Ecology: Key Concepts, Levels, Population Dynamics, and Interactions

What is ecology?

The study of how organisms interact with each other and with their environment.

What are the levels of organization in ecology?

Populations, Species, Communities, Ecosystems, Biomes, and Biosphere.

What constitutes a population?

Individuals of the same organism that live together.

What defines a species?

All the populations of a particular organism.

What is a community in ecological terms?

Populations of different species that live together in the same place.

What is an ecosystem?

A community and the nonliving factors with which it interacts.

What are biomes?

Major terrestrial assemblages of plants, animals, and microorganisms that occur over wide geographic areas.

What is the biosphere?

All the world's biomes, along with its marine and freshwater assemblages.

What key elements determine the habitat of organisms?

Temperature, Water, Sunlight, and Soil.

How do organisms adapt to environmental changes?

Through morphological, physiological, or behavioral adaptations.

What is population range?

The total geographic area where a species lives.

What factors influence population distribution?

The spatial arrangement and density of inhabitants.

What are the three main population distribution patterns?

Randomly spaced, Uniformly spaced, and Clumped.

What is population growth?

The increase in the number of individuals in a population over a specific period.

What is the difference between population size and population density?

Population size is the total number of individuals, while population density is the number of individuals per unit of area or volume.

What is biotic potential?

The maximum reproductive rate of a population under ideal conditions.

What limits a population's growth?

Environmental resistance and shortages of important environmental factors.

What is the carrying capacity?

The maximum population size that an environment can sustain.

What is the formula for the exponential growth model?

Growth rate (G) = riN, where N is the population size and ri is the intrinsic rate of natural increase.

How is the actual rate of population increase defined?

r = (b - d) + (i - e), where b is the birthrate, d is the death rate, i is immigration, and e is emigration.

What happens to populations when they reach a new habitat with abundant resources?

They may experience rapid exponential growth.

What is the significance of carrying capacity in population ecology?

It represents the limit at which a population stabilizes due to environmental constraints.

What is the carrying capacity symbolized by?

K

What does carrying capacity refer to?

The maximum number of individuals that an area can support.

What equation approximates the growth curve of a population approaching its carrying capacity?

G = rN [(K - N)/K]

What happens to the rate of population growth (G) as N approaches K?

The rate of population growth begins to slow until it reaches zero at N = K.

What is characteristic of most biological populations' growth curves?

The sigmoid growth curve.

What are density-dependent factors?

Biological influences that regulate population growth based on its density.

How do density-dependent factors affect population growth?

They limit growth and help determine carrying capacity, becoming more intense as population density increases.

What is an example of competition as a density-dependent factor?

Individuals compete for limited resources like food, water, and space.

How does predation relate to population density?

In a denser prey population, predators can find food more easily, increasing predation.

What are density-independent factors?

Environmental influences that affect a population's size regardless of its density.

Give an example of a density-independent factor.

Natural disasters like earthquakes or wildfires.

What is the goal in natural systems exploited by humans?

To maximize productivity by exploiting the population early in the rising portion of its sigmoid growth curve.

What does r/K selection theory describe?

Two extreme strategies for population growth and survival: r-selected and K-selected species.

What characterizes r-selected species?

They produce many offspring with little parental care and prioritize high reproductive rates in unstable environments.

What characterizes K-selected species?

They produce fewer offspring, invest heavily in each one, and prioritize survival near the environment's carrying capacity (K).

What is demography?

The statistical study of populations, measuring characteristics and predicting changes in population sizes.

What determines if a population grows or shrinks?

If births outnumber deaths, the population grows; if deaths outnumber births, it shrinks.

What is fecundity?

The number of offspring produced in a standard time.

What does age distribution refer to?

The proportion of individuals in different age categories within a population.

What is a survivorship curve?

A graph showing the number of individuals surviving from a cohort over time.

What are the three main types of survivorship curves?

Type I (high survival until old age), Type II (constant mortality rate), Type III (high early-life mortality).

What is the sex ratio in a population?

The proportion of males and females.

What are the three main types of ecological interactions?

Competition, predation, and symbiosis.

What is a niche in ecology?

The sum total of all the ways an organism utilizes the resources of its environment.

What is competition in ecological terms?

An interaction when two organisms attempt to use the same resource when there is not enough to satisfy both.

What is interspecific competition?

Competition that occurs between individuals of different species.

What is intraspecific competition?

Competition that occurs between individuals of the same species.

