BIOLOGY 3 Marks Question

1. Neanderthal man lived in near east and Central Asia, between 1,00,000-40,000 years before.
2. His brain capacity was 1400cc.
3. He used hides to protect the body. He buried the dead. His brain size was more (1400cc) than that of Homo erectus which was 900cc.

The organs, which have similar functions but are different in their structural details and origin are called analogous organs. The analogous structures are the result of convergent evolution. Fins of fishes and flippers of whales are analogous organs.

1. The rate of appearance of new forms is linked to the lifespan of the species.
2. Microbes have the ability to divide and multiply to produce millions of individuals within hours.
3. A colony of bacteria (say A) growing on a given medium, has built-in variation in terms of ability to utilise a food component.
4. A change in the composition of the medium will allow only those individuals who can survive in the changed condition.
5. In due course of time, the variant population (say B) would outgrow the population A and appear as a new species; this would happen within a few days.
6. This is also true for microbes to develop antibioticresistant varieties.
7. Use of pesticides like DDT against mosquitoes has resulted in mosquito populations with DDT resistance within a few years.
8. For a change to occur in a fish or fowl would take million years, as their lifespans are in years.

1. When disruptive natural selection operates.
2. Mutation, gene flow genetic drift, recombination.
3. Charles Darwin.

1. Homology.
2. Analogy.
3. Analogy.
4. Analogy.
5. Analogy.
6. Analogy.

1. Psilophyton.
2. Zosterophyllum.
3. Progymnosperm.

Molecular homology is the similarity among organisms at the molecular level. The amino acid sequence for the protein cytochromic-C is the same in humans and chimpanzee. Molecular homology shows phyllogenetic relationships.

1. Invertebrates-500 mya
2. Jawless fish-350 mya
3. Sea weeds-320 mya

1. Anthropogenic actions, i.e. human activities have been found to enhance evolution.

Example:

1. Use of DDT has resulted in evolution of DDT-resistant mosquitoes.
2. Evolution of antibiotic or drug-resistant microbes.

2. When DDT was used for the first time, many mosquitoes died, but a few survived.
3. These few mosquitoes showed resistance to DDT and reproduced in the presence of DDT.
4. Most of the offspring were also resistant to DDT.
5. Hence, the mosquito populations of today consist mainly of DDT-resistant mosquitoes and hence, DDT is not effective.
6. In the absence of DDT, these DDT-resistant mosquitoes had no advantage over those mosquitoes, which were sensitive to DDT.
7. This is an example of evolution due to anthropogenic activities, i.e., anthropogenic evolution.

The origin of life on the earth took place million of years ago and the study of history of life forms on earth is called evolutionary biology. The history of life actually comprises of two events, i.e. firstly origin of life and secondly the mechanism involved in the changes of living organisms through time or evolution of life. The origin of life is considered a unique went in the history of universe.

Fossils are the remains or impressions of pre-historic organisms preserved in sedimentary rocks or other media.Two ways in which study of fossils support biological evolution:

1. The study of Archaeopteryx reveals that birds have evolved from reptiles. This shows fossils provide evidence for evolution.
2. Phylogeny can be constructed from fossils.
3. The habitat and behaviour of extinct organisms can be inferred from well-preserved fossils.

Any disturbance in Hardy-Weinberg's genetic equilibrium indicates an evolutionary change.It is caused by one or more of the following:

1. Gene migration/ Gene flow:

• When a section of a population migrates to another population in another place, the gene frequencies change in both the populations.
• When gene migration occurs a number of times, there is gene flow.

2. Genetic drift: Due to some chance events, the allele frequency becomes so different that they become new species.
3. Natural selection: It is a process in which heritable variations enabling better survival are made to reproduce and leave more progeny; hence, there is a change in the allele frequency.
4. Genetic recombination: In sexually reproducing organisms, recombination of maternal and paternal alleles occurs during gametogenesis, it is a major cause of variation in the allele frequency

The nature builds some pressure on the population of a species and as a result few individuals are eliminated and few adapt to adjust with changes and become fit. This biological phenomenon is called natural selection.

S. No	Natural selection	Artificial selection
(i)	It is a natural phenomenon.	It is the practice done by man.
(ii)	As a result only fit individual increases in a population.	As a result commercially high yielding and disease resistance varieties increase.

Artificial selection have been operated in the followings cases:
Plants: Cabbage, wheat. Animals: High milk yielding varieties of cows.

1. When the allele frequencies in a population remain stable and is constant from generation to generation, it is said to be in genetic equilibrium; it means the gene pool of the population remains constant.
2. Hardy-Weinberg principle
3. Two factors are:

• Genetic drift.
• Gene flow.

4. Gene flow/ Migration: When the individuals of a population migrate to another population, gene frequencies change in both the populations.

• New genes/ alleles are added to the second population while they are lost from the first population. If this migration happens a number of times, there will be gene flow.

