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Bellringer
Q. What theory states that all organisms on
Earth have descended from a common
ancestor?
R.
Evidence of Evolution
• How can we be confident that Evolution has
occurred?
1. Fossil record- Fossils provide a record of
species that lived long ago. Many ancient
fossils share similarities with species that now
live on Earth.
Fossils are divided into two major classes of traits
Derived- newly evolved features i.e feathers
which did not appear on ancestral fossils.
Ancestral- more primitive features i.e. teeth
and tails that do appear in ancestral forms.
Evidence of Evolution cont..
• 2. Comparative anatomy
Q. Why do vertebrate forelimbs have different
functions but appear to be constructed of
similar bones in similar ways?
Evidence of Evolution
2. Comparative Anatomy
• Homologous structures-anatomically similar
structures inherited from a common ancestor
 Vestigial Structures- a kind of homologous
structure that is the reduced form of functional
structures in different species.
Evidence of Evolution
Comparative Anatomy
• Q2. What do you think will happen to features
that no longer have a function for that
species?
• R. Evolutionary theory states that they will
become smaller and smaller until they are
eventually lost.
Evidence of Evolution
2. Comparative Anatomy
• Analogous structures – not inherited from a
common ancestor. Just because they have the
same function does not indicate an
evolutionary relationship.
Evidence of Evolution
3. Comparative Embryology
• Embryo- an early, pre-birth stage of an
organisms development. Many vertebrate
embryos exhibit homologous structure during
certain phases of development but become
totally different structure in the adult forms.
Evidence of Evolution
4.Comparative Biochemistry
• Evolutionary theory predicts that molecules in
species with a recent common ancestor
should share certain ancient amino acid
sequences. The more closely related the
species are. The greater number of sequences
will be shared.
Evidence of Evolution
5. Geographic Distribution
• The distribution of plants and animals that
Darwin saw during his travels along South
America first suggest that animals on the S.A
mainland were more similar to other S.A
animals then they were to animals living in
similar environments in Europe.
 Biogeography- study of the distribution of plants
and animals around the world.
Adaptation
• The five previous categories; fossil record,
comparative anatomy, comparative
embryology, comparative biochemistry, and
geographic distribution offer evidence for
evolution.
• At the heart of Darwin's theory of Evolution by
Natural Selection is Adaptation.
Adaptation Defined
• Adaptation- trait shaped by natural selection
that increases an organisms reproductive
success. One way to determine how
effectively a trait contributes to reproductive
success is to measure fitness.
 Fitness- Measure of the relative contribution an
individual trait makes to the next generation. The
better an organism is adapted to its environment, the
greater is changes of survival and reproductive success.
i.e. Because the Finches were each adapted to their
individual islands, they had variation in their beaks.
Common Types of Adaptation
• Camouflage- morphological adaptations that
allows organisms to blend in with their
environment.
Types of Adaptation cont..
• Mimicry- a type of morphological adaptation.
One species has evolved to resemble another
species.
Consequences of Adaptations
• Antimicrobial resistance
- An antibiotic is a
medicine that slows or
kills the growth of
bacteria.
• Some bacteria have
evolved a resistance to
certain antibiotics.
• People infected with
resistant bacteria can
never get rid of it.