Pyramid of energy and number is upright in pond ecosystem. Pyramid of biomass is inverted in an aquatic ecosystem because the biomass of fishes far exceeds the biomass of phytoplanktons.

Desertification is the degradation of land in arid, semi-arid and dry sub-humid areas. It is caused primarily by human activities and climatic variations. Desertification does not refer to the expansion of existing deserts.
It occurs because dryland ecosystems, which cover over one third of the world‘s land area, are extremely vulnerable to overexploitation and inappropriate land use.
Established in 1994, the United Nations Convention to Combat Desertification (UNCCD) is the sole legally binding international agreement linking environment and development to sustainable land management. The Convention addresses specifically the arid, semi-arid and dry sub-humid areas, known as the drylands, where some of the most vulnerable ecosystems and peoples can be found.

Main reasons that cause desertification in India are:
• Water erosion (10.98 per cent)
• Wind erosion (5.55 per cent)
• Human-made/settlements (0.69 per cent)
• Vegetation degradation (8.91 per cent)
• Salinity (1.12 per cent)
• Others (2.07 per cent)

A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Also called molecular marker and signature molecule.
It can also be a substance whose detection indicates a particular disease state, for example, the presence of an antibody may indicate an infection. More specifically, a biomarker indicates a change in expression or state of a protein that correlates with the risk or progression of a disease, or with the susceptibility of the disease to a given treatment.
One example of a commonly used biomarker in medicine is prostate-specific antigen (PSA). This marker can be measured as a proxy of prostate size with rapid changes potentially indicating cancer.

Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.
Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants. Therefore, it varies in different types of ecosystems.