Bio Zoology [ 2 Marks Questions ]

Wisdom teeth, Mammae in male, Body hair and Coccyx.

Analogous structures are not anatomically similar though they perform same function.

The term evolution describes heritable changes in one or more characteristics of a population of species from one generation to the other.

Homo sapiens or modem humans arose in Africa some 25,000 years ago and moved to other continents and developed into distinct races. They had a brain capacity of 1300 – 1600 cc. “They started cultivating crops and domesticating animals.

Natural selection, Genetic drift, Mutation and Geneflow

Gene mutation refers to the changes in the structure of the gene. It is also called gene/point mutation. It alters the phenotype of an organism and produces variations in their offsprings.

Sewell Wright, Dobzhansky, Huxley and Simpson.

Gene mutation, Chromosomal mutation, Genetic recombination, Natural selection and Reproductive isolation.

Mutation theory was put forth by Hugo de Vries. Based on the experiments in Oenothera Lamarckian (The evening primrose plant).

Gregor Mendel, August Weismann, Russel Wallace and Heinrich.

Overproduction, the struggle for existence, Universal occurence of variation, Survival of fittest and Natural selection.

The theory of acquired characters was proposed by Jean-Baptise de Lamarck and it was disproved by August Weismann.

Cope, Osborn, Packard and Spencer.

Ernst Von Haeckel proposed the theory of recapitulation, which states that life history of an individual briefly repeats the evolutionary history of the race.

Sudden appearance of vestigial organs in highly evolved organisms is called atavistic organs. For example, the presence of tail in human baby is an atavistic organ.

Peripatus is a worm that shown the characters of both Annelidia and Arthropoda. Hence it is a connecting link between Annelida and Arthropoda.

Archaeopteryx – connecting link between Reptiles and Aves.
Peripatus – Connecting link between Annelida and Arthropoda.

The organisms which possess the characters of two different groups (transitional stage) are called connecting links. Example Peripatus (connecting link between Annelida and Arthropoda) Archaeopteryx (connecting link between Reptiles and Aves).

Human appendix is the remnant of caecum which is functional in the digestive tract of herbivorous animals like rabbit. Cellulose digestion takes place in the caecum of these animals. Due to change in the diet containing less cellulose, caecum in human became functionless and is reduced to a vermiform appendix, which is vestigial.

Structures that are of no use to the possessor, and are not necessary for their existence are called vestigial organs. Vestigial organs may be considered as remnants of structures which were well developed and functional in the ancestors, but disappeared in course of evolution due to their non-utilization.
E.g: Human appendix.

Homologous structures brings about divergent evolution. Analogous structures brings about convergent evolution.

The thorn of Bougainvillea and the tendrils of Curcurbita and Pisum sativum represent homology. The thorn in former is used as a defence mechanism from grazing animals and the tendrils of latter is used as a support for climbing.

Flippers of whale, wings of bat, wings of bird and forelimb of horse.

Organisms having different structural patterns but similar function are termed as analogous structures. For example, the wings of birds and insects are different structurally but perform the same function of flight that brings about convergent evolution.

When animals die the original portion of their body may be replaced molecule for a molecule by minerals and the original substance being lost through disintegration. This method of fossilization is called petrifaction. The principal minerals involved in this type of fossilization are iron pyrites, silica, calcium carbonate and bicarbonates of calcium and magnesium.

Iron pyrites, silica, calcium carbonate and bicarbonates of calcium and magnesium.

Fossilization is the process by which plant and animal remains are preserved in sedimentary rocks. It is of three major types,

1. Actual remains
2. Petrifaction
3. Natural moulds and casts.

Both the wings of cockroach and bird are different in structure but similar in their function. Thus, they are analogous structure that brings about convergent evolution.

Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes

According to the theory of spontaneous generation or Abiogenesis, living organisms originated from non-living materials and occurred through stepwise chemical and molecular evolution over millions of years. Thomas Huxley coined the term abiogeneis.