Biology end of years

What are abiotic factors in an ecosystem, and how do key examples impact organisms?

Abiotic factors are non-living physical factors that set the limits of an ecosystem and determine species survival and reproduction: • Temperature: Affects enzyme activity and metabolic rate. • Water availability: Limits species distribution. • Light intensity: Affects photosynthetic rate in producers, influencing total energy in the food web. • Sudden changes: Events like drought or fire rapidly reduce carrying capacity and trigger population decline.

What are biotic factors in an ecosystem?

Biotic factors are living components including predators, prey, competitors (same or different species), pathogens/parasites/disease, decomposers, producers, symbiotic partners, and human activity.

How do predator and prey population sizes interact over time?

Predation regulates prey size and drives coevolution (e.g., camouflage, speed, toxins). Predator and prey populations show a cyclical relationship where changes in the predator population lag behind changes in the prey population.

What is the difference between Intraspecific and Interspecific Competition?

• Intraspecific competition: Competition between individuals of the SAME species for identical resources (most intense form), such as males competing for mates or territory. • Interspecific competition: Competition between individuals of DIFFERENT species for shared, overlapping resources, such as introduced weeds competing with crops.

What are the three main types of symbiosis, their population effects, and examples?

• Mutualism (+/+): Both benefit (e.g., bees pollinating flowers for nectar). • Commensalism (+/0): One benefits, other unaffected (e.g., remoras attaching to sharks). • Parasitism (+/-): One benefits, host harmed (e.g., tapeworms in host intestine).

Compare Habitat vs Niche, and Fundamental Niche vs Realised Niche.

• Habitat vs Niche: Habitat is WHERE an organism lives; niche is its functional ROLE and way of life within that habitat. • Fundamental Niche: The full range of conditions/resources a species COULD use without competition. • Realised Niche: The actual range of conditions/resources a species DOES use once competition and biotic interactions are accounted for.

What is the Competitive Exclusion Principle?

Two species cannot occupy exactly the same niche indefinitely; one will outcompete and displace the other, or the species will diverge via niche differentiation.

How do Quadrat, Line Transect, and Mark-Release-Recapture sampling techniques work?

• Quadrat sampling: A square frame of known area is placed randomly/systematically to count small or sessile organisms, averaged, and scaled up. • Line/Belt transect: A line/belt laid across an environmental gradient records species presence/abundance to reveal zonation. • Mark-Release-Recapture: Used for mobile animals; estimated with Lincoln Index N = (n1 * n2) / m2.

What biotic and abiotic factors caused the extinction of the Tasmanian Tiger (Thylacine)?

• Biotic factors: Intensive European hunting; canine-distemper-like epidemic in the early 1900s; official government bounty system (£1 per adult); vilification as a sheep killer. • Abiotic factors: Rapid agricultural and pastoral expansion destroyed hunting grounds and reduced prey.

What were the ecosystem consequences of the Thylacine's extinction?

Loss of the apex predator caused overpopulation of herbivores, leading to overgrazing, vegetation damage, and soil erosion. It also caused mesopredator release (increase in feral cats).

How do Aboriginal Rock Paintings provide evidence of past ecosystems?

They form an ancient cultural record depicting extinct species (e.g., thylacines, megafauna), proving former appearance, behavior, and range. Shifts in subjects over time reveal historical changes in vegetation and climate.

What are Stromatolites and why are they significant in Earth's history?

Layered, dome-shaped structures formed by photosynthetic cyanobacteria colonies trapping sediment. Dated to ~3.5 billion years old, they released oxygen that caused the Great Oxidation Event, enabling aerobic life to evolve.

Compare Sedimentary, Igneous, and Metamorphic rocks as biological evidence.

• Sedimentary: Main source of fossils; dated relatively via the Law of Superposition. • Igneous: Formed from cooled lava/magma; radiometrically dated to give absolute ages. • Metamorphic: Heat/pressure transformed rock; fossils are generally destroyed.

How does Ice Core Drilling reconstruct past climate and atmosphere?

• Annual snowfall layers compact into distinct countable lines. • Trapped air bubbles measure ancient CO2 and methane levels directly. • Oxygen isotope ratios (O-18 : O-16) reveal past global temperatures.

