Rikunarita-ORG/Wikinium huggingface dataset:
# Transitional fossil

The London specimen of *Archaeopteryx*, discovered only two years after the publication of *On the Origin of Species*
**Transitional fossils** (or **missing links**) are the fossilised remains of lifeforms that show features typical of two distinct groups. It may be a rare fossil, such as *Archaeopteryx*, which shows early features of a group which later becomes widespread.

The rarity of transitional forms is interesting. It suggests the new forms are not yet dominant in the ecology of their time, and their populations are relatively small. It follows that their fossils would be scarce. In the Solnhofen limestone where *Archaeopteryx* was found, there are more examples of pterosaurs of several genera than there are of the proto-bird. In the Jurassic, the pterosaurs were dominant in the air.

Large numbers of different bird species are found in the famous Chinese lagerstatten deposits such as the Jehol biota. The Lower Cretaceous birds are clearly more bird-like, and the features they developed enabled them to invade habitat niches which had been the preserve of pterosaurs, or maybe were not previously exploited at all.

Pterosaur decline (if present) seems unrelated to bird diversity. In fact, at least some bird niches were reclaimed by pterosaurs just before the KT event.

## Mosaic evolution

Typical of transitional fossils is that some features are clearly basal or primitive. Other features are advanced ('derived'). With *Archaeopteryx*, the front legs are derived, and show clearly the capacity for flight. Also, the feathers had the rachus (stem) off-centre, a feature of all bird flight feathers. The rest of the skeleton was just like any other small carnivorous dinosaur.p35

Transitional fossil flatfish are known, where the process of eye movement is not yet complete. In a typical modern flatfish, the head is asymmetric with both eyes on one side of the head. In *Heteronectes*, the transition from the symmetric head is incomplete, with one eye positioned near the top of the head, similar to its Italian relative *Amphistium*. The existence of these intermediate stages was predicted by Darwin.

When transition takes place between one group and another, not all features change at the same time. This is called mosaic evolution.408 Transitions between higher groups would involve a series of transitional species, only a few of which may be found as fossils.
# List of extinction events

An **extinction event** is a relatively fast drop in the number of species living on Earth. It occurs when the rate of extinction increases more than the rate of speciation. This is a list of the largest. Major extinction events are important to both geology and evolution.

## The Phanerozoic

Marine extinction intensity increases over time. The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized.
### Major extinction events

There are five major extinction events in the Phanerozoic eon, and many smaller events. In order of time, latest first:

1. K/T extinction event. The Cretaceous/Tertiary extinction event ended the Mesozoic era and started the Cainozoic era.

2. End–Triassic extinction event or events.

3. P/Tr extinction event. The Permian/Triassic extinction event ended the Palaeozoic era and started the Mesozoic era.

4. Late Devonian extinctions, at the Frasnian/Famennian junction.

5. End–Ordovician extinction event. After a series of lesser events, the end-Ordovician extinction resulted in an estimated 84% species loss.

### Other extinction events

Other extinction events in the Phanerozoic had a significant impact on the evolution of the biota. Overall, it seems that climate changes caused some extinctions, and hits by asteroids sometimes caused extinctions.

### Before the Phanerozoic

Before the Phanerozoic eon, there were even larger extinction events, which are often forgotten:

* The formation of the moon by a planet-sized body striking the Earth would probably have eliminated any early forms of life.
* Pre-Palaeozoic ice ages would have been extinction events. They were:
	+ The Huronian 2.5 to 2.2 billion years ago.
	+ The Cryogenian which lasted for the whole of the second period of the Neoproterozoic.
# Evolutionary linguistics

**Evolutionary linguistics** is a sub-discipline of linguistics that explores where human language came from.

A central question within evolutionary linguistics is how old language is, and when humans started to use language. There are many other questions within the field that linguists are trying to answer. For example, whether language is something that only humans have, or if other animals can use language as well. Another issue is whether the ability to use language is genetic or whether it is something that early humans learned from the environment.

