Biology 2024 Jamb Examination

I – Paramylum granules
II – Contractile vacuole
III – Chloroplasts
IV – Nucleus

The chloroplasts represent the plant-like characteristic of Euglena, allowing it to perform photosynthesis and produce its own food.

Paramecium reproduces asexually by binary fission, where the single-celled organism duplicates its organelles and genetic material and then divides into two genetically similar daughter cells. Although conjugation (a form of sexual exchange) also occurs in paramecium, the primary asexual method is binary fission.

Population density is calculated as population divided by area.$$D_p = \dfrac{N}{A}$$$$D_p = \dfrac{ 2,310,000}{2,310 } = 1,000 $$ Thus 1000 people per square kilometre.

Primary succession occurs on newly formed or exposed surfaces where no soil or prior community exists (for example, on bare rock after a volcanic eruption or on newly exposed glacial till). Pioneer species colonize, alter the environment, and enable subsequent communities to establish.

Photosynthesis releases oxygen as a by-product when plants, algae, and some bacteria convert carbon dioxide and water into glucose using light energy. Respiration, combustion, and decomposition consume oxygen or release carbon dioxide rather than releasing oxygen.

• Oral groove: 
  This is the shallow depression on the paramecium's body lined with cilia, where food particles are collected. 
• Gullet: 
  This is the tube-like structure that follows the oral groove, where the food is transported further into the cell. 

Liverwort rhizoids are unicellular and unbranched structures that anchor the plant to the substrate and help in absorption of water and minerals. Unlike mosses, which have multicellular branched rhizoids, liverworts have simpler rhizoids.

Glycolysis is the anaerobic breakdown of glucose into pyruvic acid, producing a net gain of 2 ATP molecules. This process occurs in the cytoplasm with the help of enzymes and does not require oxygen.

In unicellular organisms like paramecium, gases diffuse directly through the plasma membrane because their high surface-area-to-volume ratio allows efficient exchange of oxygen and carbon dioxide. Hydra also exchanges gases through diffusion, but paramecium is the classic single-celled example.

Secondary succession occurs on surfaces where a community has previously existed and been disturbed, such as abandoned farmland or cleared forest. It starts on an already colonized surface and generally progresses faster than primary succession.