Natural selection: adaptation or abaptation? 


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Natural selection: adaptation or abaptation?



 

The phrase that, in everyday speech, is most commonly used to describe the match between organisms and environment is;" 'organism X is adapted to' followed by a description of the conditions where the organism is found. Thus, we often hear that 'fish are adapted to live in water', or 'cacti are adapted to live in conditions of drought'.

Unfortunately, biologists use the words 'adapted' or 'adaptation' to mean various. quite different things. The word 'adaptation' implies that the way that organisms react to present circumstances, prepares them for the future, is predictive and implies some sort of forward planning. But, organisms are not designed for, or matched to or fitted to, the present or the future—their character or properties are entirely consequences of the past—they reflect the successes and failures of ancestors. Abaptation (or exaptation) would be a better word than adaptation because its etymology brings the implication that the aptness (match) of organisms for their environment is a product of their past rather than a programme for the future. The properties of organisms appear to be apt for the environments that they live in at present only because present environments tend to be similar to those of the past.

An individual will survive, reproduce and leave descendants in some environ­ments but not in others. This is the sense in which nature may be loosely (and anthropomorphically) thought of as selecting. It is in this sense that some environ­ments may be described as favourable or unfavourable, and it is in this same sense that some organisms can be considered to be fit or not. If, because some individuals leave more descendants than others the heritable characteristics of a population change from generation to generation, then evolution by natural selection is said to have occurred.

Of course, the present properties of an organism have not all been selected in the type of environment in which it now lives. Over the course of its evolutionary history (its phylogeny) an organism's remote ancestors may have been single-celled aquatic eukaryotes, and as its evolutionary pathway has led to the present specialized organism—peacock, orchid, shrimp or elephant—it has accumulated some, and shed other properties that it acquired in its evolutionary progress. This baggage of evolutionary history places limits on, and constrains, future evolution and much of what we now see as precise matches between an organism and its environment are either these inherited constraints (e.g. that koala bears can live only on Eucalyptus foliage), or detailed fine-tuning.

 

Ex.6. Render the sentences into English and pay attention to the translation of the ones, where such words as: one, it are their subjects:

 

1. Экологи имеют дело с организмами и окружающей средой. Важнопонимат ь взаимосвязь между ними.

2. Необходимо знать, что различия в окружающей среде определяются, главным образом, различиями в количестве солнечной радиации, поступающей в разные части земли, топологией и природой ее геологических образований.

3. Известно, что биологическая активность на земле вызвана энергией, высвобождаемой в результате неорганических преобразований, таких как, например, окисление различных химических соединений. Однако, также очевидно, что основной поток биологической активности на земле зависит от солнечной энергии, фиксируемой в процессе фотосинтеза.

4. Можно представить экологию нашей планеты зажатой между горячей сковородкой и морозильником.

5.Земля заселена различными типами организмов, которые неоднородно расселены по поверхности земного шара и совершенно естественно  искать соответствие между биологией различных видов и природой окружающей среды в том месте, где вид обнаружен.

6. Понятно, что  настоящие свойства организма проходили отбор не в той среде, в которой он сейчас обитает.

Эволюционная история накладывает ограничения на будущую эволюцию и многое из того, что мы сейчас видим как точное соответствие между организмом и его окружающей средой, является или унаследованными свойствами, или приспособлением до мельчайших деталей.

 

Unit Three

 

Grammar:

 

Passive Voice

Ex.1. Read the sentences. Render them into Russian paying attention to the Passive form of the predicates:

 

1. The book is aimed at all those whose degree programme includes ecology.

2. Very little is known about the flora of previous interglacial periods.

3. The cultivated form has been selected to produce large seeds which are easily harvested.

4. Both convergent and parallel evolution are often recognized by striking visual resemblances.

5. The number of biomes that are recognized differs between biogeographers, and it is rather a matter of taste how many should be recognized.

6. Millions of people are killed each year by various types of infection and many millions more are debilitated or deformed.

7. When the effects of parasites on domesticated animals and crops are added to this, the cost in terms of human misery and economic loss becomes incalculable.

8. The disagreement needs to be resolved by carefully designed and controlled experiments.

9. Leaves on plants that carried a population of ants lived nearly 1.8 times as long as those on plants from which ants had been deliberately removed.

10. Every organism can be truly represented only by its whole life history.

11. Pest control could be described as having twin aims: controlling the pest and minimizing the disturbance to other species in the community.

12. A community can be defined at any size, scale or level within a hierarchy of habitats.

 

Word study

Ex.1. Read the words. Give their Russian equivalents:

 

Analogous, homologous [                ], convergent, reptiles, metabolism, phylogeny [               ], phylogenetic [                    ] – филогенетический (adj.), radiation, placental – плацентарный, evolutionist, biome, biogeographer, flora, fauna, continental tropics, phosphoras, chemical composition

 

Ex. 2. Translate the following words and word combinations:

 

A match between; a similarity in form and behavior; similar environment; belonging to different phyletic (филетические ветви) lines; far removed from each other; convergence of form; to conceal profound differences; selective forces; the same property; acquired from; evolutionary origins; to gain access to; supporting tissues; evolutionary pathways; related groups; set of constraints and potentials; a common ancestral line; to excavate burrows; to occupy the areas; massive movements; mineral input; nutrient-rich waters; this accounts for; phylogenetically related groups

 

 

Ex.3. Words to be remembered:

 

