Class-8 General Science Notes (By Gaba Books)- Unit-3 - CONTROL AND COORDINATION - SLO-Based Short and Brief Questions and Answers

Class-8 General Science Notes
(By Gaba Books)
Unit-3 - CONTROL AND COORDINATION
SLO-Based Short and Brief Questions and Answers

Q. What is coordination in living organisms?

Ans.

The working together of the different systems of an organism in order to produce an appropriate reaction to stimuli is coordination in living organisms.

Q. What is a stimulus called? or define stimulus.

Ans.  A situation that makes an organism react is known as a stimulus (plural: stimuli). 

Q. What is a response called? or define a response.

Ans.

The reaction of the organism to the situation is called a response. 

Q. What types of stimuli are? or write and explain the types of stimuli.

Ans. 

Stimuli are of two types

1. external Stimuli 

2. internal Stimuli 

1. external Stimuli 

External stimulus is provided by environmental factors, such as heat, cold, water, wind, or other animals. 

For example, 

1. if the weather is very hot, it acts as an external stimulus for organisms to protect them from the heat. It could be due to other organisms also. 

2. The sight of a dragonfly provides a stimulus to a frog. Its response is to catch the dragonfly and eat it. The response of the dragonfly will be to try to fly away to protect itself.

2. internal Stimuli 

Internal stimulus arises from within the organism. For example, excess secretion of hormones or enzymes and abnormal functioning of some organs of the body provide internal stimulus.

Q. What types of responses are? or write and explain the types of responses. 

Types of responses

There are two main ways in which an organism responds to an external stimulus. 

1. Reflex or involuntary response:

This response is spontaneous and is done without thinking.

For example, if one accidentally touches a hot object, the first response is the quick withdrawal of the hand. 

2. Modified response:

This response is voluntary and done with thinking

After accidentally touching a hot object, as 2nd response one will examine the hand to see how badly it is burnt and take remedial action like putting it in cold water and applying a medicine. This is called the modified response.

Q. What is a conditioned response?

Ans. It is a behaviour that does not come naturally but must be learned by the individual by pairing a neutral stimulus with a potent stimulus-response is known as a conditioned response.

For Example: The associated activities of the pet animal e.g when the bell was rung or producing some other voice on which their mouth began to watering, even though no food was present. 

Q. Which plant folds its leaflets upon touching?

Ans.

The Kachnar plants fold their leaflets in the evening and open up in the morning.

Q. Which organ systems are responsible for coordination in human beings? 

Ans.

Two systems in the human body carry out this job of coordination, the nervous system and the endocrine system. These systems work very closely with each other.

Q. What is the nervous system in human beings? Explain briefly.

Ans.

THE NERVOUS SYSTEM: The nervous system can be thought of as the body's communication system.

The following are the features of the nervous system:

• It receives information from the environment and from various parts of the body. 
• It records this information and sends messages to different parts of the body, instructing them to perform certain functions. This develops response. 
• The central nervous system consists of brain and spinal cord.
• The peripheral nervous system consists of nerves which link the central nervous. 

The nervous system is made up of nerve cells known as neurons. They are the smallest structural and functional units of the nervous system. 

• Each nerve cell consists of the cell body or cyton. 
• Finger-like extensions arising from the cell body are called dendrites.
• A long tube-like part is called the axon enveloped in a sheath called myelin sheath.

Q. What are the longest cells found in the human body?

Ans.

Neurons are the longest cells in the human body. They are up to a few centimeters long. Neurons join together to form nerves. The human being is made up of about 100 billion neurons.

Q. Briefly explain the brain and its parts. 

Ans.

It is a very complex and delicate organ. It is protected by the bony skull. It has three main parts- the cerebrum, the cerebellum and the medulla oblongata (or brainstem). These different regions of the brain carry out different functions.

THE CEREBRUM: The cerebrum, the largest part of the brain, performs the following functions:

• It is the body's thinking and control centre.
• It receives messages from the sense organs and gives responses.
• It controls memory and learning.

THE CEREBELLUM: The cerebellum is situated towards the back of the brain, below the cerebrum. Its functions are as follows:

• It maintains the body's balance.
• It controls and coordinates the muscles to perform voluntary actions like walking, talking, and feeding.

THE MEDULLA OBLONGATA: The medulla oblongata forms the lower portion of the brain. It narrows down to join the spinal cord. It controls all involuntary actions, i.e. muscular actions that occur on their own, for example, the muscular activities of the internal organs such as the beating of the heart.

Q. What is the spinal cord? write its function.

Ans.

The spinal cord is a tube-like extension of the brain and forms the main link between the brain and the rest of the body. It also controls reflex actions. It is attached to the medulla oblongata and runs down the middle of the back. It is protected by the vertebrae of the backbone. 

