Biology Ecology and Biodiversity

Taxon

A group of organisms classified together as a unit

Taxonomy

The science of classifying organisms into groups based on shared characteristics

Taxon

A group of organisms classified together as a unit

Hierarchy of taxa

The system of organizing organisms in nested ranks of increasing specificity: domain - kingdom - phylum - class - order - family - genus - species

Binomial nomenclature

the system of naming species using two words: the genus name (capitalized) and the species name (lowercase), written in italics

Clade

a group of organisms that includes a common ancestor and all of its descendants

Cladogram

a branching diagram that shows the most probable sequence of divergence in clades

Node

the branching point on a cladogram that represents the most recent common ancestor of the descendant groups

Root

the base of a cladogram, representing the most common ancestor of all organisms shown

Terminal branch (tip)

the end of a line on a cladogram that represents a present-day species of taxon

Synapomorphy (derived trait)

a trait that appears in an ancestor and is shared exclusively by its descendants in a clade

Phylogeny

the evolutionary history and relationships of a species or group of organisms

Molecular clock

the concept that mutations in DNA or proteins accumulate at a roughly constant rate and can be used to estimate the time of divergence between species

Molecular evidence

the use of DNA base sequences or amino acid sequences to determine evolutionary relationships

Parsimony

the principle that the simplest explanation requiring the fewest evolutionary changes is preferred when constructing cladograms

rRNA sequencing

comparing ribosomal RNA sequences to study evolutionary relationships, especially for determining the three domains of life

Evolution

The cumulative change in the heritable characteristics of a population over time

Theory

A well-substantiated explanation of natural phenomena supported by evidence

Homologous Structures

Structures with a common evolutionary origin, even if their functions differ

Selective Breeding

Human-directed breeding of organisms for desired traits

Common Ancestor

The shared ancestral species from which two or more descendant species evolved.

Pentadactyl Limbs

A limb structure with five digits, found in many vertebrates.

Population

A group of organisms of the same species living in the same area at the same time.

Convergent Evolution

the independent evolution of similar features in different lineages

Analogous Stuctures

Structures that perform similar functions but have different evolutionary origins

Speciation

the formation of new species through evolution

Species

A group of similar organisms that can breed and produce fertile offspring.

Extinction

The termination of a species

Reproductive Isolation

Mechanisms preventing interbreeding between species.

Geographical Isolation

Populations separated by physical barriers

Sympatric Speciation

speciation without physical seperation

Hybrid

Offspring of two different species

Allopatric Speciation

Speciation due to geographical isolation

Prezygotic Barriers

prevent mating or fertilization between species

Postzygotic Barriers

Barriers that occur after fertilization, reducing hybrid viability or fertility

Behavioural Isolation

Differences in mating behavior prevent interbreeding

Sterile

Unable to produce offspring

Temporal Isolation

Species reproduce at different times

Hybrid Inviability

Hybrid offspring fail to survive or develop properly

Biodiversity

Variety of life in all forms, levels, and combinations

Hybrid Infertility

Hybrid is healthy but cannot reproduce

Hybrid Breakdown

Hybrids are fertile, but their offspring are weak or sterile

Adaptive Radiation

Rapid evolution of many species from a common ancestor to exploit different niches

Polyploidy

Possession of more than two sets of chromosomes

Divergent Evolution

Evolution of different traits in species from a common ancestor

Triploid

Organisms with three sets of chromosomes

Hybridization

Crossing of two different species or varieties

Tetraploid

Organisms with four sets of chromosomes

Competition

The struggle between organisms for limited resources such as food, space, or mates

Biotic Factors

Living components of an ecosystem that affect other organisms (e.g., predators, pathogens, competition)

Abiotic Factors

Non-living environmental factors (e.g., temperature, pH, water, sunlight) that influence organisms

Selection Pressure

An environmental factor that influences which individuals are more likely to survive and reproduce

Phenotype

The observable characteristics of an organism resulting from its genotype and environment

Genotype

The genetic makeup of an organism; the set of alleles it possesses

Density Independent Factors

Environmental factors that affect all individuals in a population regardless of population size (e.g., natural disasters)

Intraspecific competition

Competition between individuals of the same species for resources

Sexual Selection

A form of natural selection in which individuals with traits that enhance mating success are more likely to pass on their genes

Natural Selection

The process by which individuals with advantageous traits are more likely to survive, reproduce, and pass on those traits to offspring

Paradigm

A widely accepted scientific framework or model used to interpret observations

Paradigm Shift

A fundamental change in scientific thinking that replaces one framework with a new one

Mutation

A change in the DNA sequence that can introduce new alleles into a population

Sexual Reproduction

The fusion of gametes from two parents, resulting in offspring with a mix of genetic material

Variation

Differences between individuals in a population

Genetic Variation

Differences in DNA sequences among individuals in a population

Allele

One specific form of a gene that differs from other forms by one of more bases

Gene

A heritable factor consisting of a DNA sequence that influences a specific trait

Meiosis

A type of cell division that produces haploid gametes, reducing the chromosome number by hald

Crossing Over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis, increasing genetic variation

Independent Assortment

The random orientation of homologous chromosomes during metaphase I of meiosis, leading to genetic variation in gametes

Gametes

Haploid sex cells (sperm and egg) that unite during fertilization to form a diploid zygote

Carrying Capacity

The maximum number of individuals of a species that an environment can sustainably support

Gene Pool

The collection of all the genes and the various alleles of those genes within a population

Gene flow

Any movement of individuals, and/or the genetic material they carry, from one population to another (no gene flow, each population will have its own gene pool)

Allele Frequency

prevalence of a specific allele out of all alleles for a gene in a gene pool

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection

Founder Effect

change in allele frequencies as a result of the migration of a small subgroup of a population

Neo-Darwinism

A cohesive theory of evolution that integrates Darwin's idea of natural selection with understandings of genetics and gene pools of populations (tracked at the molecular level by observing changes in allele frequencies in a gene pool over time)

Hardy-Weinberg Equilibrium

When the allele frequency of a specific gene in a population remains stable over time

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Directional Selection

occurs when natural selection favors one of the extreme variations of a trait

Disruptive Selection

favors individuals at both extremes of the phenotypic range

Meiotic non-disjunction

the failure of separation of homologous chromosomes during meiosis, unreduced gametes and leads to polyploidy

Intrasexual selection

Individuals of the same sex compete for mating access to the opposite sex

Intersexual selection

On sex (usually female) choosing mate based on desired traits

Founding Effect

When the species moves and develops a new population creating a new gene pool