Class 10 Biology Chapter 2 Important Questions Kerala Syllabus Paths of Evolution

A thorough understanding of Class 10 Biology Notes Kerala Syllabus Chapter 2 Important Questions Paths of Evolution can improve academic performance.

SSLC Biology Chapter 2 Important Questions Paths of Evolution

Paths of Evolution Class 10 Important Questions

Question 1.
Analyse the assertion and reason and choose the correct answer.
Assertion: Acquired traits are not inherited
Reason: Spontaneous mutations do not change the genetic makeup of organisms.
(a) The assertion and reason are correct, and the reason is the correct explanation of the assertion.
(b) Assertion and reason are correct but reason is not the correct explanation of assertion
(c) Assertion is correct, reason is wrong
(d) Assertion is wrong, reason is correct
Answer:
(a) Assertion and reason are correct and reason is the correct explanation of assertion

Question 2.
Choose the correct answer
Statement 1: There are about fourteen different species of finches in the Galapagos archipelago Statement 2: The major difference these species exhibit is the shape and size of the beak.
(a) Statement 1 and 2 are correct
(b) Statement 1 and 2 are wrong
(c) Statement 1 is wrong, statement 2 is correct
(d) Statement 1 is correct, statement 2 is wrong
Answer:
(a) Statement 1 and 2 are correct

Question 3.
The theory of inheritance of acquired characters was proposed by:
(a) Charles Darwin
(b) Alfred Russell Wallace
(c) Jean Baptiste Lamarck
(d) Hugo de Vries
Answer:
(c) Jean Baptiste Lamarck

Question 4.
Complete the following statement:
Darwinism became uncritically rationalised as more evidences and further studies from the fields of population genetics, palaeontology, environmental science, etc. were added to Darwinism to form ___________
Answer:
Neo Darwinism

Question 5.
Choose the correct statements from the following:
(a) As Darwin continued his studies, in 1858, the evolutionary studies of the British naturalist Alfred Russell Wallace also came to his attention.
(b) In 1859, Malthus expanded and presented his ideas through the book ‘On the Origin of Species’.
(c) Darwin’s theory of evolution is one of the scientific ideas that has influenced the world the most.
Answer:
A and C

Question 6.
The statements given in the box refers to a great scientist.
(a) Identify the scientist
(b) What was the idea he put forwarded?

❖ Origin of species ❖ HMS Beagle ❖ Galapagos Islands ❖ Survival of the fittest

Answer:
(a) Charles Darwin
(b) Theory of Natural Selection

Question 7.
Why was Lamarck’s idea rejected by the scientific world?
Answer:
Lamarck’s theory was not accepted by the scientific world because it was proven that acquired characteristics are not inherited.

Question 8.
Arya has given the following explanations for Darwin’s theory. Which of the following explanation is incorrect?
(a) When the resources are limited, organisms compete for survival.
(b) Those with favourable variations survive
(c) Acquired traits are passed on to the next generation
(d) Those with unfavourable variations die out.
Answer:
(c) Acquired traits are passed on to the next generation

Question 9.
Even using permanent mosquito repellents, mosquitoes cannot be completely destroyed. Write a scientific explanation for this statement based on the theory of evolution.
Answer:
Some mosquitoes develop resistance to insecticides. This is survival of the fittest. Those that are resistant to insecticides survive and the others die.

Question 10.
Choose the correct answer and write it:
Statement 1: Fossils are the remains or traces of organisms of ancient times.
Statement 2: Archaeopteryx is the connecting link between amphibians and birds
(a) Statement 1 and 2 are correct
(b) Statement 1 and 2 are wrong
(c) Statement 1 is correct, statement 2 is wrong
(d) Statement 1 is wrong, statement 1 is correct
Answer:
(c) Statement 1 is correct, statement 2 is wrong

Question 11.
Complete the following statement:
__________ and __________ fossils prove that they became extinct that were living on Earth in the past.
Answer:
Dinosaurs and Mammoths

Question 12.
Which are the main evidences in the process of evolution?
Answer:
Study of fossils, comparative anatomy, evidence from biochemistry and physiology, and evidence from molecular biology.

Question 14.
Choose the correct answer:
Statement 1: The first link in the human evolutionary series is Astralopethecus
Statement 2: Fossils of Sahel anthropus tchadensis have been excavated from Germany
(a) Statement 1 and 2 are correct
(b) Statement 1 and 2 are wrong
(c) Statement 1 is correct, statement 2 is wrong
(d) Statement 1 is wrong, statement 2 is correct
Answer:
(b) Statement 1 and 2 are wrong

Question 15.
Identify and complete the word pair. Also write the relationship between this word pair. Contemporaries of modern man: Homo neanderthalensis :: Modern man: __________
Answer:
Homo sapiens. Organisms and their characteristics on the path of human evolution

Question 16.
The sequence of some organisms in the order of evolution is given. Find the missing links.

