Biology - Chapter 10.4 Evidence for Theory of Evolution

What is evolution?

The theory that describes the way in which organisms evolve, or change over many years as a result of natural selection.

What did Darwin realize?

Organisms best suited to their environment are more likely to survive and reproduce, passing on their characteristics to their offspring

On what and where did Darwin carry out his observations?

Finches in the Galapagos Islands

What did Darwin notice in the Galapagos Islands?

Different islands had different finches. The birds were similar in many ways and so must be closely related, but their beaks and claws were different shapes and sizes

What were the design of the finches' beaks linked to?

Foods available on each island

What did Darwin conclude after his visit to the Galapagos Islands?

A bird born with a beak more suited to the food available would survive longer than a bird whose beak was less suited.

Therefore, it would have offspring, passing on its advantageous characteristic beak

Over time, the finch population on that island would all share this characteristic

Which other scientist was developing ideas at the same time as Darwin

Alfred Wallace, in Borneo. In 1858 sent his ideas to Darwin for peer review before publication.

His ideas were similar to Darwin's

What did Darwin and Wallace do as a result of sharing the same ideas?

Proposed the theory of evolution through a joint presentation of 2 scientific papers to the Linnaean Society of London (1858)

What did Darwin release in 1859?

'On the Origin of Species'

He named the theory he and Wallace presented independently as 'THE THEORY OF EVOLUTON BY NATURAL SELECTION'

Was controversial at the time due to contradictions with religion.

What are the evidence for evolution?

Paleontology, Comparative Anatomy, Comparative Biochemistry

What is paleontology?

The study of fossils and the fossil record

How are fossils formed?

Animal and plant remains are preserved in rocks. Over long periods of time, sediment is deposited on earth, forming layers of rock.

What do different rock layers correspond to?

Different geological eras.

Most recent layer is found on the top

What does the fossil record show about the simplest organisms (e.g. bacteria and simple algae), and the more complex organisms (vertebrates)?

How does it support evolutionary theory?

Simplest - Found in the oldest rocks.

Complex - Found in more recent rocks

Supports that simple life forms gradually evolved over an extremely long time period into more complex ones.

What does the fossil record show about the sequence in which organisms are found in?

How does it support the evolutionary theory?

The sequence matches their ecological links to each other. E.g. plant fossils appear before animal fossils

Is consistent with the fact animals require plants to survive.

What can scientists show by studying similarities in the anatomy of fossil organisms?

They can show how closely related organisms have evolved from the same ancestor.

What does fossils allow?

Relationships between living and extinct organisms to be investigated

What are the downsides of paleontology? (4)

1. Fossil record is not complete

2. Many organisms are soft-bodies and decompose quickly before they can fossilize

3. Conditions needed for fossils to from are not often present (anaerobic conditions needed to fossilize)

4. Earth's movements (e.g. volcanoes) have destroyed fossils ; some remain undiscovered.

What is comparative anatomy and why do scientists use it?

The study of similarities and differences in the anatomy of different living species.

They use it as fossil record is incomplete ; they look for other sources of evidence to determine evolutionary relationships.

What does the term homologous structure means and what is an example of it?

A structure that appears superficially different (and may perform different functions) in different organisms, but has the same underlying structure.

Example = Pentadactyl limb - same structure but different functions in different organisms.

What does the presence of homologous structures provide evidence for?

Divergent evolution. Describes how, from a common ancestor, different species have evolved, each with a different set of adaptive features.

When does divergent evolution occur?

This type of evolution occurs when closely related species diversify to adapt to new habitats as a result of migration or loss of habitat.

What is comparative biochemistry?

The study of similarities and differences in the proteins and other molecules that control life processes, like nucleic acid/DNA of an organism.

Changes in highly conserved molecules can help identify evolutionary links.

How did Lyell contribute to the theory of evolution?

Suggested fossils were actually evidence of animals that had lived millions of years ago

How did Hutton contribute to the theory of evolution?

Proposed theory of uniformitarianism. ( The idea that in the past, the Earth was shaped by forces you can still see in action today, e.g. sedimentation in rivers, wind erosion, etc)

Prompted Darwin to think of evolution as a slow process, one in which small changes gradually accumulate over very long periods of time.

What are the most common molecules studied?

Cytochrome c and rRNA ( has v. slow rate of subsitution)

In comparative biochemistry, how is discovery of species' relation done?

Comparing molecular sequence of a particular molecule (e.g. order of DNA bases or order of amino acids in protein)

More similar = species closely related

Less similar = distantly related