Ecology Exam 1 Review: Evolution, Physiological Ecology, and Nutrient Cycling

Vocabulary practice flashcards covering core concepts of evolutionary biology, physiological ecology, and nutrient cycling based on the Ecology Exam #1 study guide.

Genetic variation

Differences among individuals in genetically influenced traits or alleles.

Rapid evolution

Evolutionary change over relatively few generations, driven by strong ecological pressures such as predation or repeated pesticide exposure.

Pesticide treadmill

A cycle where repeated use of the same control method strongly favors resistant individuals, causing resistance to become more common, the treatment to become less effective, and requiring stronger or new control measures.

Mutation

A change in DNA that creates new alleles and serves as the source of new genetic variation, though by itself it usually does not cause large, immediate shifts in allele frequency.

Natural selection

The process by which heritable variants differ in survival or reproductive success under current environmental conditions, causing associated alleles to change in frequency.

Gene flow

The movement of individuals and their alleles between populations, which can change allele frequencies suddenly or continuously and connect populations.

Genetic drift

Random change in allele frequencies caused by chance, which has its strongest effects in small populations and can cause alleles to disappear or become fixed.

Ecological trade-off

A situation where a benefit in one function or environment comes with a cost in another, influencing fitness and how traits evolve.

Requirements of natural selection

1. Individuals vary genetically

2. Some of that variation is heritable

3. Survival and reproduction differ among phenotypes/genotypes

Evidence supporting natural selection

Fossil records, geological gradualism, artificial selection and inheritance/genetics

Gradualism

The geological idea that large changes can result from small changes accumulating over long periods.

Population genetics

The study of genetic differences within and among populations and how the genetic composition of populations changes over time.

Requirements of modern genetics

Individuals vary in phenotype

Some phenotypic differences reflect genotype

Some pheno/genotypes survive and reproduce at higher rates than others

Modern definition of evolution

A change from one generation to the next in allele frequencies within a population.

Allele

An alternative version of a gene found at a particular locus.

Fitness

An individual's relative contribution of genes to future generations through survival and reproduction.

Genotype frequency

The number of individuals with a specific genotype divided by the total number of individuals in the population.

Allele frequency

The number of copies of a particular allele divided by the total number of allele copies in the population, where total allele copies equals $2N$ for a diploid population.

Character vs. Trait

Character is the general phenotypic category (like coat color), while trait is the specific expression of that character (like a brown coat)

Quantitative trait

A continuously varying trait that is commonly influenced by multiple genes and the environment.

Adaptation

A heritable trait that evolved by natural selection and increases the fitness of individuals that inherit it.

Local adaptation

A population has traits that provide relatively high fitness in its local environment compared to individuals transplanted from other environments.

Reciprocal transplant

An experimental setup where individuals from two populations are moved into each other's environments and their performance or fitness is compared.

Bottleneck effect

Genetic drift occurring after a population is sharply reduced by a chance event, causing survivors to potentially not represent the original allele frequencies.

Founder effect

Genetic drift occurring when a new population is established by a small subset of the original population, leading to a new gene pool that may differ by chance.

Drift (Random chance)

Allele frequencies can change between generations simply because a small sample of individuals reproduces, even when environmental conditions do not favor one trait

Evolution: time and place

Selection depends on current local environmental conditions; drift and migration also depend on chance events and population history

Species distribution

Temperature and moisture/precipitation

Vegetation

Key biotic feature of ecosystems that is affected by temperature and moisture and affects habitat conditions

Biomes

Large, broadly contiguous regions with similar climatic conditions and characteristic resident biota. The Whittaker diagram organizes biomes by temperature and precipitation.

What powers the water cycle?

The sun

Physiological tolerance

The range of environmental conditions an organism can tolerate and still function or survive.

Niche

The sum of environmental conditions under which a species can survive, including both abiotic conditions and biotic interactions.

Law of the minimum

The principle that growth or distribution can be controlled by the single resource or condition that is most limiting, even if other resources are abundant.

Acclimation

A physiological change by an individual during its lifetime in response to environmental conditions.

Does not require a change in population allele frequencies.

Adaptation

A heritable population-level change produced by natural selection across generations

Irreversible acclimation

An acclimatory change that cannot be rapidly reversed or reverses only very slowly.

Homeostasis

The maintenance of relatively constant internal conditions within an organism's physiological tolerance range.

Temperature regulation factors

Absorption of solar energy, metabolic heat, re-radiation, conduction, convection, and evaporative heat loss.

Poikilotherm

An organism whose body temperature varies substantially with environmental conditions.

Homeotherm

An organism that maintains a relatively stable body temperature.

Heterotherm

An organism that maintains a stable body temperature at some times but allows substantial fluctuation at others, such as during hibernation.

Ectothermy

A thermoregulatory pattern where most body heat comes from external environmental sources.

Endothermy

A thermoregulatory pattern where metabolic processes generate substantial internal heat used to regulate body temperature.