Answer:
A – Orangutan, B – Chimpanzee

Question 17.
Choose the correct answer.
Statement 1: Myelin sheath in the nerves is produced by oligodendrocytes.
Statement 2: Ependymal cells plays an important role in the formation of cerebrospinal fluid.
(a) Statement 1 and 2 are correct
(b) Statement 1 and 2 are wrong
(c) Statement 1 is correct, Statement 2 is wrong
(d) Statement 1 is wrong, Statement 2 is correct
Answer:
(d) Statement 1 is wrong, Statement 2 is correct

Question 18.
Complete the following statement:
The tip of the dendrites which contains receptors for receiving neurotransmitters is the ____________
Answer:
Post Synaptic membrane

Question 19.
A person could not walk easily after drinking alcoholic beverage. Can you say why?
Answer:
Alcohol affects the normal functioning of his cerebellum which maintains the equilibrium of the body through muscular coordination and hence he could not walk easily.

Question 20.
After a road accident, a person lost his memory for a few days. Which part of his brain got injured?
Answer:
Cerebrum

Question 21.
Rajesh is taking his food watching blood cold scenes of a film on TV. Will this affect his digestion? Make inferences in connection with his sympathetic and parasympathetic system.
Answer:
When excitement occurs, sympathetic nervous system enhances the physiological activities except the activities related to the digestion. Parasympathetic system should work during digestion. Since sympathetic system worked in Rajesh, it will affect his digestion and related activities.

Question 22.
Find out the relationship between the pair of words and fill up the blanks.
Relay of impulses : Thalamus
_________ : Hypothalamus
Answer:
Maintenance of homeostasis

Question 23.
Find out the odd one and identify the common features of others: Dendrite, Acetylcholine, Axon, Synaptic knob.
Answer:
Acetylcholine, others are parts of the neuron

Question 24.
Find out the word pair relation and fill in the blanks:
Cerebellum : Equilibrium
___________ : Functions as the relay station of impulses.
Answer:
Thalamus

Question 25.
Find the odd one out. Justify your answer.
a) Blinking of eyes in intense light.
b) Withdrawal of hands on touching an hot object
c) Withdrawal of legs when in contact with thorns.
Answer:
a) Blinking of eyes in intense light which is an example of cerebral reflex. Others are examples of spinal reflexes.

Question 26.
The illustration of a nerve based on its function is given below:

(a) Identify the nerve depicted in the illustration.
(b) Identify the nerve that carries impulses to and from A and B
Answer:
(a) Sensory nerve
(b) Mixed nerve

Question 27.
Observe the image given below and answer the following questions:

(a) What does this image indicate?
(b) What do the parts A and B represent?
Answer:
(a) Spinal cord
(b) A – Dorsal root, B – Ventral root

Question 28.
Complete the following table:

Organ/Part	Sympathetic system	Parasympathetic system
Adrenal gland	________(a)_______	________(b)_______
Urinary bladder	_________(c)________	_________(d)________

Answer:
(a) Increases hormone production
(b) No direct influence
(c) Retains urine
(d) Empties urine

Question 29.
Suppose that the formation of cerebrospinal fluid ceases in the meninges, what would be the after effect of this?
Answer:
CSF provides nutrition and oxygen to brain tissues, regulates the pressure inside the brain and also protects the brain from injuries.

Question 30.
Any mild injury to the medulla oblongata may lead to sudden death. Why?
Answer:
Medulla oblongata controls involuntary actions like heart beat and breathing. Any mild injury to the medulla oblongata may result in the dysfunctioning of breathing and heart beat and may lead to death.

Question 31.
Find out the odd one. Write down the common feature of others: Intelligence, Hearing, Breathing, imagination.
Answer:
Breathing, all others are being controlled by the cerebrum

Question 32.
Redraw the given diagram and answer the following questions:

(a) Identify a, b and c in the given diagram.
(b) What is the function of myelin sheath?
Answer:
(a) a – Synaptic knob, b – Axon, c – Dendron.

(b) The functions of myelin sheath are to increase the speed of transmission of messages, by acting as an insulator, to provide nourishment to the neuron and to protect the axon from external injuries.

Question 33.
Appu was taken by fear, on seeing a snake on his way back to school and then ran back.
(a) Which part of the autonomous nervous system controls the body activities of Appu in the above situation?
(b) What are the changes that takes place in the intestine and eye during the above situation?
Answer:
(a) Sympathetic nervous system
(b) Peristalsis slows down in the intestine and the pupil in the eye dilates

Question 34.
A synapse is only the junction between two neurons. Do you agree with this statement? Why?
Answer:
1 do not agree with this statement because synapse is also the junction between two neurons, between a neuron and a muscle cell and also between a neuron and a glandular cell.

