Week 2: Evolution

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Special Creation

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Previous Ideologies

1. All species are independent and are unrelated to each other

2. Life on Earth is young- perhaps just 6000 years old

3. Species are immutable/incapable of change

These beliefs were explain by the instantaneous and independent creation of living organism by a supernatural being

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Characteristics of a scientific theory

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1. Pattern: a statement that summarizes a series of observations about the natural world. The pattern component is about facts - about how things are in nature

2. Process: mechanism that produces that pattern or set of observations

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What is a scientific revolution?

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it overturns an existing idea about how nature works and replaces it with another, radically different, one

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Plato

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he thought that every organism was an example of a perfect essence, or type, created by God and that these types were unchanging

He acknowledged that some individual organism on earth did vary, but he said that it was to be ignored and to focus on the perfect essence.

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Typological Thinking

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based on the idea that species are unchanging types and that the variations within species are unimportant or even misleading

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Aristotle and the Great Chain of Being

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He proposed that species were organized into a sequence based on increased size and complexity, with humans at the top

1. species are fixed types

2. some species are higher- in the sense of becoming more complex or "better"- than others

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Jean-Baptiste de Lamark and Evolution

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species are not static, but change through time it was still initially based on the great chain of being.

He thought that simple organism originate at the base of the chain by spontaneous generation than evolve by moving up the chain over time

Lamarckian evolution is progressive in the sense of always producing larger and more complex, or better, species

He also thought that species change through time via the inheritance of acquired characters. As an individual develops in response to challenges posed by the environment, its phenotype changes, and it passes on these phenotypic changes to offspring

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Evolution

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Occurs because traits vary among the individuals in a population, and because individuals with certain traits leave more offspring that others do

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Populations

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Consists of individuals of the same species that are living in the same area at the same time

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Population thinking

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Variation among individuals in a population was the key to understanding the nature of species

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What was the theory of evolution by natural selections importance?

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1. species aren't static and unchanging

2. replaced typological thinking with population thinking

3. It was scientific. It proposed a mechanism that could account for change through time and made predictions that could be tested through observation and experimentation.

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Descent with Modification

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Darwins theory

species that lived in the past are the ancestors of the species existing today, and that species change through time

1. species change through time

2. species are related by common ancestry

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Fossil

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any trace of an organism that lived in the past

These can range from bones and branches to shells, tracks or impressions, and dung

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Fossil Record

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this is all the fossils that have been found on earth and described in the scientific literature

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Extant species

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Those species living today

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Sedimentary Rocks

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form from sand or mud or other materials deposited at locations such as beaches or river mouths.

they like volcanic ash or lava are known to form in layers- younger layers are deposited on top of older layers

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Evidence of Evolution through Relative Ages

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initially fossils were organized according to their relative ages based on a series of principles derived from observations about rock formation

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Geologic Time Scale

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a sequence of named intervals called eons, eras, and periods that represent the major events in Earth's History.

They also realized that it takes vast amounts of time to form the thick layers of sedimentary rock that they were studying, because erosion and deposition are such slow processes

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Radioactive Decay

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Allows researchers to estimate how long ago a rock formed

the steady rate at which unstable or "parent" atoms are converted into more stable "daughter" atoms

This allowed a way for geologists to assign absolute ages to the relative ages in the geologic time scale

Based on

1. Observed decay rates of parent to daughter atoms

2. ratio of parent to daughter atoms present in newly formed rocks

3. The ratio of parent to daughter atoms present in a particular rock sample

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How old is Earth?

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Approximately 4.6 billion years old

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When were the earliest signs of life on Earth?

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3.4-3.8 billion years ago

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Extinct Species

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a species that no longer exists

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Baron George

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1812- found fossil of the Irish Elk and because this deer was too large to have escaped discovery and too distinctive to be classified as a large-bodied population he determined that species are not static

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Species extinction on Earth

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over 99 percent of species that have ever lived are extinct

species have gone extinct continuously throughout Earth's history

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Law of Succession

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resemblances between the fossils found in the rocks underlying certain regions and the livign species found in the same geographic areas.

The general observation was that extent species in the fossil recored were succeeded, in the same region, by similar species.

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Transitional feature

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a trait in a fossil species that is intermediate between those of ancestral (older) and derived (younger species)

shows a gradual change over time

ex: aquatic animals had fins to terrestrial animals that had limbs

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Vestigal Trait

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a reduced or incompletely developed structure that has no function, or reduced function, but is clearly similar to functioning organs or structures in closely related species.

the existence of vestigial traits is inconsistent with the idea of special creation but instead supports that species have changed over time

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Phylogenetic Tree

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a branching diagram that describes the ancestor-descendant relationships among species or other taxa.

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Homology

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is the similarity that exists in species because they inherited the trait from a common ancestor

1. genetic

2. structural

3. developmental

They all interact and influence each other

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Genetic Homology

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Occurs in DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences.

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Developmental homology

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This is the similarity in embryos

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Structural Homology

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the similarity in adult morphology or form

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speciation

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process that results in one species splitting into two or more descendants species

in most cases the identity of the ancestral species is known meaning that biologists have established a direct link between ancestral and descendant species. Also the reason for the splitting event is usually known

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internal consistency

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observation that data from independent sources agree in supporting predictions made by a theory

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Artifical Selection

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manipulating the composition of the population

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Darwin's 4 Postulates

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1. individual organisms that make up a population vary in the traits they posses

2. Some of the trait differences are heritable

3. In each generation, many more offspring are produced than can possibly survive. Therefore only some individuas in the population survive long enough to produce offspring, and among the individuals that produce offspring, some will produce more than others

4. The individuals that survive best and produce the most often is not a random sample of the population. Natural selection will occur

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Natural Selection

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occurs when individuals with certain characteristics produce more offspring than do individuals without those characteristics. The individuals are selected naturally- meaning by the environment

The frequency of these selected traits increases from one generation to the next

Affects indviduals

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Fitness

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the ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in the populations.

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Adaption

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a heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait. Adaptions increase fitness- the ability to produce viable, fertile offspring

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Natural experiment

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Instead of comparing groups created by direct manipulation under controlled conditions, natural experiments allow researchers to compare treatment groups created by unplanned change in conditions

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polygenic

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many genes - each one exerting a relatively small effect - influence the trait

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Acclimation

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a change in an individual's phenotype that occurs in response to a change in natural environmental condition. These changes are not passed on to offspring because no alleles have changed as a result acclimatization does not cause evolution.

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What does Evolution not do?

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1. It is not goal directed- it does not occur to solve problems mutations just happen not becauase the organism wanted or needed it.

2. It is not progressive- organisms have not gotten 'better' over time. Traits are routinely lost or simplified over time as a result of evolution by natural selection

3. There is no such thing as a higher or lower organism

4. Organisms do not act for the good of the species

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What does evolution not do?

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1. Evolution is not goal directed- mutations do not occur to solve problems they just happen

2. It is not progressive- organisms have not gotten better overtime instead complex traits are routinely lost of simplified over time as a result of evolution by natural selection

3. There is no such thing as a higher or lower organism

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Contraints on Natural Selection

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1.