D4 Continuity and Change: Ecosystems

D4.1 Natural Selection, D4.2 Stability and Change, D4.3 Climate Change

Define natural selection

Natural selection is the process by which individuals with traits better suited to their environment are more likely to survive and reproduce, passing on those advantageous traits to their offspring.

Outline the observations and inferences that lead to the development of the theory of evolution by natural selection

Observations include variation among individuals, overproduction of offspring, and limited resources; inferences are that individuals with advantageous traits survive and reproduce more, leading to adaptation over generations.

Outline the theory of evolution by natural selection as an example of inductive reasoning

The theory is built from specific observations (e.g., variation, inheritance, and differential survival) to a general principle that explains the evolution of species.

Outline the theory of evolution by natural selection as an example of the correspondence, coherence and pragmatic theories of truth

It corresponds with observable facts (fossils, genetic data), coheres with other scientific theories (e.g., genetics), and is pragmatically useful in fields like medicine and agriculture.

State that natural selection has operated continuously over billions of years, resulting in the biodiversity of life

Natural selection has been a continuous process over billions of years, shaping the diversity of life on Earth.

Explain why natural selection can only function if there is variation in a species

Variation provides the raw material for selection; without it, all individuals would be equally fit or unfit in a given environment.

Outline sources of genetic variation (mutation, meiosis and sexual reproduction)

Mutation introduces new alleles; meiosis reshuffles alleles through crossing over and independent assortment; sexual reproduction combines alleles from two parents.

Compare variation that results from mutation to that generated from sexual reproduction

Mutation creates entirely new alleles, while sexual reproduction generates new combinations of existing alleles.

State that species have the ability to produce more offspring than the environment can support

All species tend to produce more offspring than can survive due to limited resources.

Use an example to illustrate the potential for overproduction of offspring in a population

A pair of rabbits can produce dozens of offspring annually, far more than the environment can support long-term.

State two evolutionary benefits of overproduction of offspring

Increases the chance that some offspring survive; provides more variation for selection to act upon.

Describe competition for resources as a consequence of overproduction of offspring

Too many individuals compete for limited food, space, mates, etc., driving selection.

Define carrying capacity

The maximum number of individuals of a species that an environment can sustain.

List examples of resources that may limit population size

Food, water, shelter, nesting sites, mates.

Compare direct and indirect competition

Direct competition involves physical confrontation over resources; indirect competition involves usage of resources that are limited without direct interactions.

Define selective pressure and density

independent - A selective pressure is an environmental factor that affects an organism's fitness; density-independent factors affect population regardless of size, such as natural disasters.

State example biotic and abiotic selective pressures

Biotic: predation, disease; Abiotic: temperature, water availability.

Outline how a selective pressure acts on the variation in a population

Individuals with traits that provide an advantage under the pressure are more likely to survive and reproduce.

Define adaptation and fitness

Adaptation is a heritable trait that increases fitness; fitness is the ability to survive and reproduce in a particular environment.

Explain the effect of the selective pressure on the more and less adapted individuals in a population

More adapted individuals are more likely to survive and reproduce; less adapted individuals may die or reproduce less.

Explain adaptation as a consequence of natural selection

Over generations, advantageous traits become more common as selected individuals pass them on.

Distinguish between heritable and acquired characteristics

Heritable characteristics are encoded in DNA and passed to offspring; acquired characteristics arise during an individual's life and are not inherited.

Explain why only heritable characteristics can be acted upon by natural selection

Only traits encoded in genes can be passed to the next generation and thus selected over time.

Outline the two major mechanisms of sexual selection in evolution of courtship behavior and anatomical features

Intrasexual selection (competition within a sex for mates) and intersexual selection (mate choice based on traits).

Describe examples of sexual selection, including for color, size, and courtship behaviors

Peacocks with brighter tails attract more mates (color); larger elk outcompete others (size); birds of paradise perform dances (behavior).

Outline the selective pressures for and against coloration in guppies

Colorful males attract mates but are also more visible to predators.

Summarize John Endler's experiments with guppies which demonstrate selection for and against coloration in different habitats

In predator-rich environments, drab males survived better; in predator-free environments, bright males were more successful.

Explain what models are and their purposes in science

Models are simplified representations of systems used to explain, predict, or test scientific concepts.

Define gene pool, gene, allele and gene flow

Gene pool: all genes in a population; gene: unit of inheritance; allele: variant of a gene; gene flow: movement of alleles between populations.

Describe how it is possible for multiple gene pools to exist in a single species

Isolated populations of the same species may have distinct gene pools due to lack of gene flow.

Define allele frequency

The proportion of a specific allele among all alleles of a gene in a population.

Calculate allele frequency from gene pool data

Allele frequency = (number of copies of allele) / (total number of alleles for the gene).

Outline reasons when allele frequencies may be different in geographically isolated populations of the same species

Different environments, genetic drift, mutations, or founder effects.

Use a database to search for allele frequency of a human gene

Online databases like Ensembl or ALFRED provide allele frequency data by population.