Question 35.
One of the components of the nervous system is illustrated below. Fill in the blanks appropriately.

Answer:
A – Cranial nerves, B – 31 pairs, C – Autonomous nervous system, D – Sympathetic system

Question 36.
The illustration given below indicates the transmission of impulses from one neuron to another. Observe the illustration and answer the following question.

(a) Identify the part in the illustration.
(b) Identify the chemical substance which is secreted from A. Give one example for this chemical substance.
Answer:
(a) Synapse
(b) Neurotransmitters. Acetylcholine/dopamine/ serotonin/endorphin

Question 37.
Identify the correct statements from those given below:
(a) The central nervous system consists of the brain and the spinal cord.
(b) The peripheral nervous system consists of 31 pairs of cranial nerves and 12 pairs of spinal nerves.
(c) The sympathetic system and the parasympathetic system are parts of the central nervous system.
(d) The autonomous nervous system which is a part of the peripheral nervous system helps to overcome the emergency situations.
Answer:
Correct statements are (a) and (d)

Question 38.
Balu: In the spinal cord and the cerebrum, white matter is seen outside, and grey matter is seen inside.
Ramu: In the cerebrum, the grey matter is seen outside, and the white matter is seen inside, But in the spinal cord, the white matter is seen outside, and the grey matter is seen inside.
In the group discussion related to the nervous system, Balu and Ramu said so.
(a) Whose opinion do you agree with?
(b) Explain white matter and grey matter.
Answer:
(a) Ramu’s opinion

(b) In the brain and the spinal cord, the part where myelinated neurons with are more abundant is called the white matter and the part where the cell bodies and parts of the neurons without a myelin sheath are seen is called the grey matter.

Question 39.
Some of the activities of the autonomous nervous system are given below. Analyse the activities and tabulate them under appropriate headings.
(a) Saliva production increases
(b) Retains urine
(c) Increases hormone production
(d) Stimulates the process of digestion
(e) Decreases heartbeat
(f) Pupil of the eye dilates

Sympathetic system	Parasympathetic system

Answer:

• Sympathetic system – (b), (c) and (f)
• Parasympathetic system – (a), (d) and (e)

Question 40.
Compare the nervous systems of Hydra, Planaria and Insects
Answer:
In hydra, a neural network with no control center is seen. In Planaria, a pair of nerve ganglia in the head region coordinates the instmetions. In insects, the neurons in the head region unite to evolve into a clear and somewhat developed brain. The ganglia of paired nerve fibers emerging from this are seen in each segment.

Question 41.
Radha is running away with fear from a snake.
(a) State what happens to the functioning of the following organs? Heart, Pupil, Trachea and Liver.
(b) Which nervous system is activated during such emergency situations?
Answer:
(a) Rate of the heartbeat increases. Pupil of the eye dilates, Trachea dilates, Glycogen is converted into glucose.
(b) Sympathetic nervous system.

Question 42.
Hypothalamus has an important role in maintaining homeostasis. Analyse this statement and note down the ideas to justify your views.
Answer:
Hypothalamus, produces certain neurosecretory honnones which influence the production of various stimulating hormones secreted by the pituitary gland. These hormones in turn stimulate the production of hormones of certain other important endocrine glands. Pituitary glands stimulate other glands to produce the hormones only according to the need of the body. So, hypothalamus indirectly helps in maintaining homeostasis.

• Changes in the internal environment affects the rhythm of life activities.
• Secretion of hormones is increased or decreased according to the changes.
• Life activities are regularised this way.
• Thus, hypothalamus prepares the body to overcome different situations and maintain a normal balance.

Question 43.
All reflex actions take place under the control of the spinal cord. Evaluate the statement and justify with suitable examples.
Answer:
All reflex actions are not under the control of the spinal cord. Some reflex actions are under the control of the cerebrum. These reflexes are known as cerebral reflexes. E.g., We blink our eyes when light suddenly falls on our eyes.

Question 44.
The flow chart given below indicates the transmission of impulse from one neuron to another. Complete the flow chart using the data given in the box.

Answer:
A. Dendron, B. Cell body, C. Axon, D – Axonite, E – Synaptic knob, F – Neurotransmitter

Question 45.
Analyse the illustration of impulse transmission through axon and answer the following questions.

(a) What are the changes that take place in illustration B when compared to A? Give reason for this change.
(b) Explain how this change brings about the transmission of impulses through axon.
Answer:
(a) When stimulated, ionic equilibrium in the particular part changes, and the outer surface of the plasma membrane of axon becomes negatively charged while the inner surface becomes positively charged.

(b) These changes generate impulses. The momentary charge difference in the axon stimulates its adjacent parts. Similar charges occur there also and impulses get transmitted through the axon.