Some linguists claim that a gene mutation in the FOXP2 gene gave humans the ability to learn and use language. There is evidence that a version of this gene existed in Neanderthals, which suggests that this ability emerged over a long period of time.
# Evolutionary psychology

**Evolutionary psychology** is a branch of psychology that investigates behavior which has evolved. It is similar in this respect to ethology, which has always used ideas from evolutionary biology.

## Abstract

This field seeks to identify which human psychological traits are evolved adaptations, that is, functional products of natural selection or sexual selection. Evolutionary psychology usually focuses on behavior most people share. Sex and social behavior are some of the more common areas that evolutionary psychology focuses on. Events like violent behavior need explanation in evolutionary terms.

Evolutionary psychology is related to other fields of science like sociobiology, social psychology, and sociocultural anthropology. Evolutionary psychologists argue that much of human behavior is the result of adaptations that evolved to solve recurrent problems in human ancestral environments.

The adaptationist approach is steadily increasing as an influence in the general field of psychology. Evolutionary psychologists hold that behaviors or traits that occur universally in all cultures are good candidates for evolutionary adaptations. This includes our ability to infer others' emotions, discern kin from non-kin, identify and prefer healthier mates, and cooperate with others. They report successful tests of theoretical predictions related to such topics as infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price and parental investment.

"The recognition that psychological mechanisms are evolved adaptations connects evolutionary biology to psychology in the strongest possible fashion, allowing everything we know about the study of adaptations to be applied to the study of psychological mechanisms".
## Books

* Barkow, Jerome H; Cosmides, Lena & Tooby, John (eds) 1992. *The adapted mind: evolutionary psychology and the generation of culture*. Oxford University Press. ISBN 978-0195101072
* Buss, David 2011. *Evolutionary psychology: the new science of the mind*. 4th ed, Pearson. ISBN 0-205-01562-X

## Related pages

* Adaptive unconscious
* Sociobiology
* *The Expression of the Emotions in Man and Animals*

## Other websites

* Frans de Waal 2012 Moral behavior in animals
# Phylogeny

This type of diagram shows geological periods and relative abundance.
A **phylogeny** is a proposal of how organisms are related by their evolutionary history.p336 It is based on the evidence that all living things are related by common descent. The evidence for phylogeny comes from palaeontology, comparative anatomy, and DNA sequence analysis.

The main product of **phylogenetics** is a **phylogenetic tree** or tree of life. This is a diagram showing a pattern of ancestor/descendent relationships. Information may be related to geological periods or estimated dates. A biological classification is another type of product.
# Artificial selection

This mixed-breed Chihuahua and Great Dane show the range of dog sizes produced by artificial selection
Selective breeding transformed teosinte's few fruitcases (left) into modern corn's rows of exposed kernels (right)
**Artificial selection** is the intentional breeding of plants or animals. It means the same thing as **selective breeding** and is an ancient method of genetic engineering.

Selective breeding is a technique used when breeding domesticated animals, such as dogs, pigeons or cattle. Some of these animals may have traits that a breeder will want to carry over to the next generation. The breeder will therefore select those animals to breed which have that quality, rather than those that do not.

Inbreeding is a particular kind of selective breeding, designed to produce a population which is genetically virtually identical. Such populations are rarely viable outside the laboratory. They lose fertility. To control this, most breeds are outcrossed or backcrossed to wild-type individuals, or at least less inbred stock. The details differ from breed to breed. The improvement when outcrossing is done is called hybrid vigour.

Charles Darwin used the example of artificial selection to introduce his idea of natural selection. Artificial selection may be contrasted with the process of natural selection. In natural selection, the differential reproduction of organisms with certain traits happens. This is because some variations help the organism to have better survival and reproduction. The process maintains or enhances the fitness of a population in its natural habitat.