Outline "neo

Darwinism" as the integration of genetic inheritance and the mechanism of natural selection - Neo-Darwinism combines Mendelian genetics with Darwin's theory, explaining how traits are inherited and selected.

State that change in the allele frequencies of a gene is evidence of evolution

Evolution occurs when allele frequencies in a gene pool change over time.

List processes that can change allele frequency in a population

Mutation, gene flow, genetic drift, natural selection, and non-random mating.

Explain how natural selection can lead to change in allele frequency in a gene pool

Advantageous alleles increase in frequency because they improve survival and reproduction.

Outline the change in allele frequencies associated with stabilizing, disruptive and directional selection

Stabilizing favors average traits; directional favors one extreme; disruptive favors both extremes.

Use graphs to illustrate or identify stabilizing, disruptive and directional selection

Graphs show changes in trait distribution: narrower (stabilizing), split (disruptive), or shifted (directional).

Outline an example of stabilizing, disruptive and directional selection

Stabilizing: human birth weight; directional: antibiotic resistance; disruptive: beak size in finches with distinct food sources.

State the Hardy

Weinberg equations - p + q = 1 and p² + 2pq + q² = 1

Given data, calculate allele frequencies of a gene in a gene pool

Use p = freq. of dominant allele; q = freq. of recessive; p + q = 1

Given data, calculate genotype frequencies of a gene in a gene pool

Use p² (homozygous dominant), 2pq (heterozygous), q² (homozygous recessive)

List the conditions under which populations maintain Hardy

Weinberg equilibrium - Large population, random mating, no mutation, no migration, no selection.

Explain how comparison of allele frequencies between two isolated populations of the same species can serve as evidence that divergence is (or is not) occurring

Differences in frequencies suggest divergence and potential speciation.

Explain how comparison of allele frequencies between one population at two points in time can serve as evidence that evolution is (or is not) occurring

Changes in frequency over time indicate evolution.

Define artificial selection

Intentional breeding for desired traits.

Outline the mechanism of artificial selection in evolution of crop plants and domestic animals

Humans choose parents with desired traits and breed them to enhance these traits in the population.

Describe an example of artificial selection of a crop plant or domestic animal

Dairy cows bred for high milk yield; corn selected for larger kernels.

Define stability as a property of an ecosystem.

Stability refers to the ability of an ecosystem to maintain structure and function over time, despite external stress or disturbances.

Describe an example of a stable ecosystem.​

A mature tropical rainforest is an example of a stable ecosystem due to its high biodiversity, nutrient cycling, and resistance to change.

Outline requirements for stability in an ecosystem.

Requirements include biodiversity, nutrient availability, resilience to disturbance, efficient energy flow, and interactions between organisms that regulate populations.

Outline types of environmental change that can interfere with ecosystem stability.

Changes include habitat destruction, climate change, pollution, invasive species, and overexploitation of resources.

Define "tipping point" in relation to ecosystem stability.

A tipping point is a critical threshold at which a small change can lead to drastic and often irreversible changes in the ecosystem.

Discuss the impact of Amazon deforestation as an example of an ecosystem at a tipping point.

Amazon deforestation reduces biodiversity, disrupts water cycles, increases carbon emissions, and risks shifting the rainforest to a savannah-like biome, threatening global climate regulation.

Define mesocosm.

A mesocosm is a controlled, experimental ecosystem set up to study ecological processes under natural conditions.

Outline requirements of setting up a sustainable mesocosm.

Requirements include balanced biotic and abiotic components, nutrient cycling, waste management, and appropriate energy input (e.g. light).

Discuss the benefits and limitations of using mesocosms as models of ecosystems.​

Benefits: controlled environment, replicability, ethical testing. Limitations: lack of full complexity and scale of natural ecosystems.

State the role of a keystone species in an ecosystem.

A keystone species has a disproportionately large effect on its ecosystem relative to its abundance.

Outline an example of a keystone species in an ecosystem. ​

Sea otters in kelp forests; they control sea urchin populations, maintaining kelp forest health.

Describe requirements for sustainability in ecosystems.

Requirements include maintaining biodiversity, nutrient cycling, energy flow, and limiting human impact and pollution.

Define resource harvesting.

Resource harvesting is the extraction of natural resources for human use, such as timber, fish, or crops.

Define sustainable in relation to resource harvesting.

Sustainable resource harvesting ensures that resources are extracted at a rate that allows natural regeneration and long-term ecological balance.

Discuss the sustainable resource harvesting of a marine fish. ​

Example: regulated cod fishing with quotas and protected areas to prevent overfishing and allow population recovery.

Assess the sustainability of resource harvesting by identifying the maximum sustainable yield of a resource on a population growth curve.

The maximum sustainable yield is at the point of the steepest slope on the logistic growth curve, before the population reaches carrying capacity.

Discuss the sustainable resource harvesting of a terrestrial plant. ​

Example: bamboo harvesting, where only mature stalks are cut, allowing continuous growth and soil protection.

Discuss factors that negatively impact the sustainability of agriculture.