Question 46.
Complete the following illustration:

Answer:
A – Central canal, B – Sensory impulses, C – Ventral root

Question 47.

(a) How are these responses known as?
(b) Prepare a flow chart related to the pathway of impulses mentioned in A?
Answer:
(a) Reflex actions
(b) Receptor generates impulses → Sensory neuron → Intemeuron → Motor neuron → Related muscles

Question 48.
Select the suitable code from the indicators and write them on the basis of correct features in the given statements
Cerebrum – CRB, Cerebellum – CRL, Medulla oblongata – MOG, Hypothalamus – HYP, Thalamus – THL
Answer:
(a) It plays an important role in problem solving, planning and voluntary movements – CRB
(b) Helps to maintain equilibrium of the body by coordinating muscular activities – CRL
(c) Helps in maintaining homeostasis by regulating body temperature, hunger, thirst and emotions – HYP
(d) Controls involuntary activities like heartbeat, ventilation, vomiting, cough, sneezing etc. – MOG
(e) Acts as the relay station of messages to and from the cerebrum – THL
(f) Centre of memory, intelligence, thinking and imagination – CRB
(g) The second largest part of the brain – CRL
(h) Pain killers act on this part of the brain – THL

Question 49.
Tabulate the following activities based on the type of nervous system that controls and give proper headings.
(a) Recognizes smell of flower
(b) Taking decisions at the emergency situations.
(c) Rate of heartbeat increases at times of crisis
(d) Production of hormone decreases after overcoming the crisis
Answer:
(a) Central nervous system
(b) Autonomous nervous system
(c) Sympathetic nervous system
(d) Parasympathetic nervous system

Question 50.
Redraw the picture and answer the following questions:

(a) Identify and label the parts according to the functions given below:
A. The part which maintains balance and equilibrium of the body.
B. The part which controls heartbeat.
C. The part which controls voluntary activities.
(b) Write one more function for each of these three identified parts.
Answer:
(a) Redrawing figure
A. Cerebellum
B. Medulla oblongata
C. Cerebrum

(b) Cerebellum – Coordinating muscular activities,
Medulla oblongata – Controls breathing,
Cerebrum – Centre of intelligence.

Question 51.
Draw the diagram and label the following parts:
(a) The part which secretes acetylcholine.
(b) The part which receives impulses from the adjacent neuron.
(c) The part which carries impulses from the cell body to outside.
Answer:

(a) Synaptic knob
(b) Dendrite
(c) Axon

Question 52.
Draw the diagram and label the following parts:

(a) The part that helps in the maintenance of homeostasis.
(b) That which acts as relay station of impulses to and from the cerebrum.
(c) The second largest part of the brain.
Answer:

(a) Hypothalamus
(b) Thalamus
(c) Cerebellum

Question 53.
Observe the illustration and answer the questions:

(a) Which action does the illustration depict?
(b) Identify A, B and C.
Answer:
(a) Reflex action
(b) A – Sensory nerve, B – Motor nerve, C – Interneuron

Question 54.
What laid the foundation for the science of evolution?
Answer:
Organisms adapt to or survive changes in their environment. Many such processes are involved in the formation of the biodiversity we see today from the primitive cell. Investigations into such processes laid the foundation for the science of evolution. Many scientists have been able to explain them in the form of theories.

Question 55.
Explain Lamarckism.
Answer:
Giraffes used to have short necks that ate food from the ground. Due to the scarcity of food, giraffes’ necks lengthened as a result of stretching their necks to reach leaves from higher branches. Acquired traits are passed down through generations, resulting in giraffes with longer necks.

Question 56.
How was Lamarckism proven wrong?
Answer:
Later scientists proved that acquired characters do not impart change in the genetic structure of organisms and therefore, are not inherited.

Question 57.
What was the Malthusian view of Charles Robert Darwin?
Answer:
English economist and demographer Thomas Malthus argued that when the human population increased rapidly, food production would not increase in line with it, leading to problems such as poverty, disease, and war. Malthus’s views also influenced Darwin.

Question 58.
How did Charles Robert Darwin’s theory of evolution gain acceptance?
Answer:
As Darwin continued his studies, in 1858, the evolutionary studies of British naturalist Alfred Russell Wallace also came to attention. Darwin and Wallace’s papers were presented at a scientific conference. In 1859, Darwin expanded and refined his ideas through the book ‘On the Origin of Species’. Initially, his observations were opposed by the society of the time, but as more evidence emerged, Darwin’s theory of evolution gained widespread acceptance.

Question 59.
What are the applications of the theory of evolution by Darwin?
Answer:
Darwin’s theory of evolution is one of the scientific ideas that has influenced the world. This theory has applications in fields such as medicine, agriculture, and ecology beyond biology.

