Cell Structure And Components

When the bark of a tree is removed in a circular fashion near its base, it damages the phloem, which is responsible for transporting sugars and other nutrients produced by photosynthesis in the leaves down to the roots for energy and growth. This process is called translocation. With the phloem damaged, the roots are starved of the energy they need for essential functions such as absorption of water and minerals from the soil, leading to their gradual drying up and eventual death.

Among marine creatures, the sea cow and sea lion are mammals, while the sea horse is a fish. **1. Sea Cow:** The sea cow, a herbivorous marine mammal, resides in the Indian and Pacific Oceans, growing to 3m and weighing around 600kg. Sadly, it's vulnerable due to habitat degradation and hunting. **2. Sea Horse:** The sea horse, a carnivorous marine fish, is found in shallow tropical waters. It grows to 35cm, weighs around 200g, and is vulnerable due to habitat damage and fishing. **3. Sea Lion:** The sea lion, a carnivorous marine mammal, breeds on Pacific beaches. It grows to 2.5m, weighs around 350kg, and is Endangered.

  **Statement 1 is correct.** Plant cells have rigid cell walls made of cellulose, a complex carbohydrate, which animal cells lack. Animal cells rely on a plasma membrane for structure and protection. **Statement 2 is incorrect.** Both plant and animal cells have a plasma membrane, a phospholipid bilayer that controls what enters and leaves the cell. It's a fundamental component for all cells. **Statement 3 is correct.** Mature plant cells typically have a single, large central vacuole that stores water, nutrients, and waste products. Animal cells can have vacuoles, but they are usually smaller and more numerous.

**Fern:** * Ferns typically require soil and moisture to grow, as they rely on water-conducting tissues and need a substrate to anchor their roots. **Lichen:** * Lichens are a symbiotic association between a fungus and an algae or cyanobacteria. * Lichens are well-adapted to survive on surfaces without soil, such as rocks, tree bark, and even bare ground, as they can obtain their nutrients and moisture directly from the air and precipitation. * Lichens are sensitive to airborne pollutants, such as sulfur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), and heavy metals (like lead and mercury). Sulfur dioxide, for instance, causes chlorosis (yellowing) and necrosis (cell death) in lichen thalli. This sensitivity makes lichens an effective indicator of air quality. **Moss:** * Mosses are non-vascular plants that can grow on surfaces without soil, such as rocks, tree trunks, and even roofs. * Mosses have specialised structures that allow them to absorb water and nutrients directly from the environment. **Mushrooms:** * Mushrooms are the reproductive structures of fungi, and they typically require a substrate, such as decaying organic matter, to grow. Mushrooms are not able to directly survive on a surface without soil or a nutrient-rich medium. Therefore, among the given options, lichens and mosses are the most likely to be found surviving on a surface without soil in the natural environment.