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.

Adaptation is generally due to selection of pre-existing variations and not due to new mutations or variations. This tends to support Darwin’s theory of natural selection. The basis was proved by replica plating experiment of Joshua Lederberg and Esther Lederberg.  A number of sterile agar plates having antibiotic streptomycin were prepared. Bacteria  were inoculated on the renicilling plates from the master plate by sterile velvet plate. Most bacterial colonies did not form replicas and inoculum died. Moreover a few colonies survived showing that they were resistant to streptomycin.

De Vries gave his mutation theory on organic evolution while working on Oenothera lamarckiana. Oenothera lamarckiana is an annual plant commonly called as evening primose. De Vries in his experiment observed that original plant showed some offsprings with different phenotypes. These mutations were passed from offsprings to their progeny. However, late it was observed that the variations were due to chromosomal segregations and not due to mutations.

Miller and Urey were the two scientists who recreated the conditions of primitive earth in laboratory and abiotically synthesized amino acids and bases. They synthesized glycine, aspartic acid and alanine in abundant quantities while glutamic acid is not synthesized in their experiment.

Jurassic period of meoszoic era was about 19-20 crore years ago & lasted for about 5.5-6 crore years. The climate was hot and damp. It is called the age of dinosaurs. Ist primitive bird Archaeopteryx evolved from reptiles. Ist angiosperm appeared as a dicotyledon but gymnosperms were dominant.

Paleontolog y is the study of fossils. Ontogeny is the process of development of organism in the embryo stage and phylogeny is known as the history of an organism through ages during evolution.

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 finches of Galapagos islands provides an evidence in favour of biogeographical evolution 

Only birds and mammals are homeothermous.

Leech possesses a ventral central nervous system. Scorpion has a dorsal heart. Pharyngeal gill slits and post- anal tail are characteristic features of chordates. Chameleon is a chordate, so it possesses pharyngeal gill- slits in embryonic stage. Octopus is a non-chordate.

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.

The characteristic feature which indicates that birds have reptilian ancestry is the presence of scales on their hind limbs
The digestive system of reptiles is similar to that of all higher vertebrates whereas the bird's digestive is the crop, the proventriculus, and the gizzard.
Birds lay hard-shelled calcareous eggs, but most reptiles lay soft-shelled ones.
Most reptiles have 3 chambered heart whereas birds have a four chambered heart.

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. 

A protobiont is an aggregate of abiotically produced organic molecules surrounded by a membrane or a membrane-like structure. Protobionts exhibit some of the properties associated with life, including simple reproduction, metabolism and excitability, as well as the maintenance of an internal chemical environment different from that of their surroundings. It has been suggested that they are a key step in the origin of life on earth. Experiments by Sidney W. Fox and Aleksandr Oparin have demonstrated that they may be formed spontaneously, in conditions similar to the environment thought to exist on an early Earth.

Protobionts are excitable, metabolically active, inaccurately reproducing protein clusters. These clusters form when their protein parts are mixed with cold water: they self-assemble into microspheres. Protobionts also can release voltage like a neuron because some protobionts store energy through a similar method of membrane potential as organelles. If coated with a semipermeable membrane, a protobiont will swell and contract osmotically when in solutions of differing salt concentrations. The protobiont shares its weak catabolic capabilities with the liposome. They were partially isolated from environment, but, they could not separate combinations of molecules from the surroundings. Other statements are correct and only option B is incorrect. Thus, the answer is option B