Theories of evolution

Introduction

One of the primary question for any intelligent species is to try to understand the meaning of its own existence. A species cannot truly be cast as intelligent until it starts to wonder where it comes from. These are very important philosophical questions and can be very troubling. There are many answers available from religious to scientific view.

What is evolution?

Evolution is a change in heritable characteristics of the biological population over successive generations. Evolutionary processes give rise to biodiversity at every level of biological organization, including the levels of species, individual organisms, and molecules.

POSSIBLE HYPOTHESIS

Today we will discuss what science has to say on this matter. Some of possible hypothesis are: Life has always existed either on this planet or elsewhere in the universe, for infinite time in the past. At some point in the past God created the earth and the human beings. At some point in the past, life originate on its own. According to 3^rd hypothesis, under the right conditions, the right ingredients and enough time, life can come to be from simple atoms. And eventually life-forms can become so intelligent that they start pondering the meaning of their own existence.

What science says on this matter?

On the origins of species was published after almost lifetime of work by Charles Robert Darwin, in which he proposed a comprehensive theory of evolution. Darwin and his voyage on the ship HMS Beagle, his theory of evolution, and the evidence and the basic insights that led him to this theory.

WORKS BEFORE DARWIN

IMMUTABLE SPECIES

One of the leading views of time was that species were immutable. It is believed that God created life with distinct plants and animals. The species has an order. At the bottom there are plants, then animals and on the top were the humans.

CARL LINNAEUS

He was a Swedish botanist who laid the foundations of modern biological nomenclature. In the Linnaean system, organisms were organized as distinct species. Animals from the different species could not interbreed. A single species give a number variety.

THEORY OF LAMARCK

Lamarck proposed that species evolved over time and also provided a rough mechanism for this evolution. Lamarck primarily focused on two things: In every animal, a more frequent use of any organ gradually strengthen that organ, while its permanent disuse weakens it until it finally disappear. All such acquired characteristics are preserved by reproduction and passed on to the children. This work was slightly incomplete and incorrect. He states that the organisms had a tendency to become more complex and move up a ladder of progress. But why organisms want to become more complex was not answered.

POSTULATES

·         New Needs:

Any living organism is found in a type of environment. Changes in environmental factors such as temperature, medium, food, air, etc. or animal migration lead to the origin of new needs in living organisms, especially animals. In order to meet all the new requirements, living organisms must pay particular attention to behavior.

Ä   Use and disuse of organ:

The new practice involves more use of certain organs to meet new needs and unused or less use of certain other organs has not been used in new condition. This use and use of members with great influence on the form, structure and function of bodies. Continuous use of organs and, moreover, makes them more effective while the constant degradation of some other organs leads to degeneration and possible adjustment. So lamarckism is also called "theory of use and abuse of organs." So the organism acquires some new figures as a result of direct or indirect environmental impacts throughout its lifetime and is called adaptive or acquired grades.

Ä   Inheritance of acquired characters:

Lamarck believed that nature is inherited and passed on to offspring because they were born to meet 

the changing circumstances and the chance of their survival has increased.

Ä   Speciation:

Lamarck believed that new characters were acquired in each generation, and to the next generation, thus 

generating new characters generation after generation. After several generations a new species has been 

formed. Thus, according to Lamarck, an existing individual is the total sum of the characters acquired 

by a number of previous generations and art formation is a gradual process.

Summary
© Acquired characters developed by people throughout their lives are hereditary and accumulate over a period of time, resulting in a new form.

© Living organisms tend to grow in size.

© No use of the body results in degeneration while using an organ that develops.

© The production of a new body stems from a new need.

EVOLUTION OF GIRAFFE S NECK

I fish Environments, for example. Where the fruits are high in the tree. And giraffe born with and slightly longer neck and will have a better chance of survival, and other will not get friends short neck DEM Fruits. Finally, the long neck features two of the next generation. For sugars generations from the neck will continue with becoming longer longer OL SA the long giver and competitive advantage In camps for survival.

(Stage of evolution in giraffe’s)

DARWIN THEORY OF EVOLUTION

Charles Darwin was born in England in 1809. His father wanted him to cure. Darwin would be naturalist. Darwin went to Cambridge and studied Natural Theory published by William Paley. Paley suggested that the large number of species and the complexity of their bodies called the work of the higher power. After graduating, Darwin decided to take a trip around the world to take on HMS Beagle. Beagle England left late in 1831, the trip was originally planned to last two years, but the ship would not return for five years.

Postulates of Darwinism:

·   Geometric profit.

·   Limited food and room.

·   The struggle for existence.

·   Variations.

·   Natural selection or survival of the fittest.

·   Heritage of useful variations.

·   Arts Education.

Ø  Geometric increase:

According to According to Darwinism, people tend to multiply geometrically, and living organisms are

 reproductive forces (biotic potential) much more than necessary to maintain their number, for example.

Paramecium cleaves binary cleavage for three hours under favorable conditions. At this rate, a Paramecium

 produces a clone of approximately 280 million pantoffs for just one month and five years, which can 

produce pigs with a mass equal to 10,000 times the size of the earth.

Other fast-growing organisms: Cod (1 million eggs per year); Oysters (114,000,000 eggs in a pie); 

Ascaris (70, 00000 eggs for 24 hours); Home flight (120 eggs in one leg and six times in a summer season); 

A rabbit (producing 6 boys in a nest and four nests a year, and the young start breeding in six months).

Similarly, plants reproduce very quickly, for example, a single flower plant produces about 1, 18,000 

seeds and planting a few million spores.

Even long, some breeding organs plant at a rate much higher than is needed, for example an elephant

 set at 30 years and in the 90's, only six off-feathers were produced. In this class, when all elephants 

survive, some elephants produce about 19 million elephants in 750 years.

