12th Class Biology Chapter 5 Growth and Development Short Question Answers
12th Class Biology Chapter 5 Growth and Development Short Question Answers Below
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1.What are growing points?
In higher plants growth is limited to certain regions known as growing points e.g.shoot apex and root tip.
2.What is secondary growth?
The growth of secondary tissues i.e, secondary xylem and phloem,by the intercalary or vascular cambium leading to increase in thickness is called secondary growth.
3.Name the factors by which rate of growth is influenced?
The growth rate is influenced by number of factors both external and internal.External factor are temperature light oxygen carbon dioxide etc.While internal factors are hormones water vitamins etc.
4.What is correlation?
The development of a plant is usually correlated with its growth and different organs grow at different rates in different directions and the development of different parts takes place.Such reciprocal relationship is known as correlation.
5.What is embryology?
Embryology is the study of growth and differentiation undergone by an organism in the course of its development from a single fertilized egg into a highly complex and an independent living being like his parents.
6.What is discoidal cleavage?
In bird’s egg the process of cell division is confined to the small disc of protoplasm lying on the surface of the yolk at the animal pole.This type of cleavage is referred to as discoidal cleavage.
7.What is the role of cytokinins in apical dominance?
Cytokinins play important role in apical dominance and in many cases if cytokinins is applied directly on the inhibited bud it allows lateral buds to be released from apical dominance.
8.Which process is defined as negative physiological changes?
Aging can be defined as negative physiological changes in our body.
9.Due to what factors normal process of development is disturbed?
The normal process of development is disturbed by abnormalities inherited from parents abnormalities due to chromosomes or genes environmental factors or metabolic defects.
10.Define embryonic induction?
The influence of notochordal cells on the ectodermal cells to become nervous system was called embryonic induction by spemann.
11.Differentiate between growth and development?
Growth is the permanent and irreversible increase in size that occurs as an organism matures.While the progressive changes which are undergone before an organism becomes adult constitute embryonic development.
12.What is meristem?
Meristems are young tissues or population of cells that retain the potential to divide.
13.What is open growth?
A plant has a growth pattern called open growth because throughout life,the plant adds new organs such as branches leaves and roots enlarging from the tips of roots and shoots.
14.What is Apical Meristem?
The apical meristems are found at the tips of roots and shoot and are primarily concerned with the extension of plant body.These are perpetual growth zones found at the apices of roots and stems.They play important role in primary growth.
15.What are Intercalary Meristems?
These are the parts of apical meristem which get separated from apex by permanent tissues.They are situated at the bases of internodes in many plants.They play important role in the production of leaves and flower.These are of temporary nature.
16.What are Lateral Meristems?
Lateral Meristems are cylinders of dividing cells present in dicots and gymnosperms.Vascular and cork cambium are the examples of lateral meristems.They play an important role in the increase in diameter of stem and root and are involved in secondary growth.
17.Define differentiation?
Differentiation is the formation of specialized tissues.
18.What was the work of Thimann and Skoog?
Thimann and Skoog in 1934 performed experiments and showed that apical dominance was caused by auxin diffusing from the apical bud.
19.Differentiate between inhibitory and compensatory effects?
Auxin released from apical bud inhibited the growth of lateral shoots or buds and it is called inhibitory effect.While the removal of apex releases the lateral buds from apical dominance.It is called compensatory effect.
20.What is the temperature for incubation for chick eggs?
In incubating eggs artificially the incubators are usually regulated at temperature between 36-38ᵒC.At this temperature the chick completes development and is hatched on the twenty first day.
21.Define Cleavage?
The egg undergoes a series of mitotic divisions called cleavage.
22.What is Morula?
Cleavage results in the formation of a rounded closely packed mass of blastomers.This is morula.
23.What is Blastula?
The morula stage is short lived and soon changes into blastula and is characterized by the presence of a segmentation cavity or blastocoele.
24.What is blastoderm?
The discoildal cap of cells above the blastocoels is called blastoderm.
