past paper questions

Describe the population removal estimation technique, its uses and its assumptions

The population removal technique, such as the Zippin method, involves multiple sampling passes where captured individuals are removed from the habitat each time. The declining catch rate is used to estimate the total population.

Uses: Estimating fish populations in small streams or ponds where full capture is possible.

Assumptions: Closed population (no immigration/emigration during sampling) Constant catchability No significant recruitment or mortality between passes

Example: Brown trout populations are often estimated in Scottish upland burns using electrofishing and depletion methods.

How would you attempt to estimate the total population size of a trout population in a small stream? Describe the techniques you might use and any assumptions you would make

Two main techniques are commonly used:

Mark-Recapture (Lincoln-Petersen method): Fish are captured, marked (e.g., fin clipping or PIT tagging), released, and a second capture is used to determine the proportion of marked to unmarked fish. Assumptions: Closed population, no tag loss, equal catchability.

Depletion Method (Zippin): Multiple passes with decreasing catch numbers are used to estimate population size based on catch-effort decline. Assumptions: Closed system, equal catchability across passes.

Example: Brook trout populations in North America are often studied with these methods.

How does water differ from other similar compounds in terms of its chemical and physical properties?

Water's unique properties are crucial for life and make it distinct from other compounds of similar molecular weight.

High specific heat: Stabilizes temperatures in aquatic systems.

Density anomaly: Maximum density at 4°C means ice floats, insulating aquatic life.

High surface tension: Aids in capillary action and supports small invertebrates.

Solvent capacity: Dissolves gases and nutrients, supporting metabolic processes.

Example: Ponds freezing from the top down allows fish to survive below the ice layer.

How might you compare the diversity of freshwater invertebrate communities between sites?

To compare invertebrate diversity between sites:

Sampling methods: Standardized kick sampling, Surber sampler, or pond netting.

Quantitative metrics: Species richness Evenness Diversity indices (e.g., Shannon-Wiener Index, Simpson's Index)

Environmental variables should also be measured (e.g., temperature, flow, substrate).

Example: Urban vs rural streams might show reduced diversity and dominance of tolerant taxa (e.g., Chironomidae) in polluted sites.

Describe the most important things you need to consider when designing a field study to compare two aquatic sites.

Clear hypothesis and objectives

Replication and random sampling

Control of confounding variables (e.g., time of day, weather, season)

Standardized methodology (e.g., same sampling effort, equipment)

Measurement of environmental parameters (temperature, DO, pH)

Ethical considerations (especially with vertebrate animals)

Example: Comparing nutrient levels and invertebrate community structure in a lake inflow vs outflow.

Why are aquatic plants useful in the assessment of water quality?

Aquatic macrophytes respond predictably to water quality changes and are useful bioindicators.

Indicators of eutrophication: Fast-growing species (e.g., Myriophyllum) dominate in nutrient-rich waters.

Oxygenation role: Submerged plants increase oxygen levels via photosynthesis.

Habitat function: Support invertebrates and fish; structural complexity influences biodiversity.

Example: EU Water Framework Directive uses macrophyte communities in ecological status assessments.

What is river "discharge"? How is it measured?

Discharge is the volume of water flowing past a point in a river per unit time (usually m³/s).

Measurement methods: Velocity-area method: Cross-sectional area × average velocity Float method: Surface velocity measured and corrected Current meters: More accurate subsurface velocity readings

Importance: Determines flood risk, sediment transport, pollutant dilution.

Example: Hydrologists monitor discharge in the River Clyde to manage urban flood risks.

Compare and contrast the two life-history stages of the Cnidaria.

Cnidaria exhibit a dimorphic life cycle with two stages:

Polyp (sessile): Asexual reproduction (budding), attached to substrate, cylindrical shape.

Medusa (motile): Sexual reproduction (gametes), free-swimming, bell-shaped body.

Ecological roles: Polyps often form colonies (e.g., coral reefs); medusae dominate in open water (e.g., jellyfish).

Example: Aurelia aurita (moon jellyfish) alternates between sessile polyp and planktonic medusa.

Detail the different methods of reproduction found in echinoderms, discussing the costs and benefits of each strategy.

Broadcast spawning (e.g., sea urchins): Benefits: High dispersal potential. Costs: High predation risk on gametes, lower success rate.

Brooding (e.g., some starfish): Benefits: Protection of young. Costs: Fewer offspring, limited dispersal.

Asexual reproduction (e.g., fission in brittle stars): Benefits: Fast population growth. Costs: No genetic variation.

Example: Leptasterias sp. brood their young under the central disc.

What features contribute to the success of insects?

Exoskeleton: Protection, prevents desiccation.

Flight: Escape predators, expand range.

Metamorphosis: Reduces competition between life stages.

Small size: Access to microhabitats.

High reproductive rate: Rapid colonization.

Example: Bees (pollination), mosquitoes (disease vectors), beetles (diverse feeding strategies).

Discuss why climate change poses a problem for birds and other organisms, beyond just adjusting to warmer weather.

Phenological mismatches: Breeding no longer coincides with peak food availability. Example: Great tits (Parus major) missing caterpillar peak.

Habitat shifts: Alpine and polar species lose range.

Trophic cascades: Altered predator-prey dynamics.

Ocean acidification & warming: Affect marine birds (e.g., puffins) dependent on cold-water fish.

Increased disease risk and novel competitors in new ranges.