For this experiment, Louis Pasteur used a sterilized flask and another flask which was open to air. Killed yeast did not produce new organism in sterilized flask, while yeast new organisms could come into origin in the second flask. This experiment helped in rejecting the theory of spontaneous generation. But lager experiments by Miller showed that organic molecules could develop from inorganic molecules; subsequently leading to origin of life. So, Pasteur’s observation could be corrected to some degree by Miller’s experiment.

The conditions which favour origin of life are:

1. Reducing atmosphere, i.e. the presence of hydrogen.
2. The absence of free oxygen.
3. High temperature and storms to provide energy.

1. When DDT was first used, most of the mosquitoes were sensitive to it and were therefore killed.
2. In the original population of mosquitoes, some individuals were resistant to DDT.
3. They did not have any advantage over the DDT-sensitive mosquitoes, in the absence of DDT.
4. They survived in the presence of DDT and reproduced; the offspring were also mostly DDT-resistant.
5. As a result, over a period of time almost the entire population came to consist of the resistant type.

1. S.L. Miller used this set up.
2. In the diagram, 'a' refers to electrode through which electric discharge was created
3. Miller observed a large number of simple organic compounds and some amino acids. He proved that organic compounds were basis of life.

Industrial Melanism is an adaptation, where the moths living in the industrial area developed melanin pigments to match their body to the tree trunk that were covered with black soot.
Before industrialisation, in Great Britain, it was observed that there were more white winged moths. However, after industrialisation the white coloured lichen covered the tree trunks. In that background the white winged moths survived but the dark coloured moths were eaten by predators. During the post industrialisation periods the tree trunks became dark due to industrial smoke and soots. Under such conditions, the white winged moths did not survive due to predators and dark winged moths survived.
In areas where industrialisation did not occur, the count of moths were low.
Thus, industrial melanism supports evolution by natural selection.

1. The relative frequency of alleles of sexually reproducing organisms in a given population remains constant from generation to generation.
2. Hardy-Weinberg equilibrium.
3. Gene mutation, recombination, gene flow, genetic drift and natural selection.

1. Psilophyton.
2. Seed ferns.
3. Chlorophyte ancestors.
4. Ferns, Conifers, Seed ferns.
5. Tracheophyte ancestors.
6. Chlorophyte ancestors.

Theory of special creation:

1. All living organisms (different species or types of plants and animals) that we see today were created as such.
2. The diversity of life forms was always the same, since the time of creation and will remain the same in future too.
3. Earth is about 4000 years old.

Opuntia spines and pea tendrils are homologous because both are leaf modifications. Lemon thorns and Cucurbita tendrils are homologous because both are modified stems having same basic design and developmental origin but different functions.

Australopithecus africanus was about 1.5 metres tall and had human as well as ape characters. It was with bipedal locomotion, omnivorous diet and had erect posture. It had human like teeth but it had more of an ape brain than a human brain. Its brain capacity was about 500cc, similar to that of an ape Australopithecus africanus existed about million year ago and gave rise to Homo habits about two million years ago.

According to Darwin, fitness refers to reproductive fitness. A fit species will leave more progenies. This will result in greater chances of survival. Greater the number of progenies which will survive, more they will be selected by nature to continue the species. This is called natural selection.

The study of fossils, i.e. palaeontological evidences support theory of organic evolution, i.e. evolution in plants and animals. The transitional fossil organisms show evolutionary relationship between two groups and are called connecting links, e.g. Archaeopteryx is a connecting link between reptiles and birds.
The study of fossil in different sedimentary layers indicates the geological period in which they existed, the life forms varied over time and life forms that are restricted to certain geological time scale. Hence, new forms of life have evolved at different times in the history of earth. All this forms palaeontological evidence. The ages of these fossils are estimated by using methods like radiocarbon and ting.

The periods in Palaeozoic era are:

1. Silurian Zosterophyllum. (Psilophyton, Rhynia type plants).
2. Devonian Progymnosperms.
3. Carboniferous seed ferns.
4. Permian Arborescent lycopods.

Industrial Melanism:

1. In England, before industrial revolution, there were more white-winged or dull-grey moths on the tree trunks, than the dark-winged or melanic moths.
2. In the collection of moths, carried out in the same area after industrial revolution, there were more dark-winged moths.
3. The explanation given for this observation was that predators will spot a moth against a contrasting background.
4. During the post-industrialisation period, the trunks became dark with the industrial smoke and soot.
5. Under this condition, white-winged moths did not survive as predators could easily spot these, while dark-winged or melanic moths survived better.
6. Before industrialisation, there used to be a thick growth of the almost white-coloured lichens on the tree trunks and in that background, the white-winged moths survived better, the dark-coloured moths were easily spotted and picked up by their predators.
7. In this case, the moths which were able to camouflage and hide in the background survived and increased their population size through reproduction.

flippers of penguins and dolphins or eye of octopus and mammals In plants, these organs can be seen in sweet potato (root modification) and potato (stem modification). They are anatomically dissimilar structure though they perform similar function. This type of evolution is called convergent evolution.