Question 60.
What influenced Charles Darwin to formulate the idea of evolution?
Answer:
Charles Darwin was influenced by the diversity of the beaks of the finches on the Galapagos Islands.

Question 61.
Explain the features of Darwin’s theory of evolution.
Answer:

• The foundation of modern evolutionary theories is the theory of natural selection, or Darwinism, formulated by the English naturalist Charles Darwin.
• Charles Darwin was born on 12 February 1809, at Shrewsbury, England, into a family of well educated background.
• In 1831, at the age of 22, he embarked on a 5-year voyage on the ship HMS Beagle for cartographical purposes. During this voyage, Darwin explored areas including South America, Australia, and the Galapagos Islands.
• Returning to England in 1836, Darwin analysed the specimens and observations he had made and deeply studied them by correspondence with other scientists through letters.
• Thomas Malthus, an English economist and demographer, argued that when the human population grows rapidly, food production will not increase in accordance with that, and it may lead to problems such as poverty, disease, and war. This perspective of Malthus had greatly influenced Darwin-, too.
• While Darwin continued with his studies in 1858, he noticed the evolutionary studies of the British naturalist Alfred Russell Wallace.
• The papers of Darwin and Wallace were presented at a science conference.
• In 1859, he elaborated and presented his ideas in the book ‘On the Origin of Species’.
• Although his observations were initially opposed by society, as more and more evidence emerged, Darwin’s theory of evolution gained widespread acceptance.
• Darwin’s theory of evolution is a key scientific idea used in medicine, agriculture, and environmental science, apart from biology.
• Charles Darwin was influenced to formulate the theory of evolution by observing the diversity in the beaks of finches at the Galapagos Islands.

Question 62.
A plant produces hundreds of seeds. However, only a few among them attain complete maturity. What would be the circumstances that might lead a new plant species to evolve from this plant after millions of years?
Answer:

• Overproduction – The plant produces more seeds than the environment can support. Most of them fail to grow due to limited resources.
• Variations – Among the seeds that sprout, there are differences in traits like size, immunity, and seed production. Some variations are favourable, while others are not.
• Struggle for Existence – Because of limited food, space, and other resources, the seedlings compete with each other for survival.
• Survival of the Fittest – Only those plants with favourable variations, like better adaptability, survive and grow to maturity. They are able to reproduce more effectively.
• Natural Selection – Favourable traits get passed on to the next generation. Over a long period of time, more variations accumulate, and new plants with different traits may emerge. Eventually, this leads to the evolution of a new species.

Question 63.
Differentiate between Lamarckism and Darwinism
Answer:

	Lamarckism	Darwinism
Proposed by	Jean Baptiste Lamarck	Charles Darwin
Key idea	Inheritance of acquired characters	Natural selection of favourable variations
How changes occur	Due to the use and disuse of organs	Due to natural variations in a population
Example used	Giraffes of earlier periods possessed short necks. Giraffes began to stretch their neck to obtain food. By continuous use, giraffes with longer necks emerged.	Giraffes with necks of varying length. Only the giraffes with longer necks survived in the competition for food. Only the giraffes with longer necks survived and became a new species.
Role of environment	The environment causes variations in organisms	The environment selects the favourable variations in organisms.
Scientific validity	Not supported by modem genetics	Supported by modem genetics and evolution theory

Question 64.
Write a note on Neo Darwinism.
Answer:
Darwin’s theory of evolution has also been criticised because Charles Darwin did not understand the genetic basis of variation and inheritance. However, with the discoveries of Gregor Mendel and the understanding of chromosomes and genes, it was recognized that the changes that cause evolution are due to genetic mutations, genetic recombination during sexual reproduction, and gene flow. With the addition of evidence and further studies from fields such as population genetics, palaeontology, and ecology to Darwinism, Neo-Darwinism became more rational than it had been criticised.

Question 65.
How does the process of speciation takes place?
Answer:
Members of a species can reproduce and produce offspring that are different, but they remain a single species. If members of a species are separated from each other by environmental factors or other factors, many variations can accumulate over time. When members of a species are no longer able to reproduce and produce fertile offspring, they evolve into different species.

Question 66.
What are fossils?
Answer:
Fossils are the remains or traces of ancient organisms.

Question 67.
How does fossils helps us to understand the evolution of life?
Answer:
Fossils can help.us to understand the evolution of life in the following ways:

• Organic evolution is a gradual process. E.g., the ancestors of horses had shorter legs than the ones in out times.
• Fossils which are connecting links reveal the evolutionary relationship between organisms. E.g., Archaeopteryx that possess the characteristic features of both reptiles and birds.
• It is proven that many species have become extinct that were living on Earth in the past. E.g., Dinosaurs, Mammoths.