Using relevant examples, discuss how biological traits possessed by male birds are used by female birds to choose a mate.

Sexual selection drives elaborate traits: Plumage brightness (indicator of health) - e.g., peacock train. Song complexity - e.g., zebra finch females prefer males with varied songs. Courtship displays - e.g., manakins' acrobatic dances.

Indicator traits: Often costly, signaling good genes or parental investment potential.

Describe the differences in physiology, morphology and behaviour between the two suborders of the Cetacea.

Mysticeti (Baleen whales): Filter feeders (krill, plankton), 2 blowholes, no echolocation. Large migratory species - e.g., blue whale.

Odontoceti (Toothed whales): Predatory (fish/squid), echolocation, 1 blowhole. Social behavior - e.g., killer whales in pods.

Physiological adaptation: Fat-rich milk, high oxygen storage in muscles.

Importance of understanding the population structure and life history of commercially harvested species like Atlantic cod for fisheries management.

Life history traits: Growth rate, age at maturity, fecundity.

Population structure: Stocks may differ genetically and demographically.

Management relevance: Avoid overfishing juveniles Set quotas by stock Account for spawning seasons and locations

Example: Collapse of NW Atlantic cod due to overestimation of biomass and unregulated fishing.

Discuss the causes and consequences of eutrophication in coastal ecosystems.

Causes: Runoff of nitrates and phosphates (agriculture, sewage).

Consequences: Algal blooms Oxygen depletion (hypoxia) Loss of biodiversity Fish kills

Example: Dead zones in the Gulf of Mexico near Mississippi River mouth.

Benthic-pelagic coupling - stages that slow or speed the cycle.

Coupling involves: Organic matter sinking, nutrient recycling.

Slow stages: Deep sediment burial, cold temperatures.

Fast stages: Upwelling zones, shallow systems.

Example: Antarctic shelf has rapid recycling due to productive benthic communities.

Marine animals benefiting from human impacts and ecosystem consequences.

Winners: Opportunistic species - e.g., jellyfish blooms with overfishing. Artificial reefs - e.g., fish attracted to offshore oil platforms.

Consequences: Trophic imbalance Invasive species spread Shifts in community structure

What are the important elements of designing a field study?

Clear hypothesis or research question.

Site selection with appropriate controls and replication.

Standardized methods: Consistency in sampling effort and tools.

Variables management: Identify and control confounding factors (e.g., time of sampling, flow rate, weather).

Ethical considerations: Minimizing harm to organisms, permits for protected species.

Pilot study: Helps refine methods and identify unforeseen issues.

Data recording and analysis plan.Example: Comparing macroinvertebrate diversity in agricultural vs forested catchments.

Define the physical characteristics of water.

Water has several key physical properties that influence aquatic ecosystems:

High specific heat capacity: Stabilizes temperatures.

Density anomaly: Maximum density at 4°C means ice floats.

High surface tension: Enables capillary action and supports some surface-dwelling insects.

Transparency: Allows light penetration for photosynthesis.

Universal solvent: Dissolves gases and nutrients essential for life.

Viscosity: Affects flow and movement for small organisms.Example: Ice floating in lakes protects aquatic organisms in winter by insulating the water below.

Outline the methods for estimating fish population size

Mark-Recapture (Lincoln-Petersen): Fish are marked and released; the proportion of marked fish in a second catch is used to estimate population.

Depletion/Removal method (Zippin): Successive removals are made; the decline in catch is used to estimate the population.

Catch per unit effort (CPUE): Used for relative abundance, not absolute numbers.

Assumptions: Closed population, equal catchability, no tag loss.Example: Electrofishing and marking trout in a headwater stream.

What are the important physical characteristics of a stream?

Flow rate/velocity: Affects oxygen levels and sediment transport.

Substrate composition: Gravel, sand, silt - influences benthic communities.

Gradient: Steep gradients lead to high energy environments.

Temperature: Affects metabolism and species distributions.

Light availability: Influences primary production.

Channel morphology: Pools, riffles, and runs support different organisms.Example: Mayflies prefer cold, fast-flowing streams with rocky substrates.

How is community diversity measured?

Species richness (number of species)

Species evenness (relative abundance)

Diversity indices: Shannon-Wiener Index: Sensitive to rare species. Simpson's Index: Emphasizes common species.

Beta diversity compares between habitats.Example: Comparing diversity of benthic macroinvertebrates in upstream vs downstream sections of a river.

Importance of cephalisation and differentiation in Platyhelminthes evolution.

Cephalisation: Development of a head region with sensory structures improves directional movement and foraging efficiency.

Differentiation: Specialized organs (excretory, reproductive) represent evolutionary advancement from cnidarians.

Significance: Marks transition to bilateral symmetry and active lifestyles.Example: Planarians exhibit clear cephalisation and eye spots for light detection.

Two feeding strategies of polychaetes with examples.

Raptorial feeding: Use eversible pharynx with jaws to capture prey. Example: Nereis virens.

Deposit feeding: Ingest sediment and extract organic material. Example: Arenicola marina (lugworm).

Adaptations: Parapodia, palps, and specialized mouthparts reflect their ecology.

Five ways modern agriculture benefits phytophagous insects.

Monocultures: Provide abundant, predictable food sources.

Extended growing seasons: Due to irrigation and greenhouses.

