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Арсланова_Г_А_и_др_Essential_English_for_Biology_Students (1). Kazan federal university


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UNIT VI. EVOLUTION

Text 6.1. Theories Of Evolution


Essential targets:

By the end of this text you should be able to:

● explain the biological meaning of evolution;

● distinguish between neo-Darvinism and Darvinism.

Pre-reading

Working in pairs, try to answer the following questions before you read the text. When you have finished, check your answers by reading the text.

    1. What is evolution? How does it happen?

    2. What is a species?

    3. What is natural selection?

    4. What theory did Darwin develop?


Read the given text and make your essential assignments:

One of the most fundamental questions in biology is: where do all living things come from? According to most biologists, the millions of species living on Earth today (including humans) are descended from other species that inhabited the world in the past. This change has come about by a process called evolution. Evolution happens when the genetic composition (allele frequency) of a population changes over successive generations. When the changes are sufficiently great, a new species may be formed. (A species is a group of closely related organisms potentially capable of interbreeding to produce fertile offspring.)

The mechanism of evolution.

Evolution is not a modern concept. Since ancient times, a number of philosophers and naturalists (including Confucius and Aristotle in Greece) have suggested that complex species evolve from simpler pre-existing ones by a process of continuous and gradual change. However, it was not until the 19th century that scientists came up with plausible mechanisms for evolution. The mechanism that is widely accepted among biologists today is called neo-Darwinism. It is modern theory based on the work of the nineteenth- century naturalist Charles Darwin.

B etween 1831 and 1836, Darwin was the naturalist on board HMS Beagle, a research vessel engaged in mapping different parts of the world. After spending over three years surveying the coast of South America, the Beagle landed on the Galapagos Islands in the Pacific Ocean. Darwin compared the organisms on these islands with those on the South American mainland, and this led him to develop his theory of evolution. He came to the conclusion that, over successive generation, a new species comes into being by slow and gradual changes from a pre-existing one. He believed that these changes are brought about by a process which he called natural selection.

Darwin’s theory was based on three main observations:

1. Within a population are organisms with varying characteristics, and these variations are inherited (at least in part) by their offspring.

2. Organisms produce more offspring than are required to replace their parents.

3. On average, population numbers remain relatively constant and no population gets bigger indefinitely.

From these observations, Darwin came to the conclusion that within a population many individuals do not survive, or fail to reproduce. There is a “struggle for existence”. For example, members of the same population compete to obtain limited resources, and there is a struggle to avoid predation and disease, or to tolerate changes in environmental conditions such as temperature. In this struggle for existence those individuals that are best adapted to their environment will have a selective advantage: they will be more likely to survive and produce offspring than less well-adapted organisms.

The origin of species

For more than 20 years, Darwin collected evidence to support his theory and refined his ideas. He delayed publishing his ideas until 1858, when Alfred Russel Wallace sent him a letter describing a theory of evolution identical to Darwin’s own. Wallace was a British naturalist who had worked in the Malay Archipelago for eight years. He concluded from his research that some organisms live while others die because of differences in their characteristics, such as their ability to resist disease or escape predation. Darwin and Wallace published a paper jointly describing their theory of evolution by natural selection. However, Darwin’s name has become more strongly linked with the theory because of a book he published on 24 November 1859. The book, entitled “The Origin of Species by Means of Natural Selection or the Preservations of Favoured Races in the Struggle for Life”, has been called the most important biology book ever written. It not only gives a full description of the theory of evolution by natural selection, but also contains a huge mass of evidence to support the theory.

The reaction to Darwin.

Many people found it difficult to accept Darwin’s ideas, especially the idea that modern humans and apes are probably descended from a common ancestor. However, his theory is supported by so much evidence that the majority of biologists accept it. Evolution by natural selection has become a central theme which underpins much of modern biology. The modern theory of evolution is called neo-Darwinism because it incorporates new scientific evidence, particularly from genetics and molecular biology. For example, we know that the variations that are so important in natural selection come about by random and spontaneous changes in genes, particularly from mutations in reproductive cells. Despite modifications to Darwin’s theory in neo-Darwinism, natural selection is still the driving force behind evolution, or the theory of evolution by the natural selection of inherited characteristics.

Glossary of essential terms for you to know



English term

Russian equivalent

1

to accept

принимать

2

to inhabit

населять

3

to descend

происходить

4

to interbreed

скрещивать

5

offspring

потомство

6

to suggest

предполагать

7

to bring about

осуществлять; вызывать

8

capable of

способный

9

species

вид

10

to evolve

развивать

11

gradual

постепенный

12

to compete

соревноваться

13

coast

побережье

14

to obtain

получать

15

to refine

совершенствовать

16

pre-existing

ранее существовавший

17

to develop

развивать

18

to replace

заменять

19

mainland

материк

20

to reproduce

размножаться

21

successive

последующий

22

selection

отбор

23

to vary

меняться

24

on average

в среднем

25

relatively

относительно

26

observation

наблюдение

27

to fail

не суметь, провалить

28

struggle

борьба

29

existence

существование

30

to exist

существовать

31

disease

болезнь

32

generation

поколение

33

environment

окружающая среда

34

advantage

преимущество

35

well-adapted

хорошо приспособленный

36

evidence

свидетельство

37

to describe

описывать

38

to produce

производить

39

to conclude

сделать вывод, заключить

40

to resist

сопротивляться

41

research

исследование

42

by means

посредством

43

to support

поддержать

44

apes

приматы

45

genetics

генетика

46

cell

клетка

47

to survive

выжить; пережить

Your Essential Assignments

I. Quick check:
1. Give the biological meaning of evolution.

2. How does neo-Darwinism differ from Darwin’s original theory of evolution?
II. Fill in the missing words:

Term (verb)

Noun

Adjective

exist

.......