Question 68.
Name the connecting link between reptiles and birds.
Answer:
Archaeopteryx

Question 69.
What are the common features of primates?
Answer:
The common ancestors of mammals such as monkeys, apes and humans belonged to the group of primates. The common characteristics of primates are: a thumb that can be opposed to the other fingers, binocular vision, a large and developed brain, flat claws instead of sharp ones, and flexible limbs and joints.

Question 70.
Did humans evolve from monkeys? Find out.
Answer:
No, humans did not evolve from monkeys. Monkeys belong to the category of Cercopithecoidea and the features of this category include having a small sized brain and a tail is also present. Humans belong to the category of Hominoidea where they have large sized brain and tail is also absent.

Question 71.
What is the evolutionary trend in the development of human cranial capacity?
Answer:
The first link in human evolution, Sahclanthropus tchadensis, had a small-sized brain. By the time Homo sapiens were evolved, the size of the brain had nearly tripled. There is a gradual increase in size from early hominid ancestors to modem humans.

Question 72.
What influence does brain development have on human evolution?
Answer:
One of the main trends in human evolution over the past three to four million years has been an increase in brain capacity. Over a period of two million years, the brain’s size almost tripled. This made it possible to utilise language, create tools, engage in complicated social activity, and carry out higher-order cognitive processes. The expansion of human brain capacity has also aided in the development of culture, the application of cutting-edge technologies, and adaptation to shifting environmental conditions. The evolution of the brain prepared the way for the evolution of Homo sapiens from “small-brained” ancestors.

Question 73.
Write a short note on neurons.
Answer:
Neurons, also known as nerve cells, are the basic building blocks of the nervous system. They are specialised cells which are capable of receiving stimuli from the surroundings and to form suitable messages.

Question 74.
Prepare a brief description on the structure of neuron with a neat labelled diagram
Answer:
Neurons are the structural and functional unit of the nervous system. It consists of the following parts: cell body or cyton, Dendron, dendrite, axon, axonite and synaptic knob.

Cell body or cyton is the centre of the neuron where cell membrane, cytoplasm, nucleus and cell organelles are present. Dendrons are the fine fibres which arises from the cell body. Dendrites are the branches of dendrons. The messages received by the dendrites from adjacent neurons are transmitted to cyton through the dendrons. Axon is the longest fibre from the cell body. Axonites are the branches of axons. The impulses from the cell body reaches the axonites through axons. Synaptic knob are the knob-like structures seen at the tip of the axonite which contains the neurotransmitter which helps to transfer chemical messages to its adjacent neuron.

Question 75.
Illustrate a flow chart, showing the path of messages through the neuron.
Answer:

Question 76.
What are neurotransmitters? What is its function? Give examples for neurotransmitters.
Answer:
Neurotransmitters are chemical substances which are secreted by the synaptic knob. They help to transfer chemical messages from one neuron to its adjacent neuron. Examples: Acetylcholine, Dopamine, Serotonin, Endorphin, Histamine, Glycine.

Question 77.
What are neuroglial cells? List down the different types of neuroglial cells.
Answer:
Neuroglial cells are those cells that make up more than half of the brain and spinal cord. Neuroglial cells have the ability to divide but cannot receive stimuli or transmit messages. The different types of neuroglial cells include ependymal cells, oligodendrocytes, microglial cells, schwann cells and astrocytes.

Question 78.
Explain the functions of different types of neuroglial cells
Answer:
The functions of different types of neuroglial cells are as follows:

• Astrocytes: Provides nourishment to the neurons.
• Microglial cells: It helps in immunity
• Oligodendrocytes: It helps in the formation of the myelin sheath in the central nervous system
• Schwann cells: Helps in the formation of myelin sheath in nerves.
• Ependymal cells: Helps in the production of cerebrospinal fluid.

Question 79.
What is myelin sheath, and what are its functions?
Answer:
Axons of some neurons are covered by a layer known as myelin sheath. It is made up of a shiny white fat called myelin.

The major functions of myelin sheath are as follows:

• Increase the speed of transmission of messages
• It acts as an insulator
• It provides nourishment to the neuron
• It protects the axon from the external injuries.

Question 80.
Differentiate between oligodendrocytes and Schwann cells.
Answer:
Myelin sheath in the brain and spinal cord is produced by specialised cells called oligodendrocytes whereas the myelin sheath in the nerves is produced by Schwann cells.

Question 81.
What are the different parts of the nervous system?
Answer:
The nervous system is divided into two: central nervous system and peripheral nervous system. The central nervous system includes the brain and spinal cord. The peripheral nervous system includes 12 pairs of cranial nerves and 31 pairs of spinal nerves which connect central nervous system to the organs. It also includes receptors and nerve ganglia.

