intro to evolution Flashcards
- Why do we talk about evolutionary theory?
Evolutionary theory was developed to explain empirical observations of the natural world
- Quests on our observations of nature: Why?
Living things are
well-suited to their environments.
Living things show deep similarities.
There is an enormous diversity of living things.
There exists fossils.
Figure on homologous structures
van Leeuwenhoek was the first to observe and describe single-celled organisms, including
bacteria and protozoa – a previously unknown diversity of living things!
- Beginning in the European Age of Exploration (15th-17th centuries), a much greater diversity
of species than had previously been known was being discovered.
- In 1735, Linnaeus published his first
comprehensive listing of the living species of the world.
It is a small booklet of 11 pages. In 1766-1768, Linnaeus publishes the 12th edition of his comprehensive listing of the living world. It is in multiple volumes with over 3000 pages.
7.The Natuurlyke Historie, a Dutch work
derived from Linnaeus’ 12th edition, enlarged, amended, and with illustrations (8600 pages).
- Construction excavations, stone-quarrying, and road-building were uncovering the
apparent remains of many organisms not alive in Europe at the time.
- Cuvier (1796): “yet today there are elephants and rhinoceros only in the tropical zone of the Old World. How is it that their carcasses are found in such great numbers in the north of both continents?”
He used a hypothesis called catastrophism to explain these extinctions
- In 1842, Sir Richard Owen proposed that these three species belong to a distinct, extinct group
of animals and called this group Dinosauria (terrible lizards).
- To recap: Evolutionary theory was developed to explain
Living things are
well-suited to their environments.
Life has deep similarity.
There are a lot of living things (large and small) in the world.
Different types of animals have been alive at different times in different places (as evidenced by fossils).
- Evolutionary theory includes many interconnected pieces (hypotheses).
The extinction hypothesis proposes that it is possible for all members of a species to die without leaving living descendents.
The common descent hypothesis proposes that groups of similar plants or animals share features because they all descend from a common ancestor. Darwin’s universal common descent hypothesis predicts that all living things should have fundamental similarities – and they do, with the most astonishing observations coming from molecular and genetic studies.
Closely connected to the common descent hypothesis is the speciation hypothesis that proposes that it is possible for new species to be derived from existing species, e.g. hawthorn fly (apple maggot fly). Speciation is part of the evolutionary explanation for why there are so many living things.
The descent with modificationhypothesis proposes that the characteristics of species can change over time. A critical component of the descent with modification hypothesis is how exactlythe modifications could happen, which is what Charles Darwin’s hypothesis of natural selection provided.
- Darwin’s hypothesis of natural selection is reasoned from 5 observations about the natural world.
Observation 1: Most natural populations are relatively stable in size.
Observation 2: All living things are capable of having many, many offspring and, on average, most attempt to have more than two offspring.
Observation 3: Natural resources are limited.
Observation 4: No two individuals are exactly the same.
Observation 5: Offspring are not exactly like their parents, but resemble their parents more than they resemble other individuals in most features.
- Darwin then reasoned that if the differences among individuals affects their ability to win resources, then the individuals with more f
avorable features are more likely to live to reproduce. And since offspring resemble their parents, each successive generation has the features of successful individuals from the prior generation.
- Darwin’s hypothesis of natural selection is the mechanism for the modification part of the
descent with modification hypothesis.
Species change over time because each generation is
produced only by those members of the previous generation that had attributes that allowed them to successfully obtain limited resources. (Darwin hyp.)
- Evolutionary biologists call the successful features adaptations because they are
the result of successive generations becoming adapted to their environment.
- A skeleton of evolutionary theory
*Living things are
well-suited to their environments. (natural selection, descent with modification)
*Life has deep similarity. (common descent,speciation)
*There are a lot of living things (large and small) in the world. (speciation)
*Different types of animals have been alive at different times in different places (as evidenced by fossils). (speciation, extinction)
Interconnected hypotheses in evolutionary theory:
Extinction -
Common descent
Speciation
Descent with modification
Natural selection (contributed by Charles Darwin)
Heritability = traits can be passed from
parents to offspring
A requirement for natural selection to operate – natural selection doesn’t work on non-heritable traits
Hereditary material
DNA!
DNA is a double helix - has a sugar/phosphate backbone & a base = nucleotide
Hereditary mechanisms
Maurice Wilkins, Rosalind Franklin, John Watson, Francis Crick
Structure of DNA
Structure of a nucleotide (know how the pieces fit together – be able to draw a diagram of a nucleotide)
Complimentary base pairing allows DNA to be copied and transmitted from parent to offspring