Artificial selection may sometimes be unintentional; it is thought that domestication of crops by early humans was largely unintentional.
# Paleontology

**Palæontology** or **paleontology** is the study of fossils of living things, and their phylogeny (evolutionary relationships). It depends on basic sciences such as zoology, botany and historical geology. The term **palaeobiology** implies that the study will include the palaeoecology of the groups in question.

In *palaeozoology*, the evolution of those animal phyla with fossil records are studied. In *palaeobotany*, fossil plants are studied. In historical geology the formation, sequence and dating of rock strata give information about past environments.

A fossil is any kind of life that is more than ten thousand years old and preserved in any form that we can study today. The fossil record is always incomplete, and later discoveries may extend the known survival of a group. See Lazarus taxon.

Some palaeontologists study fossils of microorganisms, living things that are too small to see without a microscope, while other palaeontologists study fossils of giant dinosaurs.

* **Vertebrate palaeontology**: the palaeontology of vertebrate animals
* **Invertebrate palaeontology**: the palaeontology of invertebrate animals

## Related pages

* Lagerstätte
* Paleoanthropology
* Palaeoclimatology
# Systematics

**Systematics** is one of the main fields in biology. It is closely related to taxonomy.

Systematics is the study of the diversification of life on the planet Earth, both past and present, and the relationships among living things through time.

Relationships are usually seen as evolutionary trees (cladograms, phylogenetic trees, phylogenies).

Phylogenies have two components, *branching order* (showing group relationships) and *branch length* (showing amount of evolution). Phylogenetic trees of species and higher taxa are used to study the evolution of traits (anatomical or molecular characteristics), and the distribution of organisms (biogeography). Systematics is used to help us understand the evolutionary history of life on Earth.

"Systematic biology" and "taxonomy" are terms that are often confused and used interchangeably. They were defined as follows:

>
> Systematics is the field which (a) provides scientific names for organisms, (b) describes them, (c) preserves collections of them, (d) provides classifications for the organisms, keys for their identification, and data on their distributions, (e) investigates their evolutionary histories, and (f) considers their environmental adaptations.
> Taxonomy is that part of systematics concerned with topics (a) to (d) above.
>
>
>
# Dysgenics

**Dysgenics** (also called **cacogenics**) is the belief that peoples' genes may get worse over the course of generations.

The adjective "dysgenics" is the antonym of "eugenics". It was first used about 1915 by David Starr Jordan. He thought there might be dysgenic effects in World War I. Jordan believed that healthy men were as likely to die in modern warfare as anyone else and that war killed only the physically healthy men of the populace whilst preserving the disabled at home.

The theme was picked up more recently. Neither version has been proved.
# Theistic evolution

**Theistic evolution**, or **evolutionary creationism**, is the belief that God, or another higher power, used evolution as a tool to create the different species of living creatures on Earth. It says that evolution does not deny the existence of God.
# Nature versus nurture

The **nature versus nurture** debate is about the causes of differences between people. The phrase 'nature versus nurture' was suggested by the Victorian polymath Francis Galton. He was influenced by Darwin's *On the Origin of Species*. He investigated the influence of heredity and environment on social advancement.

Galton did not oppose nature to nurture as two alternatives. The phrase 'nature vs nurture' has been criticized for its over-simplification. Almost all writers have realised that both play a part in our make-up. Both nature and nurture play interacting roles in development, and many modern psychologists and anthropologists think the contrast is too simple.
# Ancient Greek

| Ancient Greek |
| --- |
| Ἑλληνική **Hellēnikḗ** |
| Inscription about the construction of the statue of Athena Parthenos in the Parthenon, 440/439 BC |
| Region | eastern Mediterranean |
| Era | 9th century BC to the 4th century AD |
| Language family | Indo-European
* Hellenic
	+ **Ancient Greek**
 |
| Writing system | Greek alphabet |
| Language codes |
| ISO 639-2 | `grc` |
| ISO 639-3 | `grc` (includes all pre-modern stages) |
| *Glottolog* | `anci1242` |
| Map of Ancient (Homeric) Greece |

**Ancient Greek** was an Indo-European language spoken in Ancient Greece from about 1500 BC to about 300 BC. Ancient Greek and Latin are very important languages. Although they are no longer spoken, they influenced almost all modern European languages.