Reduced natural enemies: Pesticides may remove predators/parasitoids.

Artificial fertilizers: Lead to more nutritious plant tissue.

Habitat modification: Creates suitable microclimates.Example: Aphid outbreaks are more frequent in fertilized crop fields.

Two main arthropod gas exchange methods.

Tracheal system (insects): Network of tubes delivering oxygen directly to tissues. Air enters through spiracles. Efficient for small body sizes.

Gills (aquatic arthropods like crustaceans): Thin-walled structures for gas exchange with water. Found in species like crabs and amphipods.

Trade-offs: Water vs air environment adaptations.

Advantages and disadvantages of brood protection in echinoderms.

Advantages: Increased offspring survival. Avoidance of predation on early life stages.

Disadvantages: Reduced number of offspring. Limited dispersal → reduced gene flow.Example: Amphipholis squamata broods juveniles within the body cavity.

Effects of light at night on city-dwelling species.

Disruption of circadian rhythms: Alters activity cycles and hormone regulation.

Disrupted migration/navigation: Nocturnal birds and insects affected by artificial lights.

Predation risk: Prey becomes more visible.

Reproductive cycles: Altered timing due to perceived photoperiods.Example: Blackbirds in cities sing earlier and breed sooner than rural counterparts.

Plastic pollution impacts on marine animals.

Ingestion: Can cause gut blockages, starvation. Example: Sea turtles ingest plastic bags mistaken for jellyfish.

Entanglement: Leads to injury or drowning.

Chemical contamination: Leaching of toxins or accumulation of PCBs.

Microplastics: Enter food webs, bioaccumulate.Example: Fulmars in the North Sea have high rates of plastic ingestion.

Life history variation and reproductive success.

Variation within species: Different maturation rates, size at maturity.

Between species: r/K strategies affect fecundity and parental care.

Impacts: Influence on recruitment, population stability, and evolution.Example: Chinook salmon show both early and late-maturing males (jacks vs full-size), promoting genetic diversity.

Importance of benthic-pelagic coupling.

Nutrient recycling: Organic matter sinks, decomposed by benthic organisms, nutrients returned to pelagic zone.

Energy flow: Tight coupling sustains productivity in coastal zones.

Feedbacks: Benthic respiration affects oxygen levels.

Disturbances: Bottom trawling and hypoxia disrupt the link.Example: Soft-bottom benthos in the North Sea facilitates coupling.

Main factors limiting oceanic primary productivity.

Light availability: Limits productivity in deeper waters.

Nutrients: Nitrogen, phosphorus, and iron are key.

Grazing pressure: Zooplankton can regulate phytoplankton.

Temperature: Affects metabolic rates.Example: Subtropical gyres are nutrient-poor, while coastal upwelling zones are nutrient-rich and highly productive.

Factors determining marine habitats around the UK.

Geology: Influences substrate type (rocky, sandy, muddy).

Tides and currents: Shape estuaries and intertidal zones.

Temperature and salinity: Vary with latitude and river inflow.

Human influence: Coastal development, fishing, pollution.Examples: Rocky shores dominate western coasts; saltmarshes common in estuaries.

Positive and negative PCR controls

Positive control: Known male DNA - should produce a band

Negative control: No DNA template - should have no band

Confirms reagents work and rules out contamination

What is a thermocline in lakes and why is it important?

A thermocline is a distinct temperature gradient layer between the warmer epilimnion (surface) and colder hypolimnion (deep water) in a stratified lake.

Importance: Prevents mixing of oxygen and nutrients between layers. Can lead to hypoxia in deeper layers during summer. Influences species distribution (e.g., fish migrate to preferred temperature zones). Breakdown of thermocline in autumn (turnover) allows reoxygenation.

Example: Found in temperate lakes like Loch Lomond during summer.

What is the basis for population removal sampling (Zippin) techniques?

Multiple passes of sampling (e.g., electrofishing) are made, removing individuals each time.

A decline in catch per pass is used to estimate total population.

Assumptions: Closed population Constant probability of capture No recruitment or mortality during sampling

Application: Especially suitable in small streams where full coverage is feasible.

Example: Brown trout in upland streams.

Describe and contrast 3 quantitative methods for sampling fish.

Electrofishing: Effective in streams/rivers. Fish are stunned and collected. Quantitative if effort and area are recorded.

Netting (seine or gill nets): Suited for still waters. May bias by size or species. Gill nets: more passive; seine nets: active collection.

Trapping (e.g., minnow traps): Good for small fish in still water. Effort must be standardized. Less effective in flowing systems.

Comparisons: Electrofishing is most quantitative and controlled. Nets and traps are more variable but practical for different habitats.

Why is primary production in lakes important?

Primary production forms the base of the aquatic food web.

Driven by: Light, temperature, nutrients (especially P & N).

Supports zooplankton, which in turn feed fish.

Overproduction can lead to eutrophication.

Measured by oxygen production, chlorophyll-a, or carbon uptake.

Example: Phytoplankton blooms support fish fry recruitment in spring.

What are freshwater macroinvertebrates and why are they important?

Macroinvertebrates are visible aquatic invertebrates, e.g., insect larvae, snails, worms.

Ecological roles: Detritivores and herbivores Food for fish and amphibians

Bioindicators: Presence/absence reflects water quality Tolerant (e.g., Chironomids) vs sensitive (e.g., Ephemeroptera) species

Example: BMWP (Biological Monitoring Working Party) scoring system uses these organisms to assess pollution.

