Genetics and Plant Biology Quiz

Defining Terms and Giving Examples

• Species: A group of organisms that can interbreed to produce viable, fertile offspring (e.g., Grey squirrels, Hazel trees).
• Population: All the organisms of one species in a particular place at a particular time (e.g., the Human population of Britain in 2014).
• Community: All the populations of all the species in a particular place at a particular time (i.e., all life in an area including animals, plants, fungi, bacteria...everything living).
• Habitat: The place, with a distinctive set of conditions, where an organism lives.
• Niche: The role an organism plays in its environment or how an organism exploits (uses) its environment. Most importantly it describes what it eats/where it is located in a food chain/its trophic level. But it also includes where it shelters and the times it is active. Only one species can survive in a single niche. If a second species inhabits exactly the same niche they will compete and one species will die out.
• Environment: The external surroundings including all of the biotic (living) and abiotic (non-living) factors.
• Interspecific competition: Competition for resources (e.g., light, space, food, minerals) between individuals of different species.
• Intraspecific competition: Competition for resources (e.g., light, space, food, minerals) between individuals of the same species.

Species

• A group of organisms capable of interbreeding to produce viable, fertile offspring. Named examples include Grey squirrels and Hazel trees.

Population

• All the organisms of one species in a specific area at a specific time. An example is the human population of Britain in 2014.

Community

• All the populations of all species in a particular area at a specific time. This encompasses all living organisms in a region.

Habitat

• The specific place where a particular organism lives, with its unique conditions.

Niche

• An organism's role in its environment, including what it eats, where it lives, and when it's active. No two species can occupy the exact same niche.

Environment

• The surroundings (both living and non-living) of an organism.

Interspecific Competition

• Competition for resources (like food or space) between different species.

Intraspecific Competition

• Competition for resources (like food or space) between individuals of the same species.

Behavioural Adaptations

• Actions that help an organism to survive or reproduce. Examples include hibernation, migration, hunting strategies, and herding for protection.

Physiological Adaptations

• Features of an organism's body chemistry that help it survive or reproduce. Examples include chemicals acting as pigments, modified hemoglobin, venom, and heat-stable enzymes.

Anatomical Adaptations

• Physical structures that help an organism survive or reproduce. Examples include lungs, muscles in arterioles, antlers on deer, claws, and large ears on elephants.

Natural Selection

• A population has naturally occurring genetic variation.
• A change in the environment prompts a change in selection pressures.
• An allele previously unimportant becomes beneficial.
• Organisms possessing the advantageous allele are more likely to survive and reproduce.
• Offspring of these organisms are more likely to possess the benefitfull allele, making it increasingly common.

Gene Pool

• All the alleles of all the genes in a population at a given time. Greater genetic diversity exists when a larger number of different alleles are present.

Hardy-Weinberg Equilibrium Assumptions

• Large population size to prevent inbreeding effects.
• Random mating – individuals of a particular genotype shouldn’t preferentially mate with each other.
• Absence of selection pressures impacting allele frequency.
• No mutations to affect allele frequency.
• No immigration or emigration preventing gene flow into/out of the population.

Biodiversity Components

• Genetic diversity – Variation in alleles within a species' gene pool. This increases over time due to mutations.
• Species diversity – Number of species and the number of individuals within a community. It tends to increase over time.

Sources of Genetic Diversity

• Mutations – Changes in DNA that can create new alleles.
• Meiosis – Crossing over during meiosis shuffles genetic material, also independent assortment during meiosis provides new gene combinations.

Biodiversity, Species Richness and Endemism

• Biodiversity: the variety of life on Earth at all its levels, from genes to ecosystems. It is made up of genetic diversity and species diversity.
• Species richness: the number of different species in a particular habitat at a particular time. It does not consider abundance
• Endemism: a characteristic of a species restricted to a certain geographic location. Islands usually have a high degree of endemism because species have been isolated for a long time.

Statistical Test for Species Diversity

• Simpson's Biodiversity Diversity Index (D) where N = total number of organisms of all species and n = total number of organisms of a particular species.

Plant Cell Organelles

• Cell wall: Provides structural support and protection for plant cells.
• Chloroplasts: Site of photosynthesis.
• Amyloplasts: Store starch.
• Vacuole: Stores water, minerals, and other substances maintaining turgidity.
• Tonoplast: Membrane surrounding the vacuole.
• Plasmodesmata: Perforations in the cell walls allowing substances to pass between adjacent plant cells.
• Pits: Thin areas of the cell wall facilitating the movement of substances between cells.
• Middle lamella: Layer between adjacent plant cell walls.

Cellulose Structure and Function

• Cellulose is a structural polysaccharide composed of beta-glucose molecules joined by beta-1,4 linkages to form linear chains. The straight chains lie parallel to one another and are linked together by hydrogen bonds, forming strong microfibrils. This structure results in cellulose having high tensile strength. Cellulose's large size makes it insoluble in water

Starch and Cellulose Comparison

Xylem Vessels, Phloem Sieve Tubes and Sclerenchyma Fibres Diagram Identification and Location

• Xylem vessels are tube-shaped cells located in the vascular bundles, often near the outside of the stem.
• Phloem sieve tubes are also part of the vascular bundles and are located near the xylem.
• Sclerenchyma fibres have cross-walls and are located outside the vascular bundle.