Evidence, to belong to, internal structure, mammals, carnivores, to indicate, plants, vegetation, ecological niche, resemblance, larvae, grazing herbivore,  guild (a group of species that exploit the same class of environmental resources in a similar way), lifestyle, drought desert, extend, evaporate, rainforest, abundant, to distinguish, coniferous forests, precipitation, evaporation, to absorb, mineral nutrients, dilute, estuaries, land drainage, water catchments, to inhabit

 

 

Reading A:    CONVERGENTS AND PARALLES

Notes to the Text:

Convergent evolution – конвергентная эволюция (the process by which organisms of different evolutionary lineages come to have similar form or behavior)

Placental – плацентарный (mammals which develop a persistent placenta; i.e. all mammals other than marsupials and monotremes)

Marsupial [                ] – сумчатый

Monotreme - одноапертурный (a primitive mammal belonging to one of only three genera, laying eggs but having hair and secreting milk)

Parallel evolution - the evolution along similar lines of systematic groups that had been separated geographically at an earlier stage in their history.

Bandicoot – сумчатый барсук

Canopy – покров [          ]

Nitrogen - азот [           ]

 

Ex.1. Read the text and be ready to explain what convergent and parallel evolution is:

   

A match between the nature of organisms and their environment can often be seen as a similarity in form and behaviour between organisms living in a similar environment, but belonging to different phyletic lines (i.e. different branches of the evolutionary tree). Such similarities also undermine further the idea that for every environment there is one, and only one, perfect organism'. The evidence is particularly persuasive when the phyletic lines are far removed from each other' and when similar roles are played by structures that have quite different evolutionary origins, i.e. when the structures are analogous (similar in superficial form or function), but not homologous (derived from an equivalent structure in a common ancestry). When this is seen to occur, we speak of convergent evolution. Large swimming carnivores have evolved into four quite distinct groups: amongst fish' reptiles, birds and mammals. The convergence of form is remarkable because it conceals profound differences in internal structures and metabolism, indicating that the organisms are far removed from each other in their evolutionary history. Many flowering plants use the support of others to climb high and so gain access to more light than if they depended on their own supporting tissues. The ability to climb has evolved in many different families, and quite different organs have become modified into climbing structures: they are analogous structures but not homologous. In other plant species the same organ has been modified into quite different structures with quite different roles: they are therefore homologous, although they may not be analogous.In this case we can argue that similar selective forces have acted so that the same property has been acquired from quite different evolutionary starting points. A comparable series of examples can be used to show the parallels in the evolutionary pathways of phylogenetically related groups..

The classic example of such parallel evolution is the radiation amongst the placental and marsupial mammals. Marsupials arrived on the Australian continent in the Cretaceous period (around 90 million years ago), when the only other mammals present were the curious egg-laying monotremes.An evolutionary process of radiation then occurred that in many ways accurately paralleled what occurred in the placental mammals on other continents. The subtlety of the parallels in both the form of the organisms and their lifestyle is so striking that it is hard to escape the view that the environments of placentals and marsupials contained 'ecological niches’ into which the evolutionary process has neatly 'fitted' ecological equivalents. (It is important to remember that, in contrast with convergent evolution, the marsupials and placentals started their radiative evolution with an essentially common set of constraints and potentials because they sprang from a common ancestral line.)

Both convergent and parallel evolution are often recognized by striking visual resemblances. The marsupial bandicoot looks rather like a placental rabbit (the long ears make the resemblance particularly striking), and both species excavate burrows, but the bandicoot is largely carnivorous, feeding on insect larvae, whilst the rabbit is a herbivore. By contrast, kangaroos and sheep look remarkably different although both are large grazing herbivores which, when they live side-by-side, have very similar diets. The kangaroo and the sheep are members of the same guild (a group of species that exploit the same class of environmental resources in a similar way), but they look very different. The rabbit and the bandicoot look very similar, but belong to quite different guilds. An ecologist looks for the match of organisms to their environment in their lifestyle (e.g. what they feed on and what feeds on them), and an evolutionist emphasizes their phylogeny.

 

Ex.2. Comprehension check-up:

 

1. How can a match between the nature of organisms and their environment be seen?

2. In what case do we speak of convergent evolution?

3. Why do fish, birds and mammals belong to convergents?

4. Are organs in plants, modified into climbing structures, called analogous or homologous?

5. How do the parallels differ from convergents?

6. Can you give example of parallel evolution?

7. How is it possible to explain the striking subtlety of the parallels in the form and lifestyle of organisms?

8. What’s the difference of the scientific approach of an evolutionist and ecologist looking for the match of organisms to their environment?

 

 

Ex.3. Tell your partner what an ecologist should know looking for the match between organisms and their environments.

 

 

Reading B:    Patterns in Community structure

 

Ex.1. Read and answer the following questions:

 

 1. Why is it important for ecologist to consider ‘biomes’?

2. How many biomes are there in the world?

3. What factors influence the biological activity of the oceans?

4. How can the concentration of many of the world’s fisheries be explained?

5. Where do freshwater biomes occur?

6. What does the chemical composition of the water depend on?

7. How do salt lakes develop?

8. Do the differences between biomes help to recognize an exact difference of the communities of organisms?

Before examining the differences and similarities between communities it is important to consider the larger groupings, ‘biomes’, in which biogeographers recognize marked differences in the flora and fauna of different parts of the world. These biomes occupy the areas between the frozen wastes of the polar regions and mountain tops and the drought deserts of the continental tropics. They extend from regions that are too dry because most of the water is frozen, to regions that are too dry at some seasons because water evaporates too fast. In tropical rainforest, both liquid water and radiation are usually abundant.

