Evidence of Evidence of Evolution Evolution

Main Types of Main Types of EvidenceEvidence

1. Fossils

2. Homologous structures

3. Embryology

Fossil recordFossil record• Layers of rock contain fossils

onew layers cover older ones• creates a record over time

o fossils show a series of organisms have lived on Earth • over a long period of time

Fossils tell a story…Fossils tell a story…

the Earth is oldthe Earth is old

Life is oldLife is old

Life on Earth has changedLife on Earth has changed

Fossil RecordFossil Record• Fossils are evolutionary evidence

• Fossils show that ancient species share similarities with species that now live on Earth.

• Fossils records provide evidence that living things have changed over time.

Glyptodont Armadillo

Comparing AnatomyComparing Anatomy• Homologous structures

• Analogous structures

• Vestigial structures

Compare the bonesCompare the bones

• The same bones under the skino limbs that perform different functions are built from the same

bones

How could thesevery different animalshave the same bones?

Homologous Homologous structures structures

• Structures that come from the same origin• homo- = same• -logous = information

• Anatomically similar structures inherited from a common ancestor

• These structures can be similar in arrangement and/or function.

Homologous Homologous structuresstructures

• Forelimbs of human, cats, whales, & bats o same structure

• on the insideo same development in embryo o different functions

• on the outsideo evidence of common ancestor

Analogous Structures Analogous Structures • Structures that do not have a common

evolutionary origin but are similar in structure.

• Shows that functionally similar features can evolve independently of each other

• Ex: wing of an insect and wing of bird

Analogous Structures Analogous Structures

Vestigial Structures Vestigial Structures • A body structure that has no function in a

present-day organism but was probably useful to an ancestor.

• This shows a change over time

• Hind leg bones on whale fossils

Why would whales have pelvis & leg bones if they were always sea creatures?

Why would whales have pelvis & leg bones if they were always sea creatures?

Because they used to walk on land!

EvolutionChapter 15

Comparing Embryos Comparing Embryos • Embryo: the earliest

stage of growth and development of both plants and animals

• Vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms.

Comparing EmbryosComparing Embryos• Similar embryo development may suggest a

common ancestor

Biochemical Evidence Biochemical Evidence • Common ancestry

can be seen in the complex metabolic molecules that many different organisms share.

• Comparison of the DNA or RNA of different species produce biochemical evidence for evolution

Biochemical Evidence Biochemical Evidence • Comparisons of the similarities in amino acids

and other molecules across species reflect evolutionary patterns seen in comparative anatomy and in the fossil record.

Knowledge CheckKnowledge Check

True or False

Organisms with similar anatomy share

similar DNA sequences.

Knowledge Check Knowledge Check Which of the following best explains how the fossil record provides evidence that evolution has occurred?

A It indicates the exact cause of structural and behavioral adaptations of organisms.

B It shows that the form and structure of groups of organisms have changed over time.

C It shows how the embryos of many different vertebrate species are very similar.

D It indicates that forms of life existed on Earth at least 3.5 billion years ago.

Knowledge CheckKnowledge CheckThe occurrence of the same blood protein in a group of species provides evidence that these species

a. evolved in the same habitat.

b. evolved in different habitats.

c. descended from a common ancestor.

d. descended from different ancestors.