Consider statements about mitochondria: 1. They have a single membrane. 2. They contain their own circular DNA. 3. They are the site of aerobic respiration. Which are correct? MCQ with Answer and Explanation

Explanation:
Primary consumers are herbivores that feed directly on producers (plants). Grasshopper feeds on grass/plants, thus a primary consumer. Lion and eagle are secondary/tertiary consumers (carnivores). Fungi are decomposers. In a food chain: Grass (producer) → Grasshopper (primary consumer) → Frog (secondary consumer) → Snake (tertiary consumer) → Eagle (quaternary consumer). Energy flows unidirectionally.

Explanation:
Bacterial infections (like tuberculosis, pneumonia) are effectively treated with antibiotics, which target specific bacterial structures or metabolic pathways. Many viral diseases (like polio, measles, influenza) can be prevented through vaccination, which stimulates the immune system to develop memory against the virus. Fungal diseases (like ringworm, candidiasis) are caused by fungi, not protozoa; protozoa cause diseases like malaria and amoebiasis. Thus, statements 1 and 2 are correct.

Explanation:
The lymphatic system drains excess tissue fluid (lymph) back to the venous blood. Blood circulation is the cardiovascular system; lymph nodes filter lymph; thymus is a primary lymphoid organ.