Compare Prokaryotic and Eukaryotic cell structures.

• Eukaryotic cells: Larger, contain a nucleus and membrane-bound organelles (mitochondria, chloroplasts, rough ER), can be unicellular or multicellular. • Prokaryotic cells: Smaller, lack a nucleus and membrane-bound organelles, unicellular only, DNA floats free in cytoplasm.

What are the primary functions of key cell organelles?

• Nucleus: Stores genetic material, regulates gene expression. • Ribosome: Protein synthesis. • Mitochondrion: Converts food nutrients into ATP energy via respiration. • Chloroplast: Conducts photosynthesis using chlorophyll. • Golgi Apparatus: Sorts and packages proteins and lipids from ER. • Lysosome: Waste disposal using digestive enzymes (animals).

Compare Light, Fluorescent, and Scanning Electron Microscopes (SEM).

• Light Microscope: Uses visible light/lenses, max 1000x magnification, 0.2 µm resolution. • Fluorescent Microscope: Excites specific molecules to emit light against a dark background, 1500x magnification. • SEM: Scans sample surface with electron beam, producing 3D surface images with <1 nm to several nm resolution.

Describe the Fluid Mosaic Model and factors affecting cell membrane permeability.

• Fluid Mosaic Model: Phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward, embedded with functional proteins. • Permeability factors: Small size (high permeability); uncharged molecules (e.g., O2, CO2 high permeability); lipid solubility (e.g., alcohol, urea high permeability).

Differentiate Passive Transport mechanisms: Diffusion, Facilitated Diffusion, and Osmosis.

• Diffusion: Passive movement from high to low concentration along a gradient. • Facilitated Diffusion: Passive movement from high to low concentration via protein channels. • Osmosis: Passive movement of water across a semipermeable membrane toward higher solute concentration.

What is Active Transport, Endocytosis, and Exocytosis?

• Active Transport: Energy-requiring movement from low to high concentration against a gradient. • Endocytosis: Cell membrane folds around a large particle to engulf it into a vesicle. • Exocytosis: Vesicle fuses with cell membrane to release contents outside the cell.

Why is Surface Area to Volume (SA:V) ratio critical for cells?

A high SA:V ratio allows fast diffusion of oxygen/nutrients in and waste out. If a cell gets too large, SA:V drops and transport slows down, limiting cell size.

What are the chemical equations for Photosynthesis and Respiration?

• Photosynthesis: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2. • Cellular Respiration: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP.

How do Temperature, pH, and Substrate Concentration affect enzyme activity?

• Temperature: Optimal at ~37°C; high temps denature enzymes; low temps reduce energy/collision rate. • pH: Each enzyme has a narrow optimal pH range; outside this range causes denaturation. • Substrate Concentration: Increases reaction rate until the saturation point is reached (all active sites occupied).

Compare Unicellular, Colonial, and Multicellular organisms.

• Unicellular: 1 cell performs all life functions; no specialisation (e.g., Amoeba). • Colonial: Many similar cells; minimal specialisation; cells can survive independently if separated (e.g., Volvox). • Multicellular: Highly specialized cells; full division of labor; cells cannot survive independently (e.g., humans, plants).

What are four structural adaptations of cells suited to their function?

• Red Blood Cell: No nucleus, biconcave disc -> maximizes space and SA for O2 transport. • Neuron: Long axon, myelin sheath -> rapid electrical signal transmission. • Root Hair Cell: Elongated projection -> maximizes SA for water/mineral absorption. • Sperm Cell: Flagellum, abundant mitochondria -> motility and energy to reach egg.

List the four main animal tissue types and their functions.

• Epithelial: Lines surfaces for protection and secretion. • Connective: Supports, binds, and transports (e.g., blood, bone). • Muscular: Contraction and movement. • Nervous: Electrical signal transmission.

What are the key requirements that distinguish Autotrophs from Heterotrophs?

• Autotrophs: Produce organic molecules from inorganic CO2 using light/chemical energy; require CO2 and minerals. • Heterotrophs: Consume organic food molecules; require oxygen for respiration and release CO2.

What four common features are shared by all efficient gas exchange structures?

