Detailed explanations in West Bengal Board Class 10 Life Science Book Solutions Chapter 2D Growth and Development offer valuable context and analysis.
WBBSE Class 10 Life Science Chapter 2D Question Answer – Growth and Development
Short Snswer Type Questions : 2 Marks
Question 1.
Define growth.
Answer:
Growth may be defined as an irreversible permanent increase in size, volume or mass of a cell or organ or whole organism accompanied by an increase in dry weight.
Question 2.
Differentiate between differentiation, dedifferentiation and redifferentiation of cells.
Answer:
Differentiation is a process during which cells undergoes structural changes in the cell wall and protoplasm. An undividable differentiated cell sometimes regains the power of division. This process is called dedifferentiation. The new cells produced by dedifferentiated cells again loose the power of division and become a part of permanent tissue. This process is called redifferentiation.
Question 3.
What is a sigmoid curve?
Answer:
It is an ‘S’ shaped curve obtained when growth is plotted against time. It is also called growth curve.
Question 4.
Name the phases of growth curve.
Answer:
The four phases of growth curve are lag phase, log phase, diminishing phase and steady phase.
Question 5.
What are phytohormones?
Answer:
Plant hormones are chemically diverse substances produced in minute quantity and they involve in most of the plant cell activities. They regulate the growth process both by promoting and inhibiting growth. They are produced in certain parts of the plant and transported to other tissues where their action is shown.
Question 6.
Name growth promoters and growth inhibitors. List their functions. Answer:
Answer:
Question 7.
What is photoperiodism?
Answer:
This flowering response in plants to the relative length of light and dark periods within a 24 hour cycle is called ‘Photoperiodism’.
Question 8.
Classify the plants based on their photoperiodic response.
Answer:
There are three types of plant based on their photoperiodic response. They are long day plants, short day plants and day neutral plants.
Question 9.
Define vernalization.
Answer:
Some biennials like carrot, cabbage and sugar beet need a cold/low temperature treatment before they flower. This is called ‘vernalization’.
Long Answer Type Questions : 5 Marks
Question 1.
Define growth. Explain types of growth in plants.
Answer:
Grow th may be defined as an irreversible permanent increase in size, volume or mass of a cell or organ or whole organism accompanied by an increase in dry weight.
Types of growth :
Primary and secondary growth: The mitotic division of meristematic cells present at the root and shoot apex increases the length of the plant body. This is called the primary growth. The secondary meristem increases the diameter of the plant body and it is called the secondary growth.
Life Sc. Comp. (x) : 8
Unlimited Growth: The root and the shoot system of plants grow continuously from germination stage to the death or throughout the life span of the plant. It is called ‘Unlimited’ or ‘indeterminate’ type of growth.
Limited growth: The leaves, fruits and flowers stop growing after attaining certain size. This is called ‘limited’ or ‘determinate’ type of growth.
Vegetative growth : The earlier growth of plant producing leaves, stem and branches without flowers is called Vegetative growth/ phase.
Reproductive growth : After the vegetative growth, plants produce flowers which is the reproductive part of the plant. This is called reproductive growth/phase.
Question 2.
What do you mean by growth curve? Explain with a graph.
Answer:
Growth curve : It is an ‘S’ shaped curve obtained when we plot growth against time. It is also called ‘sigmoid ‘curve. This curve mainly shows four phases of growth- (i) initial slow growth (Lag phase), (ii) the rapid period of growth (log phase/grand period of growth/ exponential phase) where maximum growth is seen in a short period and (iii) The diminishing phase where growth will be slow and (iv) Stationary / steady phase where finally growth stops.
Question 3.
What do you mean by differentiation, dedifferentiation and redifferentiation of cells ?
Answer:
The three phases of cell growth are cell division, cell enlargement and cell differentiation. The first two stages increase the size of the plant cell while the 3rd stage brings maturity to the cells. Differentiation, is a process during which cells undergoes structural changes in the cell wall and protoplasm (Fig). A differentiated cell cannot divide.
