Assignments to do:

I Remember:

1. Gg is pronounced as follows:

Before e,i,y [dʒ] : page, gene, biotechnology

Before constants and other vowels [g]: game, glad, bag

2. Suffixes –ic, -al form adjectives from the nouns:

person – personal

history – historical

base - basic

II Read the words paying attention to the pronunciation:

Gate, gem, gas, age, gym, page, egg, gene, game, gag, green, geography.

III Give the transcription to the following words:

Bag, page, big, give, guess, gloves, go, great, general.

IV Read and translate the following words:

Central, experimental, academic, electric, prokaryotic, practical, monumental, historical, bacterial, social.

V Read and translate the text about evolution of eukaryotes

The Evolution of Eukaryotes

Biologists generally believe that life arose on Earth in the form of very simple organisms, similar to prokaryotic cells, about 3.5 to 4 billion years ago. About 2.5 billion years ago, the first eukaryotic cells evolved from prokaryotic cells. Recall that prokaryotes and eukaryotes differ mainly in that eukaryotes contain highly specialized organelles. The theory explaining the origin of eukaryotes from prokaryotes, pioneered by Lynn Margulis, is the endosymbiotic theory. According to this theory, larger bacterial cells lost their cell walls and engulfed smaller bacterial cells. This relationship, in which one organism lives within another, is called endosymbiosis.

According to the endosymbiotic theory, the ancestral eukaryote developed a rudimentary nucleus when the plasma membrane folded around the chromosome. This cell, called a nucleoplasm, may have ingested aerobic bacteria. Some ingested bacteria lived inside the host nucleoplasm. This arrangement evolved into a symbiotic relationship in which the host nucleoplasm supplied nutrients and the endosymbiotic bacterium produced energy that could be used by the nucleoplasm. Similarly, chloroplasts may be descendants of photosynthetic prokaryotes ingested by this early nucleoplasm. Eukaryotic flagella and cilia are believed to have originated from symbiotic associations between the plasma membrane of early eukaryotes and motile spiral bacteria called spirochetes.

Studies comparing prokaryotic and eukaryotic cells provide evidence for the endosymbiotic theory. For example, both mitochondria and chloroplasts resemble bacteria in size and shape. Further, these organelles contain circular DNA, which is typical of prokaryotes, and the organelles can reproduce independently of their host cell. Moreover, mitochondrial and chloroplast ribosomes resemble those of prokaryotes, and their mechanism of protein synthesis is more similar to that found in bacteria .

VI Remember the following word and word-combinations:

To arise, simple organisms, the first eukaryotic cells evolved from prokaryotic cells, to differ, to pioneer, relationship, ancestral, rudimentary nucleus, to ingest, nutrient, descendant, cilia, to originate, host cell.