Chapter 2: Evolutionary Biology

Tiktaalik roseae

Transitional fossil between fish and tetrapods "fishapod" discovered in 2004 on Ellesmere Island

Charles Darwin

An english naturalist who discovered natural selection and published origin of species he did not "invent" the theory of evolution he discovered how it occurs by tying together pattern with process

What is natural selection?

The process whereby organisms better adapted to their environment tend to survive and produce more offspring

What is the belief of special creation?

Each organism created by a deity independently and they are perfectly matched to environment, species never changed or went extinct, the earth is very young

What did Hutton propose?

That the interior of earth was hot and that the heat was driving the creation of new rock, land was eroded by air and water and deposited as layers in the sea, heat then consolidated the sediment into stone and uplifted new lands

Lamarck's hypothesis of evolution

Proposed that species evolve

First law, use or disuse of an organ causing it to change ( grow larger or deteriorate)

Second law, All changes are heritable

Giraffe neck growth example

Information about Darwin

Dropped from medical school and went to cambridge to study to become a clergyman, completed BA and sailed aboard HMS Beagle as a naturalist for almost 5 years

Darwin's observation in biogeography

Plants and animals of temperate south america were more like those of tropical south america than like those of temperate europe

Darwin's geological observations

He found rocks that contain seashell fossils in the mountains and dug up fossils of large extinct organisms which was evidence organisms used to look different, he found more recent fossils of living plants and animals

What is Uniformitarianism? (Lyell's principles of biology)

The belief that the Earth's past geological changes can be fully explained by current processes. Aka earth has been undergoing the same natural processes since the beginning.

Lyell's Principles of Geology

The theory that the earth has been formed over long periods of time with the geological features, the earth is really old

What were the most important observations made in the Galapagos islands?

Animals were most similar to those in south america and were likely derived from there, since the islands have different environments the plants and animals have differed which concluded that the species adapted to their new environment to form new species

An Essay on the Principle of Population - Thomas Malthus

Book that said populations of organism if unchecked would over produce and cause famine and disaster which raised the question how do populations remain stable

Darwin publishing

Formulated theory of evolution by natural selection but shelved it for 16 years until Alfred Wallace independently developed the same concept and wrote to Darwin which pushed him to publish

Descent of Man - Darwin

Book that outlined how similar humans are to other animals anatomically, embryos, and vestigial organs

What is descent with modification?

The principle that living species descend with changes, from other species over time

Selective breeding

The process of selecting a few organisms with desired traits to serve as parents of the next generation, species are able to change and derive from other species

Homology

Similarity due to common ancestry seen in anatomy and embryology, can be structural developmental or genetic

What is a homologous structure?

Structures that are inherited from a common ancestor but may have different functions ex: human arm and dolphin flipper

What is a analogous structure?

Result of homoplasy where structure is similar in appearance and function but details of structure differ and are not derived from a common ancestor. Analogous structures are the result of converge evolution. ex: bird wing and bat wing

What is convergent evolution?

When two or more unrelated lineages acquire the same biological trait because of selection for a shared ecological niche

Homoplasy

A similar (analogous) structure or molecular sequence that has evolved independently in two species.

What are vestigial structures?

remnants of organs or structures that had a function in an early ancestor, functionless structures ex: hip bones in whales, human tail bone

What are Pseudogenes?

Vestigial genetic structures that are carried along with functional DNA but are nonfunctional and arise from reverse transcription of mRNA where resulting DNA is inserted at another locus

Processed pseudogene

Non functional gene that is missing introns and promoters

Mutation evolution and pseudogenes

Evolve at a constant rate, when compared to original gene they can be aged, older processed pseudogenes will be shared by more distantly related species

Where do pseudogenes come from?

A mother gene is transcribed and the mature mRNA goes through reverse transcription and is inserted at another locus creating a pseudogene

Evidence of evolution from natural populations

Variation within a population due to different resource use, formation of sub populations that can still interbreed, distinct populations with limited inbreeding and reduced fitness of hybrids, eventually becomes multiple reproductively isolated populations (species) and produces infertile offspring when hybridized

Evidence from the fossil record

Fossils are unlike currently living species and reflects change over time, Scientists used to think if we searched we would find all fossilized species still alive, Extinction eventually became known as a fact

Extinction and succession

Mammalian faunas of the two continents (south america and australia) are markedly different, yet the fossil each continent's extinct fauna is strikingly similar to the continents recent fossil forms

What is the law of succession?

States that extinct species are ancestors of living species

What are transitional forms?

Usually show a blend of traits that you would expect at an intermediate stage in evolution

Archaeopteryx

Crow sized with modern feathers but had a reptilian skeleton with teeth, claws, and a long bony tail

Why was the Archaeopteryx important?

It is a transitional species because it is not in the direct line of descent from dinosaurs to modern birds but shows a combination of traits supporting that it shared a common ancestor with both dinosaurs and birds

Cetaceans

First fossil found that had limb bones strong enough to walk on land, steady accumulation of extinct transitional fossils show most major changes in cetacean evolution

Pakicetus

52 million year old whale ancestor that walked on land

Epigenetics and lamarck's theory

Epigenetics suggests environmental influence and affect gene expression but does not imply that traits can be inherited in a purposeful way

Living transitional forms

Species: Alticus terrestrial and amphibious

Terrestrial form never voluntarily go into the water

They breathe air through gills and skin

Excellent climbers

Archaeopteryx relation to dinosaurs

Thought to be closely related to Theropod dinosaurs ( ex: velociraptor or T rex) which led to prediction that bird like theropods with feathers would be found and dozens of fossils of these theropods have been found

Turtle transitional form

Modern turtles ribs pass under their shoulder blades while most amniotes ribs pass over shoulder blades, the intermediate step is expanded ribs that don't pass over or under the shoulder blade

The universal genetic code

With minor exceptions all organisms studied to date use the same nucleotide triplicates (codons) to specify the same amino acids, this is evidence that we are all descended from a common ancestor

Common ancestry

The conceptual foundation which all of modern biology and biomedical science is built on

Principle of catastrophism (geology is a result of past catastrophic events)

James hutton countered idea with uniformitarianism and said that the same geological processes we see today have always been acting and acting at the same relative intensity such as volcanoes and earthquakes

Creation of geological time scale

Geologists have measured rock forming processes and erosion rates, accumulation of shells and sand and gravel at beachs, concluded earth is very old

Used relative dating to put the rock formations of europe and fossil bearing layers into sequence by age assuming the deepest were oldest

When did earth form?

4.6 billion years ago

Radiometric dating

The process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products

Continental drift

Proposed by Alfred Wegener and was denounced by geologists fossil biogeography was major evidence, noted continental shelved fit together like jigsaw puzzles

Marie Tharp

Combined data from research ship soundings and seismographic data from undersea earthquakes to make the first map of the north atlantic seafloor and later global maps she paved the way for acceptance of continental drift and plate tectonics

Marie Curie

Laid the foundation for radiometric dating or absolute dating of rocks using unstable isotopes and naturally occurring elements

How does radiometric dating work?

Unstable isotopes and naturally occurring elements decay at a constant rate that isn't affected by temp pressure or moisture, half life of isotopes is known so you can measure the amount of parent and daughter isotopes in a rock sample and calculate the age of the rock

What is half life?

The amount of time it takes for 50% of the parent isotope to be converted into the daughter isotope, different isotopes have different half lifes which is useful for dating different time scales

Life is...

around 3.7 billion years old based on microbial fossils