Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Lichens are symbiotic associations between an algal component (phycobiont) and a fungal component (mycobiont). The alga prepares food via photosynthesis, while the fungus provides shelter and absorbs water and minerals.
Ecological Role of Lichens as Pioneer Species: They are the first organisms to colonize bare rocks. They secrete organic acids that weather rocks into soil, initiating the process of primary ecological succession.
Lichens as Bio-indicators: Lichens are highly sensitive to air pollution, particularly sulfur dioxide (). Their absence in an industrial area indicates high levels of pollution.
Viruses are considered at the borderline of living and non-living. They lack a cellular structure and a membrane, showing characteristics of life only when they enter a living host cell and use its machinery to multiply.
Ecological Role of Viruses: They act as natural population controllers by causing diseases in various species. In modern biotechnology, they serve as vectors for gene transfer.
Biological Classification: Viruses are not included in the Five Kingdom Classification system (Monera, Protista, Fungi, Plantae, Animalia) proposed by Whittaker because they are not truly 'living' organisms.
📐Formulae
💡Examples
Problem 1:
In an industrial city, it was observed that the bark of trees was devoid of any lichen growth, whereas trees in a nearby forest were covered in them. Explain this phenomenon.
Solution:
Lichens are sensitive to air pollutants, especially .
Explanation:
Lichens obtain their nutrients from the atmosphere. In industrial areas, the concentration of is high. This gas interferes with the chlorophyll of the algal partner in the lichen, leading to its death. Therefore, lichens act as natural pollution indicators.
Problem 2:
Why are viruses not classified under the Five Kingdom System?
Solution:
Because they are non-cellular and do not show metabolism outside a host.
Explanation:
The Five Kingdom system is based on cell structure and complexity. Viruses are composed of a protein coat surrounding a nucleic acid (DNA or RNA) and do not perform any metabolic activities like respiration or growth unless they are inside a host cell.
Problem 3:
How do lichens contribute to soil formation?
Solution:
Through chemical weathering of rocks.
Explanation:
Lichens grow on bare rocks and produce acidic substances. These acids break down the rocky surface into fine particles, which eventually leads to the formation of soil, allowing other plants like mosses to grow.