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Apr

2012

Species Concepts | EvoEcoLab, Scientific American Blog Network

blogs.scientificamerican.com/...species-concepts

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species concepts evolution biology

Jan

2008

Species (Stanford Encyclopedia of Philosophy)

The nature of species is controversial in biology and philosophy. Biologists disagree on the definition of the term 'species.' Philosophers disagree over the ontological status of species. A proper understanding of species is important for a number of reasons. Species are the fundamental taxonomic units of biological classification. Environmental laws are framed in terms of species. Even our conception of human nature is affected by our understanding of species. In this entry, three philosophical issues concerning species are discussed. The first is the ontological status of species. The second is whether biologists should be species pluralists or species monists. The third is whether the theoretical term 'species' refers to a real category in nature.

plato.stanford.edu/...species

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evolution species philosophy

This entry discusses three philosophical issues concerning species. The first issue is their ontological status. Are species natural kinds, individuals, or sets? The second issue concerns species pluralism. Monists argue that biologists should attempt to find the correct definition of ‘species.’ Pluralists disagree. They argue that there is no single correct definition of ‘species’ but a plurality of equally correct definitions. The third issue concerns the reality of species. Does the term ‘species’ refer to a real category in nature? Or, as some philosophers and biologists argue, is the term ‘species’ a theoretically empty designation?
Species are also units of evolution
23 more annotation(s)...
- fundamental units of biological classification
- all and only the members of a kind have a common essence
- the essence of a kind is responsible for the traits typically associated with the members of that kind
- knowing a kind's essence helps us explain and predict those properties typically associated with a kind
- The universality of a biological trait in a species is fragile.
- species have vague boundaries and that such vagueness is incompatible with the existence of species specific essences
- Contemporary biology can explain variation within a species without positing a species' essence. So according to Sober, species essentialism has become theoretically superfluous.
- Individuals, unlike classes, consist of parts that are spatiotemporally restricted.
- A number of processes can cause a trait to become prominent in a species. Hull highlights selection. Selection causes a trait to become prominent in a species only if that trait is passed down from one generation to the next. If a trait is not heritable, the frequency of that trait will not increase cumulatively. Hereditary relations, genetic or otherwise, require the generations of a species to be causally connected. Reproduction requires the generations of a species to be causally and hence spatiotemporally connected. So, if species are to evolve in non trivial ways by natural selection, they must be spatiotemporally continuous entities. Given that species are units of evolution, species are individuals and not classes.
- When Hull asserts that species are units of evolution, he does not simply mean that the gene frequencies of a species change from one generation to the next. He has a more significant form of evolution in mind, namely a trait going from being rare to being prominent in a species.
- the relationship between an organism and its species is not a member/class relation but a part/whole relation
- From an evolutionary perspective, there is no biological essence to being a human. There is no essential feature that all and only humans must have to be part of Homo sapiens. Humans are not essentially rational beings or social animals or ethical agents.
- Proximate explanations cite the more immediate cause of a trait, for example, the genes or developmental pathways that cause the occurrence of a trait in an organism. Ultimate explanations cite the evolutionary cause of a trait in a species, for example, the selection forces that caused the evolution of thumbs in pandas and their ancestors.
- species are natural kinds on a proper conception of natural kinds. These authors adopt Boyd's Homeostatic Property Cluster (HPC) theory of natural kinds. HPC theory assumes that natural kinds are groups of entities that share stable similarities.
- An HPC kind consists of entities that share similarities induced by that kind's homeostatic mechanisms. According to Boyd, species are HPC kinds and thus natural kinds because "species are defined . . . by . . . shared properties and by the mechanisms (including both "external" mechanisms and genetic transmission) which sustain their homeostasis" (1999b, 81)
- In addition to Boyd's ‘homeostatic’ mechanisms we need to recognize ‘heterostatic’ mechanisms that maintain species variation
- The Biological Species Concept defines a species as a group of organisms that can successfully interbreed and produce fertile offspring. The Phylogenetic Species Concept (which itself has multiple versions) defines a species as a group of organisms bound by a unique ancestry. The Ecological Species Concept defines a species as a group of organisms that share a distinct ecological niche.
- Perhaps there is a process or a pattern that occurs in species but not in other types of taxa.
- process of interbreeding
- stabilizing selection
- genetic and developmental homeostasis.
- species are bound by different types of processes
- ontological structure,