The number of biomes that are recognized differs between biogeographers, but it is possible to distinguish and describe eight terrestrial biomes: Tundra, Taiga, Temperate forests, Grassland, Chaparral, Deserts, Tropical rainforests, Northern coniferous forests and two aquatic biomes: marine and freshwater. The oceans cover about 71% of the earth’s surface and reach depths of more than 10000m. They extend from regions where precipitation exceeds evaporation to regions where the opposite is true. There are massive movements within this body of water that prevent major differences in salt concentrations developing (the average concentration is about 3%). Two main factors influence the biological activity of the oceans. Photosynthetically active radiation is absorbed in its passage through water and so photosynthesis is confined to the surface region. Mineral nutrients, especially nitrogen and phosphorus, are com­monly so dilute that they limit the biomass that can develop. Shallow waters (e.g. coastal regions and estuaries) tend to have high biological activity, because they receive mineral input from the land and less incident radiation is lost than in passage through deep water. Intense biological activity also occurs where nutrient-rich waters from the ocean depths come to the surface; this accounts for the concentra­tion of many of the world's fisheries in Arctic and Antarctic waters.

Freshwater biomes occur mainly on the route from land drainage to the sea. The chemical composition of the water varies enormously, depending on its source, its rate of flow and the inputs of organic matter from vegetation that is rooted in or around the aquatic environment. In water catchments where the rate of evaporation is high, salts leached from the land may accumulate and the concentrations may far exceed those present in the oceans and form brine lakes or even salt pans in which little life is possible. Even in aquatic situations liquid water may be unavailable, as is the case in polar regions.

The differences between biomes allow only a very crude recognition of the sorts of differences and similarities that occur between communities of organisms. Within biomes there are both small- and large-scale patterns of variation in the structure of communities and in the organisms that inhabit them. It has proved quite difficult to devise ways in which even very obvious similarities and differences between communities can be described and measured.

 

Ex.2. Try to say in a few sentences what you have learnt about biomes and how the knowledge of differences between them helps to examine the communities’ structure.

 

Reading C:     The ‘Life form’ spectra of communities

 

Ex.1. Read and summarize the article according to the following questions:

 

1. Why isn’t it easy to compare two areas from ecological point of view according to a list of the names of species present in them?

2. What could Raunkiaer’s way of plant forms classifications reveal and demonstrate?

3. What did an attempt to classify the ecological diversity of mammalian faunas give ecologists?

In the vast majority of cases, natural communities contain a spectrum of life forms and biologies. A consequence of evolutionary divergence is that taxonomically closely related species may live in different environments. A consequence of evolutionary convergence is that taxonomically unrelated species may live in the same environment. For these two reasons a list of the names of species, genera or even families present in two areas may tell us virtually nothing about how similar the areas are ecologically.

However, serious attempts have been made to develop and refine the ways in which the life and form of higher plants can be described, irrespective of their taxonomy and systematics. Still the simplest, and in many ways the most satisfying, classification of plant forms that disregards their systematics is that of the Danish botanist Raunkiaer (1934). He emphasized that the growth of higher plants depends on the initiation of tissues at apices (meristems), and he classified plants according to their ‘life forms’ defined by the way in which these meristems were held and protected.

 

The relative frequency of different life forms is then used to construct spectra from the flora of different regions. He compared these with a 'global spectrum' obtained by sampling from a compendium of all species known and described in his time (the lndex Kewensis), biased by the fact that the tropics were, and still are, relatively unexplored. Striking differences between vegetation types are exposed in this way which demonstrate not only matches of organisms to environments but of whole community complexes.

Raunkiaer's methods are clearly a step on the way to a definitive analysis of the ecological diversity of communities, and attempts have been made to improve  Raunkiaer's methods,  to quantify the ecological diversity (life-form spectra) of mammalian fauna.l       

They classified the mammals of forest communities in Malaya, Panama, Australia and Zaire according to their means of locomotion: (i) aerial (bats and flying squirrels); ii) arboreal (species found on small branches in the upper canopy, e.g. primates); iii) scansorial (clawed species of large branches such as squirrels); and (iv) small round mammals (species living mainly on the ground, although coming a little way into the lower canopy). They also classified the mammals according to their feeding habits: (i) plant eaters (herbivores and fruit eaters (fructivores); (ii) insectivores; (iii) carnivores and (iv) mixed feeders. The percentages of species falling into the various categories were then presented in graphical form as 'life-form' spectra. The spectra from the four continents are strikingly similar. Particularly remarkable is the very close similarity of the ecological diversity spectra for the Australian and Malayan forests, bearing in mind that the fauna of Australia is marsupial and that of Malaya is placental. This is a spectacular confirmation that the parallel evolutionary divergence within marsupial and placental phylogenies has resulted in ecologically matched faunas.

 

 

Ex.3. Render the article in English using the words below:

 

1. Сосуществующие виды обычно несколько различаются, но каждый соответствует своей среде и живет в ней своей жизнью, т.к. среда – гетерогенна (разнородна).

2. Разница в экологии видов, существующих в пределах одного сообщества, заметнее, когда виды родственны, т.к. эти различия наиболее четко проявляются на фоне общих черт. Однако, необходимо понимать особенности сосуществования членов, по крайней мере, одной гильдии, которые необязательно должны находиться в близком родстве.

