Unit 2, Environmental Biology

Vocabulary Notes. Unit 2

Reproductive isolation

A condition where members of one species do not interbreed with members of other species due to breeding barriers, keeping groups separated while they may be evolving into separate species.

Geographic isolation

Isolation based on physical barriers such as mountains and rivers.

Temporal isolation

Isolation based on differences in breeding seasons.

Behavioral isolation

Isolation based on courtship rituals, such as songs or dances.

Structural isolation

Isolation caused by differences in reproduction structures.

Extinction

The dying out or extermination of a species naturally or through human influence, which has occurred for over $99\%$ of all species that have lived.

Mass extinction

Massive extinction occurring planet-wide in a short period of time, of which $5$ mass extinctions have naturally occurred.

Background extinction

The average rate of extinction events that is always occurring.

Pre-agricultural period

The period during which human population grew as humans expanded into new territories and developed new traits.

Agricultural period

The period beginning $10{,}000$ years ago that stimulated rapid human population growth.

Industrial period

The current period that began between the $1700\text{s}$ and $1800\text{s}$, characterized by technological advances in fossil fuels, sanitation, and healthcare, causing death rates to decline.

Demographic transition model

A model describing four stages of change in birth rates, death rates, and growth rates of human populations associated with economic development.

Pretransition (Stage 1)

The preindustrial stage of the demographic transition model where birth and death rates are both high, resources are limited, and diseases spread easily.

Mortality transition (Stage 2)

The stage of the demographic transition model where the death rate declines and birth rate remains high as technology is embraced, leading to rapid population growth.

Fertility transition (Stage 3)

The industrial stage where the death rate stays low, birth rate decreases as people have fewer children later in life, and population growth slows.

Stability transition (Stage 4)

The post-industrial stage characterized by low, equal birth and death rates, resulting in zero or negative population growth.

Interspecific competition

Competition between two or more different species competing amongst each other.

Intraspecific competition

Competition between members of the same species fighting or competing for the same resource within a population.

Ecological niche

The role an organism fills and performs within its habitat or ecosystem, including all activities and interactions.

Niche differentiation

The process where competing species evolve or adapt to use resources differently, occupy different habitats, or behave differently to minimize direct competition and coexist in the same ecosystem.

Fundamental niche

The complete range of areas in which an organism could easily exist.

Realized niche

The range in which an organism actually exists due to competition.

Herbivory

The interaction where animals with specialized digestive systems eat plants, driving plants to evolve anti-herbivory chemical and mechanical defenses and herbivores to evolve detoxification mechanisms.

Coevolution

The process where two or more species reciprocally affect each other's evolution through natural selection in a positive feedback loop.

Artificial selection

Non-adaptive, non-random evolution where humans use animal and plant breeding to selectively develop traits by choosing which males and females sexually reproduce.

Differential reproduction

A condition in which some individuals in a population have more offspring than others due to their traits.

Natural selection

Process where certain members of a population better suited to their environment are more likely to survive and produce offspring that inherit beneficial traits.

Fitness

The ability of an organism to produce viable offspring, measured in the ability to have grand-offspring.

Adaptations

Inherited structures, functions, or behaviors that increase the ability of an organism to survive and reproduce in its environment over time.

Adaptive radiation

Evolutionary process where several species evolve from a single ancestral species to occupy new niches.

Darwin's finches

A group of $14$ species occupying a variety of different niches, whose rapid evolution was shown in recent studies to be driven by a severe drought on the island.

Directional selection

Selection in which one extreme end of the range of variation is favored.

Stabilizing selection

Selection in which the middle range of variation is favored.

Disruptive selection

Selection in which both extreme ends of the variation are favored over average traits.

Genetic drift

A change in the frequency of an inherited trait caused by a chance event; a non-adaptive, random form of evolution where small populations are more variable.

Founder effect

A change in the frequency of an inherited trait caused by a small subset of the population.

Species

The basic unit of classification and biodiversity.

Exponential growth

Growth where the rate becomes more rapid in proportion to the growing total, often forming a J-shaped curve when resources are available in a new environment.

Population growth rate

Percentage of population change per year, calculated as $\frac{\text{new}}{\text{time}}$.

Doubling time

The length of time required for a population to double in size, calculated as $\frac{70}{\text{population growth rate}}$ and usually accurate within $10\%$.

Carrying capacity

The maximum number of organisms the environment can support, where resource limitation reduces reproduction rate.

Logistic growth

Growth represented by $\mathbf{N_t = \frac{K}{1 + e^{-r t}}}$, where $N_t$ is population size at time $t$, $K$ is carrying capacity, $r$ is per capita population growth rate, and $e = 2.71828$.

Environmental resistance

Factors affecting population growth such that as resources deplete, birth rate decreases and death rates increase.

Habitat

The complex environment an organism depends on for survival, including temperature, humidity, and living elements like food and nutrients.

Survivorship

The probability of an organism dying during a particular interval, divided into Type 1 (most die old), Type 2 (constant death rate for old and young), and Type 3 (most die young).

Evolution

Inherited genetic changes in a population over time across generations, defined by Charles Darwin as "descent with modification."

Adaptive evolution

Evolutionary changes driven by natural selection in which species become better suited to their environment over time.

Non-adaptive evolution

Evolutionary changes in which species do not become better suited to their environment, such as artificial selection or genetic drift.

Mutations

Random changes in DNA from which all evolution starts.

Age structure

The distribution of individuals by age and sex within a population, determined by survivorship and age-specific birth rate.

Age structure pyramid

A graphical display of age structure whose shape indicates population growth trends.

Ecological footprint

The area of land needed to supply resources consumed by people, varying in size by country.

Biocapacity

The area and quality of land available to supply resources.

Ecological debtors

Populations whose ecological footprints exceed their biocapacity, requiring goods to be imported (e.g., the USA).

Ecological creditors

Populations whose biocapacity exceeds their ecological footprint, allowing them to export goods.

Community ecology

The study of the organization and functioning of communities, examining how organisms in a community interact with each other and their environment.

Competition

Interaction where two or more groups must use the same limited resource, reducing fitness and causing more energy and time to be spent gaining fewer resources.

Exploitative competition

Competition where competitors consume or use the same limited resource without direct fighting or aggression.

Interference competition

Competition where competitors deny each other access to the limiting resource.