BIOLOGY 3 Marks Question

For example the fore limbs of some animals (Vertebrates) like whales, bats, cheetah and human have similar anatomical strucuture (i.e. humerus, radius, ulna, carpals, metacarpals and phalanges) develop differently to meet different needs/to perform different functions.

1. Darwin finches/black birds (on Galapagos islands), evolved from original seed eating features, into insectivorous & vegetarian features in different habitat/islands.
2. Australian marsupials and placental mammals. Convergent evolution, more than one adaptive radiation occured in isolated geographical area.

• Disturbance in Hardy-Weinberg equilibrium is an indicator of change of frequency of alleles in a population, resulting in evolution.
• It is caused by genetic drift/gene flow or gene migration/mutation/genetic recombination/natural selection.

1. The rates are faster/accelerated/current species extinction rate are estimated to be 100 - 1000 times faster than in the pre-human times.
2. Human activities.
3.  

1. Preventing habitat loss and fragmentation.
2. Checking overexploitation.
3. Preventing alien species invasion.
4. Preventing co-extinction.
5. Conservation/Preservation of species.

1. Gene frequencies in a population are stable, constant from generation to generation, until some change in frequency happens, due to some factor.
2. Gene migration/gene flow/gene drift/mutation/genetic recombination/natural selection.

1. From the original seed eating features, many other forms with altered beaks arose, enabling them to become insectivorous and vegetarian finches.
2. The process of evolution of different species in a given geographical area starting from one point, and literally radiating to other areas of geography (habitats), is called adaptive radiation.

1. Fossils in different sedimentary layers indicate the geological period in which they existed.
2. They show that life forms varied over time.
3. New forms of life have arisen at different times in the history of earth.

1. Life could have come from pre-existing non-living organic molecules, and that formation of life was preceded by chemical evolution.
2. (S. L. Miller created condition similar to prehistoric earth in the laboratory) He created electric discharge in a closed flask, containing CH₄ H₂ NH₃ and water vapour, at 800⁰C observed formation of amino acid (organic molecules)

1. The excess use of herbicides and pesticides in the agricultural field by the humans to kill pests and insects has resulted in selections of resistant variety of pests and insects over a short time span the change favored resistance pests and insects which lead to their evolution.
2. The excess use of antibiotics has caused selection of drug-resistant microbes, the microbes sensitive to antibiotics died but few variants having resistance against it survived. This led to evolution of more fatal microbes.

1. Australia.
2. Adaptive Radiation The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitat) is called adaptive radiation.
3. (Convergent evolution/Adaptive Convergence) Organisms coming from different stock, evolved similar features and adapted to same habitat.

2. Following are the analogous structure from the given list:

1. Wings of butterfly and birds.
2. Tubers of sweet potato and potato.

2. Silurian, Carboniferous, Jurassic.

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

1. One flask was kept closed and the other was left open.
2. He showed that in the closed pre-sterilised flask, life did not come from the killed yeast; in the other flask that was kept open, life appeared from killed yeast. This dismissed the theory of spontaneous generation.
3. He concluded that life can come from pre-existing life.

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.

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

• Population must be sufficiently large.
• Free flow of genetic materials is ensured through sexual reproduction.
• There should be negligible or nil migration in the population.

1. The rocks of early era contain less number of fossils than the rocks of later era and fossils of only simple marine invertebrates are in these rocks, which indicate that life originated in sea as simple form.
2. The distribution of fossils indicates that fossils became more and more complex as we proceeded from earliest to recent rocks.
3. On the basis of fossil study, it has been shown that the early organisms were very different from their modern forms.

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.

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

Artificial selection have been operated in the followings cases: