Reproduction, Growth and Survival | Life History Strategies

Definition of Life

So far we have been trying to know the mystery of life. We have covered only a short distance and we have to march a long way to know what life is. With our limited knowledge, let us try to define life. If we try to put it most briefly, the definition of life would be “Life is a unique, complex organisation of molecules, expressing itself through chemical reactions which lead to growth, development, responsiveness, adaptation and reproduction.”

What is the Significance of death

  1. Organisms have enormous power of reproduction but death reduces the population growth and contributes to homeostasis in population.
  2. After death the organisms are decomposed by microbes. Elements such as carbon,hydrogen, oxygen, nitrogen, phosphorus, sulphur are made free from their bound form and are returned to air, water and soil for recycling. This is an important event to maintain balance in nature.
  3. Dead cells and their derivatives provide protection to the living process. Nails, horns,hooves, down feathers, hair provide support, protection, defence and offence. The outer layer of skin is also made up of dead cells which protect the body from loss of fluids and from the entry of harmful microbes. Similarly different dead cells of plants are highly helpful to them.

What is Reproduction, Growth and Survival

To produce more of one’s own kind is reproduction. Individual organisms die but leave there offsprings through reproduction. The role of reproduction is. illustrated by the statement,

“nothing lives forever, yet life continues.”

Reproduction and death are two terminals of the life span, growth and survival come in the life span. The number of individuals died in a population should be restored by reproduction. Failure to reproduce shall lead to elimination of the race or species because existing individuals have limited it span. Reproduction is not essential for growth or survival of the individual but is required for survival of the population, race and species. Reproduction may be of sexual, asexual or vegetative type about which we will learn in details later. Here, let us know the master molecule which is behind any type of reproduction It is DNA.

DNA is the molecular basis of reproduction because it is capable of replication. It is the store house of all hereditary Informations. All the information necessary for growth, differentiation, survival and reproduction is contained in DNA molecule. Hence DNA is regarded as “Blue-print of Life.” It produces mRNA for protein synthesis. Bulk of the protein form protoplasm and some of them act as enzymes. The enzymes control the biochemical reactions of the cell. Raw materials drawn ii om outside are converted into living protoplasm and this is molecular basis of growth. DNA replicates and cell division occurs. The daughter cells possess the same genetic material as that of the parent cell. Reproduction of DNA is molecular reproduction. It is followed by cell division. In single celled organism, cell division is the mode of multiplication or reproduction. In multicellular organisms, a large number of cell division occurs leading to growth. The daughter cells differentiate into tissues and organs. A few specialised cells differentiate into reproductive cells called gametes. The gametes take part in formation of offspring which is referred to as sexual reproduction. The whole process can be summed up in the Survival is the phenomenon of remaining alive. It is the life span of the organism which differs from species to species. It is maintenance of life both during normal conditions as well as in stress conditions. During normal condition, a steady state is maintained but during stress there are so many in built mechanisms to encounter it. Animals have nervous system and locomotory organs by which the stressful situations are effectively dealt. Animals avoid stress conditions through migration, burrowing, hibernation and running away etc. Plants are fixed forms and have no nervous system but they have enough of flexibility to tolerate stress. They can have physiological adaptations like fall of old leaves, dormancy, hairyness, thick cuticle, thick bark etc.

What is Adaptation

The word is derived from two Latin terms, ad = towards and ‘apt’ = adjust. In simple terms, the meaning of adaptation is better adjustment to the surrounding. Adaptations are new traits that help an organism to meet specific requirements of environment. Every organism has some inherent potentialities to change. AS a result or this change, there is wide variation among the individuals of a population. When this change is heritable, the character is handed over to the off- springs. If this change is useful, the organism possessing this would have better scope to adjust to the environment and this adjustment is adaptation.

“Adaptation is the physical or behavioural characteristic of an organism that helps an organism to survive better in the surrounding environment.”

What are the three types of adaptations?

  1. Physiological Adaptations
  2. Behavioural Adaptations
  3. Structural Adaptations

Living organisms possess two types of adaptations : short term and long term adaptations The examples of each type is given below:

What is Short term Adaptations?

(I) Short term Adaptations: These are useful changes which appear in response to specific conditions. These changes are meant for with standing the unfavourable conditions. After the perioid is over, again they go back to their original situation. Examples:

  1. Exposure to high intensity of sunlight causes darkening of skin due to spreading of melanin pigments which absorb solar radiation and protect the internal organs.
  2. Frogs and toads go into winter sleep when they minimise all body activities, remain at alow metabolic rate and use their stored fat as food. On the approach of spring they again become active. The same phenomenon in summer is called summer sleep.
  3. Migratory birds fly thousand miles from Siberian plains to tropical and sub tropical regions in winter to save themselves from cold and on return of spring they go back to their native places.
  4. Anabas, the climbing perch is adapted to make journey on wet field by using its accessory respiratory organ for aerial respiration but after coming to water, gills are used as normal aquatic respiratory organs.

