Biology Test - 7

The polyploid organism contains more than two sets of chromosomes. There are many naturally occurring flowering species which are polyploid. Polyploidy breeding is performed to create the plants with polyploids. There are two types of polyploids which can be generated, as allopolyploid and autopolyploid. The somatic cells are fused to generate the polyploid hybrids which can be used to study the natural polyploids and to develop new polyploid species.

Hence option B is the correct answer.

A. Sexual selection is an evolutionary model that explains the selection of mates by organisms.

B. Convergent evolution is a process during which organisms with different evolutionary history evolve similar phenotypic adaptations in response to common environmental conditions.

C. Genetic drift is a random change in allele frequencies over the generation. In small populations frequencies of particular alleles may change drastically by chance alone. Such changes occur randomly as if frequencies were drifting and thus, are known as genetic drift.

D. Isolation is condition when an organism is in the state of being isolated.

Hence  the species that have slightly different diets, behaviours, and habitats within the lake, diverged from a common ancestor as a result of Convergent evolution.

So, the correct answer is 'Convergent evolution'.

Flavr Savr is a genetically modified tomato. This was the first commercially grown genetically engineered food. Flavr Savr tomato is more resistant to rotting. This feature is due to the introduction of an antisense gene which interferes with the production of enzyme polygalacturonase. This enzyme is responsible for the degradation of pectin which is present in the cell wall of the fruit. This results in the softening and makes the fruit susceptible to fungal infections. The modified fruit has extended shelf life due to the reduction in the ripening rate.

Hence option B is the correct answer.

Shoot-tip culture refers to the culture of the terminal portion of a shoot comprising the shoot apical meristem together with primordial and developing leaves and adjacent stem tissue. As the meristematic tissues are the tissues with the rapid cell division property and hence are free from viral infection. Thus, this technique is used for the production of virus-free plants.

Hence option A is the correct answer.

a) Cybrids are artificial hybrid cell produced by inserting nuclear material from one organism into an enucleated cell.

b) Hybrids are the recombinant individuals, that have genes from both parents and thus, show new combination of traits.

c) Clones are the population of genetically identical individuals which are produced by asexual or vegetative reproduction. Sexual reproduction does not produce clones owing to the three processes that causes recombination of genetic material and produce variations in progeny. These three processes are cross over during meiosis, independent assortment of chromosomes during meiosis and random fusion of gametes. The resultant progeny will be a hybrid. Asexual reproduction does not include meiosis and fusion of gametes; omits the variation creating processes and produce clones.

So, the correct answer is 'Clone'

Hence option C is the correct answer.

Fossorial adaptation is seen in those animals which live underground and dig ground for their food. These animals are diggers and burrowers. In these animals, forelimbs are modified into broad, strong and stout limbs with long clawed digits as forelimbs are used to loosen the earth. Girdle bones are also modified to provide strength during digging. Examples of fossorial animals include moles, mole rat, hedgehogs, etc. Arboreal animals lives on land but come to trees for shelter. Cursorial animals are runner. They are adapted to run fast. Volant animals are those which are adapted in such way that they are able to fly in air for long time.

Hence option C is the correct answer.

PUFA is the abbreviated form of polyunsaturated fatty acid. These are the fatty acids which contain more than one double bond in their carbon structure. This is the group of fatty acids which contains essential oils like the omega-3 fatty acids, omega-6, omega-9 and other conjugated fatty acids. These compounds are required in the diet for the growth and development of animals

Hence option A is the correct answer.

Darwin's finches are known for their diverse beak shapes and structures. This arises due to different feeding habit and habitat and is an example of adaptive radiation. Adaptive radiation refers to the diversification of organisms from their ancestral species due to change in habitat, feeding habit etc.

So, option D is the right choice.

Xerophytic plants have the following adaptations. A thick cuticle on stems and leaves which protect from excessive transpiration. These plants show the presence of sunken stomata which reduce the loss of water. There are certain thick walled cells of hypodermis which do not allow the passage of water and prevents water loss. The leaves are reduced in size and may be modified to form the spines that reduce the surface area for transpiration. The root system is highly developed for water absorption. In these pants the stem also performs photosynthesis.

Hence option C is the correct answer.

Besides dung, the weed that can be used in biogas production is Eichornia crassipes. An aquatic weed like water hyacinth (Eichhornia crassipes) is used as a source of biogas through harvesting, chopping and crushing.

Hence, the correct answer is option C.

As a result of the struggle for existence, only those organisms could survive which have the favourable variations or changes to adapt to the environmental conditions. In other words, the struggle for existence results in the survival of the fittest. This is called natural selection that tends to favour those organisms that are most fit to survive and reproduce in a particular environment.

The adaptations are genetically controlled and are heritable. Natural selection can alter the frequency of the heritable traits in three ways: Directional, stabilizing and disruptive selection.

Under Directional selection, the frequency distribution of the trait is shifted from where it was present in the parental generation.

Under Stabilizing selection, the population is kept well adapted to the environment at the genetic level and therefore, the population remains genetically constant.

Under Disruptive selection, the populations which are homologous previously break into different adaptive forms.

Hence option B is the correct answer.

Non-indigenous animals and plant species introduced from other countries and which are not otherwise found local are termed exotic. In India, large varieties of exotic animal and plant species have been introduced from other parts of the world through the ages. Some exotic plants have turned into weeds, multiplying fast and causing harm to the ecosystem, e.g., water hyacinth and Lantana camara. Water hyacinth was introduced into Indian waters to reduce pollution. It has clogged water bodies including wetlands at many places resulting in the death of aquatic organisms.

Hence option C is the correct answer.

Genetic engineering is the direct manipulation of an organism's genome by using biotechnology. This new gene or DNA may result in the development of certain characters. The genetic monsters are developed due to genetic engineering are the organisms which disturb the balance of nature. These are evil animals which are formed during genetic experiments and have abnormal genes and chromosomes. They can destroy humanity and other animals by interbreeding. There are institutions which propose guidelines for the development of organisms by genetic engineering. This institution is against the formation of genetic monsters due to fatal consequences.

Hence option B is the correct answer.

Nandankanan is famous for birth of white tiger from normal coloured tigers. It is one of the major host zoo for the white tigers. A unique white tiger safari was established in the zoological park, on 1st October 1991.

Hence option C is the correct answer.

Submerged hydrophytes grow below the water surface and thus they have the numbers of adaptation to live in water such as they respire through general leaf surface due to the absence of stomata. They do not possess an external layer on the epidermis and thus easily absorb nutrients, water and gases.

So, the correct answer is 'General surface of plants'.

Hence option D is the correct answer.