework
• Visit Berkeley Evolution website and follow
the tutorial on Homologous Structures
• Textbook:
– Read pages 332-335
– Pg. 336 #7-10
3. Anatomy
• Homologous structures have similar structural
elements and origin but may or may not have a
different function. (eg. hair in mammals)
Although, hair
performs different
functions in different
animals, the structure
of hair is the same
amongst them all!
• Organisms that share a common ancestor will
show homologous structures. (see Fig 8.9)
 All forelimbs of
vertebrates have the
same pattern of
bones even though
they serve a different
function
• Functional similarity in anatomy does not
mean that those species are closely related.
– eg. wings in insects, birds, bats and
pterosaurs(extinct flying reptiles) all serve the
same function but show no structural similarities
• Analogous structures have similar functions
even there the organisms do not share any
common evolutionary origin
4. Embryology
• The study of early
pre-birth stages of
an organisms'
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