The Bases of Human Behaviour NCERT Textbook PDF

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Chapter 3: The Bases of Human Behaviour

You must have observed that people differ with respect to their physical and psychological characteristics. The uniqueness of individuals results from the interaction of their genetic endowments and environmental demands.

In this world, there are millions of different species of organisms differing in a variety of ways.

Biologists believe that these species were not always like this; they have evolved to their present form from their pre-existing forms.

 It is estimated that the characteristics of modern human beings developed some 2,00,000 years ago as a result of their continuous interaction with the environment.

Evolution refers to gradual and orderly biological changes that result in a species from their pre-existing forms in response to the changing adaptational demands of their environment.

Physiological as well as behavioural changes that occur due to the evolutionary process are so slow that they become visible after hundreds of generations.

Evolution occurs through the process of natural selection. You know that members of each species vary greatly in their physical structure and behaviour.

The traits or characteristics that are associated with high rate of survival and reproduction of those species are the most likely ones to be passed on to the next generations.

When repeated generation after generation, natural selection leads to the evolution of new species that are more effectively adapted to their particular environment.

This is very similar to the selective breeding of horses or other animals these days. Breeders select the fittest and the fastest male and female horses from their stock, and promote them for selective breeding so that they can get the fittest horses.

Fitness is the ability of an organism to survive and contribute its genes to the next generation.

Three important features of modern human beings differentiate them from their ancestors: (i) a bigger and developed brain with increased capacity for cognitive behaviours like perception, memory, reasoning, problem-solving, and use of language for communication, (ii) ability to walk upright on two legs, and (iii) a free hand with a workable opposing thumb.

These features have been with us for several thousand years. Our behaviours are highly complex and more developed than those of other species because we have got a large and highly developed brain.

Human brain development is evidenced by two facts. Firstly, the weight of the brain is about 2.35 per cent of the total body weight, and it is the highest among all species (in elephant it is 0.2 per cent).

Secondly, the human cerebrum is more evolved than other parts of the brain. These evolutions have resulted due to the influence of environmental demands.

Some behaviours play an obvious role in evolution. For example, the ability to find food, avoid predators, and defend one’s young are the objectives related to the survival of the organisms as well as their species.

The biological and behavioural qualities, which are helpful in meeting these objectives, increase an organism’s ability to pass it on to the future generation through its genes.

The environmental demands lead to biological and behavioural changes over a long period of time.

AuthorNCERT
Language English
No. of Pages21
PDF Size0.8 MB
CategoryPsychology
Source/Creditsncert.nic.in

NCERT Solutions Class 11 Psychology Chapter 3 The Bases of Human Behaviour

Question 1. How does the evolutionary perspective explain the biological basis of behaviour?
Answer:

  • Evolution refers to gradual and orderly biological changes that result in a species from their pre-existing forms in response to their changing adaptation demands of their environment.
  • Physiological and biological changes that take place as a result of evolutionary processes are so slow that they become visible after hundreds of generations.

Three important features of modem human beings include:

  • A trigger and developed brain with increased capacity for cognitive behaviours (like perception, memory, thinking, reasoning, etc).
  • Ability to walk upright on two legs and
  • Free hands with a workable opposing thumb.

The environmental demands had to biological and behavioral changes over a long period of time. In the human brain, the earliest to the most recent structures in the process of evolution are: Limbic system, brain stem and cerebellum are the oldest; and cerebral cortex is the latest developed.

Question 2.Describe how neurons transmit information.
Answer:  Neuron is the basic unit of our nervous system. Neurons are specialized cells which convert various forms of stimuli into electrical impulses.

They receive information from sense organs or from adjacent neurons, carry them to the central nervous system and bring motor information from the central nervous system to motor organs.

Neurons transmit information with the help of dendrites, soma, axon and terminal buttons by converting stimuli into electrical impulses. This is done by the following method:  Dendrites —> soma —> axon —> terminal buttons

  • Dendrites receive the informing neural impulses from adjacent neurons or directly from sense organs.
  • The nerve impulse is then passed on the main body of the neuron i.e. soma.
  • From soma the impulse is passed on to the axon.
  • The axon transmits the information/impulse along its length to terminal buttons.
  •  The terminal buttons transmit the information to another neuron, gland or muscle.

NCERT Class 11 Psychology Textbook Chapter 3 The Bases of Human Behaviour With Answer PDF Free Download

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