semester 2 bio cornell note

Struggle for existence

All populations have the potential to produce more offspring than can survive, leading to competition for environmental resources.

Adaptation

Heritable characteristics that increase an organism's ability to survive and reproduce in a specific environment.

Fitness

The ability of an organism to survive and reproduce in its environment, influenced by its adaptations.

Natural selection

The process where organisms with variations suited to their environment survive and reproduce, leading to differential reproductive success.

Descent with modification

Living species are descended with changes over time from common ancestors.

Artificial selection

Selective breeding of plants and animals to promote desirable traits in offspring.

Biogeography

The study of past and present distribution of organisms to understand evolution and adaptation.

Homologous structure

Structures similar in different species due to common ancestry, with similar structure but different functions.

Vestigial structure

Inherited structures from ancestors that have lost their original function.

Genotype

The combination of alleles an individual possesses.

Phenotype

All physical, physiological, and behavioral characteristics of an organism, influenced by genotype and environment.

Genetic variation

Produced by mutations, genetic recombination, and lateral gene transfer, leading to diversity and adaptation.

Genetic drift

Random changes in allele frequency in a population due to chance events, like the bottleneck effect or founder effect.

Speciation

The formation of new species through reproductive isolation, such as behavioral, geographic, or temporal isolation.

Founder Effect

A phenomenon where a small group of individuals separates from a larger population and establishes a new population, leading to genetic differences.

Geographic Isolation

The separation of populations by physical barriers, such as land or water, leading to reproductive isolation and potential speciation.

Natural Selection

The process by which organisms better adapted to their environment tend to survive and produce more offspring, influencing the frequency of traits in a population over time.

Adaptations

Traits or characteristics that help an organism survive and reproduce in its environment.

Evolution

The process of change in species over time, driven by mechanisms like natural selection, genetic drift, and gene flow.

Gene Pool

The complete set of genes or genetic material present in a population.

Behavioral Isolation

A type of reproductive isolation where individuals prefer to mate with partners that exhibit specific behaviors or traits.

Ecological Competition

The competition between species for limited resources in an ecosystem, influencing the evolution of traits and adaptations.

Biomass Pyramid

Illustrates the relative amount of living organic matter in each trophic level of an ecosystem.

Number Pyramid

Represents the relative number of individual organisms at each trophic level in an ecosystem.

Energy Transfer Efficiency

Only a small portion of the energy stored in any trophic level is available to organisms in the next level due to energy being used for life processes.

Biogeochemical Cycles

Cycles involving the biosphere, geosphere, hydrosphere, and atmosphere where elements are recycled among ecosystems.

Limiting Nutrients

Single essential nutrients that limit productivity in an ecosystem.

Habitat

The area where organisms live, influenced by biotic and abiotic factors.

Microhabitat

Small areas within a habitat where many organisms live.

Tolerance

The ability of an organism to survive and reproduce under different environmental conditions.

Niche

The full range of physical and biological conditions in which an organism lives and interacts with its environment.

Keystone Species

A species that exerts strong control on the structure of a community despite not being abundant.

Symbiosis

Relationship in which two species live closely together, including commensalism, mutualism, and parasitism.

Ecological Succession

Gradual changes in a community following a disturbance, including primary and secondary succession.

Biomes

Groups of ecosystems sharing similar climate and typical organisms.

Aquatic Ecosystems

Ecosystems described by factors like salinity, depth, temperature, and flow rate, including marine and freshwater ecosystems.

Population Density

The number of individuals per unit area in a population.

Age Structure

The distribution of males and females of each age in a population.

Exponential Growth

Population growth that increases rapidly due to unlimited resources.

Logistic Growth

Population growth that slows and stops following a period of exponential growth, reaching carrying capacity.

Limiting Factors

Factors that cause population growth to decrease, including density-dependent and density-independent factors.

Carrying Capacity

The largest number of individuals of a species that an environment can support.