"Free-living Platyhelminthes are evolutionarily more advanced than Cnidaria." Explain.

Bilateral symmetry: Unlike Cnidaria (radial), flatworms show a defined head and tail end.

Cephalisation: Centralized nervous system and sensory organs.

Three tissue layers (triploblastic): Allows for organ development (Cnidaria are diploblastic).

Excretory system: Flame cells regulate osmoregulation.

Movement: Ciliated ventral surface, muscular control, vs pulsatile Cnidarian movement.

Example: Planarians (Dugesia) vs Hydra.

Compare and contrast locomotion in the three classes of Annelids.

Polychaetes: Parapodia with setae, used for crawling and swimming. Circular and longitudinal muscles.

Oligochaetes (e.g., earthworms): Peristaltic movement via coordinated muscle contractions. Setae anchor body in soil.

Hirudinea (leeches): Use suckers at both ends for inchworm-like crawling. No setae.

Contrast: Polychaetes are often marine and mobile; oligochaetes are burrowers; leeches are adapted for parasitic/surface life

Torsion in gastropod Molluscs - process, pros, cons, adaptations.

Torsion: 180° rotation of visceral mass during development.

Advantages: Head enters shell first for protection. Anterior placement of sensory organs.

Disadvantages: Fouling: anus over head.

Adaptations: Shell perforation (e.g., Haliotis), detorsion (opisthobranchs).

Example: Limpets show reduced torsion; sea hares (Aplysia) have partial detorsion.

Explain the decline of global whaling from the 1850s to 1982 with reference to specific locations.

1850s-1900s: Open-boat whaling (e.g., New England, Norway) targets sperm and right whales.

1920s-30s: Industrial whaling expands with factory ships (e.g., South Georgia).

Post-WWII: High catches of blue and fin whales in Antarctic waters.

1970s-1982: Overexploitation leads to collapse; public pressure and IWC regulations.

1982: IWC moratorium on commercial whaling.

Example: Blue whales reduced to <1% of original population in Southern Ocean

Shoaling in fish - dilution & confusion effects, plus thermal effects.

Dilution effect: Risk per individual decreases in larger groups.

Confusion effect: Predators struggle to target one fish among many.

Temperature effects: Higher temps increase metabolism, oxygen demand. May favor solitary behavior due to increased competition. Example: Sticklebacks shoal less in warmer water due to higher aggression.

Trade-offs: Shoaling reduces predation but increases disease risk and food competition.

Plastic life-history traits & population diversity in salmonids.

Life-history plasticity: Variation in age and size at maturity, smolt timing.

Influences: Temperature, food, predation pressure.

Genetic diversity: Maintained by different strategies (e.g., precocious males "jacks").

Importance for conservation: Buffer against environmental change.

Example: Atlantic salmon (Salmo salar) show river-specific adaptations in timing and morphology.

Why do polar and tropical systems differ in primary productivity?

Polar: Light-limited in winter, strong blooms in summer. Cold temps = slow decomposition, nutrient-rich.

Tropics: Light-rich but nutrient-poor due to stratification. Productivity low except upwelling regions.

Drivers: Light, nutrient cycling, temperature, mixing regimes.

Example: Antarctic krill bloom during short productive season.

Role of the benthic environment in ocean organic matter cycling.

Organic material from surface sinks and is: Consumed by benthic fauna Decomposed by microbes, recycling nutrients Buried in sediment, removing carbon from cycle

Ecosystem services: Support fisheries, carbon sequestration

Example: Continental shelf sediments are hotspots for benthic recycling.

Advantages and disadvantages of 2 marine sampling methods.

Grab samplers (e.g., Van Veen): Quantitative, useful for soft sediments. Limited area, unsuitable for hard substrates.

Underwater visual census (UVC): Good for mobile species and reefs. Observer bias, limited depth.

Comparison: Method depends on habitat and target taxa.

Example: UVC used for coral reef fish; grabs for benthic infauna.

Define river discharge and explain how it is measured.

River discharge is the volume of water flowing through a cross-section of a river per unit time, typically expressed in cubic meters per second (m³/s).

Measurement methods: Velocity-area method: Measure stream width and depth at several points. Measure water velocity with a flow meter. Discharge = Area × Velocity. Float method: Surface velocity measured by timing an object over a set distance. Requires correction factor for average velocity.

Importance: Crucial for understanding flooding, sediment transport, aquatic habitat.

What factors influence the oxygen levels in streams and rivers?

Temperature: Higher temps decrease oxygen solubility.

Turbulence/flow rate: Increases air-water gas exchange.

Photosynthesis: Aquatic plants and algae add oxygen during daylight.

Respiration & decomposition: Consume oxygen, especially at night.

Pollution: Organic waste can trigger bacterial oxygen consumption.Example: Eutrophic rivers may suffer from hypoxia due to algal blooms.

What are the characteristics of a "good" field sampling method?

Repeatability: Same result under same conditions.

Standardization: Consistent use of effort and equipment.

Representative sampling: Captures true variation in target population.

Minimal disturbance: Avoids altering the system or harming organisms.

Example: Kick sampling with a standard time and mesh size to compare invertebrate diversity.

How do invertebrate assemblages differ between riffles and pools?