An undividable differentiated cell sometimes regains the power of division. This process is called dedifferentiation. Dedifferentiation is a common process in plants during secondary growth and in wound healing mechanisms. A dedifferentiated cell can divide and produce new cells. Thus produced new cells again loose the power of division and become a part of permanent tissue. This process is called “redifferentiation”. Tumour cells form good example for redifferentiated cells.
Question 4.
What is development? What are plant hormones regulating development.
Answer:
Development : Development is defined as sum total of growth and differentiation. Development is governed by both environmental and internal factors. One of the internal factors that regulate growth and development is ‘plant hormones’.
Plant hormones/ Phytohormones/ Growth regulators : Plant hormones are chemically diverse substances produced in minute quantity and they involve in most of the plant cell activities. They regulate the growth process both by promoting and inhibiting growth. They are produced in certain parts of the plant and transported to other tissues where their action is shown. Based on their promotory and inhibitory activity they have been classified into growth promoters and growth inhibitors.
e.g. Growth Promoters : Auxins
Growth inhibitors : Ethylene.
Question 5.
What do you mean by human development?
Answer:
Human development is a lifelong process of physical, behavioral, cognitive, and emotional growth and change. In the early stages of life-from babyhood to childhood, childhood to adolescence, and adolescence to adulthood-enormous changes take place. Throughout the process, each person develops attitudes and values that guide choices, relationships, and understanding.
Sexuality is also a lifelong process. Infants, children, teens, and adults are sexual beings. Just as it is important to enhance a child’s physical, emotional, and cognitive growth, so it is important to lay foundations for a child’s sexual growth. Adults have a responsibility to help young people understand and accept their envolving sexuality. Read on to learn more about human growth and development.
- Infants & Toddlers-Ages 0 to 3
- Preschoolers-Ages 4 to 5
- Grade Schoolers -Ages 6 to 8
- Preteens-Ages 9 to 12
- Teens-Ages 13 to 17 young
- Adults-Ages 18 and Over
Question 6.
Describe different stages of growth in human.
Answer:
Different stages of growth.
- There are stages of growth that a person goes through.
- Infancy
- Early childhood
- Childhood
- Late childhood
- Adolescence
- Adulthood
Infancy :
-
- Infancy : from birth to 18th months
- Physical changes :
- Bones are still soft and flexible
- Learns to sit, to crawl, to stand and to sit.
- Mental changes :
- Gets what it needs by crying
- Can recognize parents and siblings
Early childhood :
-
- 18th month to 3 years
- Physical changes :
- Learns to walk and to talk
- Arms and legs get longer
- Mental changes :
- Learns to use the toilet
- Social changes :
- Not ready to share or to play interactively with others
Childhood :
-
- 3 to 6 years
- Physical changes :
- Begins to lose milk teeth
- Mental changes :
- Learns to behave while in a group
- Social changes
- Learns to play interactively and to make friends
- Emotional changes
- Physical contact becomes less frequent
Late childhood :
- Physical changes :
- Appetite increases
- Process of sexual maturity begins
- Mental changes :
- Acquires high-level thinking skills
- Emotional changes :
- Self-centeredness lessens
- Choose friends of the same sex
Adolescence :
-
- The period of gradual change from childhood to adulthood the time of life between childhood and adulthood.
- Physical changes :
- Rapid physical growth
- Body starts to look more like an adult
- Mental changes :
- Begins to question oneself
- Starts to enjoy participating in adult conversation
Adulthood :
-
- Period from the twenties onward
- Physical changes :
- A slow weakening of the five senses
- A slow loss of calcium in the bones
- Bones become brittle
- Stiffening of the joints and weakening of the muscles
- Emotional changes :
- Feeling very quickly from being happy to being lonely
- Sees people as having needs like his
- Social changes
- Friends’ views become more important
Multiple Choice Questions : 1 Mark
Question 1.