1. Large surface area (maximizes diffusion rate). 2. Thin membrane (minimizes diffusion distance). 3. Moist surface (gases must dissolve to cross). 4. Rich blood supply (maintains concentration gradient).

Explain the forces driving the Transpiration-Cohesion-Tension Theory in plants.

• Transpiration pull: Water evaporation from stomata creates a suction pull. • Cohesion: Hydrogen bonds between water molecules form a continuous column in xylem. • Tension: Negative pressure pulls the water column upward. • Adhesion: Water sticks to xylem walls, preventing backward movement.

Compare Physical and Chemical Digestion in mammals across digestive regions.

• Physical Digestion: Mechanical breakdown increasing SA without chemical change (teeth chewing in mouth, churning in stomach, bile emulsification in small intestine). • Chemical Digestion: Enzymatic cleavage of bonds (salivary amylase in mouth, pepsin/HCl in stomach, pancreatic amylase/lipase/trypsin in small intestine).

Compare Arteries and Veins in structure and function.

• Arteries: Thick muscular walls, small lumen, no valves; carry high-pressure oxygenated blood away from heart. • Veins: Thin walls, large lumen, internal valves; carry low-pressure deoxygenated blood to the heart.

Compare Open and Closed Circulatory Systems.

• Open System: Haemolymph bathes organs directly in haemocoel under low pressure; slow delivery (insects, molluscs). • Closed System: Blood stays confined inside vessels under high pressure; fast, targeted delivery (vertebrates).

What are the four components of human blood and their primary functions?

• Red Blood Cells: Transport oxygen via hemoglobin. • White Blood Cells: Immune defense (phagocytosis, antibodies). • Platelets: Clotting plug formation. • Plasma: Fluid transporting dissolved nutrients, CO2 (as HCO3-), hormones, urea, and heat.

Why did Cane Toads experience exponential population growth in Australia?

They have no natural predators in Australia due to their venomous sacs. High competition for resources drives rapid westward spread, with longer-legged toads evolving to reach new areas first.

Define Structural, Behavioural, and Physiological Adaptations with examples.

• Structural: Physical body features (e.g., rose thorns, giraffe long neck). • Behavioural: Actions/behaviours (e.g., reptiles shade-seeking, wolves hunting in packs). • Physiological: Internal chemical/functional processes (e.g., milkweed toxic sap, antarctic fish antifreeze proteins).

What are the five essential conditions/steps for Natural Selection?

1. Variation: Individuals possess varied traits. 2. Inheritance: Beneficial traits are passed to offspring. 3. Selection: Environmental selection pressures give specific traits an advantage. 4. Time: Favorable genes increase across generations. 5. Adaptation: Leads to population evolution.

What evolutionary evidence did Darwin derive from Galapagos Finches?

13–14 finch species shared a common South American ancestor but possessed distinct beak shapes (crushing, pointed, short, sharp) adapted to specific island food sources, showing natural selection driven by geographic isolation.

How do Monotremes demonstrate Macroevolution?

Diverging ~160–187 mya, monotremes retain ancestral reptilian traits (egg laying, cloaca) alongside mammalian traits (fur, milk), serving as transitional evidence for mammalian lineage divergence.

Differentiate Convergent, Divergent, and Coevolution.

• Convergent evolution: Unrelated species develop similar traits due to similar selection pressures (e.g., marsupial mole vs European mole). • Divergent evolution: Species with a common ancestor adapt to different pressures, splitting into distinct species (e.g., Darwin's finches). • Coevolution: Two or more species reciprocally change and adapt together.

What are the four main lines of evidence for Evolution?

• Biochemical: Comparing DNA and amino acid sequences. • Comparative Anatomy: Homologous structures showing common descent. • Comparative Embryology: Shared embryonic features (e.g., gill slits, post-anal tail). • Biogeography: Geographic distribution of related species (e.g., flightless birds across Gondwana landmasses).

How does Antibiotic Resistance evolve in bacteria?

Exposure to antibiotics acts as a selection pressure, killing susceptible bacteria while resistant mutants survive, reproduce, and pass on resistance genes. Overuse or incomplete antibiotic treatment accelerates this process.