Riffles: Faster flow, higher oxygen, coarse substrate. Dominated by Ephemeroptera (mayflies), Plecoptera (stoneflies).

Pools: Slower flow, finer sediment, less oxygen. More Chironomids, Oligochaetes, and burrowing species.

Significance: Habitat heterogeneity supports biodiversity.

Why is it important to replicate sampling in field studies?

Statistical validity: Allows for confidence in results.

Controls for natural variability: Rivers and lakes are heterogeneous.

Reduces bias: One sample may be misleading.

Facilitates comparison: Across sites, times, and treatments.

Example: Multiple kick samples used to estimate average invertebrate richness.

Describe major evolutionary trends in Mollusca.

Body plan variation: From simple monoplacophorans to highly specialized cephalopods.

Torsion: Seen in gastropods, results in anterior placement of anus and gills.

Shell evolution: Loss (e.g., octopus), internalization (squid), heavy armor (chitons).

Nervous system complexity: Especially in cephalopods - problem-solving, learning.

Feeding adaptations: Radula (e.g., snails), beak and arms (cephalopods), gill rakers (bivalves).

Example: Octopuses show advanced neural control and no external shell.

What are the key features of a successful terrestrial insect?

Exoskeleton with waxy cuticle: Prevents desiccation.

Tracheal system: Delivers oxygen directly to tissues.

Metamorphosis: Reduces intraspecific competition.

Wings: Enables dispersal and escape from predators.

Complex behavior: Including communication and sociality.

Example: Ants (Formicidae) have colonized nearly all terrestrial habitats.

Describe the role of annelids in marine sediments.

Bioturbation: Mixing of sediment improves oxygen penetration.

Burrowing: Creates microhabitats for microbes and other fauna.

Nutrient recycling: Excretion helps nutrient regeneration.

Food web role: Important prey for fish and birds.

Example: Arenicola marina (lugworm) moves sediment as it feeds.

How do urban habitats differ from rural ones, and what implications does this have for vertebrate ecology?

Abiotic differences: Higher temperatures (urban heat island effect), more impervious surfaces, pollution.

Biotic changes: Altered predator-prey dynamics, new competitors, reduced species richness.

Behavioral changes: Increased boldness, reduced wariness in birds and mammals.

Genetic differentiation: Due to habitat fragmentation and gene flow barriers.

Example: Urban blackbirds (Turdus merula) show reduced migration and altered song structure.

Compare viviparity in squamate reptiles

Viviparity: Embryos develop inside the mother; live birth.

Types: Lecithotrophy: Embryo relies on yolk. Matrotrophy: Nutrients provided by maternal tissues.

Advantages: Embryo protection, temperature regulation.

Disadvantages: Energetic burden on mother, reduced mobility.

Example: Zootoca vivipara (common lizard) shows both oviparity and viviparity depending on region.

What are the advantages of hibernation in mammals? Give examples.

Energy conservation: Reduces metabolic rate during resource scarcity.

Avoids harsh weather: Especially important in temperate climates.

Physiological adaptations: Lowered body temperature, slowed heartbeat, fat storage.

Example: Bats use torpor to survive winter. Ground squirrels undergo deep hibernation with periodic arousals. Bears enter torpor but can be roused.

What makes seagrasses important to marine ecosystems?

Primary production: Photosynthesis supports coastal food webs.

Habitat provision: Nursery grounds for fish, invertebrates.

Sediment stabilization: Roots trap particles, reduce erosion.

Carbon sink: Long-term storage in sediments.

Threats: Eutrophication, dredging, anchoring damage.

Example: Zostera marina (eelgrass) beds are critical for coastal health.

How can marine organisms benefit from human-modified environments?

Artificial structures: Act as reefs (e.g., oil rigs, breakwaters).

Urban marine habitats: Provide hard substrate for colonization (barnacles, mussels).

Increased food availability: From waste or eutrophication.

Examples: Anemones and fish colonizing shipwrecks. Seals using harbor structures for haul-outs.

Caveat: May facilitate invasive species or trophic shifts.

What factors limit marine primary productivity, and how do these vary spatially?

Key limiting factors: Light: Limited at depth or polar winter. Nutrients: Nitrogen, phosphorus, iron - vary by location.

Spatial variation: Coastal zones: Nutrient-rich from upwelling and runoff. Open ocean gyres: Nutrient-poor due to stratification.

Example: Equatorial upwelling zones like the eastern Pacific are highly productive.

What are the most important elements of a well-designed field study and why?

Clear Research Question: A well-defined question helps focus the study on specific objectives. This ensures that data collection is relevant and that results can address the problem at hand.

Sampling Design: Proper planning of how data will be collected is essential. This includes selecting the appropriate study sites, determining sample sizes, and choosing suitable sampling techniques (e.g., random sampling, stratified sampling).

Control of Variables: In a field study, it is important to minimize or control for confounding variables that could affect the results. This may include using controls or randomizing treatments.

Replicability: To ensure results are generalizable, a study must be replicable. This means the study should be designed so that it can be repeated under similar conditions with similar outcomes.

Data Collection Methods: The methods for collecting data should be reliable, precise, and suitable for the type of research. This could include tools like quadrats, traps, or sensors for measuring physical variables like temperature, pH, or water flow.

Statistical Analysis: Data should be analyzed using appropriate statistical methods to test hypotheses. Ensuring proper statistical design, like power analysis, helps ensure the study's conclusions are valid.