Q. Define a motor or efferent nerves.

Ans.

The nerves that transmit messages from the brain to all parts of the body are known as motor or efferent nerves. 

Q. Define a sensory or afferent nerves. 

Ans.

The nerves that carry messages back to the brain are known as sensory or afferent nerves. 

Q. What are spinal nerves?

Ans. 

Nerves of spinal cord are called spinal nerves. 

Q. What are cranial nerves?

Ans. 

Nerves of brain are called cranial nerves. 

Q. What are receptors? How many receptors does human have?

Ans. 

The organs that received information about the environment is called receptors. 

Humans have five receptors referred to as sense organs-eyes, ears, nose, tongue and skin. 

Q. what are hormones?

Ans.

Hormones are chemicals that coordinate different functions in the human body by carrying messages through the blood to organs, skin, muscles, and other tissues.

Q. What is the endocrine system? Explain.

Ans.

The endocrine system consists of several glands which release substances called hormones into the blood. Hormones regulate many functions in the body. Each hormone is required in very small quantity and has its own specific function. Hormones control growth, development, behaviour and reproduction. Glands that produce hormones are located in various parts of the body. There are nine major endocrine glands in human body. Some of them are as follows:

• Adrenal glands secrete the hormone adrenalin when a person is angry or afraid. It prepares the body to fight or flight.
• Pancreas secretes the hormone insulin, which regulates the amount of sugar in the blood.

Q. What is the meaning of endocrine?

Ans. 

The name 'endocrine' means 'ductless'. This name is given to these glands because they release their hormones directly into blood without ducts or tubes.

Q. Do plants have nerve system? Explain how coordination takes place in plants?

Ans.

Plants do not have a nervous system, and coordination takes place only by means hormones. Therefore, it is called chemical coordination. For example, the branched trees grow in such a way that the form or the shape of the tree is maintained. 

Q. Define phytohormone.

Ans.

The hormones that take part in the coordination in growth called phytohormone.

Q. What is tropism?

Ans.

The response, which a plant makes to an external stimulus, such as light, gravity and water is known as tropism.

Q. What is phototropism?

Ans.

The behaviour of plants to grow towards light is called phototropism. The stem of a plant is positively phototropic, i.e. it grows towards light. The root is negatively phototropic, i.e. it moves away from light.

Q. How can you show that stem grows towards light?

Ans.

By placing a potted plant near an open window through which light is coming in. It is observed after a few days that the stem bends towards the window which means towards light. This movement occurs because of hormones called auxins. It is because of the concentration of auxin increases on the shaded side of the stem. This causes the cells to grow faster on the shaded side than on the lighted side. The unequal growth rate causes the stem to bend towards the light. This behaviour of plants to grow towards light is called phototropism. 

Q. What is geotropism?

Ans.

The growth of the stem in an upward direction, while the root grows in a downward direction is called geotropism. The root is positively geotropic, i.e. it grows towards gravity. Stem is negatively geotropic, i.e. it grows away from gravity.

Q. Why do plants donot move from place to place in search of food?

Ans.

We can see that animals move about mainly in search of food and shelter while plants do not have to go from place to place to procure it because they manufacture their own food.

Q. What is hydrotropism?

Ans.

The growth or turning of plant roots towards moisture is called hydrotropism. The root grows towards water, i.e. it is said to be positively hydrotropic.

Q. What is sleep movement?

Ans.

The movement of the leaves of plants like Oxalis or Clover open during the day and close at night. This type of movement is known as sleep movement.

Q. Describe the movement in animals briefly.

Ans.

Movement in animals is faster and of many different types. Animals possess two kinds movement-locomotion and movement of body parts. Locomotion in animals/help to find food and shelter, to shift from an unfavourable environment to a favourable environment, to escape from predators, to find mates for reproduction and to find suitable places for laying eggs or giving birth to babies and rearing their young ones. 

Short Questions on different organisms use different organs for locomotion:

Q. What is amoeboid motion?

Ans.

The slowly motion of Amoeba by extending one or more pseudopodia from its unicell body is known as amoeboid motion.

Q. What is ciliary motion?

Ans.

The swimming of Paramecium by using the organ cilia present in its body is known as ciliary motion.

Q. What is flagellar motion?

Ans.

Euglena has a long thread-like structure called a flagellum which it uses for movement. This is known as flagellar motion.

Q. What is muscular motion?

Ans.

Most animals use muscles or both muscles and bones for locomotion. This type of motion is known as muscular motion. 

Q. What are arthropods?

Ans.

The jointed legs of animals such as insects, crabs and spiders are known as arthropods. 