Например, рачок-криль является богатым пищевым ресурсом для тюленя-крабоеда и морского леопарда Антарктики, а также поедается кальмаром, рыбой, птицами, китами и, поэтому, полный анализ соответствия между составными загадки существования такого сообщества должен учитывать не просто определенную таксономическую группу, а все гильдии в целом.

 3. При исследовании группы систематически соотнесенных видов, неправильно рассматривать каждый вид как независимый продукт естественного отбора. Сходство между видами возможно возникло в процессе конвергентной эволюции или как результат наличия общих предков. Пример с тюленем и другие подобные примеры ставят больше вопросов, чем ответов, и ни на один вопрос нельзя сегодня ответить однозначно.

 

Coexisting species; to differ in subtle ways; to match environment; a style of life; heterogeneous; closely related; relevant differences; against a background; common features; the same guild; krill; an abundant resource; Antarctic waters; crabeater-seal; leopard seal; to specialize on; squid; whale; jigsaw puzzle; take into account; taxonomic group; whole guilds; systematically related species; as if it has arisen; similarities; ancestors in common; to provide questions; a straightforward answer.

 

 

                                           Unit Four

 

 

Grammar:

  Degrees of Comparison

 

Ex.1. Translate the following sentences. Pay attention to the translation of the degrees of comparison.

 

1. The differences are less striking than the resemblances.

2. A mammal, that changes the thickness of its coat as a reaction to cold weather, may start to develop the thicker coat in advance of the event.

3. Where two species have evolved a mutual dependence, the fit may be even tighter.

4. Most of the more obvious heterogeneities in a population arise only when parts become isolated geographically.

5. No environments are constant, but some are more constant than others.

6. Mutualisms are represented in a much more varied range of species interactions than competition, predation and parasitism.

7. The records of climatic change in the tropics are far less complete than those for temperate regions.

8. A different interpretation is that the present distributions are relicts of populations once distributed more widely.

9. The balance between birth rate and death rates is as important for the determination of species abundance and distribution as a species ability to disperse.

10. Organisms have lived in environments that were not quite the same as at present.

 

Word Study

Ex.1. Read the words. Find their Russian equivalents.

 

Homogeneity [                   ]; genetic; heterogeneity [                 ]; reproduction; recombination; genotypes; gene, gamete [             ] – половые клетки; transplant [              ]; hydroid – гидроид; crab, daily cycle; mobile; dramatic.

 

 

Ex.2. Translate the following words and word combinations:

 

Genetic exchange; isolated geographically; forces of natural selection; locally favored genotypes; to be at an advantage; gene flow; the same species; specialized races; become differentiated - видоизмененным, дифференцированным; unfavorable environment; higher plants; to have freedom; to search out resources; vagaries of passive dispersal; to tolerate life in two extremes; shore-feeding birds; to oscillates between; to move with the tides.

 

Ex.3. Words to be remembered:

 

To interbreed; to eliminate; exchange; mobility; to override; to arise; obvious; to occur; to remain; to depend on; sessile organisms; pollen; seeds; motile; seaweed; to settle; to escape from; to uproot itself – искоренять;

algae [          -pl. ]; alga – [       ] - морская водоросль; seashore; fixed organisms; shrimp –мелкие креветки; tides; descendant;

to hazard [           ] – рисковать; mussel – мидия; tolerance  

 

Reading A: SPECIALIZATION WITHIN SPECIES

 

Notes to the text:

Moss – мох

Lethal [        ] – фатальный, смертоносный

Sponge - губка; губки –pl.

Barnacle – морская уточка (ракообразное)

 

 

Ex. 1. Read and explain the contrast between the ways in which mobile and fixed organisms ‘match’ their environment:

 

The homogenizing effects of genetic exchange (and recombination) tend to mean most of the more obvious heterogeneities in a population rise only when  become isolated geographically and cease to interbreed. However, if the local forces of natural selection are very powerful, they can override the homogenizing forces of sexual reproduction and recombination. Then, even where there is some   interbreeding, locally favoured genotypes may be at such an advantage that ill-favoured combinations are continually eliminated. Gene flow continues to occur, populations remain part of the same species, but local specialized races appear within it. The exchange of genetic material through a population depends on the mobility of whole organisms or, in the case of sessile organisms, on the mobility of gametes, pollen or seeds.

Local, specialized populations become differentiated most conspicuously amongst organisms that are sessile for most of their lives. Motile organisms have a large measure of control over the environment in which they live; they can recoil or retreat from a lethal or unfavourable environment and actively seek another. However, the sessile higher plants, for example moss, seaweed and coral, have no such freedom. After dispersal they must live, or die, in the conditions where they settle. The most that a higher plant can do is to search out resources or escape from an unfavourable site by growing from one place to another; it can never uproot itself and choose to transplant itself elsewhere. Its descendants (seeds, pollen or gametes) are hazarded to the vagaries of passive dispersal on the wind or water, or in or on the bodies of animals. Populations of non-mobile organisms are therefore exposed to forces of natural selection in a peculiarly intense form.

The contrast between the ways in which mobile and fixed organisms 'match' their environment is seen at  mostly on the seashore, where the intertidal environment continually oscillates between being terrestrial and being aquatic. The fixed algae, hydroids, sponges,mussels and barnacles all meet and tolerate life in the two extremes. But, the mobile members of the community, for example the shrimps, crabs and fish, travel with and track their aquatic habitat as it moves, whilst the shore-feeding birds move back and forth, following the advance and retreat of their terrestrial habitat. The fixed organisms have to tolerate the whole daily cycle of change in their environment, but those that are mobile have no need for such tolerance—they move with the tides. There is a sense in which the match of such mobile organisms to their environment enables them to escape many of the forces of natural selection. Mobility enables the organism to match its environment to itself. The immobile organism must match itself to its environment.