.......

suggest

.......

.......

reproduce

.......

.......

develop

.......

.......

inherit

.......

.......

inhabit

.......

.......

evolve

.......

.......

select

…..

……

III. Use monolingual English dictionary and write down what could the words given below mean:

change, naturalist, complex, to escape, to collect, humans.

IV. Match these words with their definitions:

1

generation

A.

an illness or unhealthy condition in your body

2

evolution

B.

the air, water and land in which people, animals and plants live

3

evidence

C.

a member of your family who lived a long time ago

4

reproduce

D.

the careful choice of a particular person or thing from among a group of similar people or things

5

species

E.

to continue to live or exist

6

survive

F.

to change into a larger, stronger, or more advanced state

7.

ancestor

G.

to produce young animals from parents of different breeds or groups

8.

develop

H.

all the members of a group of things which have been developed from a previous group

9.

naturalist

I.

an animal’s baby or babies

10

environment

J.

the state of existing

11

selection

K.

the gradual change and development

12.

disease

L.

to produce young animals or plants

13.

interbreed

M.

someone who studies plants or animals, especially outdoors

14.

offspring

N.

facts that make you believe that something exist or is true

15.

existence

O.

a group of closely related organisms

V. Find English equivalents to the following word combinations:



Russian term

English equivalent



произошедший от






тесно связанный






последующие поколения






живущие на земле






производить оплодотворенное потомство






генетический состав






придти к выводу






относительно постоянный






собирать свидетельства






сопротивляться болезни






генетика и молекулярная биология






случайные и спонтанные изменения






мутации в репродуктивных клетках






большинство биологов






естественный отбор




VI. Give Russian equivalents to the following English terms:



English term

Russian equivalent

1

according to




2

inhabited the world in the past




3

sufficiently great




4

continuous and gradual change




5

widely accepted among biologists




6

to develop the theory




7

natural selection




8

with varying characteristics




9

struggle for existence




10

to obtain limited resources




11

best adapted to their environment




12

to escape predation




13

a full description of the theory of evolution




14

a common ancestor




VII. Find synonyms among the pool of words:

Pool of words

Synonyms

1)1.develop/2.accept/3.change/4.alter/5.evolve/6.obtain




2)1.support /2.happen/3.exist/4.occur/5.underpin /6.live




3)1. investigation /2.selection /3.research /4. choice




4)1.escape/2.disease/3.individual/4.get away/5.illness/

6.human being




VIII. Answer the following questions. Use all information given before:

        1. How does the evolution usually take place?

        2. What led Charles Darwin to develop his theory of evolution?

        3. What did Darwin mean by “natural selection”?

        4. What are three main observations of Darwin’s theory?

    1. What does “struggle for existence” mean?

    2. What book has been called the most important biology book ever written?

    3. Do the majority of biologists accept Darwin’s theory?

    4. What is called neo-Darwinism?

IX. Match the sentence halves. Make complete sentences:

1.

According to most biologists, the millions of species living on Earth today

A.

is called neo-Darwinism.

2.

Evolution happens

B.

than are required to replace their parents.

3.

The mechanism that is widely accepted among biologists today

C.

to support his theory and refined his ideas.

4.

Organisms produce more offspring

D.

which underpins much of modern biology.

5.

Members of the same population compete

E.

are descended from other species that inhabited the world in the past.

6.

For more than 20 years, Darwin collected evidence

F.

come about by random and spontaneous changes in genes.

7.

Evolution by natural selection has become a central theme

G.

to obtain limited resources.

8.

The variations that are so important in natural selection

H.

when the genetic composition of a population changes over successive generations.

X. Read and translate the short text without any dictionary:

Fact of life: Highly sensitive dating techniques tell us that the Earth is between 4.5 and 5.0 thousand million years old. It is generally agreed by scientists that the Earth was originally devoid of life, and that the first living organisms arose by biochemical evolution from complex organic chemicals formed in the atmosphere and seas of early Earth. These first forms of life gave rise to countless millions of species. Most have become extinct, but some have evolved into organisms found today. According to the latest estimates, 20-30 million species share our planet.

XI. Food for thought:

In 1809 Jean-Baptiste de Lamark suggested that the driving force behind evolution was the need for organisms to adapt to changing environmental conditions. His theory became known as the theory of evolution by the inheritance of acquired characteristics. He believed that adaptations developed by an organism during its lifetime could be passed on to its offspring. According to Lamark, modern giraffes might have evolved from a short-necked ancestors in the following way. Giraffes feed on leaves ripped off the branches of trees. When leaves on the lower branches were removed, or when the trees became taller, the ancestral giraffe needed to stretch to reach leaves on higher branches. By continually stretching, their necks lengthened and the ability to grow a slightly longer neck was inherited by the next generation which carried on stretching, and so on.

We know that this explanation of the evolution of the giraffe’s neck is untrue because activities such as stretching to feed do not affect the gametes. Therefore, this type of characteristic acquired during the life of an organism is not inherited by its offspring. Expressed in modern terms, Lamarckism would mean that changes in phenotype could determine the genotype of future generations. This does not agree with modern genetics, and there are no generally accepted examples of acquired characteristics being inherited. Suggest a neo-Darwinian explanation for the evolution of the modern long-necked giraffe from a short-necked ancestor.
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