What is the fundamental niche?

The entire niche that an organism may theoretically occupy.

What is the realized niche?

The actual niche that an organism is able to occupy due to competition.

What does the Principle of Competitive Exclusion state?

Two species competing for the same limited resource cannot coexist in the same ecological niche.

What are the two outcomes when niches overlap?

Competitive exclusion or resource partitioning.

What is resource partitioning?

Dividing up resources to create two niches to reduce competition.

What is coevolution?

The process where two or more species evolve in response to each other.

What is symbiosis?

A relationship where species live in close physical association.

What is mutualism?

A symbiotic relationship in which both species benefit.

What is parasitism?

A symbiotic relationship in which one species benefits while the other is harmed.

What are ectoparasites?

External parasites that feed on the exterior surface of a host.

What are endoparasites?

Internal parasites that feed internally on their hosts.

What is brood parasitism?

A form of parasitism where the parasite lays eggs in the nest of other species for the host to raise.

What is commensalism?

A symbiotic relationship that benefits one species but neither hurts nor helps the other.

What is predation?

The consuming of one organism by another.

What is mimicry?

The resemblance of one organism to another to gain an advantage, such as protection from predators.

What is Batesian mimicry?

When a palatable species resembles a poisonous one.

What is Müllerian mimicry?

When several unrelated but protected species come to resemble one another.

What is ecological succession?

The orderly replacement of one community with another.

What is primary succession?

Succession that occurs on bare, lifeless substrates.

What is secondary succession?

Succession that occurs after an already established community has been disturbed.

What is tolerance in ecological succession?

Early successional stages are characterized by weedy r-selected species that tolerate harsh conditions.

What is facilitation in ecological succession?

Weedy species introduce changes in the habitat that favor non-weedy species.

What is inhibition in ecological succession?

Changes in habitat caused by one species may inhibit the growth of the species that caused them.

What are the five factors that can alter allele frequencies in a population?

Mutation, Nonrandom mating, Genetic drift, Migration, Selection

What is mutation in the context of evolution?

A change in a nucleotide sequence in DNA that serves as the ultimate source of variation in a population.

How does nonrandom mating affect genotype frequencies?

It alters genotype frequencies but not allele frequencies.

What is genetic drift?

Random changes in allele frequencies, particularly impactful in small populations.

What is the founder effect?

Occurs when a few individuals migrate and establish a new population, significantly affecting the genetic makeup.

What is the bottleneck effect?

Occurs when a population is drastically reduced in size, resulting in a random genetic sample of the original population.

What is the role of selection in evolution according to Darwin?

Selection occurs if some individuals leave behind more progeny than others, influenced by their characteristics.

What are the three types of natural selection?

Stabilizing selection, Disruptive selection, Directional selection.

What is stabilizing selection?

A form of selection that eliminates both extremes, increasing the frequency of the common intermediate phenotype.

What is disruptive selection?

A form of selection where the two extremes become more common, while intermediate phenotypes are eliminated.

What is directional selection?

A form of selection that eliminates one extreme from an array of phenotypes.

What is sickle-cell anemia?

A hereditary disease affecting hemoglobin, where homozygous individuals have reduced lifespans due to sickled red blood cells.

Why has the sickle-cell allele not been eliminated in Central Africa?

Heterozygous individuals are less susceptible to malaria, providing a survival advantage.

What is the Biological Species Concept?

Defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups.

What are prezygotic isolating mechanisms?

Barriers that prevent the formation of zygotes between different species.

What is geographical isolation?

Occurs when species exist in different areas and cannot interbreed.

What is ecological isolation?

Occurs when species utilize different portions of the environment, reducing hybridization chances.

What is temporal isolation?

Occurs when species have different reproductive periods, preventing hybridization.

What is behavioral isolation?

Refers to courtship and mating rituals that keep species distinct even in the same habitat.

What is mechanical isolation?

Structural differences that prevent mating between related species.

What is prevention of gamete fusion?

Blocks the union of gametes even after successful mating.

What are postzygotic isolating mechanisms?

Factors that prevent zygotes from developing into normal individuals.

What is hybrid inviability?

Occurs when hybrid embryos do not develop properly or hybrid adults do not survive.

What is hybrid infertility?

Occurs when hybrids are sterile or have reduced fertility.

What is heterozygote advantage?

The survival benefit of heterozygous individuals in certain environments, such as resistance to malaria in sickle-cell carriers.