Greek had many different dialects. Attic Greek was spoken in Athens, the largest city, and in the rest of the region of Attica. It was thought to be the purest form of Greek. Later, in the educated Roman world, children were taught Greek as a second language just as many people now learn English as their second language. **Koine Greek** was the common language of Greeks. It was Attic Greek mixed with several other dialects.

Homer spoke and wrote in an old dialect that was somewhat different from Attic Greek. The *Iliad* and the *Odyssey* are long poems that tell exciting stories about warfare, travel and the Greek gods. In the 5th century BC, some great plays were written by Aeschylus, Sophocles and Euripides. The Golden Age of Ancient Greece inspired literature that has been read for centuries.

## Attic Greek

**Attic Greek** was the dialect that was spoken in Athens, the largest city, and in the rest of the region of Attica. It was the dialect that was most similar to later forms of Greek since it was the standard form of the language. It is studied in Ancient-Greek courses because it was the most common dialect.

## Changes

All languages change with time, and Greek has changed a great deal over 2500 years. Modern Greek is often said to have started in 1453 AD; until then, Medieval Greek was spoken.

Unlike Latin, Ancient Greek did not split into many languages, but it is still considered to be a separate language from Modern Greek. The pronunciation has changed; for instance, the letter beta was pronounced "b" in Ancient Greek but it is pronounced "v" and is called "vita" in Modern Greek. The spelling has not changed much, which gives the appearance of less change than actually happened. Also, many different vowels and diphthongs merged into "i", the vowel sound in the English word "ski". The tonal system of Ancient Greek has disappeared, but Modern Greek has only recently changed its spelling to match that change.

Despite those changes, much of the language has remarkably survived intact through the centuries. A community near Trabzon, Turkey, speaks a dialect that is closer to Ancient Greek than to Standard Modern Greek.

Beginning of Homer's *Odyssey*
## Related pages

* Greek alphabet
* Greek language
# Taxis

A **taxis** (plural **taxes**) is an innate behavioral response by an organism to a directional stimulus. This means the organism automatically moves towards or away from the stimulus.

A taxis differs from a tropism (turning response, often plant growth towards or away from a stimulus) in that the organism has motility and shows movement towards or away from the stimulus source.

* **Phototaxis**: movement, usually towards light. Shown by many organisms, such as many flying insects.
* **Chemotaxis**: movement towards desirable chemicals, and away from unpleasant ones.

Even single-celled organisms can show taxis.
# Taxon

A hierarchy of important ranks
A **taxon** (plural **taxa**) is a **taxonomic group** or **taxonomic unit**. It is a group of organisms which a taxonomist decides belong together.

Taxa can be big or small. A fairly small taxon is the giraffes, and a very big one is the beetles.

A taxonomist can assign a scientific name and rank to a taxon; this places it at a particular level in a hierarchy. It is not strictly necessary to assign either a name or a rank to a taxon, but a name and rank make it easier to discuss. However, many taxa have to wait for years before getting a name.

## Ranks

There is no limit to the number of ranks that may exist, but the most important ranks are, in hierarchical order:

Domain
Kingdom
Phylum or Division
Class
Order
Family
Genus
Species
Subspecies
Note: "Phylum" applies formally to any biologial domain but traditionally it was always used of animals whereas "Division" was traditionally often used of plants, fungi etc.

A simple phrase to remember the order is
"Dignified Kings Play Chess On Fine Green Silk" (there are many other such phrases).