25.What is zone of junction in developing chick embryo?
The marginal area of the blastoderm in which the cells remain undetached from the yolk and closely adherent(supporting) to it is called the zone of junction.
26.Define Gastrulation?
It is characterized by the movement and rearrangement of cells in the embryo.
27.Which two layers are formed from blastoderm during gastrulation?
During gastrulation the blastoderm splits into two layers:an upper layer of cells called epiblast and a lower layer of cells called hypoblast.
28.What is area pellucida?
The central cells of blastoderm can be separated from the yolk under these central cells a pool of fluid develops raising them off the yolk and giving the area a translucent appearance-the area pellucida.
29.What is area opaca?
The peripheral part of the blastoderm where the cells lie unseparated from the yolk is termed as area opaca.
30.What is Primitive streak?
In the chick the mesodermal cells migrate medially and caudally from both sides and create a mid line thickening called primitive streak.The primitive streak represents the dorsal and both lateral lips of blastopore.
31.What is primitive node?
The anterior end of the primitive streak is occupied by an aggregation – the primitive node or notochordal cells while rest of cells are mesodermal cells.
32.What is Hensen’s node?
At the cephalic end of primitive streak closely packed cells form a local thickening known as Hensen’s node.
33.What is Germ wall?
In sections of embryo incubatd from 18-20hourse,it is seen that ectoderm has spread and become organized into a coherent layer of cells merging peripherally with the yolk and the marginal area where the expanding germ layers merge with the under lying yolk is known as germ wall.
34.What is gastrocoele?
The cavity of the gastrula is called gastrocoele.
35.How many layers the lateral plate mesoderm is splitted into?
The lateral plate mesoderm is splitted into two sheet like layers viz somatic mesoderm and splanchnic mesoderm with a space between them.
36.What is coelom?
The cavity formed between somatic and splanchnic mesoderm is coelom.
37.What is Neurlation?
The whole process of formation of nervous system is called neurulation.
38.How neural plate is formed?
On the dorsal surface of gastrula over the notochord presumptive neural ectoderm is present in the form of a band.As gastrula elongates the band thickens to form a neural plate.
39.What is Neurula?
In 24 hour chick embryos the folding of neural plate is clearly visible.The embryo is now termed as neurula.
40.How neural tube is formed in chick embryo?
The neural plate sinks and the neural folds grow toward one another and meat in the mid-dorsal line fuse and convert the neural groove into neural tube.
41.What are neuropores?
At each end of neural tube a small opening called anterior and posterior neuropores are also seen which close later on.
42.What is neurocoel?
With the formation of neural tube there is formation of central nervous system and the cavity enclosed is known as neurocoel.
43.What was work of Dietrish?
In 1892,Hans Dietrisch took sea urchin egg at two-cell stage shook it apart and separated it into two cells.Later on it was seen that both half embryos developed into normal larvae.
44.What is Acetabularia?
It is multicellular alga.It consists of rhizoid,which is attached to the ground from which arises a long stalk with an umbrella shaped cap at its top.Two species of Acetabularia have been identified;Acetabularia mediterranea and A,crenulata.
45.What is primary induction?
Spemann designated the dorsal lip area the primary organizer because it was the only tissue capable of inducing development of secondary embryo in the host.This was called primary induction.
46.Define regeneration?
The ability to regain or recover the lost or injured part of the body is called regeneration.
47.What are neoblasts?
In flatworms and Planaria the unspecialized cells called neoblasts are always present in the body of adult and are mobilized and migrate to the site of amputation where they differentiate into specialized cell types.
48.Define abnormal development?
Sometimes under unfavorable conditions some parts of the body do not develop normally and this is called abnormal development.
49.Define Teratology?
Teratology is the branch of biology which deals with these abnormal developments and causes for such developments.
50.What are Teratogens?
Environmental factors causing or contributing to abnormal development are grouped together as teratogens e.g,lonizing radiations such as X rays.
Define growth?
Growth is the permanent and irreversible increase in size that occurs as an organism gets older.