Jan

2012

Origin of Species ch 4 Natural Selection

www.literature.org/...chapter-04.html

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evolution origin species Darwin natural-selection

infinitely complex and close-fitting are the mutual relations of all organic beings to each other and to their physical conditions of life.
This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection.
43 more annotation(s)...
- having incomparably longer time at her disposal
- external and visible characters
- Can we wonder, then, that nature's productions should be far 'truer' in character than man's productions; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship?
- We see nothing of these slow changes in progress
- In social animals it will adapt the structure of each individual for the benefit of the community;
- This depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.
- Natural selection can act only by the preservation and accumulation of infinitesimally small inherited modifications, each profitable to the preserved being
- with animals and plants a cross between different varieties, or between individuals of the same variety but of another strain, gives vigour and fertility to the offspring; and on the other hand, that close interbreeding diminishes vigour and fertility
- no organic being self-fertilises itself for an eternity of generations; but that a cross with another individual is occasionally perhaps at very long intervals -- indispensable.
- Intercrossing plays a very important part in nature in keeping the individuals of the same species, or of the same variety, true and uniform in character.
- In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be in a great degree uniform; so that natural selection will tend to modify all the individuals of a varying species throughout the area in the same manner in relation to the same conditions.
- isolation, by checking immigration and consequently competition, will give time for any new variety to be slowly improved;
- largeness of area is of more importance
- natural selection will always act with extreme slowness
- depends on there being places in the polity of nature, which can be better occupied by some of the inhabitants of the country undergoing modification of some kind
- this very slow, intermittent action of natural selection accords perfectly well with what geology tells us of the rate and manner at which the inhabitants of this world have changed.
- Natural selection acts solely through the preservation of variations in some way advantageous, which consequently endure.
- so will the less favoured forms decrease and become rare.
- rare species will be less quickly modified or improved within any given period, and they will consequently be beaten in the race for life by the modified descendants of the commoner species.
- each new variety or species, during the progress of its formation, will generally press hardest on its nearest kindred, and tend to exterminate them.
- varieties, even strongly-marked ones, though having somewhat of the character of species as is shown by the hopeless doubts in many cases how to rank them yet certainly differ from each other far less than do good and distinct species
- varieties are species in the process of formation, or are, as I have called them, incipient species.
- How, then, does the lesser difference between varieties become augmented into the greater difference between species?
- Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large an amount of difference as that between varieties of the same species and species of the same genus.
- the principle of divergence, causing differences, at first barely appreciable, steadily to increase, and the breeds to diverge in character both from each other and from their common parent.
- better enabled to seize on many and widely diversified places in the polity of nature, and so be enabled to increase in numbers.
- only by its varying descendants seizing on places at present occupied by other animals
- organic beings vary at all in the several parts of their organisation
- a severe struggle for life
- The more diversified in habits and structure the descendants of our carnivorous animal became, the more places they would be enabled to occupy
- if variations useful to any organic being do occur
- strong principle of inheritance
- sexual selection
- Sexual selection will also give characters useful to the males alone, in their struggles with other males.
- judged of by the general tenour and balance of evidence given in the following chapters
- Natural selection, also, leads to divergence of character
- more living beings can be supported on the same area the more they diverge in structure, habits, and constitution
- modification of the descendants
- In an extremely small area, especially if freely open to immigration, and where the contest between individual and individual must be severe, we always find great diversity in its inhabitants.
- Natural selection, as has just been remarked, leads to divergence of character and to much extinction of the less improved and intermediate forms of life.
- On the view that each species has been independently created, I can see no explanation of this great fact in the classification of all organic beings; but, to the best of my judgment, it is explained through inheritance and the complex action of natural selection, entailing extinction and divergence of character, as we have seen illustrated in the diagram.
- represented by a great tree
- in the general economy of any land, the more widely and perfectly the animals and plants are diversified for different habits of life, so will a greater number of individuals be capable of there supporting themselves.

origin of species ch 3 struggle for existence

www.literature.org/...chapter-03.html

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evolution origin species Darwin

individual variability
how is it that varieties, which I have called incipient species, become ultimately converted into good and distinct species, which in most cases obviously differ from each other far more than do the varieties of the same species?
27 more annotation(s)...
- Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring
- Natural Selection
- all organic beings are exposed to severe competition
- dependence of one being on another
- success in leaving progeny
- there must in every case be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with the physical conditions of life.
- naturally increases at so high a rate
- The condor lays a couple of eggs and the ostrich a score
- the real importance of a large number of eggs or seeds is to make up for much destruction at some period of life;
- The amount of food for each species of course gives the extreme limit to which each can increase
- serving as prey to other animals
- Climate plays an important part in determining the average numbers of a species
- epidemics
- in many cases, a large stock of individuals of the same species, relatively to the numbers of its enemies, is absolutely necessary for its preservation
- cattle absolutely determine the existence of the Scotch fir
- yet in the long-run the forces are so nicely balanced, that the face of nature remains uniform for long periods of time, though assuredly the merest trifle would often give the victory to one organic being over another
- so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!
- When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this!
- Throw up a handful of feathers, and all must fall to the ground according to definite laws; but how simple is this problem compared to the action and reaction of the innumerable plants and animals which have determined, in the course of centuries, the proportional numbers and kinds of trees now growing on the old Indian ruins!
- But the struggle almost invariably will be most severe between the individuals of the same species, for they frequent the same districts, require the same food, and are exposed to the same dangers
- As species of the same genus have usually, though by no means invariably, some similarity in habits and constitution, and always in structure, the struggle will generally be more severe between species of the same genus, when they come into competition with each other, than between species of distinct genera.
- the structure of every organic being is related, in the most essential yet often hidden manner, to that of all other organic beings, with which it comes into competition for food or residence, or from which it has to escape, or on which it preys.
- I suspect that the chief use of the nutriment in the seed is to favour the growth of the young seedling, whilst struggling with other plants growing vigorously all around.
- our ignorance on the mutual relations of all organic beings
- each organic being is striving to increase at a geometrical ratio
- struggle for life, and to suffer great destruction
- the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.