Ethical Considerations: Any study should be ethically designed, taking into account the welfare of any living organisms involved and the impact on the environment.

What properties of water are important for the plants and animals that live there?

Temperature: Affects metabolic rates, reproduction, and survival. Cold water can hold more dissolved oxygen, which is critical for respiration.

Dissolved Oxygen: Essential for aerobic respiration in most aquatic organisms. Low oxygen levels can cause hypoxia, which can stress aquatic life and lead to die-offs.

pH: Aquatic organisms are adapted to live within specific pH ranges. Large fluctuations in pH can harm species by disrupting cellular processes.

Salinity: Determines whether species are freshwater or saltwater organisms. Some species can tolerate brackish water, but others cannot.

Turbidity: High turbidity can reduce light penetration, limiting photosynthesis and affecting plant growth. It can also clog the gills of fish and other filter feeders.

Nutrients: Nitrogen and phosphorus are essential for plant growth but excessive levels can lead to eutrophication, causing harmful algal blooms and hypoxia.

Water Flow and Depth: The movement of water affects nutrient distribution, sediment transport, and the types of organisms that can inhabit an area. Depth can influence light availability and temperature.

Describe the field and statistical methods for estimating the size of a population of stream-dwelling fish.

Field Methods:

Mark-Recapture: This involves capturing fish, marking them with non-toxic dye or tags, and releasing them back into the stream. After a set period, fish are recaptured and the proportion of marked fish is used to estimate the population size.

Electrofishing: This involves using an electric current to temporarily stun fish, making them easier to catch. This method can provide an estimate of fish density in a given area.

Transect Sampling: This involves selecting a series of transects (straight lines or areas) in the stream. The fish density in each transect is measured, and the data can be extrapolated to estimate the total population in the entire stream.

Statistical Methods:

Lincoln-Petersen Index: This is a formula used in mark-recapture studies. The population size is estimated by the formula:N=M×CRN = \frac{M \times C}{R}N=RM×C​Where: NNN = total population size MMM = number of fish marked in the first sample CCC = total number of fish captured in the second sample RRR = number of marked fish recaptured in the second sample

Capture-Recapture Models: More complex models (e.g., Jolly-Seber, Schnabel) use multiple recapture events to estimate population size and account for fish movement and changes in the population.

What are the most important physical characteristics of a lake and its catchment that affect the plants and animals that live there?

Lake Size and Depth: Larger lakes may have more diverse habitats, while smaller lakes might be more vulnerable to changes. Depth affects temperature stratification, light availability, and oxygen levels.

Water Temperature: Affects metabolic rates and species distribution. In deeper lakes, temperature gradients (thermoclines) can create distinct layers for different species.

Water Chemistry: Factors such as pH, nutrient levels, and dissolved oxygen directly influence species' survival. Lakes with higher nutrient levels may experience eutrophication, leading to algal blooms.

Water Flow: The rate at which water enters and exits a lake (e.g., through inflows, outflows, and precipitation) can influence nutrient cycling and the types of organisms present.

Sediment Composition: The type of sediment affects plant growth, spawning sites, and habitat for invertebrates. Soft sediments may provide shelter for organisms, while rocky substrates support different species.

Catchment Land Use: The surrounding land influences water quality and availability of nutrients. Urbanization, agriculture, and deforestation can introduce pollutants and excess nutrients into the lake.

In ecology, what is the diversity of a community and how do we measure it?

Community diversity refers to the variety and abundance of different species in a particular area. It includes both species richness (the number of different species) and species evenness (the relative abundance of each species).

Species Richness: Simply counts the number of different species present in a community.

Shannon-Wiener Index (H'): A commonly used index that accounts for both richness and evenness

Simpson's Index: Another measure of diversity, focusing more on the dominance of particular species in the community

Discuss the claim that animal phyla are entirely arbitrary groupings and are not comparable.

Animal phyla are taxonomic categories that group species based on shared morphological, genetic, and evolutionary traits. The claim that phyla are arbitrary groupings may stem from the fact that the classification system is human-made and based on specific criteria, which can change as our understanding of evolutionary relationships evolves. For example, some phyla may share more distant evolutionary relationships, while others may have very diverse forms. Recent molecular data has revealed that some traditional phyla might not represent monophyletic groups, indicating that these groupings are sometimes based on observable features rather than strict evolutionary lineage.

However, the concept of phyla remains useful because it provides a framework for understanding the major evolutionary divisions of the animal kingdom. While the specific number of phyla and their classification might change over time, the grouping provides insight into the vast diversity of body plans, physiological adaptations, and evolutionary innovations in the animal kingdom.

Describe the morphological features of the two main body forms found in Cnidaria and highlight their ecological role through the life cycle of a dimorphic species.

Morphological Forms:

Polyp: A sessile, cylindrical body form that is often attached to a substrate. Polyps typically have a mouth surrounded by tentacles, and they reproduce asexually through budding or fission.

Medusa: A free-swimming, bell-shaped body form with a central mouth and tentacles hanging from the bell. Medusas typically reproduce sexually, releasing gametes into the water for external fertilization.

Ecological Role:

Polyp: Often serves as a feeding structure, filtering food from the water. It can also serve as a foundation for forming colonies (e.g., coral reefs) that provide important habitat for other marine organisms.

Medusa: The medusa stage is typically involved in dispersal. Its free-swimming nature allows for gene flow between populations, increasing genetic diversity and aiding in the spread of the species.