Xylem Vessel Structure and Function

• Structure: These are large, elongated cells with thick cell walls strengthened by lignin for support. Cross-walls are absent in most species meaning there is a continuous tube that runs up the plant.
• Function: Transport water and dissolved minerals from roots to stems and leaves, providing structural support.

Phloem Structure and Function

• Structure: Sieve tubes are composed of living cells arranged end-to-end with perforated end walls called sieve plates. Companion cells are smaller cells closely associated with sieve tubes providing metabolic support.
• Function: Transport photosynthetic products (like sucrose) throughout the plant.

Sclerenchyma Fibers Structure and Function

• Structure: Dead cells with extremely thick, lignified cell walls; small diameter lumen. Have cross-walls, but are not tube-shaped.
• Function: Provide structural support in plants.

Measuring Effect of Mineral Deficiencies on Plants

• Preparation: prepare solutions of different mineral concentrations (with one mineral missing), keep volumes constant. Provide a control tube with all minerals. Use clear film to prevent entry of other organisms. Silver foil/other shielding prevents light and encourages uniformity.
• . Setup: grow seedling roots in the different solutions and control, keeping temperature and light conditions constant.
• Observations: measure changes to stem length, biomass (mass), leaves, colour for 3 weeks.

Inorganic Ions Required by Plants

• Nitrate ions: essential for making amino acids, proteins, and chlorophyll; lack leads to stunted growth and yellow leaves.
• Magnesium ions: needed for chlorophyll production. Deficiency shows yellowing of leaves with green veins.
• Calcium ions: required for cell wall formation, pectin production and membrane integrity. Deficiency leads to stunted growth and distorted leaf shapes.

Measuring Tensile Strength of Plant Fibres

• Preparation: gather uniform plant fibres (same diameter and length).
• Setup: Attach fibres to a clamp/hook.
• Experiment: Progressively add masses of 10 grams each.
• Measurement: Record the mass at which the fibre breaks. Repeat ten times. Record the average.
• Control: Maintain constant temperature and humidity during trials, and use plants of the same age/collected at the same time.

Drug Testing Process

• Preclinical testing: Animal studies and tissue cultures to identify active ingredients, safety, and toxicity.
• Clinical trials phase 1: small group of healthy volunteers to check safety in humans, side effects are monitored.
• Clinical trials phase 2: small group of patients to evaluate effectiveness and monitor maximum tolerated dose.
• Clinical trials phase 3: large group of patients to obtain statistically significant data, determining if a drug is more effective than existing treatments or a placebo. Double-blind trials are used.
• After-licensing: data collection continues to identify any rare side effects.

Conditions for Bacterial Growth

• Temperature: Warm temperatures for optimal enzyme activity.
• Moisture: Necessary for chemical reactions (e.g., respiration).
• Oxygen: Required for aerobic respiration in aerobic bacteria.
• pH: Optimal pH for efficient enzyme activity.

Investigating Antimicrobial Properties of Plants

• Plant extraction: Crush 5g of plant material in 10 cm³ of ethanol.
• Filter paper soaking: Soak discs of filter paper in the extract and other discs in ethanol (control).
• Bacterial lawn preparation: Spread a bacterial lawn on agar plates.
• Disc placement: Gently place the soaked discs onto the lawn, tape sections on plate to prevent escape, and incubate in a controlled environment at a suitable temperature for 24 hours (avoid body temperature).
• Clear zone measurement: Measure the clear zone (area free of bacteria) around each disc for 10 repetitions per plant. This assesses the effectiveness of the extract.
• Control/Safety procedures: Use separate sterile control discs soaked in ethanol, maintaining temperature, and aseptic technique such as using sterile equipment.

Sustainability

• The principle that the use of resources should not harm the environment or reduce the availability of resources in the long term.
• Reasons why oil-based fuels/plastics are not sustainable:
  • Finite oil reserves.
  • Release of greenhouse gases, contributing to global warming
  • Accumulation of non-biodegradable plastics causing waste management.

Carbon Sinks

• A carbon sink is a long-term storage of carbon.
• Fossil fuels are carbon sinks due to the slow decomposition of dead organisms under anaerobic conditions where decomposers are suppressed. It remains long-term and does not rapidly change the carbon cycle.

Captive Breeding Programmes

• Aim to increase populations of endangered species.
• Maintaining genetic diversity using studbooks and collaborating between breeding facilities.
• Reintroduce animals into the wild if possible, with training to ensure wild adaption, and avoid overexposure to humans.

Seed Bank Storage Processes

• Seed collection.
• Seed x-ray to confirm viability.
• Seed drying and sterilization.
• Storage in large numbers at -20°C. Avoidance of germination/decomposition.
• Monitor and test seed viability, conduct periodic germination trials.