bio- evolution

study guys #imgonnacry

**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)