For example, in the life cycle of the Aurelia jellyfish, the polyp produces numerous medusae, which eventually settle and transform into new polyps, completing the cycle. This dimorphism allows the species to exploit both benthic and pelagic environments.

Describe, with examples, the advantages and disadvantages of brood protection in Echinoderms.

Advantages:

Increased Juvenile Survival: By protecting offspring, echinoderms like certain species of sea stars can shield them from predators, increasing the likelihood of survival to maturity.

Parental Investment: Protecting brood provides time for the offspring to grow and develop before they are exposed to external threats.

Disadvantages:

Energy Expenditure: Brood protection requires energy from the parent, which could otherwise be used for growth or reproduction.

Predation Risk: The parent may attract predators by staying in one place to guard the brood.

For example, in some sea cucumbers, the parent protects eggs in specialized cavities, but this behavior might reduce the adult's ability to feed or escape predators.

Discuss the selective forces that can mediate species adaptation to urban environments. Explain the traits that make a species successful in cities, as well as the phenotypic changes observed in urban vs rural populations of the same species. Use specific examples to support your arguments.

Selective Forces in Urban Environments:

Resource Availability: Urban areas often provide abundant food (e.g., human waste, artificial food sources) and shelter. Species that can exploit these resources are more likely to thrive.

Predation and Competition: Reduced predation pressure and altered competition dynamics in cities can lead to different survival strategies.

Traits for Success in Cities:

Behavioral Flexibility: Urban-adapted species often show altered behaviors, such as becoming more nocturnal (e.g., urban birds avoiding daytime human activity).

Tolerance to Pollution: Species like the House Sparrow or Rock Pigeon can tolerate pollution and thrive in cities.

Phenotypic Changes:

Coloration: Urban populations of blackbirds show darker plumage, possibly for thermoregulation in hotter environments.

Size: Urban populations of some species (e.g., rodents) tend to be smaller, possibly due to reduced space and food availability.

Describe how eutherian mammal mothers transfer antibodies to their offspring, and how this is determined by different types of placentae.

Eutherian mammals transfer antibodies to their offspring via two mechanisms, depending on the type of placenta:

Placental Transfer: Some species, like humans, transfer antibodies (IgG) from the mother to the fetus via the placenta during pregnancy. This provides the newborn with passive immunity before birth.

Colostrum: After birth, the mother provides colostrum (the first milk), which contains high levels of antibodies. This protects the offspring during the early stages of life, before their immune system is fully developed.

Types of Placenta:

Haemochorial Placenta (e.g., humans, primates): Antibodies are transferred efficiently via this type of placenta.

Endotheliochorial Placenta (e.g., carnivores): Antibody transfer is less efficient due to a thicker placental barrier.

Compare and contrast the two suborders of Cetacea in terms of physical adaptations and behavior.

Odontoceti (Toothed Whales):

Physical Adaptations: Have teeth for capturing prey, such as fish or squid. They possess echolocation for hunting and navigation.

Behavior: Often more social, live in complex social groups (pods). They display a variety of hunting strategies, such as cooperative hunting.

Mysticeti (Baleen Whales):

Physical Adaptations: Have baleen plates instead of teeth, which are used to filter plankton or small fish from the water.

Behavior: Tend to be solitary or in small groups. Their feeding behavior is less complex than odontocetes, often involving skimming or bubble-net feeding.

Discuss the ecological role of the deep sea around the UK in terms of productivity, physical environment, and biodiversity.

Ecological Role: The deep sea around the UK is an essential component of the broader marine ecosystem. Despite its low light levels and limited primary production, it plays a critical role in supporting biodiversity and providing ecological services.

Productivity: The deep sea is generally nutrient-rich, and its productivity is driven primarily by the downward flux of organic material from the surface waters (marine snow). This material is composed of dead organisms, fecal pellets, and other organic matter that sinks from the surface. The productivity in deep-sea ecosystems is not high in terms of photosynthesis but is maintained through detrital food webs, where organisms feed on sinking organic material.

Physical Environment: The deep sea is characterized by extreme physical conditions, including high pressure, low temperatures, and minimal light. These conditions select for organisms with unique adaptations, such as bioluminescence for communication or attracting prey. The deep sea is also subject to ocean currents that help in the distribution of nutrients and oxygen, maintaining life even at great depths.

Biodiversity: Despite its harsh conditions, the deep sea around the UK harbors a diverse range of species, including deep-sea fish, cephalopods, crustaceans, and benthic invertebrates. Some species, such as the anglerfish or giant squid, are adapted to the low-light environment with specialized sensory organs. Others, like deep-sea corals, form ecosystems that are crucial for habitat formation.

Describe how sub-tropical gyres are formed.

Sub-tropical gyres are large, circular ocean currents that occur in the subtropical regions, typically around 30° latitude in both the Northern and Southern Hemispheres. These gyres are formed due to a combination of factors:

Trade Winds: The trade winds blow from east to west near the equator, pushing surface waters in the same direction. These winds create surface currents that move towards the west.

Coriolis Effect: As the Earth rotates, the Coriolis effect causes moving water to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This creates a circular motion of water that leads to the formation of the gyre.

Ekman Transport: Wind-driven currents at the ocean's surface cause water to move at a 90-degree angle to the wind direction due to the Coriolis effect. This transport of water to the right in the Northern Hemisphere and left in the Southern Hemisphere helps form the circular flow characteristic of a gyre.