Temperature adaptations

Animals may use morphology, physiology, or behavior. Plant examples include transpirational cooling, leaf size, waxy/hairy surfaces, etc.

Water balance

Water gains include ingestion, metabolic water, and absorption; losses include evaporation, secretions, and osmosis. Osmoregulation helps maintain internal water/solute balance.

Water-balance adaptations

Examples include concentrated secretions and water-conserving behaviors. Conserving water can trade off with heat loss, energy use, or gas exchange.

Photosynthesis

Light reactions use light and water to produce ATP/NADPH and release O2; the Calvin-cycle reactions use ATP, NADPH, and CO2 to build sugars.

Stomata

Leaf openings that allow $CO_2$ entry and water-vapor loss.

Photorespiration

A process where Rubisco binds $O_2$ rather than $CO_2$, preventing sugar production.

C3 photosynthesis

The standard one-stage carbon-fixation pathway that initially produces a 3-carbon compound. . It generally performs well in cooler, wetter conditions but is more vulnerable to photorespiration at higher temperatures.

C4 photosynthesis

A photosynthetic pathway where $CO_2$ is first incorporated into a 4-carbon compound and concentrated in bundle-sheath cells, reducing photorespiration. C4 plants tend to perform better at higher temperatures.

CAM photosynthesis

A photosynthetic pathway where stomata open mainly at night to acquire $CO_2$, storing carbon for use in the Calvin cycle during the day while stomata remain closed. Conserves water in arid environments

Water conservation trade-offs in plants

Closing stomata or reducing water flow lowers water loss and cavitation risk but can also reduce CO2 update, photosynthesis, growth, and transpirational cooling

Macronutrients

Nutrients needed in relatively large amounts, specifically C, H, O, N, P, and S.

Micronutrients

Mineral nutrients required in much smaller amounts.

Law of the minimum

A single essential nutrient can limit growth even when other nutrients are abundant.

Co-limitation

A condition in which growth is limited by two or more independent resources or nutrients at the same time.

Excess nutrients

Can cause rapid population growth, harmful algal blooms, eutrophication, and dead zones

Dead zone

An oxygen-poor area that can develop after high nutrient inputs stimulate primary production and subsequent decomposition consumes dissolved oxygen.

Pool

The amount of a nutrient or material contained within a defined compartment.

Flux

The rate at which material moves from one pool to another, which can include chemical transformations.

Terrestrial carbon cycle

Important pools include atmospheric CO2, plant carbon, soil carbon, and animal carbon.

Key fluxes include photosynthesis, respiration, and litterfall.

Phosphorous cycle

Important pools include soil inorganic P, soil organic P, and plant P.

Key fluxes include plant uptake, immobilization, mineralization, and litterfall

Simple compartment model

A simplified representation of pools connected by fluxes, where $\text{Storage rate} = \text{total flux in} - \text{total flux out}$.

Open vs. Closed cycles

Most ecosystems are not completely closed; nutrients enter and leave. A pool may remain approximately constant through dynamic equilibrium even while material is continuously moving.

Cycle vs. Flow

Nutrients cycle through ecosystems, whereas energy flows through ecosystems and must be continually supplied because energy transfer is inefficient

Terrestrial nitrogen cycle

Major pools include atmospheric N2, NH4+, NO3−, plant N, and soil organic N.

Important fluxes include uptake, immobilization, mineralization, nitrification, denitrification, fixation, leaching, litterfall, and volatilization.

Nutrient spiral

In flowing water, nutrients repeatedly cycle between dissolved/inorganic and biological/organic forms while being transported downstream.

Nutrient budget

A system that tracks major nutrient inputs and outputs while simplifying internal cycling to indicate whether an ecosystem acts as a source or sink.

Nutrient storage

The rate at which nutrients accumulate within an ecosystem, defined as $\text{total inputs} - \text{all outputs}$.

Nutrient retention

The rate at which nutrients are prevented from leaving in surface-water export, defined as $\text{retention rate} = \text{inputs} - \text{stream output}$.

Retention efficiency

The fraction of inputs retained rather than exported in surface water, calculated as $\text{Retention efficiency} = \frac{\text{retention rate}}{\text{inputs}} \times 100\%$.

Modified budget

A framework that uses selected focal inputs and stream output to evaluate retention when all inputs and outputs are not measured, preventing calculation of storage rate.

Global phosphorous cycle

Human mining and fertilizer use accelerate phosphorus movement; excess P can contribute to eutrophication. The lecture emphasizes efficient use and recycling

Global carbon cycle

Most of Earth’s carbon is stored in rocks and cycles slowly; the active carbon cycle involves a much smaller fraction. Fossil-fuel combustion increases atmospheric CO2 and is linked to climate change

Human impacts on global nutrient cycling

P: mining/fertilizer and eutrophication.

C: fossil-fuel combustion and climate change.

N: fossil fuels and synthetic fertilizers, with effects including eutrophication and acid rain.