Question 82.
List down the functions of cerebrospinal fluid in the central nervous system.
Answer:
Cerebrospinal fluid performs the following functions in the central nervous system:

• Provides oxygen and nutrients to the tissues.
• Eliminates wastes
• Helps to regulate the pressure
• Protects from external injuries.

Question 83.
Briefly explain the peculiarities and functions of the different parts of the brain.
Answer:

• The brain and spinal cord is covered by the three-layered membrane known as the meninges.
• Cerebrospinal fluid is the fluid which is filled in between the inner membranes of the meninges, in the cavities of the brain and in the central canal of the spinal cord.
• Ependymal cells play an important role in the formation of cerebrospinal fluid.
• The functions of cerebrospinal fluid in the central nervous system are as follows:
  • Provides oxygen and nutrients to the tissues of the brain.
  • Eliminates wastes
  • Regulates the pressure
  • Protects from external injuries
• The various parts of the brain include Cerebrum, Cerebellum, Thalamus, Hypothalamus, Brain Stem (Mic brain, Pons, Medulla oblongata).
• Cerebrum:
  • It is the largest part of the brain.
  • Outer part is called the cortex because grey matter is seen, and the inner part is called the medulla because white matter is seen.
  • It plays an important role in problem solving, planning and voluntary movements.
  • It is also the centre of memory, intelligence, thinking and imagination.
  • It also provides various sensory experiences.
• Cerebellum:
  • It is the second largest part of the brain.
  • It is located behind and below the cerebrum.
  • It helps to maintain equilibrium of the body by coordinating muscular activities.
• Thalamus:
  • It is seen in the inner part of the brain.
  • It acts as a relay station of messages to and from the cerebrum.
  • Pain killers act on this part of the brain.
• Hypothalamus: It helps in maintaining homeostasis by regulating body temperature, thirst and emotions.
• Midbrain:
  • It is the centre of initial assessment of messages regarding vision and hearing.
  • It also has a role in the movement of eyes and eyebrows.
• Pons:
  • It coordinates the muscular activities of the eye and the face,
  • It regulates the rate of ventilation.
• Medulla oblongata: It controls involuntary activities like heartbeat, ventilation, vomiting, cough, sneezing, etc.

Question 84.
How do smoking, consumption of alcohol and drug abuse affect the health of the brain? Find out.
Answer:
• Smoking: Cigarette contains nicotine, which is addictive. Nicotine changes the way the brain sends the messages which affects the memory, attention span and learning process. Long term smoking reduces oxygen supply to the brain thereby increasing the risk of stroke. It is also associated with a higher risk of dementia, including Alzheimer’s disease.

• Alcohol consumption: Alcohol slows down brain function. Alcohol consumption affects decision-making, coordination and balance, memory and concentration. Excessive drinking can damage brain cells and lead to permanent memory loss and mental confusion.

• Drug abuse: Drugs like heroin, cocaine and marijuana releases large amounts of dopamine which leads to a loss of natural control over emotions and behaviour. This eventually leads to mental health problems like anxiety and depression.

Question 85.
Briefly describe the structure and function of spinal cord.
Answer:
Spinal cord

• Spinal cord is a part of the central nervous system which is the continuation of medulla oblongata.
• Spinal cord transmits messages from different parts of the body to the brain and transmits instructions from brain to the different parts of the body.

 

 

• In the spinal cord, grey matter is seen inside, and white matter is seen outside.
• The part of the spinal cord which is filled with cerebrospinal fluid is called the central canal.
• Dorsal root: It transmits messages from different parts of the body to the spinal cord.
• Ventral root: It transmits instructions from spinal cord to different parts of the body.

Question 86.
How is the transmission of nerve impulses possible?
Answer:

• The messages which are transmitted through the neurons are called nerve impulses.
• All cells, including neurons have an electric charge. The inner side of the cell membrane has a negative charge, compared to their outer side. When stimulated, positive ions from outside the cell membrane enter the cell, causing a temporary charge variation in that region.
• For a nerve impulse to be transmitted from one body part to the other, it needs to travel through different neurons.
• Synapse is the part where an impulse is transferred from one neuron to another neuron.

• Synaptic knob: It is the tip of the axon which contains vesicles that is filled with neurotransmitters.
• Synaptic cleft: It is the small gap between neurons.
• Post – synaptic membrane: It is the tip of the dendrites which contains receptors for receiving the neurotransmitters.
• The synaptic knob secretes neurotransmitters to the synaptic left when the impulses reach there, and these neurotransmitters bind with the receptors of the post synaptic membranes and stimulates the neuron.
• The function of synapse is to transmit the impulse to only one direction and to increase the speed of impulses.

Question 87.
What do you mean by the term ‘synapse’ and briefly describe the different parts of the synapse along with its functions.
Answer:
A nerve impulse gets transmitted from one part of the body to another by travelling through different neurons. The part where an impulse is transferred from one neuron to another is called a synapse.

