Explore topic-wise InterviewSolutions in Current Affairs.

Correct Answer is: (d) A and Y 

(b) 10AB, 10ab

Correct Answer is: (b) SHGL

1. The soil of northern plains contains a lot of alluvium and so it is quite fertile.

2. The climate in this region is suitable for agriculture.

3. Also, water is available here in sufficient quantity.

4. Due to these reasons, agriculture has developed well in the northern plains.

5. Hence, more and more people prefer to settle in northern plains.

Linkage: 

1. The genes present on chromosome stay close together. 

2. It involves same chromosome of homologous chromosome. 

3. It reduces new gene combinations.

Crossing over: 

1. It leads to separation of linked genes.

2. It involves exchange of segments between non-sister chromatids of homologous chromosome. 

3. It increases variability by forming new gene combinations. Leading to formation of new organism.

Tendency of genes to remain together during separation of chromosomes is called linkage. Linkage are of 2 types – complete linkage and incomplete linkage.

(b) 7 : 1 : 1 : 7

(a) Both A and R are correct

Differentiation : A biochemical or morphological change in meristemic cell (at root apex and shoot apex) to differentiate into permanent cell is called differentiation. 

Dedifferentiation : The phenomenon of regeneration of permanent tissue to become meristematic is called dedifferentiation.

Redifferentiation : Meristems/tissue are able to produces new cells that once again lose the capacity to divide but mature to perform specific functions.

The cells which are derived from root apical meristem and shoot apical meristem differentiate and mature to perform specific functions. This act leading to maturation is termed as differentiation. During this, the cells undergo a few major structural changes both in their cell walls and protoplasm. 

(i) In plants, the living differentiated cells can regain the capacity to divide mitotically under certain conditions. The sum of events are termed as dedifferentiation. A dedifferentiated tissue can act as meristem. e.g., interfasicular vascular cambium, cork cambium and wound meristem.

(ii) The product of dedifferentiated cells or tissues which lose the ability to divide are called redifferentiated cells and the term is known as redifferentiation. Secondary xylem and econdary phloem that form interfasicular vascular cambium, secondary cortex and cork are the examples of redifferentiated tissues.

The short-day plant and long-day plant can flower at the same place, provided they have been given an adequate photoperiod.

Growth:

It is an irreversible and permanent process, accomplished by an increase in the size of an organ or organ parts or even of an individual cell.

Differentiation:

It is a process in which the. cells derived from the apical meristem and the cambium undergo structural changes in the cell wall and the protoplasm, becoming mature to perform specific functions.

Development:

It refers to the various changes occurring in an organism during its life cycle from the germination of seeds to senescence.

De-differentiation:

It is the process in which permanent plant cells regain the power to divide under certain conditions.

Re-differentiation:

It is the process in which differentiated cells become mature again and lose their capacity to divide.

Determinate growth:

It refers to limited growth. For example, animals and plant leaves stop growing after having reached maturity.

Meristem:

In plants, growth is restricted to specialised regions where active cell divisions take place. Such a region is called meristem.

Growth rate:

It can be defined as the increased growth in plants per unit time.

In higher plants, some of the cells retain their capacity of cell division. Hence, growth is of open type. Moreover, some of these cells always undergo differentiation after some rounds of cell division. Hence, the scope of differentiation is also open. Thus, it can be said the both growth and differentiation in higher plants are open.

Growth and development in higher plants is referred to as being open because various meristems, having the capacity for continuously dividing and producing new cells, are present at different locations in these plant bodies. 

(a) Causes imemodal elongation in rice.

(b) If a rotten fruits get mixed with unripe fruit. Then the ethylene produced from the rotten fruit will hasten the ripening of the unripe fruits.

(c) Formation of new organs from the callus in tissue culture (Morphogenesis) will not be formed.

Meristematic, elongation and maturation Phase.

(a) Auxins

(b) Ethylene

(c) Cytokinin

(d) Cytokinin

(e) Gibberellins

(f) Abscisic Acid

Leaves are the sites of perception of light/dark duration. Hence, a defoliated plant would not respond to photoperiodic cycle.