What is Long term Adaptations?

(ii) Long term Adaptation: These are permanent heritable changes and are useful variations which have developed in the evolutionary process. These are essential for survival.
Organisms which could not develop these structures in past could not survive and become extinct. These adaptations have both survival and evolutionary significance. Examples:

  1. Kangaroo uses its thick tail as a fifth limb. Along with hind limbs, the tail supports the body while running
    2 Wall lizards possess curved claws and adhesive pads for walking over smooth walls and ceilings.
  2. Backward elongation of ankle bone in man has made him possible to stand erect,walk and run on two legs.
  3. Human beings have opposable thumbs for holding and gripping. This has helped to develop numerous skills such as use of tools, writing, spinning, weaving, etc.
  4. Toes and claws of birds are basically meant for perching. They are modified in many for specific functions. Examples:-

(a) perching in pigeon
(b) running in Ostrich
(c)grasping and striking in Eagle
(d) clinging and climbing in Wood Pecker,
(e) wading in King Fisher
(f) swimming in Duck, Cormorant and Grebe.

  1. Beaks of birds are adapted to different feeding habits-
    (a) Scooping fruits in Parrot and Hornbill,
    (b) Broad and elongated for aquatic vegetation in Spoon bill,
    (c) Worm catching in Sand piper,
    (d) Digging earth and picking insects by Hoopoe,
    (e) Tearing flesh in Hawk, Eagle and Falcon,
    (f) Seed and grain eating in sparrow,
    (g) Nectar sucking and insect eating in Humming bird
    (h) Fish eating in Cormorant,
    (i) Water and mud straining in Duck.
  2. Snakes have become limb-less and developed an elongated body as an adaptation to their burrowing habit.
  3. Birds have light and pneumatic bones for weight reduction which is a flight adaptation. Similar adaptations are also found in plants. The adaptation may be short or long termed, the basic purpose is to enable the organism to adjust in better way in the surrounding.

Theory of Adaptation

The theory of adaptation was proposed by Charles Darwin which states that an organism that is able to adapt to the changing environment will survive, the rest will be eliminated. This is known as survival of the fittest adapted.

According to the adaptation theory, there are three different changes that take place when the habitat changes quickly:

  • Habitat Tracking: This is when a species finds another similar environment to which it has inhabited before never.
  • Genetic Change: This occurs when organisms with slight genetic changes are better adapted to changed habitat with better access to resources and mating partners by DNA.
  • Extinction: When the species is unable to find such an environment, it dies or becomes extinct soon.

Importance of Adaptation

Adaptations such as camouflage and colouration protect them from predators. DNA mutations help in the longer survival of animals in dangerous enviro and these traits of survival are passed onto future generations. These adaptations make it possible for a variety of creatures to thrive on planet earth.

Charles Darwin studied turtles of two islands. The turtles present on one island had short legs, straight shells and derived food present low to the ground. A few turtles migrated to another island, where the food was much higher up. The turtles with longer legs survived. Their necks elongated and shells became rounded over the course of time. because adaptation means alteration Thus, the population on the new island grew with these adaptations in their species

Survival and Death

The individuals of a population survive for a specific average period known as their life span. May flies survive only for a day. Moths and butterflies have a life expectancy of one week or so. Similarly the life span of man-100 years, parrot-140 years, tortoise-200 years, eagle-90 years, horse-60 years, monkey-25 years etc.

The period of survival comes to an end due to ageing, disease, accident or predation and the organism dies. Death is the price paid for all living beings at the time of birth. Death is stoppage of all living activities due to degeneration of body parts. Survival is homeostasis while death is increase in entropy. It is said that the unicellular protozoans are immortal. but in true sense, they too meet natural death. Internal pollution of the protoplasm make them old. However they have the technique to discard pollutants and rejuvinate. When they fail to remove them efficiently, they also suffer from senile decay and destroyed.


  1. what is Life history strategies?
  2. What is a “life history”?
  3. Life history strategies and natural selection?
  4. Parental care and fecundity
  5. What is the theory of Adaptation?
  6. Importance of Adaptation?
  7. Which is the best definition of adaptation?
  8. What do we mean by adaptation?
  9. What is adaptation in Science
  10. adaptation in nature?


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