1.3 Features of organisms (3)
Resources |
Revision Questions |
Biology
Login to see all questions
Click on a question to view the answer
1.
Explain how the protein coat of a virus contributes to its ability to infect a host cell. Consider the structure and function of the capsid in your answer.
The protein coat, or capsid, plays a crucial role in viral infection in several ways:
- Protection: The capsid protects the viral genetic material (DNA or RNA) from damage by enzymes in the environment (e.g., nucleases) and from physical damage during transmission.
- Attachment: The capsid has specific surface proteins that can bind to complementary receptor molecules on the surface of a host cell. This specific binding is essential for the virus to attach to the correct type of cell and initiate infection.
- Recognition: The capsid structure can act as a recognition signal, allowing the virus to be recognized by the host cell's immune system, triggering an immune response.
- Entry: In some cases, the capsid may facilitate entry into the host cell. For example, some viruses can trigger endocytosis, where the host cell engulfs the virus enclosed within the capsid.
2.
Question 3: A student states: "All animals are heterotrophic because they consume other organisms." Explain whether this statement is correct. Use examples to support your answer and relate your explanation to the classification of animals into the Kingdom Animalia.
The statement "All animals are heterotrophic because they consume other organisms" is generally correct, but requires some nuance. Heterotrophic means obtaining energy from organic sources. Animals are classified into the Kingdom Animalia primarily because they are heterotrophic. This distinguishes them from plants, which are autotrophic and produce their own food through photosynthesis.
Examples supporting the statement:
- Carnivores: Animals like lions, wolves, and sharks obtain energy by consuming other animals.
- Herbivores: Animals like cows, deer, and rabbits obtain energy by consuming plants. Although they consume plants, they still rely on the organic molecules within the plant matter for energy.
- Omnivores: Animals like humans, bears, and pigs consume both plants and animals.
The classification of animals into the Kingdom Animalia is based on their heterotrophic nature. This is a fundamental characteristic that sets them apart from plants and other kingdoms. The ability to consume other organisms is a defining feature that has driven the evolution of diverse feeding strategies and complex digestive systems within the animal kingdom.
3.
Describe the key differences between a plant cell and an animal cell, relating these differences to the characteristics of the Plant Kingdom.
Key differences between plant and animal cells, and their relation to the Plant Kingdom, include:
| Cell |
| Cell Wall | Present (made of cellulose) - Provides support and protection. This is a defining characteristic of plant cells. |
| Chloroplasts | Present - Site of photosynthesis, allowing plants to produce their own food. |
| Large Vacuole | Present - Stores water, nutrients, and waste products. Helps maintain cell turgor pressure. |
| Centrioles | Absent - Plant cells do not have centrioles, which are involved in cell division in animal cells. |
| Shape | More regular and fixed shape due to the cell wall. | More flexible and irregular shape. |
These differences are directly related to the characteristics of the Plant Kingdom, which are autotrophic (photosynthetic), multicellular, and have structural support provided by the cell wall. The presence of chloroplasts and a large vacuole are essential for these characteristics.