 

Ex.2. Comprehension check-up:

 

1. When do obvious heterogeneities in a population arise?

2. In what case can locally favored genotypes override the homogenizing effects of genetic exchange?

3. What does the exchange of genetic material through a population depend on?

4. Which organisms have more control over the environment in which they live: motile or sessile ones?

5. Why are populations of fixed organisms exposed to selective forces in more intense form than mobile ones?

6. How are mobile organisms of the seashore able to escape the forces of natural selection?

7. How do mobile organisms differ from immobile ones in their efforts to ‘match’ their environment?

 

Ex.3. Summarize the article and tell what you have learnt about the specialization within species.

 

 

Reading B: The match of organisms to varying environments

Notes to the text:

Erratic – неустойчивый

Hurricane [             ] – ураган

Cyclone [             ] –циклон

Onset – натиск, начало

Cue – сигнал, намек

Phenotype [            ] – фенотип

Ecotype – a subset of individuals within a species with a characteristic ecology

 

 

Ex.1. Read the article consulting a dictionary:

 

The word ecotype' was first coined for plant populationto
describe genetically determined differences between populations within a species that reflect local matches between the organisms and their environments. The existence of different ecotypes within a species was demonstrated by transplanting plants from a variety of natural habitats into a common habitat, and allowing them to develop through one or more growing seasons. It is essential in such studies that the plants from the different places of origin should be grown and compared in the same environment.

No environments are constant over time, but some are more constant than others. No form or behaviour of an organism can match a changing environment unless it too changes. Three major categories of environmental change can be recognized.

1 Cyclic changes— rhythmicly repetitive, like the cycles of the seasons, the move­ments of the tides and the light and dark periods within a day.

2 Directional changes— in which the direction of a change is maintained over a period that may be long in relation to the life span of the organisms that experience it. Examples are the progressive erosion of a coastline, the progressive deposition of silt in an estuary and the cycles of glaciation.

3 Erratic change— this includes all those environmental changes that have no rhythm and no consistent direction, for example the erratic course and timing of hurricanes and cyclones, flash storms and fires caused by lightning.

The optimal fit of organisms to varying environments must involve some compromise between matching the variation and tolerating it.

There are two main ways in which organisms time their responses to cyclic changes in their environment: (i) by changing in response to the environmental change; or (ii) by using a cue that anticipates the change. 

If the cycle in conditions is weak and contains much variation, the organisms may best match the changing conditions by responding to them directly.

There is, however, a disadvantage, a price to be paid by organisms that respond directly to environmental change. A mammal that changes the thickness of its coat as a reaction to the weather becoming cold will have to shiver until the process of replacing its coat has taken place. But, if it reacts not to the onset of cold, but to an environmental cue that is correlated with, and therefore predicts, the onset of cold, such as the shortening of day length, it may start to develop the thicker coat in advance of the event. The use of such cues is common among  animals that live in environments with a strong and repeated cycle of environmental change, and where the variation in the cycle is relatively weak.

For an organism that cannot run away from adverse conditions, seasonal changes in its form may be the most effective solution to problems of survival in a changing environment. In arid environments, somatic polymorphism may be even more extreme than in the case of aquatic plants. Some species produce three crops of leaves within 1 year, each of different morphology.

 

Ex.2. Comprehension check-up:

 

1. What is the word ‘ecotype’ used to describe?

2. Is it possible for an organism to match a changing environment without changing itself?

3. What must the optimal fit of organisms to varying environments involve?

4. How do organisms time their responses to cyclic changes in their environment?

5. In what case do organisms match the changing conditions by responding to them directly?

6. What is the best way to survive in a changing environment for an organism that cannot run away from adverse conditions?

 

Ex.3. Work with a partner. Ask and answer questions in English according to the text and check your partner: student A and student B.

 

Student A:

 

1.Что означает слово ‘ экотип’?

 

(It is used for plant populations to describe genetically determined differences between populations within a species that reflect local matches between the organisms and their environments)

 

2. Может ли организм иметь совместимость с изменяющейся окружающей средой, не изменяясь сам?

(No form of an organism can match a changing environment unless it too changes.)

 

 

3. Что должно подразумевать наиболее оптимальное соответствие организмов изменяющимся средам?

 

(It must involve some compromise between matching the variation and tolerating it)

 

4. Как организмы реагируют на цикличные изменения в окружающей среде?

 

(There are two main ways in which organisms time their responses to cyclic changes in their environment: 1. by changing in response to the environmental change; 2. by using a cue that anticipates the change. The use of such cues is common amongst both plants and animals that live in environments with a strong and repeated cycle of environmental change, and where the variation in the cycle is relatively weak.)

 

5. В каком случае организмы приспосабливаются к меняющимся условиям непосредственно реагируя на них?

 

(If the cycle in conditions is weak and contains much variation, the organisms may best match the changing conditions by responding to them directly)

 

6. Как организм может выжить в меняющейся среде, если не может спастись от неблагоприятных условий?

 

(For an organism that cannot run from adverse conditions, seasonal changes in its form may be the most effective solution to problems of survival in a changing environment.)

