bio- evolution

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Pasteur's experiment

Pasteur's experiment

Louis Pasteur carried out an experiment in 1862 that showed life could not spontaneously appear

Miller-Urey experiment

The miller-Urey experiment recreate the conditions on a primordial earth

• Over 20 different amino acids were produced in Miller's original experiments

• This showed that these conditions could have led to complex molecules (organic molecules) being created

The RNA chicken and egg

“Chicken and egg” problem

• Genes require enzymes to form

• Enzymes require genes to form

• RNA molecules have the ability to act both as genes and as enzymes. This characteristic offers a way around this problem

RNA WORLD

The rna world hypothesis suggests that life on earth began with a simple rna molecule that could copy itself

• The first stage in the evolution of life may have involved RNA molecules performing the catalytic activities necessary to assemble themselves from a nucleotide soup

• At the next stage, rna molecules would begin to synthesize proteins

• NOTE: there is a problem with RNA as a prebiotic molecule because the ribose is unstable. This has led to the idea of a pre-RNA world (PNA).

origin of eukaryotes

Eukaryotic cells first appeared about 1.9 billion years ago

• It is thought that eukaryotic cells evolved from large prokaryotic cells that ingested other free-floating prokaryotes

• They formed a symbiotic relationship with the cells they engulfed. This is called endosymbiosis

The two most important organelles that arose in eukaryotic cells were:

• Mitochondria, for aerobic respiration

• Chloroplasts, for photosynthesis in aerobic conditions

• Primitive eukaryotes probably acquired mitochondria by engulfing purple bacteria

THE COMMON ANCESTRY OF LIFE

• Genetic evidence shows there are three main groups or domains of life. All are related to a last universal common ancestor (LUCA)

• Virtual all life uses the same genetic code and the same molecular machinery for translating the code and assembling the proteins

evolution

• the heritable genetic changes seen in a population over time

• Evolution occurs in populations

• Changes are passed onto the next generation (inherited)

Macroevolution

Large scale changes in form, as viewed in the fossil record, involving whole groups of species and genera

Microevolution

• Small-scale changes within gene pools over generations

FOSSILS:

• Fossils are the remains of long-dead organisms that have become preserved in the earth's crust. They provide a record of the appearance and extinction of organisms

THE FOSSIL RECORD

When organisms are trapped in sediments, they record that moment in time

• the fossils in each stratum of sedimentary rock are a local sample of that organisms that existed at the time the sediment was deposited

• Because younger sediments overlie older ones it is possible to determine the relative ages of fossils

• Layers of sedimentary rock are arranged in the order in which they were deposited, with the most recent layers nearer the surface

• chronological ordering

THE ARCHAEOPTERYX FOSSIL

• Transitional fossils, such as archaeopteryx, have a mixture of features found in two different, but related groups, they provide important links in the fossil record

• *like a midpoint/link between two species (dino and bird), fossils provide this link/EVIDENCE OF EVOLUTION

Comparative Anatomy

The 5 digit (pentadactyl) limb found in most vertebrates has the same bone structure

• This similarity of structure is called homology

• Homologies are indicative if common ancestry

Homologous Structures (same structure, different function)

In many vertebrates, the basic 5 digit limb has been highly modified to serve special functions locomotion

• Such homologies also indicate ADAPTIVE RADIATION; the basic limb plan has been adapted to meet the needs to different niches

• The same pattern of bones making up the pentadactyl limb can be seen on each of these examples

Analogous structures (same function, different structure)

Analogous structure are features of different species that are similar in function but not in structure and which do not derive from a common ancestral feature (compared to homologous structures) and which evolved in response to a similar environmental challenge

• Analogous structures show that different evolutionary solutions

Comparative embryology

COMPARATIVE EMBRYOLOGY is the comparison of embryo development across species

• Similar embryonic anatomy across different species highlights a COMMON ORIGIN

• Embryology provides evidence for evolution since the embryos of different groups are extremely similar at early development

Natural Selection

Natural selection: organisms that are better adapted to their environment tend to survive and produce more offspring, which passes on the genes that aided their success

• Explains how and why species change over time

• Is synonymous with the term natural selection

DARWINS 4 POINTS

1. More offspring are produced than survive

2. Individuals show variation: some variations are more favorable than others

3. Natural selection favors the best-suited traits at the time

4. Variations are inherited. The best-suited variants leave more offspring. The population changes over time.

Fitness

• Reproductive success: how good an organism is at maximizing the number of surviving offspring

• Fitness is a measure of how well suited an organism is to survive in its habitat and its ability to maximize the numbers of offspring surviving to the reproductive age

Selection Pressure

Selection pressure: Anything that reduces the reproductive success of a proportion of the population

• External things which affect an organism’s ability to survive and reproduce

• Selection pressure is usually expressed as a measure of the fitness of a particular trait relative to others in the population

• ex. length of giraffes necks

Artificial selection (genetic manipulation)

• The identification by humans of desirable traits in plants and animals and the steps taken to enhance and perpetuate those traits in the future.

• Artificial Genetic passing (Breeding)

• Bad and good life quality; not necessarily beneficial for the wild, but is desirable for humans

Adaptations

• Adaptations: a heritable behavioral, morphological, or physiological trait that maintains or increases the fitness of an organism

• Adaptations are anything heritable that make an organism better at surviving to reproduce

• Could be behavior or physical (Like birds migrating is a genetic behavioral adaptation)