Biology 2010 Jamb Examination

A food chain begins with a producer (usually green plants or autotrophs) because they are capable of manufacturing their own food through photosynthesis. They form the base of the food chain by converting solar energy into chemical energy, which is then transferred to consumers.

Mycorrhiza are symbiotic associations between fungi and plant roots. The fungi help plants absorb water and essential minerals like phosphorus and nitrates more efficiently from the soil. In return, the plant supplies carbohydrates to the fungi, promoting mutual growth.

The placenta acts as the interface between the mother and fetus. It allows exchange of nutrients, gases, and waste products without mixing maternal and fetal blood directly. It also serves as a protective barrier against harmful substances, though some drugs and pathogens may cross.

Erythrocytes (red blood cells) contain hemoglobin, a protein that binds oxygen with high affinity. This enables red blood cells to transport oxygen from the lungs to body tissues effectively. Other blood components such as leucocytes, lymphocytes, and thrombocytes do not carry oxygen.

The dogfish is a type of small shark that lives in marine (saltwater) environments. In contrast, Achatina (giant land snail) is terrestrial, Tilapia is a freshwater fish, and tortoises are land reptiles. Hence, only the dogfish is adapted to marine habitats.

The pelvic girdle consists of two hip bones joined at the front by the pubic symphysis, a cartilaginous joint that provides slight flexibility during movements such as childbirth. The ilium and pubis are individual parts of the pelvic bone, while the obturator foramen is a hole in the pelvic girdle.

Desert animals adapt by being nocturnal to avoid daytime heat, burrowing to escape harsh surface conditions, and adjusting body temperature to cope with extremes. Having many sweat pores would actually lead to water loss, which is disadvantageous in deserts.

Deserts are characterized by very low rainfall, sparse or no vegetation, extreme temperature variations between day and night, and harsh conditions requiring special adaptations by plants and animals. Tropical rainforests and savannas have much more vegetation and rainfall.

Biotic factors are interactions among living organisms in an ecosystem, such as competition, predation, and parasitism. Abiotic factors are non-living (temperature, rainfall), edaphic factors relate to soil, and physiographic factors relate to physical features of the land.

Population density refers to the number of individuals of a species per unit area (e.g., 20 rabbits per hectare). Population size is the total number in the area, frequency refers to occurrence across samples, and distribution describes how individuals are spread out spatially.