Algae is a primitive form of life, a single-celled or simple multiple-celled organism that is able to conduct the process of photosynthesis. It is generally found in water but can also be found elsewhere, growing on such surfaces as rocks or trees. The various types of algae are classified according to pigment.

Blue-green algae, or Cyanophyta, can grow at very high temperatures and under high- intensity light. This type of algae is the oldest form of life with photosynthetic capabilities. Fossilized remains of blue-green algae more than 3.4 billion years old have been found in parts of Africa.

Green algae, or Chlorophyta, is generally found in fresh water. It reproduces on the surfaces of enclosed bodies of water such as ponds or lakes and has the appearance of a fuzzy green coating on the surface of the water.

Brown algae, or Phaeophyta, grows in shallow, temperate water. This type of algae is the largest in size and is most recognizable as a type of seaweed. Its long stalks can be enmeshed on the ocean floor, or it can float freely on the ocean's surface.

Red algae, or Rhodophyta, is a small, delicate organism found in the deep waters of the subtropics. This type of algae has an essential role in the formation of coral reefs: it secretes lime from the seawater to foster the formation of limestone deposits.

Algae remnants found in Africa are ..............

Câu hỏi liên quan

• According to paragraph 1, which of the following is NOT true?

• Where did Moore spend most of her adult life?

• The word “sophisticated” in line 12 could best be replaced by?

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• What is true of Lake Vostok?

• The author’s tone in the passage is best described as .........

• In the fourth paragraph, the author implies that imagination is most important to scientists when they _______.

• According to the passage, we can infer that .........

• It can be inferred from paragraph 1 that___________

• It can be inferred from the passage that a person’s learning style ..............

• Persons on low incomes can access public housing through ______.

• The word "absorb" in the passage 2 is closest in meaning to_________.

• The passage is mainly about ...............

• Why is the Mongolian women's status in the community “elevated”?

• How many known kinds of plants and animals call the rain forests their home?

• Which of the following would be the best title for the passage?

• The word “derived” in paragraph 2 is closest in meaning to ______.

• How many Americans are involved in telecommuting?

• What does the passage mainly discuss?

• According to the passage, why do people join groups that practice secondary cooperation?

• According to the passage, what is implied about tea harvesting?