Factors include monoculture, overuse of fertilizers and pesticides, deforestation, soil erosion, water overuse, and pollution.

Discuss causes and effects of ecosystem eutrophication.

Causes: runoff of fertilizers and sewage. Effects: algal blooms, oxygen depletion, fish kills, loss of biodiversity.

Outline the process of biomagnification.

Biomagnification is the increase in concentration of pollutants as they move up the food chain.

Discuss the cause and effect of mercury biomagnification in an ecosystem.

Cause: industrial waste releases mercury. Effect: mercury accumulates in top predators like tuna, causing neurological damage in wildlife and humans.

Discuss the cause and effect of DDT biomagnification in an ecosystem.

Cause: pesticide use. Effect: DDT accumulates in birds of prey, thinning eggshells and reducing reproductive success.

Define biodegradable.

Biodegradable substances can be broken down naturally by microorganisms.

State that plastics are not biodegradable.

Plastics are not biodegradable and persist in the environment for hundreds of years.

Define microplastic and macroplastic.

Microplastics are plastic particles <5mm; macroplastics are larger plastic debris.

Discuss the cause and effect of microplastic pollution on an ocean ecosystem. ​

Cause: breakdown of larger plastics, synthetic fibers, and microbeads. Effect: ingestion by marine life, toxin accumulation, and disruption of food webs.

Define rewilding.

Rewilding is the process of restoring ecosystems to their natural state by reintroducing native species and reducing human influence.

Discuss the methods of restoration of an ecosystem by rewilding.

Methods include removing invasive species, reintroducing native species, stopping land use, and allowing natural processes to resume.

Outline the rewilding of the Hinewai Reserve in New Zealand.​

Farmland was left to regenerate; native forest regrew naturally, supporting biodiversity and ecosystem restoration.

Outline the cause and effect of ecological succession.

Cause: disturbance or colonization of new area. Effect: gradual change in species composition and ecosystem structure.

Outline an example of reciprocal interactions between living organisms and the abiotic environments that cause ecological succession.

Lichens on bare rock produce acids that break down rock into soil, enabling moss and plant growth.

State an example of ecological succession triggered by an abiotic factor.

Volcanic eruption leading to primary succession on lava flows.

State an example of ecological succession triggered by a biotic factor. ​

Abandonment of farmland leading to secondary succession and regrowth of vegetation.

Describe changes occurring during primary succession in a community, including increases in size of plants, amount of primary production, species diversity, complexity of food webs and amount of nutrient cycling.​

Over time, primary succession leads to larger plants, more biomass, higher species diversity, complex food webs, and efficient nutrient cycling.

Explain an example of cyclical succession in an ecosystem.​

In temperate forests, seasonal leaf fall and regrowth result in cyclical changes in detritus levels and nutrient availability.

Define climax community and plagioclimax.

Climax community: stable, mature ecosystem. Plagioclimax: stable ecosystem maintained by human activity preventing succession.

Discuss the impact of grazing by farm livestock on arresting succession in a community. ​

Grazing removes young plants and prevents forest regeneration, maintaining grasslands (a plagioclimax).

Discuss the impact of drainage of wetlands on arresting succession in a community.

Draining wetlands prevents normal succession to marsh and forest ecosystems, halting biodiversity development.

Outline the cause and consequence of the greenhouse effect

The greenhouse effect is caused by greenhouse gases trapping heat in the atmosphere, leading to a warmer Earth. Consequences include global temperature increases and climate changes.

Outline the cause and consequence of the enhanced greenhouse effect

Caused by increased greenhouse gas emissions from human activities, it leads to accelerated global warming and more extreme climate events.

List anthropogenic sources of atmospheric carbon dioxide and methane

Combustion of fossil fuels, agriculture (especially livestock), landfills, and deforestation.

State that methane is oxidized to carbon dioxide in the atmosphere

Methane is gradually oxidized into carbon dioxide and water in the atmosphere.

Outline climate changes that can result from the enhanced greenhouse effect

Rising temperatures, changes in precipitation patterns, sea level rise, and more extreme weather events.

Explain the correlation between atmospheric CO2 and methane concentrations since the industrial revolution and global temperatures

Both greenhouse gases have increased dramatically, correlating with rising global temperatures.

Define positive feedback

A process where a change triggers mechanisms that further amplify that change.

Outline five examples of positive feedback cycles related to global warming

Melting ice reduces albedo; thawing permafrost releases methane; warmer oceans absorb less CO2; forest dieback reduces carbon uptake; increased evaporation raises atmospheric water vapor.

Define tipping point

A critical threshold where a small change leads to drastic and possibly irreversible changes in the system.

Explain changes in boreal forest carbon cycle due to climate change

Warmer temperatures lead to more decomposition and fires, shifting forests from carbon sinks to sources.

Outline changes to polar landfast and sea ice habitat that result from global warming

Reduced sea ice extent and thickness, loss of ice cover duration.

Describe impact of changes to Antarctic polar ice on emperor penguin

Loss of breeding grounds, reduced chick survival.