## Taxonomy

A distinction is made between taxonomy and systematics. Systematics deals with how groups relate to each other. Taxonomy deals with making groups (taxa), deciding what belongs together. Taxonomy is also known as classification.

A special part of taxonomy is nomenclature. This consists of rules on what names to use. So a taxonomist first decides what does and does not belong in a group, and then uses nomenclature to decide what name this group should have. If a group is made larger or bigger it may get a different name. On the other hand, the same name may refer to a bigger taxon (according to one particular taxonomist) or a smaller taxon (according to some other taxonomist). This means that scientific names are not guaranteed to be stable. Most names are stable, but for some taxa there is no agreement on its name, because taxonomists do not agree what does belong together and what does not belong together.

A taxonomist can decide for himself what scientific reasons he adopts for making a group (a taxon). If he is not convincing in his choice, other taxonomists will not agree with him, and they will then make other arrangements. These days biological classification is mostly supposed be done according to evolutionary (phylogenetic) relationships, so far as these are known.
# Domain (biology)

The hierarchy of scientific classification
In biological taxonomy, a **domain** (also **superregnum**, **superkingdom**, or **empire**) is a taxon in the highest rank of organisms, higher than a kingdom.

Domain (or its synonyms) is the most inclusive of these biological groupings. The arrangement of taxa reflects the fundamental evolutionary differences in the genomes. There are several modern alternative domain classifications of life. Among them are:

* The 'two-empire' system, with top-level groupings of Prokaryota (or Monera) and Eukaryota empires.
* The six-kingdom system with top-level groupings of Protista, Archaebacteria, Eubacteria, Fungi, Plantae, and Animalia.
* The **three-domain system** of Carl Woese, introduced in 1990, with top-level groupings of Archaea, Bacteria, and Eukaryota domains.

After defining Archaea as a new domain, Woese redrew the taxonomic tree. His three-domain system is based upon genetic relationships. It divides life into 23 main divisions in three domains: Bacteria, Archaea, and Eukarya. Archaea are neither bacteria nor eukaryotes. Looked at another way, they are prokaryotes that are not bacteria.

The three domains
## Related pages

* Phylogenetics
* Taxonomy
# Palynology

Different Diatom species have hard shells with many different shapes and patterns. The shells stay even after they die, and are useful in palynology.
Palynology is the study of very small natural particles. The word literally means the "study of dust". A palynologist is someone whose job is to identify what the particles are. Samples of particles can come from the air or water or soil or rocks. They could be organic and inorganic. Micropaleontology is a related area of study; it involves very small fossils.

## Methods

A palynologist uses a microscope. They may also use chemical tests to find out what a particle is made of.

The methods used to study fossils in micropaleontology and in palynology are often different. Micropaleontology often involves breaking and dissolving rocks. Palynology often involves soil or sediment.

The main work of a palynologist is to identify each particle. Many different kinds of particles might be in the same sample. They may include:

* clay
* pollen
* algae with hard shells such as Diatoms, Dinoflagellates, golden algae
* spores from plants, fungi, or bacteria
* small seeds
* pieces of larger organisms
* tiny fossils

## Uses

A core taken from the bottom of a lake shows the layers of sediment, with the oldest layers at the bottom of the core.
A graph shows how pollen at different levels in a sediment core has varied through time.
When the palynologist knows what particles are present in a sample, they may be able to say what the temperature or environmental chemistry was like where the sample came from. They may also be able to say where the sample came from.

Palynology is used in forensic science to learn where something came from, by looking at the particles in or on it.

Palynology is also very important in the study of climate history. In bodies of water such as lakes, ponds, and the ocean, sediment builds up slowly, so that the oldest sediment is at the bottom. There are ways to take a sample of the sediment that doesn't disturb the layers (either using a tube, or by freezing).

In glacial lakes, the sediment may have varves, which are two layers per year that are different colours. If there are varves, a lot of detailed information can be discovered in a core sample.