These examples confirm that each type of manifold increases within a few generations and takes up 

all available space on the ground, provided all survival is repeated and the process is repeated. 

So the number of species will be much more than can be supported on the ground.

Ø  Limited food and space:

Darwinism says that although a population tends to increase geometrically, rising food prices are only arithmetic. Thus, two major limiting factors of the massive increase in population: limited food and space that form part of the largest part of the environment. These have not grown for an indefinite period, which is almost stable in size, with the exception of the seasonality.

Ø  Struggle for existence:

By spreading populations, but limited food and space, eternal competition between individuals begins with the same requirements. In this game, every living organism would have a dominance over others.

Ø  Variations:

Variation is the natural law. According to this law of nature, not two people, except identical 

(single-ended) twins are identical. This eternal competition between organisms has led them to 

change in accordance with the conditions to exploit natural resources and survive successfully.

Darwin stated that the variations are generally two types of continuous discontinuous variations 

or fluctuations and variations. Based on their effect on the survival of living organisms, 

the variations may be neutral, harmful and useful.

Darwin suggested that living organisms tend to adapt to changing environment by making use of 

appropriate continuous variations {eg Increased rate of change; Increased fluid accumulation in plants; Etc.) 

because they have a competitive edge.

Ø  Natural selection or Survival of the fittest:

Darwin saw things that clearly competing species to eat, reproduce, to avoid predators, and to 

survive more successfully. If by chance some people were born with features that made them 

more successful in this game, these species have a better chance of survival and having feathers. 

And these properties will propagate.

On the Origin of Species was published in 1859, where he put his ideas into a coherent theory. 

Darwin knew that the public would find his theory very difficult to believe. He worked almost all

 his life to gather evidence for publishing books.

These kinds of people with useful variations from a heterogeneous population of nature called 

natural selection of Darwin and the survival of the fittest by Wallace. So natural selection 

works as a limiting force and not a creative force.

Ø  Inheritance of useful variations:

Darwin believed that the chosen people by giving them useful continuous variations to their 

offspring so that they fit into the changing environment..

Ø  Speciation:

According to Darwinism useful variations in each generation inherited from generation to generation. 

So the useful variants continue to accumulate, and after several generations the variations are 

so prominent that the individual becomes a new species. Thus, according to Darwinism, evolution is 

a gradual process, and species formation takes place through gradual changes in existing species.

LYELL S PRINCIPLES OF GEOLOGY

While on the voyage, Darwin read Lyell s Principles of Geology, which argued that the earth had gradually evolved over time. The book and the idea of geology evolution had a profound impact on Darwin.

THE CREATURES OF GALAPAGOUS

Darwin was wonder by the diversity of the organisms that he observed during his voyage. In 1835, the beagle landed on the Galapagos Island, the creatures of Galapagos were distinctive, even unique in many ways. Sea-going lizards and tortoises of different shape and size of each island.

DARWIN S FINCHES

Of particular importance were Darwin s finches, a set of bird specimens that Darwin brougt back with him to England.  When the famous ornithologist John Gould inspected the specimens, he concluded that they were all finches. Darwin was surprised that these birds differ so much in appearance, some had small beaks for eating insects, some had big beaks for crushing seeds.

After return to England in 1836, Darwin began to assemble his observations into a coherent theory.

The common features between birds of Galapagos suggested they shared common ancestors and similarly different families of tortoises on different islands suggested these are derived from a common ancestors.

VARIATION UNDER DOMESTICATION

Darwin was member of pigeon club and he ran several experiments on pigeon. His own experiment convinced that the species did change over time and these characters can be passed on their children.

Through Selective breeding humans have been able to breed desired plants and animals. Strong horses who run very fast can be selectively bred.

THOMAS MALTHUS

Darwin read Principle of Population published by Thomas Malthus. Malthus argued that any species multiplied in geometric progression and grew in population very rapidly. While the supply for food and resources only increased linearly.

Thus, the species continued to increase in population until a struggle for existence ensued. All the species would be fighting to get the limited resources for their survival.

NATURAL SELECTION

Darwin saw matters clearly, species compete to eat, to reproduce, to avoid predators and those more successful would survive. If by random chance some individuals were born with characteristics that made them more successful in this game, those species would have better chance to survive and have off springs. And those characteristics will propagate.

On the Origin of Species was published in 1859 in which he put all his ideas into a coherent theory. Darwin knew that public will find his theory very hard to believe. He worked almost all his life to collect evidence before publishing book.

HOW DOES EVOLUTION WORK?

Let’s assume certain facts. Off springs of any species slightly vary. Animal characteristics can be passed down through heredity. The resources necessary for survival are limited and several individuals are fighting to get food.

FURTHURE EVIDENCE FOR NATURAL SELECTION

EVOLUTION OF PEPERRED MOTH:

Evolution generally occurs over millions of years, but under certain conditions it can occur at a much faster rate. Peppered moths in England. Majority were light colored but with passage of time dark colored were in majority due to industrial pollution.

HOW A MONKEY EVOLVE INTO A HUMAN BEING?

THE MUTABILITY OF SPECIES

Over time, pressures on population, due to predators, change in climate etc would gradually shift the average characteristics and modify a species. If a particular species was split into two populations by, say, a sudden river, then over time the average features of those two populations would vary enough ultimately resulting in new species.

OPPOSITION TO THE THEORY

The theory of evolution is an accepted part of scientific literature. Most of the people are opposed to this. There are several questions. If man evolved from monkeys, why are monkeys still around? Why don’t we see evolution around us? Why don’t we see a monkey evolving into a man?