III. Answer the questions to text 3.

1. What are the main characteristics of any population?

1. Does the term "gene pool" refer to one individual or to a whole species?

2. What interactions between individuals in the population provide the stability of the species?

3. What is the difference between a population and a community?

4. What is an ecosystem?

5. Which systems are, as a rule, more stress resistant – complex or simple?

6. What is a characteristic property of any stable ecosystem?

IV. Say it in English.

1. Каждый биологический вид характеризуется определенным генофондом.

2. Генетическая информация передается от предков к потомкам.

3. Конкуренция и размножение жизненно важны для стабильности существования вида.

4. Время жизни вида превосходит время жизни особи данного вида на много порядков.

5. Природные экосистемы – это сложные саморегулирующиеся системы.

6. Как правило, чем более сложна система, тем успешнее она противостоит внешнему воздействию.

7. Взаимодействие сообществ живых организмов с их неживым (физическим) окружением связывает компоненты экосистемы в единое целое.

UNIT 4

I. Learn the vocabulary.

Vocabulary before text 4

producers производители, продуценты

consumers потребители, консументы

surface поверхность

remarkably необыкновенно, удивительно

diverse разнообразный

array масса, совокупность, множество

despite несмотря на

capture поглощение, захват

nourishment питание, пища

herbivore травоядное животное

carnivore плотоядное животное

scavenger животное, пытающееся падалью

flesh мясо, плоть

tissues ткани

decomposer деструктор, разлагающий вид

organic matter органическое вещество

host хозяин

detritivore детритоядное животное

waste отходы, отбросы

earthworm земляной (дождевой) червь

crab краб

route маршрут, путь

ammonia аммиак (NH₃)

2. Read and translate text 4. Text 4

PRODUCERS AND CONSUMERS IN LIVING SYSTEMS

The Earth's surface is remarkably diverse. Its deserts differ from grasslands and forests differ from arctic tundra in climate, soils, plant and animal communities. Oceans, seas, lakes, and rivers differ in physical and chemical properties as well as in their arrays of organisms. Yet, despite the differences, each region functions as a system in much the same way.

All green plants and some single-celled organisms are photosynthetic autotrophs, which are the most common "self-feeding nourishment." Photosynthetic autotrophs capture sunlight energy and convert it to forms they can use to synthesise organic compounds from simple inorganic substances. By doing so, autotrophs provide the energy used by the entire biosphere. Because of their important role in ecosystems, autotrophs have been called producers, although they might better be called converters.

Energy stored in organic compounds of autotrophs is transferred through a number of heterotrophs (heterotrophs are "not self-feeding" organisms or "feeding on others") before being lost as heat to the surroundings.

There are two basically different types of heterotrophs. Those that obtain their energy from living organisms are called consumers, and those that obtain their energy from dead organisms or from organic compounds dispersed in the environment are called decomposers. The heterotrophs include:

a) consumers: herbivores (Latin herba means grass) feed upon plants, carnivores (Latin carnis means flesh or meat) eat animals, scavengers – animals or birds that live on decaying flesh, parasites that take in blood and other tissues from living hosts;

b) decomposers: mostly bacteria and fungi that obtain organic nutrients by breaking down the remains or products of other organisms. The activity of decomposers allows simple compounds to be recycled back to the autotrophs;

с) detritivores: earthworms, crabs, and other heterotrophs that feed on detritus – partly decayed dead plant and animal tissues and organic wastes (Latin detritus means worn down).

Photosynthesis dominates the energy-trapping pathways so that sometimes it is easy to overlook other, less common routes. The chemosynthetic autotrophs obtain energy for building organic compounds not from sunlight but rather from the oxidation of inorganic substances: ammonium ions, iron or sulphur compounds. That is their source of energy for building organic compounds. For example, some bacteria present in soil use ammonia (NH₃) molecules as an energy source.

During their growth, autotrophs take up water and carbon dioxide as a source of oxygen, carbon, and hydrogen along with dissolved minerals, including ionized forms of nitrogen and phosphorus. Such nutrients are essential for the synthesis of carbohydrates, lipids, proteins, and nucleic acids – which autotrophs as well as heterotrophs use in biosynthesis and other cell activities.

When decomposers and detritivores get their turn at this organic matter, they break it down completely to inorganic substances. If those substances are not washed away from the system, they can be used again as nutrients by the autotrophs.