The factors that affect growth and development of plants are : Light, temperature, oxygen carbon dioxide, water, soil minerals and growth regulators.

The period or time, in which growth takes place, has been called grand period of growth.

It is the graphic representation of the total growth against time.

In this type of growth, only one daughter cell continues to divide after the mitosis. Another daughter cell differentiates and matures. Elongation of root at a constant rate is an example of arithmetic growth. Mathematically, the arithmetic growth rate can be shown as follows:

L_t = L₀ + rt

Here, Lt is length at time ‘t’, L₀ is length at time 0 and r is the rate per unit time.

Growth curve is a plot of growth (height, weight or volume) increase plotted against time.

 In most of the cases, the initial growth is slow and is called the lag phase. After this, the growth is quite rapid and at an exponential rate. This phase is called the log or exponential phase. In this phase, both the daughter cells (formed after mitosis) continue to divide. The last phase marks a slowed down growth. This happens because of limited nutrient supply. This phase is called the stationary phase. The graph of the geometric growth gives a sigmoid curve.

The exponential growth can be mathematically represented as follows:

W₁ = W₀ert

Here, W₁ = final size (weight, height, number etc.), W₀ = initial size at the beginning of the period, r = growth rate, t = time of growth and e = base of natural logarithms.

When growth is measured in absolute terms, e.g. in terms of length or weight, it is called absolute growth. When growth is measure in terms of comparative terms; like percentage growth; it is called relative growth.

The phase of cell elongation

Correct Answer is: (c) maize

The S-shaped curve on graph; to show geometric growth is called the sigmoid growth curve.

Unripe fruits will lead to early ripening and ultimately it will result in rottening.

If a rotten fruit gets mixed with unripe fruits, then the ethylene produced from the rotten fruits will hasten the ripening of the unripe fruits.

The S-shaped growth curved obtained when plotting height, weight or volume of the plant at successive intervals against time is termed sigmoid growth curve. 

If you forget to add cytokinin to the culture medium, then cell division, growth and differentiation will not be observed.

1. Radicle

2. Coleorhiza

3. Perisperm

4. Primary Endosperm nucleus

5. Triple fusion

6. Integument

(b) The outer integument of ovule develops into tegmen

(a) one meiotic and two mitotic divisions

(b) radicle,plumule, cotyledons and sometimes endosperm

A dicot embryo has an embryonal axis and two cotyledons. The portion of embryonal axis above the level of cotyledons is the epicotyl.it terminates in plumule. The Cylindrical portion below the level of cotyledons is hypocotyl, it terminates at its lower end in radicle.

Male sex organ. - Spermatangium 

Female sex organ - Carpogonium 

• A golden brown pigment called fucoxanthin is present and it gives shades of colour from olive green to brown to the algal members of Phaeophyceae.

• Male sex organ is called Sperrnatangium.
• Female sex organ is called Carpogonium. 

Apomixis is a kind of asexual reproduction in which seeds are produced without fertilization. By retaining the seed habit, it mimics to sexual reproduction.

Animals excrete urea

Many aquatic creatures are ammonotelic which excrete ammonia as waste product. Ammonia is generally excreted by diffusion across body surfaces as ammonium ions. Kidneys do not play any significant role in its removal. Terrestrial adaptation necessitated the production of lesser toxic acid for conservation of water. Hence terrestrial animals are mostly ureotelic (excrete urea) and uricotelic (excrete uric acid).

The process of excreting ammonia is Ammonotelism. Many bony fishes, aquatic amphibians and aquatic insects are ammonotelic in nature. Ammonia, as it is readily soluble, is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions. Kidneys do not play any significant role in its removal.

Terrestrial adaptation necessitated the production of lesser toxic nitrogenous wastes like urea and uric acid for conservation of water. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtered and excreted out by the kidneys. Some amount of urea may be retained in the kidney matrix of some of these animals to maintain a desired osmolarity. Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.

Fusion between similargametes is isogamy. The fusion between dissimilar gametes is anisogamy. 

Mucus protects the stomach wall from the action of digestive juices.

Nutrition: 

They are heterotrophic, mostly holozoic, sometimes parasitic.