The phase of growth which is the first phase and represents lag phase of growth curve is
(a) Formative phase
(b) Cell enlargement phase
(c) Maturation phase
(d) Stationary phase
Answer:
(a) Formative phase
Question 2.
The lateral meristem in plant is responsible for
(a) Primary growth
(b) Secondary growth
(c) Exponential growth
(d) Growth in elongation
Answer:
(b) Secondary growth
Question 3.
Plant growth can be measured by
(a) Horizontal microscope
(b) Crescograph
(c) Auxanometer
(d) All of these
Answer:
(d) All of these
Question 4.
The rate of growth is called as
(a) Growing index
(b) Increasing index
(c) Effective index
(d) Efficiency index
Answer:
(d) Efficiency index
Question 5.
Which of the following shows secondary growth?
(a) Monocots
(b) Dicots
(c) Ferns
(d) Mosses
Answer:
(b) Dicots
Question 6.
Growth can be measured in terms of
(a) Fresh or fry weight increase
(b) Increase in girth of stem
(c) Increase is surface area of leaf
(d) All of these
Answer:
(d) All of these
Question 7.
Auxins were first isolated from the plants by
(a) Darwin
(b) F.W.Wend
(c) Boysen-Jensen
(d) Sachs
Answer:
(b) F.W.Wend
Question 8.
Apical dominance is due to
(a) Abcisic acid
(b) Gibberelic acid
(c) Auxin
(d) Cytokinin
Answer:
(c) Auxin
Question 9.
Hormone related with cell divisions is
(a) NAA
(b) IAA
(c) Cytokinin
(d) GAS
Answer:
(c) Cytokinin
Question 10.
Which of the following hormone is mainly concerned with root Initiation?
(a) Kinetin
(b) GAB
(c) IAA
(d) ABA
Answer:
(c) IAA
Question 11.
Primary precursor of IAA is
(a) Methionine
(b) Adenine
(c) Tryptophan
(d) Alanine
Answer:
(c) Tryptophan
Question 12.
Avena-Curvature biossay was conducted by
(a) Went
(b) Pal
(c) Darwin
(d) Boysen-Jenson
Answer:
(a) Went
Question 13.
Which one of the following groups comprises synthetic auxin?
(a) 2, 4-D; 2, 4, 5,-T and Zeatin
(b) Gibberellic acid, ABA, IAA
(c) 2, 4-D, 2, 4, 5-T and NAA
(d) Cytokinin, IAA, IBA
Answer:
(c) 2, 4-D, 2, 4, 5-T and NAA
Very short answer type questions : 1 Mark
Question 1.
Define growth, differentiation, development, dedifferentiation, redifferentiation, determinate growth, meristem and growth rate.
Answer:
Growth : A permanent and irreversible increase in size of an organ or its part or even of an individual cell is called growth.
Differentiation : The process which leads to maturation of cells is called differentiation. During differentiation, a few or major changes happen in protoplasm and cell walls of the cells.
Development : All the changes which an organism goes through during its life cycle become parts of development. In case of a flowering plant, right from seed germination to seed bearing, each stage is a part of the development process.
Dedifferentiation : A differentiated cell can regain its capacity for cell division under certain conditions. This phenomenon is called dedifferentiation. Formation of interfascicular cambium and cork cambium from fully differentiated parenchyma cells is an example of dedifferentiation.
Redifferentiation : A dedifferentiated plant cell once again loses its capacity to divide and becomes mature. This phenomenon is called redifferentiation.
Determinate Growth : When growth stops after a certain phase, this type of growth is called determinate growth.
Meristem : The plant tissue which has the ability to divide is called meristematic tissue. The region with such tissues is called meristem.
Growth Rate : The increased growth per unit time is called growth rate.
Question 2.
Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?
Answer:
Different parts of a plant grow in different ways. There could be one way of measuring growth for a stem, while there could be a different way of measuring growth in a leaf. Different plants can be of different sizes and measurement of growth should be done in different ways in them. Hence, there cannot be one parameter to measure growth in different plants or even at different stages of the life cycle of a flowering plant.