Ocean Basins: The movement of water is also influenced by the shape of the ocean basins. In the subtropical regions, the western sides of gyres are often stronger and faster due to the influence of the continent.

These gyres have significant implications for global climate and marine life, as they regulate ocean temperatures, nutrients, and currents.

Describe the process of freshwater eutrophication and discuss the differences between natural and man-made eutrophication.

Freshwater Eutrophication refers to the process by which a water body becomes nutrient-rich, leading to excessive plant growth and oxygen depletion.

Process: Nutrient Input: Eutrophication begins with the introduction of excess nutrients, mainly nitrogen and phosphorus, into water bodies. These nutrients often come from agricultural runoff, wastewater discharge, and industrial pollution. Algal Blooms: The increased nutrient levels stimulate the growth of algae, leading to algal blooms. These blooms can cover the surface of the water, blocking sunlight and reducing photosynthesis in submerged plants. Depletion of Oxygen: As algae die and decompose, oxygen levels in the water drop, creating hypoxic or anoxic conditions. This depletion of oxygen can kill fish and other aquatic life. Loss of Biodiversity: Oxygen depletion and the loss of sunlight for plants lead to a reduction in biodiversity. Only species tolerant to low oxygen levels, such as certain bacteria, can survive.

Differences Between Natural and Man-Made Eutrophication:

Natural Eutrophication: This process occurs over long geological timescales due to the natural accumulation of nutrients from weathering rocks and decaying organic matter. Natural eutrophication occurs slowly, allowing ecosystems to adapt to changing conditions.

Man-Made Eutrophication: Caused by the rapid influx of nutrients from human activities, such as agricultural runoff, wastewater discharge, and industrial pollution. This process occurs much more quickly and can lead to severe environmental problems, such as algal blooms, fish kills, and loss of biodiversity. Man-made eutrophication is often exacerbated by the use of fertilizers and the clearing of vegetation, which increases nutrient runoff into water bodies

Arthropods can respire in more than one way. Provide an overview of two arthropod respiratory systems, and compare and contrast them.

1. Tracheal System (Terrestrial)

Structure: Network of tubes (tracheae) that deliver oxygen directly to cells via spiracles.

Efficiency: Effective on land; bypasses circulatory system. Limits body size due to diffusion constraints.

Examples: Insects like grasshoppers, beetles, cockroaches.

2. Gills (Aquatic)

Structure: Vascularized gills extract oxygen from water, often protected by a carapace.

Efficiency: Ideal for aquatic life; water flow ensures continuous gas exchange.

Examples: Crustaceans such as crabs, shrimp, lobsters.

Comparison:

Medium: Tracheae for air; gills for water.

Adaptation: Reflects evolutionary response to environment.

Efficiency: Each system optimized for its habitat.

Polychaetes are found in either errant or sedentary forms. Explain the morphological features that are associated with each of these two forms and any implications these forms have on the animals' overall likelihood of survival.

1. Errant Polychaetes (Mobile)

Features: Well-developed parapodia & muscles; sensory head structures (eyes, antennae, palps).

Survival: Active movers; hunt, escape predators, adapt to changing environments.

2. Sedentary Polychaetes (Stationary)

Features: Reduced parapodia; burrowing tubes; feeding structures (tentacles, ciliary nets).

Survival: Filter feeders in stable habitats; energy-efficient but more vulnerable to change.

Comparison:

Mobility vs. Specialization: Errant = generalists, mobile; Sedentary = specialists, stable feeders.

Using examples, describe the different feeding mechanisms used by bivalve and gastropod molluscs highlighting their differences and how they have helped to make these groups highly successful.

1. Bivalves (e.g., clams, mussels):

Feeding: Filter feeders using gills with cilia to trap plankton/detritus.

Features: Incurrent/excurrent siphons, byssal threads for attachment.

Success: Thrive in nutrient-rich waters; help filter and clean ecosystems.

2. Gastropods (e.g., snails, slugs):

Feeding: Use radula to scrape, graze, or pierce food; herbivores, carnivores, or detritivores.

Features: Radula, sensory tentacles, eyes.

Success: Highly adaptable; occupy marine, freshwater, and land habitats.

Comparison:

Bivalves: Passive filter feeders; stable environments.

Gastropods: Versatile feeders; varied habitats and niches.

Compare and contrast the locomotor styles of the three different groups of annelids.

1. Errant Polychaetes (Mobile)

Movement: Use muscular parapodia & setae for crawling/swimming; undulatory motion in water.

Adaptation: Suited for active foraging and exploring varied habitats.

Examples: Nereis, Alitta

2. Sedentary Polychaetes (Stationary)

Movement: Minimal; adjust position within burrows or tubes; reduced parapodia.

Adaptation: Fixed lifestyle with specialized feeding (tentacles, ciliary nets).

Examples: Terebellids, Sabellids

3. Oligochaetes (Burrowers)

Movement: Peristalsis (segmental contractions); use setae to anchor and move through soil.

Adaptation: Efficient soil burrowers; aid in aeration and nutrient cycling.

Examples: Earthworms (Lumbricus terrestris)

Comparison:

Errant: Active locomotion

Sedentary: Minimal movement, fixed habitats

Oligochaetes: Burrowing via peristalsis