Evolution: Evidence

SC.912.L.15.1 Explain how the scientific theory of evolution is supported by the

fossil record, comparative anatomy, comparative embryology, biogeography,

molecular biology, and observed evolutionary change

Types of Evidence we will be covering

• Fossil Records– Transitional fossils

• Comparative Anatomy– Homologous Structures– Analogous Structures

• Vestigial Structures • Biogeography

Fossil Records • Fossils support the idea

of evolutionary progression.

• By looking at fossils Paleontologists/zoologists can: – Identify extinct animal

species – Follow the path of

evolution through different stages of development

Evolution of the Whale

Key Points of the Fossil Record

• Provides evidence of evolution from one species to another– Shows ancestral

intermediates

• Only hard tissue is preserves

• Fossil Formation

Transitional Fossils

• FLASH CARD ALERT: • TRANSITIONAL FOSSIL: fossils

that show transitions in evolution.

• Transitional fossils are RARE findings – Small proportion of

organisms become fossils

– Many fossils represent dead evolutionary branches

Support: Comparative Anatomy • Homologous Structures:

Similar features found in different species that are derived (come from) a common ancestor – Ex. Tetrapod limbs, fur,

lungs • Bone formation:

developmental and evolutionary similarities

• Evidence of intermediates

Analogous Structures

• FLASH CARD ALERT: • Analogous Structures: a trait or an organ that

appears similar in two unrelated organisms• Happens because of convergent evolution: – FLASHCARD ALERT: CONVERGENT EVOLUTION: Species

evolve in similar environments and have similar environmental stressors/survival factors

Analogous Structures

Vestigial Structures

• Vestigial Structures: characteristics found in existing species that have no known function

• Provide evidence of common ancestry• As species evolve their structures change– Two things will happen • Species will adapt the organ/structure to a new use

– penguin

• The organ or structure will no longer have a use – Whale pelvis/snake feet.

Useless for Flying but excellent for swimming

Vestigial Structures

• Stubs on pythons, boas, and other snakes– Ancestral legs

• No known function

• Useless Vestigialstructures are BETTER sourcesof evidence forevolution

Amphiuma

Flightless Wings

Plica semilunaris

CFU:

• What is the major difference between analogous and homologous structures?

• What structure is the best evidence of evolution: analogous, homologous or vestigial

• What kind of tissue/part of an animal is preserved in fossils?

• What type of fossils are paleontologists most interested in?– Why are they hard to find?

Comparative Embryology

• Incredible similarities in embryos of different species provides evidence of common ancestor – Patterns of embryo

development are also important.

Biogeography

• Zoologists seek to understand how very closely related species ended up in completely different parts of the world

Support for Pangaea

Key Point of Biogeography

• Seeks to answer the question: how/why different but similar species exist in similar yet separate parts of the world

• Can be explained by geological changes, migrations, convergent evolution

• Support ideas of common ancestor and Pangaea

EVOLUTION CFU

• What are the five steps of evolution?• How does the environment affect the process of

evolution?• Adaptations help the organism: • The three types of structures that support evolution

are: • Paleontologists are excited to find what kind of

fossil and why?