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PinkMonkey Online Study Guide-Biology

iv) Responsiveness to Stimuli

All living things are able to respond to stimuli in the external environment. Stimuli originate from different sources.

a) physical: light, heat, temperature, sound.

b) chemical: acids and alkali.

c) mechanical: friction, pressure.

The body has specialized tissue or higher centers to detect stimuli, such as eyes for light, ears for auditory stimuli, the nose for olfactory stimuli, the tongue for taste, the skin for touch, etc.

An organism must co-ordinate well to give an appropriate response to the stimuli from the environment. All systems of the body help in this co-ordination, like nerves from the nervous system, and certain chemical regulators called hormones from the endocrine system. This simultaneously produces an effect of co-ordination and acts as a sensing system. To respond to the stimuli, the organism has certain efferent units like muscles, glands, hair, etc. The process of response involves the use of energy.

The responses are of two types:

a) generalized, and

b) protective.

Protective responses help to promote survival and thus sustain life. A generalized response contribute to the behavior patterns of an organism. For certain classes, the response occurs with a definite pattern which is innate to the organism.

Nonliving things donít respond to stimuli as living things do.


v) Evolution

Living organisms normally interact with the environment for their daily requirements. There are always changes going on in the environment. To adapt to these changes, there are genetic changes in the animal. The process of adaptation in a new generation animal in the population is called evolution. Evolution allows for changes in interactions between the organism and its environment. The evolved organism is more capable of adapting to changes in the environment. This adaptation in the organism leads to the formation of a new species and also newer organisms within the species. So with evolution, a new species is formed but certain characteristics from the previous generation remain intact.

vi) Ecology

Ecology is the study of the relationships between the environment and the organism, and between various organisms . Due to interaction with the environment, the organism and its environment continuously influence each other. Animate organisms can migrate to another place if the environment is not suited to their survival in a given region. For instance, frogs cannot live in water if there are too many crocodiles on their side of the pond.

Nonliving things cannot change their environment .

Table of Contents

1.0 - Introduction
1.1 Practical Biology
1.2 Scientific Methodology

Chapter 2





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