Chapter 9: Biology for Technology

Biology is the science of living systems. It is essential for Bio-Systems Technology and gives Engineering Technology students an understanding of the environment and of biological materials (Urry et al., 2020).

Cells

All living things are made of cells. Prokaryotic cells (bacteria) lack a nucleus; eukaryotic cells (plants, animals, fungi) have one. Key organelles: the nucleus (DNA), mitochondria (respiration), chloroplasts (photosynthesis, in plants), the cell membrane (controls entry and exit), the cell wall (support in plants), and ribosomes (protein synthesis). Cells form tissues, tissues form organs, and organs form systems.

Biomolecules and enzymes

The main biological molecules are carbohydrates (energy, structure), lipids (energy storage, membranes), proteins (enzymes, structure, transport), and nucleic acids (DNA, RNA). Enzymes are biological catalysts. Their activity depends on temperature and pH; they work best at an optimum and are denatured by extremes. Enzymes are used in food processing (cheese, bread, juice clarification), detergents, and biofuel production.

Energy in living things

Photosynthesis captures light energy: . Respiration releases energy from glucose: . Without oxygen, anaerobic respiration produces ethanol and CO₂ in yeast (fermentation) or lactic acid in muscles. Plants make food; animals eat it.

Plant and animal systems

Plants take up water and minerals through roots; xylem carries water upward, phloem carries sugars; transpiration loses water through stomata and drives water uptake. Plant growth depends on light, water, nutrients, temperature, and carbon dioxide. Growth substances (auxins, gibberellins, cytokinins) are used in cuttings, tissue culture, and fruit ripening.

Animals: digestion breaks down food; the circulatory system transports materials; the respiratory system exchanges gases; the nervous and endocrine systems coordinate. Good animal husbandry rests on nutrition, health, housing, and breeding.

Genetics

DNA carries genetic information in the sequence of its bases (A, T, C, G); a gene is a section of DNA coding for a protein. Offspring inherit one allele from each parent. In a monohybrid cross of two heterozygotes (Tt × Tt), the offspring are in the ratio 1 TT : 2 Tt : 1 tt, which means 3 showing the dominant trait to 1 recessive. Selective breeding has produced high-yield crops and livestock; genetic engineering transfers genes directly and raises ethical and safety questions.

Ecology and the environment

An ecosystem includes living things and their environment. Food chains and food webs show who eats whom; energy flow is one-way and only about 10% passes to the next level (10 000 kJ at producers gives about 1 000, 100, then 10 kJ at higher levels). Nutrient cycles (carbon, nitrogen, water) recycle matter; nitrogen-fixing bacteria such as Rhizobium in legume root nodules are the basis of crop rotation with legumes. Biodiversity is the variety of life; Sri Lanka, together with the Western Ghats of India, is a recognised biodiversity hotspot with many endemic species. Threats include habitat loss, pollution, invasive species, and climate change. Conservation and sustainable use are the responsibility of every technologist.

Microorganisms

Bacteria, fungi, viruses, and protozoa are useful (yoghurt, bread, antibiotics, composting, biogas, wastewater treatment) and harmful (disease, food spoilage, crop diseases). Microbial growth depends on food, moisture, temperature, pH, and oxygen, which is why food preservation works by controlling these factors (Chapter 18). Hygiene, sanitation, vaccination, and sterilization control disease.

Biotechnology basics

Biotechnology uses living organisms or their products: fermentation, tissue culture (growing plants from small pieces of tissue), enzyme technology, DNA technology (for example the polymerase chain reaction to copy DNA), biofertilizers, and biofuels. Each application should be judged on safety, ethics, and sustainability.

Common mistakes

Confusing photosynthesis and respiration; plants do both.

Treating the 10% rule as exact; it is an approximation.

Using “evolved to” language that suggests a goal.

Practice questions

State the products of aerobic respiration.

In a cross between two heterozygous tall pea plants (Tt × Tt), what fraction of offspring are short? [1/4]

Explain why an energy pyramid has fewer individuals at higher trophic levels.