Student B

 

1. (What does the word ‘Ecotype’ mean?)

Впервые это слово применялось для популяций растений в описании генетически детерминированных различий между популяциями в рамках одного вида, которые отражают соответствия между организмами и их средами на определенном уровне.

 

 

2. (Is it possible for an organism to match a changing environment without changing itself?)

Ни один вид организма, его поведение не может соответствовать изменяющейся среде, если он сам при этом не изменяется.

 

3. (What must the optimal fit of organisms to varying environments involve?)

Оно должно подразумевать некоторый компромисс между противостоянием изменению и способностью эти изменения перенести.

 

4. (How do organisms time their responses to cyclic changes in their environment?)

Они это делают двумя способами: 1. изменяя свою реакцию на изменение в окружающей среде или 2. реагируя на различные сигналы природы, которые предупреждают о наступлении такого изменения. Учет таких сигналов распространен среди как растений, так и животных, которые живут в среде с явно выраженным и повторяющимся циклом изменений окружающей среды, и где отклонения в цикле относительно слабы.

 

5. (In what case do organisms match the changing conditions by responding to them directly?)

Если в цикле много отклонений, то организмы лучше всего вживаются в условия, непосредственно реагируя на них.

 

6. (What is the best way to survive in a changing environment for an organism that cannot run away from adverse conditions?)

В таком случае сезонные изменения в его форме могут оказаться наиболее эффективным решением проблем выживания в меняющейся окружающей среде.

 

Reading C:   Pairs of species

 

Ex.1. Read the following article and render it in Russian (in a written form)

 

Notes to the text:

Host-specific rust fungi [         ] – ржавчинные грибы, специфичные по отношению к хозяину

Leguminous plant [                  ] – бобовые растения

insect pollinator – насекомое-опылитель

herbicide [              ] - гербицид

one and for-all – навсегда

 

Some of the most strongly developed matches between organisms and their environment are those in which one species has developed a dependence upon another. This is the case in many relationships between consumers and their foods, such as the dependence of koala bears on Eucalyptus foliage or giant pandas on bamboo shoots, whole syndromes of form, behaviour and metabolism constrain the animal within its narrow food niche, and deny it access to what might otherwise appear suitable alternative foods. Similar tight matches are characteristic of the relationships between some parasites and their hosts. For example, the host-specific rust fungi fit narrow and precisely defined environments: their unique hosts.

Where two species have evolved a mutual dependence, the fit may be even tighter. The mutualistic association of nitrogen-fixing bacteria with the roots of leguminous plants, and the often extremely precise relationship between insect pollinators and their flowers are two good examples.The closest matches between organisms and their environments have evolved where the most critical factor in the life of one species is the presence of another: the whole environment of one organism may then be another organism.

When a population has been exposed to variations in the physical factors of the environment, for example a short growing season, a high risk of frost or drought or the repeated application of a herbicide, a once-and-for-all tolerance may ultimately evolve' The physical factor cannot itself change or evolve as a result of the evolution of the organisms. By contrast, when members of two species interact, the change in each produces alterations in the life of the other, and each may generate selective forces that direct the evolution of the other. In such a coevolutionary process the interaction between two species may continually escalate. What we then see in nature may be pairs of species that have driven each other into ever-narrowing ruts of specialization—an ever-closer match.

 

                                   

 

 

                                              Unit five

 

 

Grammar:

  Continuous tenses

Ex. 1. Translate the following sentences:

 1. Environments are still changing and the matching of organisms to their environments will always lag behind.

2. There are certain combinations of conditions and resources which can allow a species to maintain a viable population, but only if it is not being adversely affected by enemies.

3. A plant may be said to compete with another for a space in a canopy, this means that plants are competing for the light that might be captured in that space.

4. Censuses can be made only with the very greatest difficulty, except when the animals are moving above ground and can be trapped.

5. It is becoming realized that migration can be a vital factor in determining and regulating abundance.

6. On older leaves, the aphides may be becoming extinct as the leaf dies.

7. In western Europe by 1985, around 500 million individuals of each species were beingproduced for release each year.

8. The world is changing. Things never stay the same.

9. Ecological communities are non-uniform, continually altering and subject to the statistical events of random change.

10. The reason why simple laws are difficult to perceive in ecology is that the patterns keepchanging; organisms are heritably variable and evolve, and thus, at least, some of the rules of behavior and interaction themselves change.

11. The assumption is that when competition is operating and resources are limited, one species will inevitably exclude another.

 

 

Word study

Ex.1. Read the words. Give their Russian equivalents:

Colonize, techniques, structure, dioxide, stage, exploit, extreme, cyclone, catastrophes, physiological, migration, resources, reproduction, variation, concentration, volcanoes, activity of enzyme [           ], storms, zinc;

 

Ex.2. Translate the following words and words combinations:

 

Effects of environmental conditions; relative humidity; the concentration of pollutants; destructive storms; under conditions, measures of fitness; the respiration rate of a tissue; the growth rate of individuals; response to a condition; alkaline conditions; the earth is tilted; this drives temperature differentials; daily hazards; to hold fast to the rocks; forces of the waves and tides; disasters strike natural communities; detailed accounts of; wind velocity; undisturbed communities; continual natural gaps; enormously damaging natural occurrences; volcanic eruption; an ecological risk analysis; valuable to ecologists

 

Ex.3. Words to be remembered:

 

Resources; to require; rate of birth; migration; interaction; aquatic communities; turbulence; survivorship; reproduction; physiological state; adverse level; acid conditions; latitudinal variation; heat damage; long-term prediction; to withstand; to persist; to recur; ancestor; to suffer; to devastate; gust; regeneration; destruction

 

Reading A: CONDITIONS

Ex.1. Read the article and think about the influence of environmental conditions on the distribution and abundance of a species.

