AIM: How can we know that evolution has

actually occurred?

Warm – up:

How does Darwin explain the presence of organisms alive

today?

LaMarck• Organisms adapted to their environments

ØThrough acquired traitsØChange in their lifetime

v Use & Disuse: organisms lost parts of their body because they did not use them (like the missing eyes and digestive system of the tapeworm)

v Perfection with Use & Need: the constant use of an organ leads to an increase in size of that organ

ØTransmit acquired characteristics to next generation

LaMarck• Organisms adapted to their environments

ØThrough acquired traitsØChange in their lifetime

v Use & Disuse: organisms lost parts of their body because they did not use them (like the missing eyes and digestive system of the tapeworm)

v Perfection with Use & Need: the constant use of an organ leads to an increase in size of that organ

ØTransmit acquired characteristics to next generation

But the fossil record shows…

Descent with Modification

Darwin’s idea that each species living today arose from a pre-existing

species!

Hundreds of millions of years passed before atmospheric oxygen levels were high enough to support eukaryotes.

Evidence Supporting Evolution

Evidence Supporting Evolution

• Fossils (descent with modification)

Evidence Supporting Evolution

• Fossils (descent with modification)

• Comparative biochemistry

Evidence Supporting Evolution

• Fossils (descent with modification)

• Comparative biochemistry• Comparative cell biology

Evidence Supporting Evolution

• Fossils (descent with modification)

• Comparative biochemistry• Comparative cell biology• Comparative embryology

Evidence Supporting Evolution

• Fossils (descent with modification)

• Comparative biochemistry• Comparative cell biology• Comparative embryology

• Comparative anatomy

Fossils as Evidence

Fossils as Evidence

• A fossil is the remains of organisms that lived in the past.

Fossils as Evidence

• A fossil is the remains of organisms that lived in the past.

• They are preserved by natural processes (in ice, rock, etc.)

Fossils as Evidence

• A fossil is the remains of organisms that lived in the past.

• They are preserved by natural processes (in ice, rock, etc.)

• Examples: bones, shells, footprints, imprints

Fossils as Evidence

• A fossil is the remains of organisms that lived in the past.

• They are preserved by natural processes (in ice, rock, etc.)

• Examples: bones, shells, footprints, imprints

• Generally, found in sedimentary rock that has been quickly covered by silt. Why?

How old are fossils?

How old are fossils?

• Relative dating: Fossils can be dated in correlation with the age of the strata (layer of rock) they are in.

How old are fossils?

• Relative dating: Fossils can be dated in correlation with the age of the strata (layer of rock) they are in.

• Absolute Dating: Using radioactive isotopes (half life) to get a more accurate estimate of age.

Problems with Fossils?

Problems with Fossils?

• Dating is only an approximation

Problems with Fossils?

• Dating is only an approximation

• No fossils of early or soft-bodied organisms

Problems with Fossils?

• Dating is only an approximation

• No fossils of early or soft-bodied organisms

• Holes in the fossil record

Problems with Fossils?

• Dating is only an approximation

• No fossils of early or soft-bodied organisms

• Holes in the fossil record

Problems with Fossils?

• Dating is only an approximation

• No fossils of early or soft-bodied organisms

• Holes in the fossil record

So what do scientists turn to?

????

Land Mammal

????Where are the

Intermediates?

Land Mammal

????Where are the

Intermediates?

Land Mammal

????Where are the

Intermediates?

Land Mammal

Land Mammal

2006 Fossil Discovery of Early Tetrapod

• Missing link from sea to land animals

2006 Fossil Discovery of Early Tetrapod

• Missing link from sea to land animals

Comparative Biochemistry & Cell Biology show that…

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy• Organisms that are related often have

similar types of proteins and antibodies

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy• Organisms that are related often have

similar types of proteins and antibodies

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy• Organisms that are related often have

similar types of proteins and antibodies

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy• Organisms that are related often have

similar types of proteins and antibodies

Comparative Biochemistry & Cell Biology show that…

• the genetic code in nucleic acids is almost universal

• physiological processes follow common metabolic pathways

• ATP is the universal form of energy• Organisms that are related often have

similar types of proteins and antibodies

Comparative Embryology

Comparative Embryology

• Species that are known to be closely related show similar embryonic development.

Comparative Embryology

• Species that are known to be closely related show similar embryonic development.

• Inference: The longer two embryos stay looking similar, the more closely related they are.

Comparative Anatomy

Comparative Anatomy• Study of biological structures in different organisms

Comparative Anatomy• Study of biological structures in different organisms

Comparative Anatomy• Study of biological structures in different organisms

• Homologous structures: structures in different species that have a similar design and position but serve different purposes in species that live in different environments.

Comparative Anatomy• Study of biological structures in different organisms

• Homologous structures: structures in different species that have a similar design and position but serve different purposes in species that live in different environments.

ex. Pentadactyl limb in mammals

Comparative Anatomy• Study of biological structures in different organisms

• Homologous structures: structures in different species that have a similar design and position but serve different purposes in species that live in different environments.

ex. Pentadactyl limb in mammals• Divergent evolution

Comparative Anatomy• Study of biological structures in different organisms

• Homologous structures: structures in different species that have a similar design and position but serve different purposes in species that live in different environments.

ex. Pentadactyl limb in mammals• Divergent evolution

Comparative Anatomy• Study of biological structures in different organisms

• Homologous structures: structures in different species that have a similar design and position but serve different purposes in species that live in different environments.

ex. Pentadactyl limb in mammals• Divergent evolution

• Analogous structures: Structure of two unrelated species that can evolve to look alike on the basis that they serve a similar function in a similar environment.

Analogous structures

Analogous structures

Analogous structures

• Separate evolution of structures

Analogous structures

• Separate evolution of structures– similar functions

Analogous structures

• Separate evolution of structures– similar functions– similar external form

Analogous structures

• Separate evolution of structures– similar functions– similar external form– different internal structure & development

Analogous structures

• Separate evolution of structures– similar functions– similar external form– different internal structure & development– different origin

Analogous structures

• Separate evolution of structures– similar functions– similar external form– different internal structure & development– different origin– no evolutionary relationship

Analogous structures

• Separate evolution of structures– similar functions– similar external form– different internal structure & development– different origin– no evolutionary relationship

Solving a similar problem with a similar solution

Analogous structures

• Separate evolution of structures– similar functions– similar external form– different internal structure & development– different origin– no evolutionary relationship

Solving a similar problem with a similar solution

Don’t be fooledby their looks!

Vestigial Structures

Vestigial Structures• Modern animals may have structures that

serve little or no function

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

• some snakes & whales

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

• some snakes & whales

show remains of the

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

• some snakes & whales

show remains of the

pelvis & leg bones of

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

• some snakes & whales

show remains of the

pelvis & leg bones of

walking ancestors

Vestigial Structures• Modern animals may have structures that

serve little or no function– remnants of structures that were functional in

ancestral species

– evidence of change over time

• some snakes & whales

show remains of the

pelvis & leg bones of

walking ancestors

• human tail bone

Vestigial Structures• Hind leg bones on whale fossils

Vestigial Structures• Hind leg bones on whale fossils

Vestigial Structures• Hind leg bones on whale fossils

Why would whaleshave pelvis & leg bonesif they were always

sea creatures?

ANY QUESTIONS??

This is the time to ask…