How does the rate of growth differ throughout the life of an organism?
The growth is slow in the beginning gradually becomes rapid, attains maximum rate, then slows down and finally stops altogether.
What are meristems (growing points)?
The meristems are the regions of the body of a plant where cells are actively engaged in division.
Name the different meristems in plants and their location.
These are the apical meristems located at the tips of roots and shoots; intercalary meristems situated at the bases of internodes; and the lateral meristems found between permanent tissues such as cambium.
What is the role of intercalary meristems?
They produce leaves and flowers.
Which tissues of the plant initiate primary growth?
The apical meristems located at the tips of the root and the stem initiate primary growth.
Which tissue of the plant initiates secondary growth?
The cambium initiates secondary growth.
What is the difference between the primary and the secondary growth?
The primary growth lends to the increase in length of the plant whereas the secondary growth leads to an increase in its width (thickness) or diameter.
Where does cell division occur most intensively and where does most rapid increase in the size of cells occur in the apical regions of the shoots and the roots?
In the apical regions of the shoots and the roots, cell division occurs most intensively towards the extreme tips whereas most rapid increase in the size of cells occurs in the zones few millimeters behind the tips.
What are the phases (zones) of growth of the shoot and the root?
These are the phase of cell division, phase of cell elongation, phase of cell maturation and phase of cell differentiation.
Define cellular differentiation in plants.
The conversion of meristematic cells of plants into permanent and full grown tissues is called cellular differentiation.
In which directions do the fibers and the tracheid’s of shoots and roots elongate during their growth?
The fibers and the tracheid’s of shoots and roots elongate greatly parallel to their long axes and only slightly in other directions.
Name the environmental factors which influence the growth rate in plants?
These are the temperature, light, oxygen and carbon dioxide etc.
What internal factors influence plant growth?
These factors are hormones, water and vitamins etc.
Write down the range of temperature which can influence the rate of plant growth?
This range of temperature is form 0°C to 35°C.
Define optimum temperature. What is the range of optimum temperature for plant growth?
The temperature at which a physiological process occurs at its maximum rate is called optimum. The range of optimum temperature for plant growth is 25°C to 30°C.
In which ways does light influence growth in plants?
The light influences growth by its intensity, quality and duration.
How does the intensity of light affect the growth?
The increase in the intensity of light increases rate of growth by accelerating cell division at the growing regions of the stem.
How does quality of light affect the growth in plants?
The red light favours elongation of cells and the blue light enhances cell division but retards cell enlargement.
Of all the environmental factors which ones are the most important for controlling growth and development of plants?
These factors are temperature and light.
Give definition of growth correlation?
The relationship that exists between the different growth rates of various parts of a plant body is called growth correlation.
What did Thimann and Skoog conclude about apical dominance in 1934?
Thimann and Skoog concluded that apical dominance was caused by auxin diffusing from the apical bud which inhibited the growth of lateral buds (shoots).
What is the relationship between the apical dominance and the cytokinins?
The cytokinins play an important role in apical dominance. For example, in many plants application of cytokinins directly on the inhibited bud can release its inhibition in an intact plant.
Define embryology?
Embryology is the branch of biology which deals with the study of development of the zygote till it forms the adult organism.
Name the stages of developmental processes of animals.
These are cleavage, gastrulation, organogenesis growth and differentiation.
When is the egg shell secreted in the hens?
The egg shell is secreted in hens after the fertilization when the egg passes through the shell gland in the uterus.
Explain cleavage?
Cleavage is the process of cell division of the zygote by mitosis which gives rise to multicellular embryo.
Are the cleavage divisions of the zygote regular or irregular?
Only the initial three cleavage divisions of the zygote are regular, of which the first two are vertical and the third horizontal.
What are the daughter cells formed by initial cleavage divisions of the zygote known as?
These are known as the blastomeres.
What is blastocoel in the embryo of chick?
The blastocoel is the name of the cavity within the embryo of the chick at the blastula stage.
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