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Phoresy: A relationship between host and commensal involving only passive attachment of the commensal to the surface of the host (e.g., barnacle on whale). The supporting partner must be continuously moving.

Parasitoid: An organism that is parasitic only during its larval stage.

An animal that lives in or on another animal (the host), which it consumes and eventually kills. Hence, parasitoid may be regarded as intermediate between a true parasite and a predator.

Many wasps and other hymenopterans and also some flies, are parasitoids for part of their life cycle, laying their eggs commonly in or on the larvae of other insects. The hatched parasitoids then use the tissue of their host for food during development into free-living adults. At maturation they emerge and usually do cause death of their host (unlike most of the parasites).

Parasite:

An organism that depends on its host for some essential metabolites and must do some harm to its host, whatever small it may be.

Hyperparasitism: A situation in which a parasite occurs on or in another parasite , e.g., Rat intestine’s parasite Giardia muri is parasitized by Entamoeba pantista.

Predator: Living by preying upon other animals. The predator consumes all or part of its prey, generally killing the latter.

Parasitism is generally a heterospecific association in which one species (Parasite) depends on the other (host) for food and shelter and does harm to the other. Intraspecific parsitism is found in Schistosoma.

A critically endangered crow has re-emerged on a remote, mountainous Indonesian island thanks, discovered by a team of scientists of the Michigan State University. Many believed that Banggai Crow as extinct for a long time until  Indonesian biologists finally secured two new specimens on Peleng Island in 2007.

Rasmussen, A southern asian ornithologist studied the two century-old specimens known as Corvus unicolor in New York’s American Museum of Natural History. She compared the specimens with those collected from Indonesia to lay to rest speculation that they were merely a subspecies of a different crow. The more common Slender-billed Crow, or Corvus enca, also is found in the Banggai Islands, and likewise is all black.

“The morphometric analysis I did shows that all four unicolor specimens are very similar to each other, and distinctly different from enca specimens. We also showed that the two taxa differ in eye color — an important feature in Corvus,” Rasmussen said. “Not only did this confirm the identity of the new specimens but also the specific distinctness of Corvus unicolor, which has long been in doubt.”

Indonesian ornithologists are turning their efforts toward protecting the rare species, which is hunted by local residents. That includes making recommendations for protection of its forest habitat through sustainable agriculture methods and, perhaps, eco-tourism, to address the residents’ livelihood needs.

Source : Michigan State University

Lamarckism (Theory of Inheritance of Acquired Characters)

This theory was proposed by French biologist, Jean Baptiste de Lamark in 1809. It was published in ‘Philosphie Zoologique’ in the year 1809. It is popularly known as “The Inheritance of Acquired Characters in Organisms’.

Definition: Lamarckism or theory of inheritance of acquired characters can be defined as “The changes in structure or function of any organ acquired during the life-time of an individual in response to changes in the surrounding environment are inherited by its offsprings and keep on adding up over a period of time”. These changes lead to the origin of new species.

Postulates of Lamarckism or Inheritance of Acquired Characters

Lamarckism is based on three factors or postulates:

1. New Needs: Changes in the environment create new needs in living organisms so that these are better adapted or more suited to the changed environment. The organisms have to put in special efforts for the fulfillment of the new needs. These efforts lead to a change in the habits or behavior. The new need results in the formulation of new organ or a part in the body. If the need continues that organ or part continues to grow.

2. Acquisition of New Characters: New Characters are acquired by the living beings in two ways:

(a) By use and disuse: The new habits involve greater use of certain organs to meet the new need, and disuse or lesser use of certain other organs in changed conditions. The continuous use of an organ or organs keeps them functional and makes them stronger, larger and more efficient. Continuous disuse of an organ or organs leads to gradual reduction in their size and to their final disappearance.

Vestigial organs are examples of such non-functional organs in the modern forms. These were in the functional form in the ancestors. Thus by differential use and disuse of various body parts, an organism would change to some extent and acquire some characters and modify some other.

The changes acquired or accumulated in an organism during its life time by the use and disuse of organs or by the influence of the environment are called acquired characters.

(b) Effect of environment: Changes in temperature, light, medium, food, etc., influence the functioning and behavior of living beings and introduce changes in their structure. Thus organisms acquire certain new characters due to direct or indirect influence of environment.

3. Inheritance of Acquired Characters: The characters acquired by an organism during its life time are inherited to the next generation. In every generation some new characters were acquired or the older ones keep on increasing or improving. As a result, after a number of generations, the species gets modified into a new one.

The theory of organic evolution appears most plausible explanation for the occurrence of varied forms of plants and animals on this earth. But an absolute proof in this connection is lacking. The circumstantial proof is the only type of evidence available. The convincing evidences for the occurrence of descent with modification come from:

1. Morphology and comparative anatomy.
2. Embryology
3. Palaeontology
4. Geographical distribution
5. Taxonomy
6. Connecting links
7. Cytology
8. Biochemistry and physiology
9. Genetics

The similarities among living organisms indicate that all of them have evolved from some single common ancestor (This is called monophyletic origin). Through the process of gradual modifications, adaptations and natural selection, over a million and a half different species have evolved from a common ancestral form. This process is called evolution or organic evolution. This is described as ‘descent with modification’. Its salient features are:

1. Unicellular organisms were the first to appear.

2. Multicellular organisms evolved from them.

3. Early forms were simple in structure and evolved gradually into more and more complex forms. For example, present day seed plants have evolved from simple seedless plants. Vertebrates have evolved from invertebrates.