 

In order to understand the distribution and abundance of a species we need to know many things: (i) its history; (ii) the resources that it requires;                                                                          (iii) the individuals' rates of birth, death and migration;(iv) their interactions with their own and other species; and (v) the effects of environmental conditions.

A condition is an abiotic environmental factor which varies in space and time. Examples include temperature, relative humidity, PH, salinity and the concentration of pollutants. The 'conditions' of an environment also include a variety of hazards such as hurricanes and volcanoes and, especially in aquatic communities, destructive storms and turbulence. A condition may be modified by the presence of other organisms, for example temperature, humidity and soil pH may be altered under a forest canopy. But, unlike resources, conditions are not consumed or used up by organisms.

For some conditions we can recognize an optimum concentration or level at which an organism performs best, with its activity tailing off at both lower and higher leve ls. For an evolutionary ecologist 'optimal' conditions are most likely to be those under which the individuals of the species leave most descendants (are fittest), but these are often quite impossible to determine in practice because measures of fitness should be made over several (ideally many) generations. Instead, we more often measure the effect of conditions on some chosen properties like the activity of an enzyme, the respiration rate of a tissue, the growth rate of individuals, their rate of reproduction or survivorship or on physiological states. However, the effect of variation in conditions on these various properties will often not be the same.

The precise shape of the curve of response to a condition—whether it is symmetrical or skewed, broad or narrow—will vary from condition to condition' The generalized form of response is appropriate for conditions like temperature and pH in which there is a continuum from an adverse or lethal level (e.g. freezing or very acid conditions), through favourable levels of the condition to a further adverse or lethal level (heat damage or very alkaline conditions). A particular problem arises at very high temperatures which may increase the activity of enzymes but also the rate at which they become inactivated. A very short exposure to high temperature may then increase an activity but a longer exposure may be lethal.

Variations in temperature on and within the surface of the earth have a variety of causes: the effects of latitude and altitude, continental, seasonal and diurnal effects, microclimatic effects and, in soil and water, the effects of depth. Latitudinal and seasonal variations cannot really be separated. The angle at which the earth is tilted relative to the sun changes with the seasons, and this drives some of the main temperature differentials on the earth's surface. The hottest temperatures occur in the middle latitudes rather than at the Equator.

 

 

Ex.2. Comprehension check-up:

 

1. What is important to know in order to understand the distribution and abundance of a species?

2. What is a condition?

3. Can you give examples of the condition components of an environment?

4. How do conditions differ from resources?

5. Is condition anything inalterable?

6. What are optimal conditions for an organism?

7. How is it possible to determine the fitness of a species?

8. What is often measured instead of fitness?

9. What will be the effect of variation in conditions on various properties of an organism?

10. How harmful may high temperatures be?

 

Ex.3. Speak on conditions as variable environmental factors, having influence on the distribution and abundance of a species.

 

Reading B:   Hazards, disasters and catastrophes: ecology of extreme events

 

Ex.1. Read the following article consulting a dictionary:

 

The wind and the tides are normal daily hazards in the life of many organisms. Their structure and behaviour bear some witness to the frequency and intensity that such frequent hazards have played in the evolutionary history of their species. Thus, most trees withstand the force of most storms without falling over or losing their living branches. Most limpets, barnacles and kelps hold fast to the rocks through the normal day to day forces of the waves and tides. We can also recognize a scale of more severely damaging forces (we might call them 'disasters'), that occur occasionally, but with sufficient frequency to have contributed repeatedly to the forces of natural selection. When such a force recurs it will meet a population that still has a genetic memory of the selection that acted on its ancestors—and may therefore suffer less than they did. In the woodlands and shrub communities of arid zones, fire has this quality, and tolerance of fire damage is a clearly evolved response. There are clearly also many species of plant and animal whose life depends on opportunistically exploiting 'disasters' that have affected others.

 

When disasters strike natural communities it is only rarely that they have been carefully studied before the event. One exception is cyclone 'Hugo' which struck the Caribbean island of Guadeloupe in 1994. Detailed accounts of the dense humid forests of the island had been published only 4 years before cyclone 'Hugo'. The cyclone devastated the forests with mean maximum wind velocities of 27O km h-r and gusts of 32o km h-1. Up to 30o mm of rain fell in 40 h. Early stages of regeneration after the cyclone typify the responses of long-established communities on both land or sea to massive forces of destruction. Even in undisturbed' communities there is continual creation of gaps as individuals (e.g. trees in a forest, kelps on a seashore) die and the space they occupied is recolonized. After massive devastation by cyclones or other widespread disasters, much of the recolonization follows much the same course as the microsuccessions that were part of the natural regeneration cycle in the previously undisturbed community. Species that normally colonized only natural gaps in the vegetation come to dominate a continuous community. Whether the community is that of a rocky shore or a tropical rainforest the early succession after disasters tends to be of competition- (or shade-) intolerant, relatively short-lived species with high rates of precocious reproduction.

