This is in fact the basis of the ID-only hypothesis - the same basis used by SETI scientists in their search for ID in the form of ET-produced "artifacts".
Evolutionary biologist Ernst Mayr explains the havoc wreaked within the standard evolutionary phylogeny when it was discovered that the same gene controlled eye-development in many organisms with very different types of eyes:
Major groups of protists include protozoan – for example, amoebas, algae and slime molds. Major evolutionary acquisition of protists is through endosymbiosis which results in eukaryotic organelles, and colony behavior which results in multicellular organisms. Endosymbiotic hypothesis is an attempt to account for the major evolutionary leap from prokaryotes to protists, the first eukaryotes. The hypothesis proposes a larger prokaryote ingested a smaller prokaryote such as a nutshell, organelles such as mitochondria and chloroplasts therefore arose. Much evidence comparing similarities of mitochondria to prokaryotes supports this idea.
We focus in on the group of lineages that share the synapomorphic form of this character, an amniotic egg (A, below), and hypothesize that they form a clade (B):
We go through the whole table like this, grouping clades according to synapomorphies (C):
After Darwin, the next major leap in the study of eusociality came in mid twentieth century with J.B.S. Haldane. Haldane helped refine Darwin's hypothesis by adding that the idea of biological altruism only holds if the society in which it is present is closely related. According to biologist Maynard Smith, while in a pub together Haldane commented that "he would jump into a river and risk his life to save two brothers, but not one, and that he would jump in to save eight cousins, but not seven" (). The metaphor is exaggerated, but it makes a point about the genetics of altruistic behavior. In a brother there is a 50% chance of his same altruisticistic gene being present, while in a cousin only a 12.5% chance. Based on this, Haldane assumed that in order for an altruistic gene to dominate in a population, the individuals must be closely related. The possibility of death by jumping into the river may seem drastically different from a drone mole-rat who is sterile, but evolutionarily the two are similar: either way the host's genes will not be passed down. However, by ensuring that a close relative will survive to reproduce, the individual has a better chance of ensuring that his genes will go on to future generations. (image )
This hypothesis is supported by data on colony size, hostility of environment, food scarcity and caloric value per food item, and genetic relatedness between individuals. Both the naked mole-rat and the Damaraland mole-rat live in large groups, with a maximum size of 295 and 41 rodents, respectively. In both environments rain is very scarce, under 400 mm per year. Food items (geophytes) are scarce in both environments, with a mean digestible energy of 204.5 and 179.1 kJ per meters squared). The inter-colony relatedness index is upwards of 0.8 in the naked mole-rat (animals share 80% of their genes), with a reproductive skew of over .99 (more than 99% of animals never breed). The inter-colony relatedness is lower in the Damaraland mole-rat (statistics vary), but the reproductive skew is about .92. ().
4. See the excellent online tutorial by the UCMP: "" It makes an excellent introduction to classification, phylogenetic trees, and cladistics. This could be given as a homework assignment (online).
The biggest problem with the food-aridity hypothesis is that there are lots of animals in the world that live in hostile environments that aren't eusocial. Furthermore, even within the Bathygeridae, there are a lot of species that are solitary animals. Recently, a revision of this hypothesis has been proposed that takes these facts into account. ()
Try a recent version of this lesson developed for use in middle school Life Science classes, but probably just as useful in high school Biology. It was developed by ENSI-trained teacher Karin Westerling, and is somewhat easier to use. Besides the 4 page student handout, there are 9 pages of data tables (to distribute 1-2 per team). These are available for downloading on the . You can obtain the desired responses to the questions by emailing your request to the using your school email address.
Animals are evolved from ancestral protists. Following the evolutionary history come Eumetazoa, Bilateria, Coelomates, Deuterosomes, Chordates, and Vertebrates, all of which have a major body plan difference. One major cause of body plan change is paedogenesis, which is the act of reproduction by an organism that has not achieved physical maturity. The hypothesis is that paedogenesis of early larval urochordates leads to maintenance of motile organism with all chordate features which caused major change in body plan. Selective pressures acting on paedogenic larval urochordates lead to modifications of chordate traits. Other events during evolution: 1) Extinction events: There have been several in the triassic period alone, not the least of which being the dinosaur extinction. Some estimate that 90% of all animal species were lost during this time period with an unknown reason. 2) Super continent Pangaea forms and breaks-up ~300 – 180 million years ago, this lead to geological isolation of gene pool.
And, quite surprisingly for many scientists, many of the phylogenies based on these various genetic sequences are very inconsistent with each other and with standard Darwinian ideas based on morphologic classification models.
The idea of proto-life
If we assume life did not result from a seeding event from an asteroid or other interstellar body, then life had to have developed from inorganic materials. However, spontaneous animation to form life from non-life does not happen today. This could be due to the atmosphere environment is very different. Urey & Miller designed an experimental model of early earth atmosphere, in which organic molecules can be synthesized from inorganic molecules. With pre-biotic conditions set, Proto-life may occur according to many hypotheses: Organic compounds form polymers of repeating units, lipids & others can and do organize into spheres based on inherent properties. The lipid spheres can encapsulate organic molecules; the encapsulated organic molecules such as RNA can then self-replicate, are autocatalytic, and can act as rudimentary templates for protein synthesis. Competition for scarce resources such as RNA monomers leads to natural selection of “fittest” RNA molecule, resulting in reproduction of that RNA molecule.
Growing evidence suggests that phylogenies of animal phyla constructed by the analysis of 18S rRNA sequences may not be as accurate as originally thought.