Dec

2011

Has 'one species' idea been put to bed?

www.bbc.co.uk/...science-environment-16339313

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species

Given this array of human diversity in the Late Pleistocene, we might well be forgiven for thinking that Ernst Mayr's contention that "in spite of much geographical variation, never more than one species of man existed on Earth at any one time" had finally been put to bed.
But now we know that Neanderthals and our ancestors exchanged genes so, using the biological species definition, they must have been the same species.

Nov

2009

'Hobbits' are a new human species, according to statistical analysis of fossils

Researchers from Stony Brook University Medical Center in New York have confirmed that Homo floresiensis is a genuine ancient human species and not a descendant of healthy humans dwarfed by disease. Using statistical analysis on skeletal remains of a well-preserved female specimen, researchers determined the "hobbit" to be a distinct species and not a genetically flawed version of modern humans.

www.sciencedaily.com/...091119101034.htm

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human species hobbits evolution

Sep

2009

A list of 26 Species "Concepts" : Evolving Thoughts

Here is a working list of species concepts presently in play. I quote "Concepts" above because, for philosophical reasons, I think there is only one concept - "species", and all the rest are conceptions, or definitions, of that concept. I have christened this the Synapormorphic Concept of Species in (Wilkins 2003).

scienceblogs.com/...ist_of_26_species_concepts.php

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species evolution

in list: Evolution

Jul

2009

Study Catches Two Bird Populations As They Split Into Separate Species

www.sciencedaily.com/...090714104000.htm

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populations evolution species

Jul

2009

Speciation

The biological species concept defines a species as members of populations that actually or potentially interbreed in nature, not according to similarity of appearance. Although appearance is helpful in identifying species, it does not define species.

evolution.berkeley.edu/...VA1BioSpeciesConcept.shtml

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species speciation evolution

Populations and Species

Populations as defined here do not need to have distinct boundaries. Individuals can and do move between populations. Individuals almost never have uniform distribution within populations: there are marginal stragglers, making the boundaries fuzzy as populations intermingle. The population is a unit within which genetic change can take place, unlike an individual: the population has a gene pool.

A species is an array of Mendelian populations, and between each species there is supposed to be genetic reproductive isolation. A species is supposed to have absolute boundaries: if they are not geographical, they are behavioral or genetic.

mygeologypage.ucdavis.edu/...populations.html

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species ring-species populations evolution

Ring Species: Unusual Demonstrations of Speciation

Ring species provide a unique glimpse into how some species came to be.

* A ring of populations encircles an area of unsuitable habitat.
* At one location in the ring, two distinct forms coexist without interbreeding.
* Around the rest of the ring, the traits of one species change gradually through intermediate populations into the second species’ traits.

www.actionbioscience.org/...irwin.html

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species ring-species speciation evolution

Jul

2009

Circular overlaps: Rare demonstrations of speciation

THE SPLITTING OF a single species into two or more is a difficult process to observe, because it can take a great deal of time. Evolutionary biologists have recognized that a solution to this problem is to use geographical variation to infer how change in time might occur. Especially interesting in that regard is the phenomenon of "circular overlaps" (Mayr 1942), or "ring species" (Cain 1954), in which two sympatric and clearly distinct forms are connected by a chain of populations through which the characteristics of one form gradually change into those of the other. The possibility that ring species might exist was first suggested about a century ago by Stejneger (as quoted by Jordan 1905), and since then a number of possible examples have generated intense interest among evolutionary biologists.

findarticles.com/...ai_n9133429

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speciation species evolution

May

2009

The Origin of Artificial Species: Creating Artificial Personalities

Does your robot seem to be acting a bit neurotic? Maybe it's just their personality. Recently, a team of researchers has designed computer-coded genomes for artificial creatures in which a specific personality is encoded. The ability to give artificial life forms their own individual personalities could not only improve the natural interactions between humans and artificial creatures, but also initiate the study of “The Origin of Artificial Species,” the researchers suggest.

www.physorg.com/news161517506.html

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species personalities genetics personality grue cogsci

The Origin of Artificial Species: Creating Artificial Personalities

www.facebook.com/...share.php

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species personalities genetics personality grue cogsci

Jun

2008

Engineering Life: The Dog that Didn't Bark in the Night

"Imagine that mad scientists defied nature and violated the barriers between species. They injected human DNA into non-human creatures, altering their genomes into chimeras--unnatural fusions of man and beast. The goal of the scientists was to enslave these creatures, to exploit their cellular machinery for human gain. The creatures began to produce human proteins, so many of them that they become sick, in some cases even dying. The scientists harvest the proteins, and then, breaching the sacred barrier between species yet again, people injected the unnatural molecules into their own bodies." (Carl Zimmer)

scienceblogs.com/...ineering_life_the_dog_that.php

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genetics biology speicies grue species

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