In contrast to conditions that we have called 'hazards' and 'disasters' there are natural occurrences that are enormously damaging, yet occur so rarely that they may have no lasting selective effect on the evolution of the species. We might call such events 'catastrophes', for example the volcanic eruption of Mt St Helens or of Krakatau. The next time that Krakatau erupts there are unlikely to be any genes persisting that were selected for volcano tolerance!

Of course, what we have called ecological hazards, disasters and catastrophes are arbitrary stages on a continuum. It would be valuable to ecologists, to quantify this continuum—the equivalent of an ecological risk analysis. The bulk of statistical theory has, however, been mainly concerned with means and variances, i.e. with the 'normal' range of happenings. Ecologists require a statistical procedure that is appropriate for rare events and it is convenient that the probability structure of extreme values conforms to a generalized distribution that can be estimated by maximum likelihood techniques. Such a statistical proce­dure has been applied to sea surface temperatures, wave forces, wind speeds and human life spans and accurate long-term predictions can apparently be made from a surprisingly small number of measurements. For the distribution of organisms in nature it is usually extremes rather than averages that matter. The statistics of extreme values is therefore likely to become increasingly valuable to ecologists'

 

Ex.2. Render the first paragraph in Russian.

 

Ex.3. Try to explain what role extreme events play in the evolution of species and why their prediction is so valuable to ecologists.

 

Reading C:    Environmental pollution

 

Ex.1. Read the text and try to understand how individuals can tolerate pollution and become adapted to it.

 

A number of environmental conditions that are, regrettably, becoming increasingly important are due to the accumulation of toxic by-products of humans' activities.

Sulphur dioxide emitted from power stations, and metals like copper, zinc and lead, dumped around mines or deposited around refineries, are just some of the pollutants that limit distributions, especially of plants. Many such pollutants are present naturally, but at low, concentrations, and some are indeed essential nutrients for plants. But, in polluted areas their concentrations can rise to lethal levels and there is a succession of disappearances of one species after another. The loss of species is
often the first indication that pollution has occurred and changes in the species  richness of a river, lake or area of land provide bioassays of the extent of their pollution.

Yet, it is rare to find even the most inhospitable polluted areas entirely devoid of species; there are usually at least a few individuals of a few, species that can tolerate the conditions. Even natural populations from unpolluted areas often contain a low frequency of individuals that tolerate the pollutant. Such individuals may be the only ones to survive or colonize as pollutant levels rise, and then become the founders of a tolerant population to which they have passed on their 'tolerance' genes. Pollution, therefore, provides us with an ideal opportunity to observe evolution in action. However, sufficient genetic variability is not present in all populations; some species repeatedly give rise to tolerant populations, whilst others rarely if ever do so.

Thus, in very simple terms, a pollutant has twofold effect. When it is newly arisen or is at extremely high concentrations, there will be few individuals of any species present (the exceptions being naturally tolerant variants or their immediate descendants). Subsequently, however, the polluted area is likely to support a much higher density of individuals, but these will be representatives of a much smaller range of species than would be present in the absence of the pollutant' Such newly evolved, species-poor communities are now an established part of human environments.

 Pollution can of course have its effects far from the original source. Toxic effluents from a mine or a factory may enter a watercourse and affect its flora and fauna for its whole length downstream. Effluents from large industrial complexes can pollute and change the flora and fauna of many rivers and lakes in a region and cause international disputes. A striking example is the creation of 'acid rain' falling in Scotland and Scandinavia from industrial activities in other countries. Since the Industrial Revolution, the burning of fossil fuels and the consequent emission to the atmosphere of various pollutants, notably sulphur dioxide, has produced a deposition of dry acidic particles and rain that is essentially dilute sulphuri c acid. The history of the acidification of lakes is often recorded in the succession of diatom species accumulated in lake sediments .  

Diatom species composition, for example, has changed over the past 400 years or more in Round Loch of Glenhead, Scotland — far from major industrial sites. A sediment core containing the accumulated identifiable remains of diatoms has been analyzed section by section, and these show a rapid and dramatic decline in those species that are rarely found below pH 5.5     and at the same time an increase in species typical of acid conditions. Since about 1850 the pH has declined from about 5.5 to about 4.6.

 

Ex.2. Find in the text equivalents of the following words and word combinations:

 

Из-за накопления токсичных побочных продуктов деятельности человека;  сернистый газ, выбрасываемый энергетическими станциями; металлы, сбрасываемые вокруг приисков и шахт; загрязняющие вещества, препятствующие распространению видов; естественно присутствовать в природе; необходимое питательное вещество; летальный уровень; череда исчезновений видов; видовая насыщенность; дать биологическую оценку; в наибольшей степени загрязненные территории; полностью лишенный видов; наблюдать эволюцию в действии; достаточная генетическая изменчивость; двойной эффект; ядовитые стоки с заводов; попадать в водоток; воздействовать на флору и фауну; вызывать экологические нарушения на международном уровне;  образование кислотного дождя; сжигание ископаемого топлива; постоянные выбросы в атмосферу различных загрязнителей; осаждение сухих кислотных частиц; окисление озер; вымирание видов.

 

Ex.3. Comprehension check-up.

1. What are the origins of environmental pollution?

2. Do pollutants always effect natural populations negatively?

3. In what case does pollution provide us with an opportunity to observe evolution in action?

4. Why do we say that a pollutant has a twofold effect?

5. How far can pollution spread from the original source?

6. How harmful may acid rains be?

 

Ex. 4.  Check your knowledge of the following words and expressions. Then use them discussing the problems of environmental pollution.

 



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