31 Years NEET Previous Year Questions: Evolution - 1 - NEET MCQ

• If the same change occurs by chance, it is called genetic drift.
• Sometimes the change in allele frequency is so different in the new sample of population that they become a different species.
• The original drifted population becomes founders and the effect is called founder effect.

Evolution by Anthropogenenic action is because of the interference by human beings. Anthropogenenic shows herbicide resistant weeds, drug resistant eukaryotes and mancreated breeds of domesticated animals like dogs and darwin’s Finches of Galapagos islands is an example of natural selection.

Stabilising selection is a balancing type of natural selection that favours average-sized individuals and eliminates extreme individuals.

• Homologous organs are those organs that have the same fundamental structure but are different in functions. 

• Wings of birds and forelimbs of horse show homology because skeletal parts of their forelimbs are similar in structure and arrangement but have different functions.

• The random changes in gene frequencies in a population occurring by chance alone rather than by natural selection are called genetic drift or Sewall Wright effect. 

• The effects of genetic drift are most marked in a very small isolated population, although it occurs in all populations.

Spallanzani’s experiment : He boiled the meat and vegetables for more than an hour to prepare broth and placed them in open and sealed flasks. The maggots of housefly developed in the open flasks but did not appear in sealed flasks. This disapproved the theory of spontaneous creation. (Th. of abiogenesis).

When DDT was sprayed to kill mosquitoes, there were only few mosquitoes which were already resistant to DDT, and hence survived. Most of the mosquitoes which were sensitive to DDT died.
Due to differential reproduction the resistant mosquitoes got more chances of reproduction and multiplied. After few generations most of the mosquitoes were resistant. The sensitive were very few. This supports Darwin’s theory of natural selection and survival of the fittest.

Homologous organs represent the divergent evolution. These are the organs belonging to different organisms of different species may be for dissimilar function but they all have the same basic structure. On the other hand vestigial organs show that how a species evolved from its ancestors through the ages according to the use and disuse of organs. These are the organs which were sometime functional in humans (or may be any other organisms) but during the course of evolution their utility gradually decline and now they are present as nonfunctional and vestigial organs.

Archaeopteryx is a fossile (dead) found from the mesozoic rocks. It is a connecting link between reptiles and birds.

The analogous organs show convergent evolution due to similar adaptions which do not support organic evolution.

Homo habilis had a cranial capacity in the range of 680 - 720 c.c & that of . Homo erectus erectus 775 -  990 c.c., Homo erectus pekinesis 915-1200 c.c. Homo nenderthalensis 1300-1600 c.c.

option  ( c ) ontogeny repeats phylogeny  is correct answer. 

Explanation:- 

Recapitulation theory or Biogenetic law states that oncology (development of embryo) is recapitulation of phylogeny (ancestral  sequence) . 
So, the correct option is " Ontogeny repeats phylogeny"

The concept of chemical evolution is based on possible origin of life by combination of chemicals under suitable environmental conditions. The distribution of elements in the cosmos is the result of many processes in the history of the Universe. It provides us with a powerful tool to study the Big Bang, the density of baryonic matter, nucleosynthesis and the formation and evolution of stars and galaxies.

The analogous organs show convergent evolution due to similar adaptation. They do not support organic evolution. Whale, seal and shark shows convergent evolution due to similar habitats.

Industrial melanism is a term used to describe the evolutionary process in which darker individuals come to predominate over lighter individuals since the industrial revolution as a result of natural selection. In 1848 a black form of the moth was recorded in Manchester and by 1895, 98% of the peppered moth population in Manchester was black. This black "melanic" form arose by a recurring random mutation, but its phenotypic appearance had a strong selective advantage in industrial areas.

Adaptive radiation refers to evolution of different species from a common ancestor. The mammals are adapted for different mode of life i.e. they show adaptive radiation. They can be aerial (bat), aquatic (whale and dolphins), burrowing or fossorial (rat), cursorial ( horse), scantorial (squarrel) or arboreal (monkey). The adaptive radiation, the term by osborn, is also known as Divergent evolution.

Speciation takes place via reproductive isolation which is the most important consequence of geographical isolation.

Darwin's Finches are an excellent example of adaptive radiation. Adaptive radiation is  the occurrence of the diversification of a single or small groups of species into a large number or descendents that occupy various ecological niches. This is an evolutionary  process driven by natural selection. 

Thorn of Bougainvillea and tendril of Cucurbita are example of homologous chromosomes. 

Nephridia of earthworm and malphigian tubules of cockroch belongs to excretory organs. Earthworm has a well developed excretory system which is composed of large number of minute, coiled and glandular segmentally arranged excretory tubules called the nephridia. Malphigian tubules of cockroach are extremely fine yellowish unbranched thread like structure present at the function of midgut and hindgut.