Q. Describe the movement of vertebrates (i.e. the animals with backbone) including humans?

Ans.

The vertebrates (i.e. the animals with backbone) including humans use muscles and bones for locomotion. Vertebrates have a hard skeleton inside their bodies called an endoskeleton. It is made up of bones. Vertebrates also have a well-developed muscular system. 

• The fish uses fins and tail muscles to swim. 
• The snake has no legs, yet it can move fast. It uses its scales and ribs to crawl. 
• Birds use wing muscles to flap their wings up and down to fly. 
• Humans use their limbs and muscles for locomotion.

Exercise Q/A

 

 

Answer these questions:

Q. Use an example to discuss the importance of coordination in the human body.

Ans.

The Human body has different organs and systems performing specific jobs. The coordination between these different organs and systems is very important to carry out different tasks. 

For example, when you run a race, your legs move faster. But the movement of the legs alone cannot keep you running You need extra energy to run. Your breathing rate must go up because you need more oxygen for oxidising food to generate energy. The heartbeat must go up as more blood needs to be pumped to take the extra oxygen and nutrients to the cells. The rate of sweat production must increase, so that the excess heat generated may be lost by evaporation of sweat. These different organs and systems work very closely with each other.

 

Q. Why is the nervous system regarded as the communication system of the body? What are the different parts of our brain? What functions does each perform?

Ans.

The nervous system can be thought of as the body's communication system due the following features:

• It receives information from the environment and from various parts of the body. 
• It records this information and sends messages to different parts of the body, instructing them to perform certain functions. This develops response. 

These different regions of the brain carry out different functions.

THE CEREBRUM:

• It is the body's thinking and control centre.
• It receives messages from the sense organs and gives responses.
• It controls memory and learning.

 

THE CEREBELLUM: 

• It maintains the body's balance.
• It controls and coordinates the muscles to perform voluntary actions like walking, talking, and feeding.

THE MEDULLA OBLONGATA: It controls all involuntary actions, i.e. muscular actions that occur on their own, for example, the muscular activities of the internal organs such as the beating of the heart.

 

Q. What is the main difference between the skin and other sense organs?

Ans.

The main difference between the skin and other sense organs is that the skin is the largest sense organ covering the entire body. Primarily skin is a protective barrier that protects against environmental hazards, such as bacteria, chemicals, and physical injuries. Secondly, it contains various receptors that respond to these stimuli, allowing us to feel sensations like heat, cold, texture, and pain. 

The other five sense organs are localized to specific areas and have specific senses: the eyes in the head for sight, the ears on the sides of the head for hearing and balance, the nose in the face for smell, and the tongue in the mouth for taste.

 

Q. What are hormones? Name some important plant and human hormones and their functions,

Ans.

Hormones are chemicals that coordinate different functions in the human body by carrying messages through the blood to organs, skin, muscles, and other tissues. Some important plant and human hormones and their functions are:

• Adrenal glands secrete the hormone adrenalin when a person is angry or afraid. It prepares the body to fight or flight.
• Pancreas secretes the hormone insulin, which regulates the amount of sugar in the blood.

Q. What do you know about phototropism and geotropism in plants?

Ans.

Phototropism: It is the behaviour of plants to grow towards light is called phototropism. The stem of a plant is positively phototropic, i.e. it grows towards light. The root is negatively phototropic, i.e. it moves away from light.

Geotropism: The growth of the stem in an upward direction, while the root grows in a downward direction is called geotropism. The root is positively geotropic, i.e. it grows towards gravity. Stem is negatively geotropic, i.e. it grows away from gravity.

 

Q. What is the difference between endoskeleton and exoskeleton? Also give examples.

Ans.

Endoskeleton: The vertebrates (i.e. the animals with a backbone) including humans use muscles and bones for locomotion. Vertebrates have a hard skeleton inside their bodies called an endoskeleton. It is made up of bones. Vertebrates also have a well-developed muscular system.

Exoskeleton: Animals such as insects, crabs, and spiders have jointed legs. They are known as arthropods. They have a hard and tough protective covering over their body, known as an exoskeleton. The body muscles are attached to the exoskeleton and enable movement at the joints. Flying insects such as mosquitoes and houseflies have wings to fly. Muscles attached to the exoskeleton control the movement of the wings.

 

Q. What are the movements in Amoeba, Paramecium and Euglena called?

Ans.

The slow motion of Amoeba by extending one or more pseudopodia from its unicell body is known as amoeboid motion.

The swimming of Paramecium by using the organ cilia present in its body is known as ciliary motion.

Euglena has a long thread-like structure called a flagellum which it uses for movement. This is known as flagellar motion.