Sustainability and Plant Growth

Unit 3: Sustainability and Interdependence

• This unit addresses the factors that influence sustainability and interdependence among living organisms.

Food Supply, Plant Growth, and Productivity

• Food security is the ability of human populations to access food of sufficient quality and quantity, vital due to increasing population.
• Agricultural production is limited by factors controlling photosynthesis and plant growth.
• Increased food production relies on higher-yielding cultivars, fertilizers, and crop protection.
• Livestock is less efficient per unit area than plant crops due to energy loss between trophic levels.
• Plant crops include cereals, potatoes, roots, and legumes.
• Breeders develop crops with better nutritional value, pest/disease resistance, and suited to specific environments.
• Light energy is absorbed by photosynthetic pigments for ATP generation and photolysis.
• Pigments not absorbed transmit or reflect light
• Carotenoids broaden the absorption spectrum, transferring energy to chlorophyll.
• Electrons are excited by absorbed light and passed through an electron transport chain to release energy for ATP synthase to generate ATP.
• Energy is also used for photolysis, splitting water into oxygen and hydrogen ions transferred to NADP.
• RuBisCO fixes carbon dioxide with ribulose bisphosphate (RuBP) in the Calvin cycle.
• 3-phosphoglycerate (3PG) is phosphorylated by ATP and combined with NADPH to form glyceraldehyde-3-phosphate (G3P).
• G3P regenerates RuBP and synthesizes glucose, a substrate for other biosynthetic pathways.
• Biosynthetic pathways create metabolites like DNA, protein, and fat.

Plant and Animal Breeding

• Plant and animal breeding improves traits such as yield, nutrition, pest/disease resistance, and environmental adaptability.
• Plant field trials compare cultivars or treatments in various environments and evaluate GM crops.
• Treatments in trials are selected and randomized with a sufficient number of replicates to ensure valid comparisons and reduce bias.
• Inbreeding involves breeding selected, related organisms until they breed true, eliminating heterozygotes, but potentially increasing homozygous deleterious alleles (inbreeding depression).
• Outbreeding crossing unrelated individuals, maintains heterozygosity and avoids inbreeding depression.
• F1 hybrids often show hybrid vigor due to combined qualities from both parents.
• Genetic technology utilizes genomic sequencing to identify desirable genes for breeding, allowing for genetic modification for improved traits like pest or herbicide resistance.

Crop Protection

• Weeds, pests, and diseases reduce crop productivity.
• Annual weeds have rapid growth, high seed output, and long-term viability.
• Perennial weeds have storage organs and vegetative reproduction.
• Invertebrates (insects, nematodes, molluscs) and fungi, bacteria or viruses are major causes of crop diseases.
• Cultural methods for weed/pest/disease control include ploughing, weeding, and crop rotation.
• Selective herbicides target specific plant species, whereas systemic herbicides spread through the plant.
• Pesticides include herbicides, fungicides, insecticides, molluscicides, and nematicides.
• Pesticide problems include toxicity to non-target species, persistence, bioaccumulation, and development of resistant populations.
• Applications of fungicide based on disease forecasts are more effective.
• Biological control uses natural predators, parasites, or pathogens to control pests.
• Integrated pest management combines chemical, biological, and cultural methods. Potential risks of biological control include the control organism becoming invasive.

Animal Welfare

• Animal welfare involves costs, benefits, and ethical considerations in livestock production; intensive farming raises ethical concerns.
• Behavioral indicators of poor welfare include stereotypy, misdirected behavior, failure in sexual or parental behavior, and abnormal activity levels.

Symbiosis

• Symbiosis – close relationships between two different species.
• Parasitism: parasite benefits, host is harmed - often limited metabolism, transmitted through direct contact, resistant stages, or vectors. Parasites can use intermediate secondary hosts
• Mutualism: both partners benefit - e.g. the evolution of eukaryotic cells where prokaryotic cells engulfed another prokaryotic cell.

Social Behaviour

• Social groups enhance survival through social hierarchy, cooperative hunting, and social defense.
• In social hierarchies, dominant individuals carry out ritualistic displays, while subordinate animals perform appeasement behaviors.
• Alliances within social hierarchies increase social status.
• Cooperative hunting benefits all, conserving energy.
• Primates exhibit complex social behaviors, including reducing conflict through ritualistic display, appeasement, grooming, and alliances.
• Sterile-caste social insects promote survival of shared genes.
• Altruistic behavior harms donors but benefits recipients, often seen in kin selection.

Components of Biodiversity

• Components of biodiversity include genetic, species, and ecosystem diversity.
• Genetic diversity encompasses the number and frequency of alleles within a population.
• Species diversity includes species richness and relative abundance.
• Ecosystem diversity is the number of distinct ecosystems within a defined area.

Threats to Biodiversity

• Threats to biodiversity stem from exploitation, habitat loss/fragmentation, and introduced/invasive species.
• Overexploitation can lead to decreased genetic diversity via the bottleneck effect.
• Habitat fragmentation results in reduced species richness, which can be partially mitigated by habitat corridors.
• Introduced species naturalize and then spread and outcompete natives, and/or act invasively
• Edge species colonize small, fragmented habitats, resulting in a decreased biodiversity.
• Habitat corridors may allow for recolonization of small habitat fragments.

Exam Technique

• Answer questions fully, according to how many marks are available
• Use highlighters to identify the key words
• Reread the question to make sure the answer make sense
• Describe = Say what you see in detail
• Explain = Give an explanation for what you see

Experimental and Data Questions

• First highlight the aim. This may be needed for the conclusion
• Conclusion = Relate to the aim and answer the aim
• Controls = Everything is the same except the active factor
• Use a ruler for tables and graphs
• Independent variable = x-axis
• Dependent variable = y-axis
• Describe Data = Use numbers and units in your answer. Say what you see
• Why was percentage change used? = Relates to initial values that were all different