• Synaptic knob is the tip of the axon which contains vesicles filled with neurotransmitters.
• The synaptic cleft is the small gap present between neurons.
• Post-synaptic membrane is the tip of the dendrites, which contains receptors for receiving neurotransmitters.

Question 88.
Are synapses found anywhere else other than the junctions neurons meet? Find out.
Answer:
Synapses can be seen between two neurons, which is the most common type of synapse. Other places where synapses are found: It is found between a neuron and a muscle cell, which is called as neuromuscular junction. It is also seen between a neuron and a gland cell, and this is how the nervous system communicates with the glands.

Question 89.
Are there any organisms with brain size larger than those of humans? Find out.
Answer:
Yes. The human brain weighs about 1.3 to 1.4 kilograms. The heaviest brain on Earth is that of the sperm whale, which weighs about 7 to 9 kilograms. The elephant’s brain weighs 4.5 to 5.5 kilograms; the dolphin’s brain weighs 1.5 to 1.7 kilograms. Even though some animals have larger brains, it does not mean that they are more intelligent than humans.

Question 90.
Describe the different types of neurons. And their functions.
Answer:
There are mainly three types of neurons: Sensory neurons, Motor neurons and Intemeurons.

• Sensory neurons: It carries impulses from different parts of the body to the brain and spinal cord.
• Motor neurons: The messages from the brain and spinal cord are transmitted to different parts of the body.
• Interneurons: It is the neuron that connects both sensory neurons and motor neurons. It generates quick responses according to the sensory impulses.

Question 91.
Prepare a brief note on autonomous nervous system.
Answer:
Autonomous nervous system is a part of the peripheral nervous system that regulates the body activities by itself. It can be divided into two: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system equips the body to respond during emergency situations, whereas the parasympathetic nervous system prepares the body to relax and perform routine functions such as digestion. It also helps to regulate various physiological activities that take place beyond our consciousness.

Question 92.
Which are the different types of reflexes? Describe them with an example.
Answer:
The main types of reflexes are as follows:

• Spinal reflexes: They are a type of reflex action that is controlled by the spinal cord. Example: We pull back our hand when we touch something hot or sharp, the knee-jerk reflex is also an example of spinal reflex.
• Cerebral reflexes: They are a type of reflex action that is controlled by the brain. Examples: Blinking of eyes when light falls on it. Coughing is an example of a cerebral reflex.

Question 93.
What are the precautions and habits to be followed for the protection of the nervous system?
Answer:
PRECAUTIONS AND HABITS TO BE FOLLOWED FOR THE PROTECTION OF THE NERVOUS SYSTEM

• Use a helmet, seat belt, etc. while riding a motor bike/driving.
• Take necessary precautions while playing.
• Taking bath in stagnant water may cause infections. Therefore, avoid such situations.
• Those who engaged in jobs with the risk of brain injuries must use safety equipment such as helmets and safety belts.
• Avoid habits such as smoking, alcohol consumption and drug abuse. Do exercises.
• Lack of adequate sleep can affect brain function, which leads to memory loss, anxiety, difficulty in learning and hinders emotional development. Therefore, it is essential to sleep for at least 8-10 hours a day.

Question 94.
Prepare a short description about the nervous system in different organisms.
Answer:
The structure of the nervous system differs according to the complexity of organisms.

• Evolution is the prolonged process by which simple, unicellular organisms give rise to complex, multicellular ones.
• A notable transition from simple nervous structures to extremely complex nervous systems is also provided by evolution.
• The nervous system’s evolution is what allows organisms to adapt to and survive in a variety of environments.
• Human dominance over nature was made possible by the development of a complex brain, which also allowed for special advancements in cognition and technology.
• Humans differ from other organisms due to the presence of a neocortex that was developed over a long period of evolution and the resulting higher mental processes of language, intelligence, and creativity.
• Human sense organs do not have the same proficiency compared to other organisms, despite having a more developed brain and this can only be evaluated only when the relation between sense organs and the brain is analysed. Sensations provided together by the sense organs and brain are also to be understood.

Question 95.
How do changes in the nervous system support the process of evolution?
Answer:
Evolution is a long-term process that has seen the emergence of complex multicellular organisms from simple single-celled organisms. Evolution also provides a remarkable transition from simple nervous structures to highly complex nervous systems. This evolution of the nervous system has led to the adaptation of organisms to diverse environments and their survival. Complex brain development has played a crucial role in establishing human dominance in nature and enabling unparalleled cognitive and technological progress. The presence of the neocortex, which has developed through long-term evolution, and the higher mental functions such as language, intelligence, and creativity that are possible through it, make humans different from other animals.